Journal articles: 'Ferroelectric perovskite'

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Osman, Rozana A. M., Mohd Sobri Idris, Zul Azhar Zahid Jamal, Sanna Taking, Syarifah Norfaezah Sabki, Prabakaran A. L. Poopalan, Mohd Natashah Norizan, and Ili Salwani Mohamad. "Ferroelectric and Relaxor Ferroelectric to Paralectric Transition Based on Lead Magnesium Niobate (PMN) Materials." Advanced Materials Research 795 (September 2013): 658–63. http://dx.doi.org/10.4028/www.scientific.net/amr.795.658.

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First ferroelectric materials were found in Rochelle salt was in a perovskite structure. Lead Magnesium Niobate (PMN) is a perovskites with a formula of PbMg1/3Nb2/3O3 (PMN) and are typical representatives for most of all ferroelectrics materials with relaxor characteristic. It posses high dielectric permittivity which nearly ~ 20,000[ with a broad dielectric permittivity characteristic, known as relaxor ferroelectric below room temperature. Some of the researcher might think that the transition from relaxor ferroelectric to paraelectric is similar to the characteristic as observed from ferroelectric to paraelectric, but it is not necessary. The puzzling is how do we categorise them. How is the domain structure look like typically in ceramic materials.

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Baptista, Rosa M. F., Gonçalo Moreira, Bruna Silva, João Oliveira, Bernardo Almeida, Cidália Castro, Pedro V. Rodrigues, Ana Machado, Michael Belsley, and Etelvina de Matos Gomes. "Lead-Free MDABCO-NH4I3 Perovskite Crystals Embedded in Electrospun Nanofibers." Materials 15, no. 23 (November 25, 2022): 8397. http://dx.doi.org/10.3390/ma15238397.

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In this work, we introduce lead-free organic ferroelectric perovskite N-methyl-N′-diazabicyclo[2.2.2]octonium)–ammonium triiodide (MDABCO-NH4I3) nanocrystals embedded in three different polymer fibers fabricated by the electrospinning technique, as mechanical energy harvesters. Molecular ferroelectrics offer the advantage of structural diversity and tunability, easy fabrication, and mechanical flexibility. Organic–inorganic hybrid materials are new low-symmetry emerging materials that may be used as energy harvesters because of their piezoelectric or ferroelectric properties. Among these, ferroelectric metal-free perovskites are a class of recently discovered multifunctional materials. The doped nanofibers, which are very flexible and have a high Young modulus, behave as active piezoelectric energy harvesting sources that produce a piezoelectric voltage coefficient up to geff = 3.6 VmN−1 and show a blue intense luminescence band at 325 nm. In this work, the pyroelectric coefficient is reported for the MDABCO-NH4I3 perovskite inserted in electrospun fibers. At the ferroelectric–paraelectric phase transition, the embedded nanocrystals display a pyroelectric coefficient as high as 194 × 10−6 Cm−2k−1, within the same order of magnitude as that reported for the state-of-the-art bulk ferroelectric triglycine sulfate (TGS). The perovskite nanocrystals embedded into the polymer fibers remain stable in their piezoelectric output response, and no degradation is caused by oxidation, making the piezoelectric perovskite nanofibers suitable to be used as flexible energy harvesters.

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ZHU, XINHUA, and ZHIGUO LIU. "SIZE EFFECTS IN PEROVSKITE FERROELECTRIC NANOSTRUCTURES: CURRENT PROGRESS AND FUTURE PERSPECTIVES." Journal of Advanced Dielectrics 01, no. 03 (July 2011): 289–301. http://dx.doi.org/10.1142/s2010135x11000392.

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Perovskite ferroelectric nanostructures offer a wide range of functional properties (e.g., dielectric switchability, piezoelectricity, pyroelectricity, high permittivities and strong electro-optic effects), which have received much attention in the fields of microelectronic devices miniaturization over the last few years. Pronounced size effects of the functional properties have been demonstrated in the perovskite ferroelectric nanostructures. Besides its intrinsic scientific value, fundamental understanding of the size effects in perovskite ferroelectric nanostructures has become critical item for developing a new generation of revolutionary nanodevices. In this article, a comprehensive review of the state-of-the-art research progress on the size effects in perovskite ferroelectric nanostructures which have been achieved from both experiment and theory is provided. It begins with a historical perspective of the size effects in perovskite ferroelectrics, and then highlight the recent progress on the theoretical studies of the size effects in perovskite ferroelectric nanostructures which have been achieved by using different numerical approaches (e.g., phenomenological approaches, first-principle computations and the Ising model in a transverse field). The current progress of the experimental testing of the size effects in perovskite ferroelectric nanostructures (e.g., nanoparticles, nanowires, nanotubes and nanofilms) is summarized. Finally, the perspectives toward the future challenges of the size effects in perovskite ferroelectric nanostructures is reviewed.

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Abbasi, Pedram, David P. Fenning, and Tod A. Pascal. "Electrocatalytic Hydrogen Evolution on Ferroelectric Perovskite Heterostructures." ECS Meeting Abstracts MA2022-01, no. 38 (July 7, 2022): 1691. http://dx.doi.org/10.1149/ma2022-01381691mtgabs.

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Ferroelectric perovskites have recently attracted interest for a wide range of photocatalytic and electrochemical applications1 due to their intrinsic properties for light adsorption2, electron–hole pair separation3–5 and a hypothesized enhancement of catalytic activity by polarization switching6–8. However, most of the well-known ferroelectric perovskites e.g., BaTiO3 and Pb (Zr, Ti)O3 are known to have limited activity toward electrocatalytic reactions e.g. hydrogen evolution (HER) and water splitting.2 In this work, we demonstrate that introducing only a few mono layers of SrRuO3, a metallic oxide from perovskite family, can significantly enhance the catalytic activity of BaTiO3 toward HER. Using a combination of first principle DFT+U calculations and experiments on thin films grown by molecular beam epitaxy, we investigated the activity of heterostructures of different thicknesses toward HER in an alkaline electrolyte. Computational results show that the Gibbs free energy barrier of H* adsorption on one monolayer of SrRuO3 atop ferroelectric BaTiO3 is at least two times smaller than BaTiO3, depending on the adsorption site or the direction of ferroelectric polarization. In line with the findings from our DFT calculations, our experimental results confirm significantly higher current density and lower charge transfer resistance toward hydrogen evolution for SrRuO3/BaTiO3 heterostructures compared to bare BaTiO3 surfaces. Harnessing oxide heterostructures, as demonstrated here, opens the door to leveraging the unique properties of ferroelectrics as supports to promote electrocatalytic activity.

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Onodera, Akira, Masanori Fukunaga, and Masaki Takesada. "Ferroelectric Instability and Dimensionality in Bi-Layered Perovskites and Thin Films." Advances in Condensed Matter Physics 2012 (2012): 1–10. http://dx.doi.org/10.1155/2012/714625.

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The dielectric and thermal properties of Bi (bismuth)-layered perovskite SrBi2Ta2O9(SBT) are discussed in comparison with ferroelectric thin BaTiO3films. Although these two perovskites exhibit quite a different nature, the dielectric properties of BaTiO3thin film are similar to those in bulk SBT. The dielectric properties and pseudo-two-dimensional structure between SBT and thin film suggest that the bulk layered ferroelectric SBT is a good model of ultra-thin ferroelectric film with two perovskite layers, free from any misfit lattice strain with substrate and surface charge at the interface with electrodes. Based on the mechanism of ferroelectric phase transition of SBT, it seems plausible that the ferroelectric interaction is still prominent but shows a crossover from ferroelectric to antiferroelectric interaction in perovskite ultra-thin films along the tetragonal axis.

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Benedek, Nicole A., and Michael A. Hayward. "Hybrid Improper Ferroelectricity: A Theoretical, Computational, and Synthetic Perspective." Annual Review of Materials Research 52, no. 1 (July 1, 2022): 331–55. http://dx.doi.org/10.1146/annurev-matsci-080819-010313.

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We review the theoretical, computational, and synthetic literature on hybrid improper ferroelectricity in layered perovskite oxides. Different ferroelectric mechanisms are described and compared, and their elucidation using theory and first-principles calculations is discussed. We also highlight the connections between crystal chemistry and the physical mechanisms of ferroelectricity. The experimental literature on hybrid improper ferroelectrics is surveyed, with a particular emphasis on cation-ordered double perovskites, Ruddlesden–Popper and Dion–Jacobson phases. We discuss preparative routes for synthesizing hybrid improper ferroelectrics in all three families and the conditions under which different phases can be stabilized. Finally, we survey some synthetic opportunities for expanding the family of hybrid improper ferroelectrics.

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7

Zhang, Zhen, Zhaokuan Wen, Ting Li, Zhiguo Wang, Zhiyong Liu, Xiaxia Liao, Shanming Ke, and Longlong Shu. "Flexoelectric aging effect in ferroelectric materials." Journal of Applied Physics 133, no. 5 (February 7, 2023): 054102. http://dx.doi.org/10.1063/5.0134531.

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In spite of the flexoelectric effect being a universal phenomenon in the ferroelectric perovskites, the current understanding of flexoelectric aging in ferroelectrics is, actually, rather incomplete. In this paper, we have fabricated a series of Mn-doped BaTiO3 perovskite ceramics (BaTi1–xMnxO3, x = 0.1% and 1%, BTMO) to systematically investigate the corresponding flexoelectric aging behavior by controlling the concentration of Mn. We found that the variation of Mn dopant significantly effects the Curie temperature, dielectric constant, flexoelectric aging, and flexoelectric coefficient of the BTMO ceramics. Especially for the BTMO (0.1%) ceramics, obvious ferroelectric aging and flexoelectric aging phenomenon are observed at room temperature. The main reason for aging of BTMO ceramics is that the doping of Mn introduces oxygen vacancies, which tend to be stable under the action of strain gradient and electric field. Therefore, the results presented in this paper verify that the flexoelectric aging in Mn-doped BTO ceramics is closely related to ferroelectric fatigue.

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8

Xu, Lan, Zujian Wang, Bin Su, Chenxi Wang, Xiaoming Yang, Rongbing Su, Xifa Long, and Chao He. "Origin of Structural Change Driven by A-Site Lanthanide Doping in ABO3-Type Perovskite Ferroelectrics." Crystals 10, no. 6 (May 29, 2020): 434. http://dx.doi.org/10.3390/cryst10060434.

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Lanthanide doping is widely employed to tune structural change temperature and electrical properties in ABO3-type perovskite ferroelectric materials. However, the reason that A-site lanthanide doping leads to the decrease of the Curie temperature is still not clear. Based on the reported Curie temperature of lanthanides (Ln) doped in two classic ferroelectrics PbTiO3 and BaTiO3 with A2+B4+O3-type perovskite structure, we discussed the relationship between the decrease rate of Curie temperature (ΔTC) and the bond strength variance of A-site cation (σ). For Nd ion doped Pb(Mg1/3Nb2/3)O3-PbTiO3 (Nd-PMNT) ferroelectric crystal as an example, the internal factors of the dramatic decline of the Curie temperature induced by A-site Nd doping were investigated under a systematic study. The strong covalent bonds of Ln-O play an important role in A-site Ln composition-induced structural change from ferroelectric to paraelectric phase, and it is responsible for the significant decrease in the Curie temperature. It is proposed that the cells become cubic around the Ln ions due to the strong covalent energy of Ln-O bonding in A-site Ln doped A2+B4+O3 perovskite ferroelectrics.

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Yin, Jie, Gang Liu, Chunlin Zhao, Yanli Huang, Zhitao Li, Xingmin Zhang, Ke Wang, and Jiagang Wu. "Perovskite Na0.5Bi0.5TiO3: a potential family of peculiar lead-free electrostrictors." Journal of Materials Chemistry A 7, no. 22 (2019): 13658–70. http://dx.doi.org/10.1039/c9ta03140e.

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For perovskite ferroelectric oxides, the composition-induced transition from ferroelectrics to relaxors can enhance their electrostrictive coefficient Q₃₃ remarkably, and has been attracting more and more attention in recent years.

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10

Xue, Kan-Hao, Leonardo R. C. Fonseca, and Xiang-Shui Miao. "Ferroelectric fatigue in layered perovskites from self-energy corrected density functional theory." RSC Advances 7, no. 35 (2017): 21856–68. http://dx.doi.org/10.1039/c7ra01650f.

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We employed GGA-1/2 to investigate the band alignment between platinum and various layered perovskite Aurivillius ferroelectrics. A model is proposed for ferroelectric fatigue in bismuth titanate based on our calculation.

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11

Jiang, Xiang Ping, M. Zeng, K. W. Kowk, and Helen Lai Wah Chan. "Dielectric and Ferroelectric Properties of Bi-Doped BaTiO₃ Ceramics." Key Engineering Materials 334-335 (March 2007): 977–80. http://dx.doi.org/10.4028/www.scientific.net/kem.334-335.977.

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Barium titanate with A-site substituted by various amount of bismuth oxide (Ba1-x BixTiO3, abbreviated as BBT, x=0.05, 0.1, 0.15) were prepared by solid-state reaction. The effect of bismuth substitution on crystallographic phase, dielectric and ferroelectric properties was studied. The X-ray diffraction shows that the samples were crystallized into pure perovskite structure when x=0.05 and 0.1, while for x=0.15 sample, second phase appeared in the dominant perovskite phase. The temperature dependence of dielectric permittivity of the ceramics was investigated and the evolution from normal ferroelectrics to relaxor ferroelectric sates was observed. In the range 0≤x≤0.1, the temperature of dielectric peak Tm is independence of the frequency, indicating the normal ferroelectrics behavior. At x=0.15, dielectric relaxation process with a broadening distribution of the permittivity dielectric is observed.

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12

Fang, Chao, and Liang Yan Chen. "Research of the Mechanism of Ferroelectric Phase Transition in Perovskite: Empty Orbital Model." Applied Mechanics and Materials 130-134 (October 2011): 2809–12. http://dx.doi.org/10.4028/www.scientific.net/amm.130-134.2809.

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The empty orbital model in perovskite ATiO3-type (A=Mg, Ca, Sr and Ba) ferroelectrics with oxygen octahedra has been proposed. In this study, the impact of temperature on the bond energy of Ti-O has been discussed from the point of view of statistical thermodynamics, then the temperature dependence of equilibrium position of Ti ion has been calculated. The results show that because of the existence of empty orbital, with temperatrue decreasing the repulsion energy of Ti and O ions reduces and the Ti ion shift the equilibrium position in the cooling through the Curie temperature owing to Coulomb interaction. Ferroelectric phase transition in perovskite are successfully explained. Theoretical and experimental results for perovskite ATiO3-type ferroelectrics are compared and discussed.

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DORFMAN, SIMON, DAVID FUKS, ALEX GORDON, and PETER WYDER. "WETTING OF THE FERROELECTRIC DOMAIN STRUCTURE IN (Ba,Sr)TiO3." Surface Review and Letters 06, no. 06 (December 1999): 1221–27. http://dx.doi.org/10.1142/s0218625x99001372.

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Wetting of the ferroelectric domain walls is studied in external magnetic fields and for composition changes in (Ba,Sr)TiO 3. We discuss the sensibility of the domain structure to concentration of alloying element in perovskite ferroelectrics. A considerable magnetic-field and concentration-induced variation of the ferroelectric domain size and the paraelectric layer width is demonstrated. The concentration-temperature "phase diagram," showing the range of the wetting existence, is calculated.

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Sivasubramanian, Venkatasubramanian, Sarveswaran Ganesamoorthy, and Seiji Kojima. "Anomalies of Brillouin Light Scattering in Selected Perovskite Relaxor Ferroelectric Crystals." Materials 16, no. 2 (January 8, 2023): 605. http://dx.doi.org/10.3390/ma16020605.

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Compositionally disordered perovskite compounds have been one of the exotic topics of research during the past several years. Colossal piezoelectric and electrostrictive effects have been observed in disordered perovskite ferroelectric materials. The key ingredient in the physical behavior of disordered perovskites is the nucleation and growth of the local dipolar regions called polar nanoregions (PNRs). PNRs begin to nucleate far above the temperature of the dielectric maximum Tm and exhibit varied relaxation behavior with temperature. The evidence for the existence of various stages in the relaxation dynamics of PNRs was revealed through the study of the temperature evolution of optical phonons by Raman scattering. The quasi-static regime of PNRs is characterized by the strong coupling between the local polarization and strain with the local structural phase transition and the critical slowing of the relaxation time. Strong anomalies in the frequency and the width of the acoustic phonons, and emergence of the central peak in the quasi-static region of the relaxation dynamics of PNRs have been observed through Brillouin scattering studies. In this review, we discuss the anomalies observed in Brillouin scattering in selected disordered perovskite ferroelectrics crystals such as Pb(Mg1/3Ta2/3)O3, Pb(Sc1/2Ta1/2)O3, 0.65PIN-0.35PT and Sr0.97Ca0.03TiO3 to understand dynamical behavior of PNRs.

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Nuraje, Nurxat, and Kai Su. "Perovskite ferroelectric nanomaterials." Nanoscale 5, no. 19 (2013): 8752. http://dx.doi.org/10.1039/c3nr02543h.

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Yu, Limin, Lijing Wang, Yanmeng Dou, Yongya Zhang, Pan Li, Jieqiong Li, and Wei Wei. "Recent Advances in Ferroelectric Materials-Based Photoelectrochemical Reaction." Nanomaterials 12, no. 17 (August 31, 2022): 3026. http://dx.doi.org/10.3390/nano12173026.

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Inorganic perovskite ferroelectric-based nanomaterials as sustainable new energy materials, due to their intrinsic ferroelectricity and environmental compatibility, are intended to play a crucial role in photoelectrochemical field as major functional materials. Because of versatile physical properties and excellent optoelectronic properties, ferroelectric-based nanomaterials attract much attention in the field of photocatalysis, photoelectrochemical water splitting and photovoltaic. The aim of this review is to cover the recent advances by stating the different kinds of ferroelectrics separately in the photoelectrochemical field as well as discussing how ferroelectric polarization will impact functioning of photo-induced carrier separation and transportation in the interface of the compounded semiconductors. In addition, the future prospects of ferroelectric-based nanomaterials are also discussed.

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Bersuker, Isaac B., and Victor Polinger. "Perovskite Crystals: Unique Pseudo-Jahn–Teller Origin of Ferroelectricity, Multiferroicity, Permittivity, Flexoelectricity, and Polar Nanoregions." Condensed Matter 5, no. 4 (November 2, 2020): 68. http://dx.doi.org/10.3390/condmat5040068.

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In a semi-review paper, we show that the local pseudo-Jahn–Teller effect (PJTE) in transition metal B ion center of ABO3 perovskite crystals, notably BaTiO3, is the basis of all their main properties. The vibronic coupling between the ground and excited electronic states of the local BO6 center results in dipolar distortions, leading to an eight-well adiabatic potential energy surface with local tunneling or over-the-barrier transitions between them. The intercenter interaction between these dipolar dynamic units results in the formation of the temperature-dependent three ferroelectric and one paraelectric phases with order–disorder phase transitions. The local PJTE dipolar distortion is subject to the presence of sufficiently close in energy local electronic states with opposite parity but the same spin multiplicity, thus limiting the electronic structure and spin of the B(dn) ions that can trigger ferroelectricity. This allowed us to formulate the necessary conditions for the transition metal perovskites to possess both ferroelectric and magnetic (multiferroic) properties simultaneously. It clarifies the role of spin in the spontaneous polarization. We also show that the interaction between the independently rotating dipoles in the paraelectric phase may lead to a self-assembly process resulting in polar nanoregions and relaxor properties. Exploring interactions of PJTE ferroelectrics with external perturbations, we revealed a completely novel property—orientational polarization in solids—a phenomenon first noticed by P. Debye in 1912 as a possibility, which was never found till now. The hindered rotation of the local dipole moments and their ordering along an external field is qualitatively similar to the behavior of polar molecules in liquids, thus adding a new dimension to the properties of solids—notably, the perovskite ferroelectrics. We estimated the contribution of the orientational polarization to the permittivity and flexoelectricity of perovskite crystals in different limiting conditions.

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Ivanov, S. A., S. G. Eriksson, Roland Tellgren, and Håkan Rundlöf. "A Neutron Diffraction Study of Magnetically Ordered Ferroelectric Materials." Materials Science Forum 443-444 (January 2004): 383–86. http://dx.doi.org/10.4028/www.scientific.net/msf.443-444.383.

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Structural, magnetic, dielectric properties and Mossbauer effect were investigated on complex perovskite with composition AFe2/3B1/3O3(A=Ca,Sr,Pb,Ba; B=W,Te). The most striking feature of this type of complex perovskites is the coexistence of magnetic and antiferroelectric types of ordering in a certain temperature interval. It was found that ferrimagnetic Ca and Sr compounds belong to a partially ordered perovskite structure, and antiferromagnetic Pb phase to a disordered one. The possible models for nuclear and magnetic structures were proposed in accordance with the observed dielectric and magnetic properties.

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Xia, Chengliang, Yue Chen, and Hanghui Chen. "Pressure-induced metal–insulator transition in oxygen-deficient LiNbO₃-type ferroelectrics." Journal of Physics: Condensed Matter 34, no. 2 (October 28, 2021): 025501. http://dx.doi.org/10.1088/1361-648x/ac2e30.

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Abstract Hydrostatic pressure and oxygen vacancies usually have deleterious effects on ferroelectric materials because both tend to reduce their polarization. In this work we use first-principles calculations to study an important class of ferroelectric materials—LiNbO3-type ferroelectrics (LiNbO3 as the prototype), and find that in oxygen-deficient LiNbO3−δ , hydrostatic pressure induces an unexpected metal–insulator transition between 8 and 9 GPa. Our calculations also find that strong polar displacements persist in both metallic and insulating oxygen-deficient LiNbO3−δ and the size of polar displacements is comparable to pristine LiNbO3 under the same pressure. These properties are distinct from widely used perovskite ferroelectric oxide BaTiO3, whose polarization is quickly suppressed by hydrostatic pressure and/or oxygen vacancies. The anomalous pressure-driven metal–insulator transition in oxygen-deficient LiNbO3−δ arises from the change of an oxygen vacancy defect state. Hydrostatic pressure increases the polar displacements of oxygen-deficient LiNbO3−δ , which reduces the band width of the defect state and eventually turns it into an in-gap state. In the insulating phase, the in-gap state is further pushed away from the conduction band edge under hydrostatic pressure, which increases the fundamental gap. Our work shows that for LiNbO3-type strong ferroelectrics, oxygen vacancies and hydrostatic pressure combined can lead to new phenomena and potential functions, in contrast to the harmful effects occurring to perovskite ferroelectric oxides such as BaTiO3.

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Chu, Rui Qing, Zhi Jun Xu, Guo Rong Li, and Qing Rui Yin. "Preparation and Dielectric Properties of the Layered Perovskite Sr₄Bi₄Ti₇O₂₄ Ferroelectric Ceramics." Key Engineering Materials 368-372 (February 2008): 98–99. http://dx.doi.org/10.4028/www.scientific.net/kem.368-372.98.

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Sr4Bi4Ti7O24 (SBT7) ceramics were prepared. X-ray powder diffraction indicated that single layered perovskite ferroelectrics were obtained. The ferroelectric and dielectric properties of SBT7 ceramics were investigated. The results showed that Sr4Bi4Ti7O24 is piezoelectric material. The dielectric properties were measured as a function of temperature and two peaks were observed in the curve.

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Zhu, W. Z., M. Yan, P. Q. Mantas, J. L. Baptista, and A. L. Kholkin. "Effect of Lanthanum-doping on the Dielectric Properties of Pb(Fe1/2Ta1/2)O3 Relaxor Ferroelectrics." Journal of Materials Research 17, no. 7 (July 2002): 1779–84. http://dx.doi.org/10.1557/jmr.2002.0263.

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This paper reports the influence of lanthanum-doping on the dielectric behavior of Pb(Fe1/2Ta1/2)O3 relaxor ferroelectrics, where the La ions are incorporated into the B-site of the perovskite constructing unit and the resultant charge imbalance is compensated by the presence of free charge carriers (holes). The formulated compositions were fabricated using one-step preparation method, and a nearly pure perovskite phase was attained, as verified by XRD analysis. Both the dielectric permittivity maximum (ε′max) and the temperature at which ε′max occurs (Tm) are progressively reduced by La-doping. The degree of frequency dispersion, however, is promoted, indicating the weakened ferroelectric couplings among the oxygen octahedra as a result of lanthanum incorporation. Moreover, the breadth of paraelectric to ferroelectric phase transition is broadened with an increase in lanthanum content, due to enhanced inhomogeneity and increase in the number of B-site cations. Frequency spectroscopy at a certain temperature below Tm reveals a widening of the size distribution of ferroelectric nanodomains, which is characteristic of relaxor microstructure, by La-doping.

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Tyunina, Marina. "Oxygen Vacancies in Perovskite Oxide Piezoelectrics." Materials 13, no. 24 (December 8, 2020): 5596. http://dx.doi.org/10.3390/ma13245596.

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The excellent electro-mechanical properties of perovskite oxide ferroelectrics make these materials major piezoelectrics. Oxygen vacancies are believed to easily form, migrate, and strongly affect ferroelectric behavior and, consequently, the piezoelectric performance of these materials and devices based thereon. Mobile oxygen vacancies were proposed to explain high-temperature chemical reactions half a century ago. Today the chemistry-enabled concept of mobile oxygen vacancies has been extrapolated to arbitrary physical conditions and numerous effects and is widely accepted. Here, this popular concept is questioned. The concept is shown to conflict with our modern physical understanding of ferroelectrics. Basic electronic processes known from mature semiconductor physics are demonstrated to explain the key observations that are groundlessly ascribed to mobile oxygen vacancies. The concept of mobile oxygen vacancies is concluded to be misleading.

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Heo, Seungyang, Daseob Yoon, Sangbae Yu, Junwoo Son, and Hyun Myung Jang. "Non-volatile ferroelectric control of room-temperature electrical transport in perovskite oxide semiconductor La:BaSnO3." Journal of Materials Chemistry C 5, no. 45 (2017): 11763–68. http://dx.doi.org/10.1039/c7tc03730a.

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Complex oxide heterostructures composed of oxide semiconductor thin films and ferroelectric single crystals have attracted substantial interest due to the electrically switchable channel resistance by the polarization reversal of ferroelectrics.

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Szafraniak-Wiza, Izabela, Bozena Hilczer, Ewa Talik, Adam Pietraszko, and Barbara Malic. "Ferroelectric perovskite nanopowders obtained by mechanochemical synthesis." Processing and Application of Ceramics 4, no. 3 (2010): 99–106. http://dx.doi.org/10.2298/pac1003099s.

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Simple perovskite nanopowders were fabricated by mechanochemical synthesis. High-energy milling process of respective oxides, leading to production of ferroelectric perovskites, was carefully investigated and characterized by X-ray diffraction, electron microscopy and X-ray excited photoelectron spectroscopy. It has been found that: (i) the powder consists of loosely packed grains with a broad distribution of sizes between a few nm and 45 nm, (ii) the grains possess core/shell structure, (iii) the grain core of sizes larger than about 20 nm exhibits well developed crystalline structure, (iv) the grains are coated by structurally disordered (amorphous) shell. Intermediate phases have been found in the process of PbTiO3 mechanosynthesis only. The obtained nanopowders were used for preparation of dense ceramics.

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Szuromi, Phil. "Perovskite ferroelectric bond-switching." Science 356, no. 6340 (May 25, 2017): 817.7–818. http://dx.doi.org/10.1126/science.356.6340.817-g.

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Volonakis, George, and Feliciano Giustino. "Ferroelectric Graphene–Perovskite Interfaces." Journal of Physical Chemistry Letters 6, no. 13 (June 17, 2015): 2496–502. http://dx.doi.org/10.1021/acs.jpclett.5b01099.

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Tyunina, M., M. Savinov, and A. Dejneka. "Small-polaron conductivity in perovskite ferroelectric BaTiO₃ films." Applied Physics Letters 121, no. 20 (November 14, 2022): 202901. http://dx.doi.org/10.1063/5.0129831.

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In ABO3 perovskite oxide ferroelectrics, electrical conductivity ranges from insulator- to superconductor-type and is virtually critical for all applications of these materials. Compared to bulk ceramics and crystals, ferroelectric thin films can enable advanced control of the conductivity. Here, small-polaron hopping conductivity was evidenced and examined in various pulsed-laser-deposited films of ferroelectric BaTiO3 and reference films of SrTiO3. For this, AC conductivity was studied in a broad range of temperatures and frequencies for films sandwiched between the bottom and top electrodes. In the BaTiO3 films, with increasing temperature, a significant increase in activation energy for small-polaron hopping was found and ascribed to strong electron–phonon coupling and complex lattice oscillations therein. Plain relations of the activation energy to microstructure, composition, or phase transitions were lacking, which corroborated the critical role of phonons. Additionally, a phonon-less transport was detected. It was anticipated that owing to strong electron–phonon coupling, rich phonon ensembles, and coexistence of phonon-stimulated and phonon-less processes, the small-polaron conductivity can heavily vary in ferroelectric films that necessitates further studies.

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Shafir, Or, and Ilya Grinberg. "Narrow bandgap potassium titanate-molybdate-based d⁰ ferroelectrics." Journal of Applied Physics 132, no. 7 (August 21, 2022): 074101. http://dx.doi.org/10.1063/5.0099143.

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The bulk photovoltaic effect observed in ferroelectric materials can enable photovoltaic performance beyond the Shockley–Queisser limit of efficiency. This requires the use of ferroelectrics with strong polarization and low bandgap ( Eg) that are typically contradictory in the common perovskite oxides ferroelectrics. Here, we use first-principles calculations to study the KNbO3–K(Ti0.5Mo0.5)O3 (KNTM) solid solutions as possible narrow-gap ferroelectric materials. KTM, the end-member of the recently discovered KNTM solid solution system, maintains a ferroelectric polarization similar to that of other K-based systems due to its d0 configuration at the B-site. The substitution of Nb in KTM reduces Eg from 2.9 of KTM to 1.83 eV for an unstrained system and 1.7 eV for a compressively strained system, while maintaining ferroelectricity. The combination of narrow Eg, strong ferroelectricity, low toxicity, and abundance of the constituent elements make Nb-substituted KTM a promising candidate material for photoferroelectric applications.

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29

Liu, Qian Li, Gao Yang Zhao, Gui Rong Zhao, and Li Lei. "Fabrication of LaNiO₃ Thin Film on the Si-Substrate by Sol-Gel Process." Materials Science Forum 695 (July 2011): 585–88. http://dx.doi.org/10.4028/www.scientific.net/msf.695.585.

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Due to its perovskite crystal structure and good conductivity, LaNiO3(LNO) can be used as the electrode for piezoelectric and ferroelectric films. With the development of the silicon-based integrated ferroelectrics, preparation of LNO electrode film with good conductivity is of great importance for high-performance ferroelectric films. In this paper, LNO sol was prepared using the nickel acetate and the lanthanum nitrate as starting materials, with the acrylic acid as stablizer. Through the sol-gel process, LNO films with certain crystal orientation were prepared on silicon substrate. The film microstructure and electrical properties were analyzed. Results indicate that through proper sol component and heat treatment process, (100)-oriented, mirror-like LNO films with low surface resistance of 50 Ω/ can be obtained, which can be used as the electrode for the ferroelectric films.

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30

Fan, Su Hua, Feng Qing Zhang, Q. D. Che, R. Yu, W. Hu, and Qing Bo Tian. "Electrical Properties of Bismuth-Layered Structural Ca_xSr_2-xBi₄Ti₅O₁₈ Ceramics." Advanced Materials Research 105-106 (April 2010): 282–85. http://dx.doi.org/10.4028/www.scientific.net/amr.105-106.282.

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Effects of amount of Ca on crystal structure, microstructure, ferroelectric properties, and dielectric properties of the CaxSr2-xBi4Ti5O18 (CSBTi-x) ferroelectric ceramics were investigated. The results show that single-phase layered perovskite ferroelectrics were obtained and no appreciable secondary phase was found.Ca-doping results in a notable enlargement of remnant polarization 2Pr. The 2Pr of CSBT-0.15 reaches a large value, the remnant polarization 2Pr and coercive field 2Ec were 18.1µC/cm2 and 120.2kV/cm, respectively. Dielectric constant and dielectric loss of CSBT-0.15 was also measured, showing dielectric constant εr=199~194 and dielectric loss tanδ=0.02~0.014 over the range of 100 kHz~1MHz, respectively.

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31

Xu, Wei-Jian, Konstantin Romanyuk, Ying Zeng, Andrei Ushakov, Vladimir Shur, Alexander Tselev, Wei-Xiong Zhang, Xiao-Ming Chen, Andrei Kholkin, and João Rocha. "Statics and dynamics of ferroelectric domains in molecular multiaxial ferroelectric (Me3NOH)2[KCo(CN)6]." Journal of Materials Chemistry C 9, no. 33 (2021): 10741–48. http://dx.doi.org/10.1039/d1tc01261d.

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32

Lefevre, M. J., D. B. Dimos, and J. S. Speck. "The role of excess Pb and PbO overpressure on the microstructural development in polycrystalline PZT thin films." Proceedings, annual meeting, Electron Microscopy Society of America 52 (1994): 582–83. http://dx.doi.org/10.1017/s0424820100170645.

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Ferroelectric thin films have recently received considerable attention because of their potential in a range of device applications including both volatile and non-volatile memories, optical data storage, and other electrooptic applications (e.g. waveguides, switches, and modulators). The Pb-based perovskites, such as Pb(Zr,Ti)O3, have many properties that make them attractive for such applications because of their high switchable remanant polarization. In addition, many applications require integration of the ferroelectric with semiconductors. In our work we are studying the crystallization sequence of PZT 40/60 (PbZr0.40Ti0.60O3) grown on platinized silicon substrates, with an overall structure given as PZT/Pt/Ti/SiO2Si. The Ti and Pt are sequentially evaporated onto the oxidized Si substrate. Alkoxide-derived films are spun onto these substrates to form a dry amorphous gel2. The crystallization of the sol-gel film proceeds upon heating to temperatures in the range of 400-700°C. Lead volatility is one of the critical issues in the crystallization of Pb-based perovskite thin films. We have carried out a systematic study on the role of a lead atmosphere in crystallization for PZT (40/60). When heat treated the film forms a transitory pyrochlore phase at intermediate temperatures before transforming to the perovskite phase. This non-ferroelectric pyrochlore phase may stabilize if lead stoichiometry is not maintained, leading to poor optical and ferroelectric properties in the thin films.

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33

Puli, Venkata Sreenivas, Shiva Adireddy, Dhiren K. Pradhan, Ram S. Katiyar, and Douglas B. Chrisey. "Nanoscale Ferroelectric Switchable Polarization and Leakage Current Behavior in (Ba0.50Sr0.50)(Ti0.80Sn0.20)O3Thin Films Prepared Using Chemical Solution Deposition." Journal of Nanomaterials 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/340616.

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Nanoscale switchable ferroelectric (Ba0.50Sr0.50)(Ti0.80Sn0.20)O3-BSTS polycrystalline thin films with a perovskite structure were prepared on Pt/TiOx/SiO2/Si substrate by chemical solution deposition. X-ray diffraction (XRD) spectra indicate that a cubic perovskite crystalline structure and Raman spectra revealed that a tetragonal perovskite crystalline structure is present in the thin films. Sr2+and Sn4+cosubstituted film exhibited the lowest leakage current density. Piezoresponse Force Microscopy (PFM) technique has been employed to acquire out-of-plane (OPP) piezoresponse images and local piezoelectric hysteresis loop in polycrystalline BSTS films. PFM phase and amplitude images reveal nanoscale ferroelectric switching behavior at room temperature. Square patterns with dark and bright contrasts were written by local poling and reversible nature of the piezoresponse behavior was established. Local piezoelectric butterfly amplitude and phase hysteresis loops display ferroelectric nature at nanoscale level. The significance of this paper is to present ferroelectric/piezoelectric nature in present BSTS films at nanoscale level and corroborating ferroelectric behavior by utilizing Raman spectroscopy. Thus, further optimizing physical and electrical properties, BSTS films might be useful for practical applications which include nonvolatile ferroelectric memories, data-storage media, piezoelectric actuators, and electric energy storage capacitors.

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34

Wang, Haoliang, Yan Chen, Engliang Lim, Xudong Wang, Sijian Yuan, Xin Zhang, Haizhou Lu, et al. "High-performance lead-free two-dimensional perovskite photo transistors assisted by ferroelectric dielectrics." Journal of Materials Chemistry C 6, no. 46 (2018): 12714–20. http://dx.doi.org/10.1039/c8tc04691c.

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35

Sakamoto, Naonori, Kotaro Ozawa, Kohei Murakoshi, Tomoya Ohno, Takanori Kiguchi, Takeshi Matsuda, Toyohiko J. Konno, Naoki Wakiya, and Hisao Suzuki. "TEM Study for Self-Orientated LaNiO₃ Film along [100]." Key Engineering Materials 582 (September 2013): 185–88. http://dx.doi.org/10.4028/www.scientific.net/kem.582.185.

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LaNiO3 (LNO) is known as a candidate for oxide electrodes with perovskite type crystal structure which is suitable for lattice matching with conventional perovskite ferroelectrics, Pb (Zr,Ti)O3 (PZT), BaTiO3 (BTO), etc. We have been investigating thermal expansion effects of the LNO film with PZT/LNO/Si and BTO/LNO/Si structures, where ferroelectric and piezoelectric properties are enhanced by a compressive thermals stress impressed from the LNO layer to the ferrelectric films. The ferroelectric films also shows high [00 orientation owing to [100] orientation of the LNO film. In the present study, further investigation of the LNO films prepared on Si substrates by CSD method is made by transmission electron microscopy (TEM) in order to understand self-orientation along [100] perpendicular to the film plane which effectively leads orientation of PZT films prepared on the LNO film. The results obviously indicates that the 1 layer deposited LNO film has almost no orientation, whereas it shows tendency of orientation of [100] perpendicular to the film plane when the layer number increased.

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36

Warren, W. L., B. A. Tuttle, and D. Dimos. "Ferroelectric fatigue in perovskite oxides." Applied Physics Letters 67, no. 10 (September 4, 1995): 1426–28. http://dx.doi.org/10.1063/1.114515.

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37

Gao, Jing-Hui, Dezhen Xue, Lixue Zhang, Yu Wang, Huixin Bao, Chao Zhou, Wenfeng Liu, Wei Chen, and Xiaobing Ren. "Aging-induced domain memory in acceptor-doped perovskite ferroelectrics associated with ferroelectric-ferroelectric transition cycle." EPL (Europhysics Letters) 96, no. 3 (September 23, 2011): 37001. http://dx.doi.org/10.1209/0295-5075/96/37001.

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38

Gareeva Z. V., Zvezdin A. K., Shulga N. V., Gareev T. T., and Chen X. M. "Mechanisms of magnetoelectric effects in oxide multiferroics with a perovskite praphase." Physics of the Solid State 64, no. 9 (2022): 1324. http://dx.doi.org/10.21883/pss.2022.09.54175.43hh.

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Magnetoelectric effects are discussed in multiferroics with the perovskite structure: bismuth ferrite, rare-earth orthochromites, and Ruddlesden--Popper structures belonging to the trigonal, orthorhombic, and tetragonal syngonies. The influence of structural distortions on magnetic and ferroelectric properties is studied, possible magnetoelectric effects (linear, quadratic, inhomogeneous) in these materials are determined, and expressions for the linear magnetoelectric effect tensor are given. Macroscopic manifestations of the inhomogeneous magnetoelectric effect in multiferroic nanoelements are considered. Keywords: multiferroics, magnetoelectric effect, perovskites, symmetry.

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39

Kimura, Tsuyoshi. "Current Progress of Research on Magnetically-induced Ferroelectrics." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C6. http://dx.doi.org/10.1107/s2053273314099938.

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Among several different types of magnetoelectric multiferroics, "magnetically-induced ferroelectrics" in which ferroelectricity is induced by complex spin orders, such as spiral orders, exhibit giant direct magnetoelectric effects, i.e., remarkable changes in electric polarization in response to a magnetic field. Not a few spin-driven ferroelectrics showing the magnetoelectric effects have been found in the past decade.[1] However, their induced ferroelectric polarization is much smaller than that in conventional ferroelectrics and mostly develops only at temperatures much lower than room temperature. Thus, the quest for spin-driven ferroelectrics with room temperature operation and/or robust ferroelectric polarization is still a major challenge in magnetoelectric multiferroics research. In this presentation, I will begin with introducing the background of research on magnetically-induced ferroelectrics, and present the following current progress. Recently, some hexaferrites have been found to show direct magnetoelectric effects at room temperature and relatively low magnetic fields.[2] Furthermore these hexferrites show inverse magnetoelectric effects, that is, induction of magnetization by applying electric fields, at room temperature. The results represented an important step toward practical applications using the magnetoelectric effect in spin-driven ferroelectrics. This presentation introduces magnetism and magnetoelectricity of several types of hexaferrites which show magnetoelectric effect at temperatures above room temperature. In addition, I will also introduce our recent work on magnetoelectric perovskite manganites with large magnetically-induced ferroelectric polarization which is comparable to that in conventional ferroelectrics. This work has been done in collaboration with T. Aoyam, K. Haruki, K. Okumura, A. Miyake, K. Shimizu, and S. Hirose.

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40

Rouquette, Jerome, Manuel Hinterstein, Julien Haines, Michael Knapp, Julia Glaum, Jurgen Eckert, Hartmud Fuess, and Hichem Dammak. "Probing the Giant Piezoelectric response of ferroelectric perovskites." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C150. http://dx.doi.org/10.1107/s2053273314098490.

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By analogy with ferromagnetism and the hysteresis of the magnetic moment with a magnetic field, materials that exhibit a macroscopic spontaneous polarization Ps, which can be reversed under electric field E were defined as ferroelectrics. Ps, the directional order parameter can give rise to different polar structural phase transitions and finally disappear as a function of temperature T and/or hydrostatic pressure P in a transformation from a non-centrosymmetric to a centrosymmetric space group. The physical properties of ferroelectric materials are the basis of many technological applications based on their hysteretic properties (Ps / E in ferroelectric random access memories) or based on their coupled properties (η (mechanical strain)/ E in piezoelectric applications). In order to understand the origin and the mechanisms associated with the ferroelectric properties, "in-situ" structural studies as a function of E, T and P have to be performed. In addition ferroelectric materials exhibit based on their directional properties (Ps) a particular domain configuration which makes the structural understanding of these compounds much more complex. Different scales should be taken into account: from the atomic scale (individual polar displacements) to the macroscopic scale (macroscopic piezoelectric effect) and finally the mesoscopic scale in between, which is governed by the domain wall motion. High piezoelectric/ferroelectric properties in lead perovskite materials (PZT, PMN, PZN) are structurally linked to strong disorder which can be characterized by the presence of diffuse scattering in diffraction experiments and by nanosized domains. Here we will present "in-situ" characterization in lead perovskite materials as a function of the applied electric field based on X-ray and neutron diffraction and EXAFS techniques. A brief overview of the challenges to solve in future studies as a function of pressure and temperature will also be discussed.

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41

Xu, Chengchao, Jun Li, Huanfang Tian, Zi-An Li, Huaixin Yang, and Jianqi Li. "Flux Method Growth and Structure and Properties Characterization of Rare-Earth Iron Oxides Lu1−xScxFeO3 Single Crystals." Crystals 12, no. 6 (May 26, 2022): 769. http://dx.doi.org/10.3390/cryst12060769.

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Perovskite rare-earth ferrites (REFeO3) have attracted great attention for their high ferroelectric and magnetic transition temperatures, strong magnetoelectric coupling, and electric polarization. We report on the flux method growth of rare-earth iron oxide Lu1−xScxFeO3 single crystals through a K2CO3-B2O3-Bi2O3 mixture as a flux solution, and give a detailed characterization of the microstructure, magnetism, and ferroelectric properties. X-ray diffraction (XRD) and energy dispersive X-ray spectroscopy (EDX) measurements revealed that the obtained single crystals can be designated to three different crystal structures of different chemical compositions, that is, Lu0.96Sc0.04FeO3 (perovskite phase), Lu0.67Sc0.33FeO3 (hexagonal phase), and Lu0.2Sc0.8FeO3 (bixbyite phase), respectively. Magnetic measurements indicate that the perovskite Lu0.96Sc0.04FeO3 is an anisotropic hard ferromagnetic material with a high Curie transition temperature, the bixbyite Lu0.2Sc0.8FeO3 is a low temperature soft ferromagnetic material, and the hexagonal Lu0.67Sc0.33FeO3 exhibits multiferroic properties. Lu0.67Sc0.33FeO3 possesses a weak ferromagnetic transition at about 162 K. We further investigate the ferroelectric domain structures in hexagonal sample by scanning electron microscope and the characteristic atomic structures in ferroelectric domain walls by atomically resolved scanning transmission electron microscope. Our successful growth of perovskite Lu1−xScxFeO3 single crystals with distinct crystal structures and stochiometric Lu-Sc substitutions is anticipated to provide a useful ferrites system for furthering exploitation of their multiferroic properties and functionalities.

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42

Lee, Chi-Hsuan, and Jen-Chuan Tung. "Large Bandgap Topological Insulator in Oxide APoO3 (A = Be, Mg, Ca, Sr, Ba, and Ra) Perovskite: An Ab Initio Study." Applied Sciences 11, no. 3 (January 26, 2021): 1143. http://dx.doi.org/10.3390/app11031143.

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Under the density functional theory framework, we have calculated the electronic and elastic properties of APoO3 (A = Be, Mg, Ca, Sr, Ba, and Ra) cubic perovskites. We found that CaPoO3, SrPoO3, BaPoO3, and RaPoO3 are topological insulators (TIs) with very large bandgaps of 0.861, 0.871, 0.820, and 0.810 eV, respectively. The nontrivial band topology together with the Z2 topological number of APoO3 perovskite are investigated. We also theoretically determine the three independent elastic constants C11, C12, and C44 of the APoO3 perovskite. The bulk modulus, shear modulus, Young’s modulus, Poisson’s ratio, and anisotropy factor are also calculated from the obtained elastic constants. We found that the Debye temperature for the APoO3 perovskite is around 330-370 K. In the bulk APoO3 perovskite, if the center Po atom is shifted 0.09Å away from the center, the induced electric polarization is quite large, being around 0.02 C/m2. In the surface band calculation, we found that both AO and PoO2 surfaces give rise to contributions to the conduction channel. If the Po atom moves both in-plane and out-of-plane, we show that both electric polarization and topologically protect surface conduction states exist in APoO3 perovskite, indicating that these oxide APoO3 perovskites are ferroelectric TIs and might be useful for spintronic applications.

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43

Noguchi, Yuji, and Hiroki Matsuo. "Polarization and Dielectric Properties of BiFeO3-BaTiO3 Superlattice-Structured Ferroelectric Films." Nanomaterials 11, no. 7 (July 19, 2021): 1857. http://dx.doi.org/10.3390/nano11071857.

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Superlattice-structured epitaxial thin films composed of Mn(5%)-doped BiFeO3 and BaTiO3 with a total thickness of 600 perovskite (ABO3) unit cells were grown on single-crystal SrTiO3 substrates by pulsed laser deposition, and their polarization and dielectric properties were investigated. When the layers of Mn-BiFeO3 and BaTiO3 have over 25 ABO3 unit cells (N), the superlattice can be regarded as a simple series connection of their individual capacitors. The superlattices with an N of 5 or less behave as a unified ferroelectric, where the BaTiO3 and Mn-BiFeO3 layers are structurally and electronically coupled. Density functional theory calculations can explain the behavior of spontaneous polarization for the superlattices in this thin regime. We propose that a superlattice formation comprising two types of perovskite layers with different crystal symmetries opens a path to novel ferroelectrics that cannot be obtained in a solid solution system.

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44

Abhishek Bhatt and Rohit Pant. "Analysis of Pervoskite Solar Cell Functional Theory." Applied Science and Engineering Journal for Advanced Research 1, no. 1 (January 22, 2022): 28–33. http://dx.doi.org/10.54741/asejar.1.1.5.

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The electronic construction estimations of a substance are the focal errand because of atomistic reenactments. They make allusions to estimates of the state of electronic mobility around fixed cores. To further develop power transformation effectiveness and strength, doping is normally taken on technique to tune and adjust the constructions CH3NH3PbI3 materials' characteristics and composition in natural inorganic crossover perovskite arising sun oriented cells perovskites are a class of materials that have a perovskite structure assorted mix of various components. Because of this, result, they display various functionalities, for example, piezoelectric, ferroelectric, pyroelectric, and ferromagnetic with applications in photovoltaic cells, huge magneto-opposition, LEDs, superconductivity, and topological covers. Perovskites have gained a reputation as a viable alternative to silicon-based conventional solar cells since 2009. By and large, halide perovskites show great photonic characteristics, oxide perovskites show great dielectric properties, and chalcogenide perovskites are utilized in applications in strong state detecting, lighting, and energy collecting. In this thesis, different kinds of perovskites going from oxide to halide are examined alongside their underlying, electronic, flexible, and optical properties.

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45

Shimizu, Takao, Hiroshi Funakubo, and Naoki Ohashi. "(Invited, Digital Presentation) Materials Aspects of New Ferroelectrics with Simple Crystal Structure." ECS Meeting Abstracts MA2022-02, no. 15 (October 9, 2022): 804. http://dx.doi.org/10.1149/ma2022-0215804mtgabs.

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Ferroelectric materials are defined as the materials, of which spontaneous polarization can be switched by an external electric field. Their crystal structural symmetry makes them exhibit a variety of electric properties, such as piezoelectricity, pyroelectricity, and ferroelectricity. Because of their characteristics, they are expected to be adapted for various applications, including sensors, actuators, and non-volatile memories. Over the past decades, perovskite type ferroelectric materials have occupied the central position in both fundamental studies and applications of ferroelectric materials. On the other hand, there are a few studies on ferroelectrics with other crystal structures. This regime is now changing since HfO2-based new ferroelectric materials have been discovered. The HfO2-based dielectric materials are employed as high-k insulators of the metal-oxide-semiconductor field-effect-transistors instead of the conventional SiOx gate dielectrics, suggesting the high compatibility with semiconductor technologies. Thus, discovering ferroelectricity in HfO2-based materials strongly encourages us to develop highly integrated ferroelectric devices that are difficult to fabricate with traditional perovskite-type ferroelectrics. Amid increasing interest in ferroelectric materials, ferroelectricity is demonstrated on another new (Al, Sc)N, which has a wurtzite structure. Both fluorite structure, the parent structure of HfO2-based ferroelectrics, and wurtzite structure are simple compounds, having only a single anion and cation sites in the crystal structure. This feature contrasts the complex crystal structure of conventional perovskite structure. This presentation will give a brief outline of these new ferroelectric materials and introduce our recent studies from the viewpoint of crystal chemistry. It is well-known that HfO2 undergoes successive phase transitions from monoclinic to tetragonal and tetragonal to cubic phases. However, these phases cannot show ferroelectricity because of their inversion center in the crystal structure. It is widely accepted that the ferroelectricity in HfO2-based materials originates from the metastable orthorhombic structure. This orthorhombic structure was confirmed by the convergence electron diffraction and scanning transmission electron microscopy. Among the HfO2-based materials, HfO2- ZrO2 materials are most extensively studied. However, the thickness that can exhibit ferroelectricity in these materials is limited to less than 50 nm because of their strong preference for the monoclinic structure. In order to investigate structural features of the HfO2-based materials, materials are demanded that have ferroelectricity over the wide thickness range. The Y-doped HfO2 meets the requirement, allowing us to grow the ferroelectric film over 1 μm in thickness. Furthermore, we demonstrated ferroelectricity in epitaxial films using this composition. A recent report on ferroelectricity in bulk single-crystal also employed the Y-doped HfO2 system. The ferroelectricity in the wurtzite structure has been discussed for a long time. Moriwake et al. put forward giant spontaneous polarization in wurtzite materials by calculation based on density functional theory. The proposed mechanism of polarization reversal is accompanied by the change in the outermost surface, namely a cation surface to an anion surface and vice versa. Such large polarization was demonstrated in (Al1-x Scx)N films by Fitchtner et al. They also confirmed the change in the surface by performing chemical etching. In addition to (Al1-x Scx)N films, the ferroelectricity has been confirmed in (Al1-x B x )N, (Ga1-x Sc x )N, and (Zn1-x Mg x )O. For the wurtzite structure, we can consider the virtual paraelectric BN phase, in which both anions and cations are located in the same plane. As the paraelectric phase is deemed an intermediate state during polarization reversal, easy polarization reversal is expected as the u-parameter of the wurtzite structure approaches 0.5. It is considered that the u parameter is closely related to the axial ratio of the c- and a-axes. In fact, the reduction of coercive field and remanent polarization is ascertained experimentally. The “simple compound” ferroelectrics have attracted much attention due to their unique features, e.g., outstanding compatibility to semiconductor technologies in HfO2-based materials and giant remanent polarization in wurtzite materials. However, quite a large coercive field compared to conventional ferroelectrics reduces the reliability of the devices, particularly endurance properties. Further studies and developments to unveil microstructures under and after applying a strong electric field will lead to the next application of these ferroelectrics.

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Lu, Xiaoyu, Bijun Fang, Shuai Zhang, Ningyi Yuan, Jianning Ding, Xiangyong Zhao, Feifei Wang, et al. "Decreasing sintering temperature for BCZT lead-free ceramics prepared via hydrothermal route." Functional Materials Letters 10, no. 04 (August 2017): 1750046. http://dx.doi.org/10.1142/s1793604717500461.

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(Ba[Formula: see text]Ca[Formula: see text])(Zr[Formula: see text]Ti[Formula: see text])O3 (BCZT) lead-free ferroelectric ceramics were prepared at low sintering temperature via a hydrothermal route. The hydrothermal-synthesized BCZT precursor powder presents phase-pure perovskite structure and rather homogenous particles with dozens nanometers, which provides high sintering activity. Pure perovskite BCZT ceramics are synthesized at rather low sintering temperature accompanied by rather uniform microstructure morphology and high relative density. Dielectric peaks of the BCZT ceramics are rather broad, and their dielectric response behavior combines the characteristics of both the normal and relaxor ferroelectrics. The BCZT ceramics exhibit excellent ferroelectricity and promising electric energy density, which can be enhanced further with increasing electric field.

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THAKUR, O. P., CHANDRA PRAKASH, and NIDHI BHARDWAJ. "STRUCTURAL AND DIELECTRIC PROPERTIES OF (1-x) PZN – x PLZT CERAMICS." International Journal of Modern Physics B 19, no. 18 (July 20, 2005): 3037–47. http://dx.doi.org/10.1142/s0217979205030815.

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The structural and dielectric properties of a PZN-PLZT solid solution were investigated. The formation of a single phase was studied by the addition of PLZT (8/60/40) in the present system. With the increase of PLZT, the content of the pyrochlore phase decreased significantly and PZN ceramics with 100% perovskite phase could be achieved with x>0.6. Dielectric properties were investigated as a function of temperature and frequency. The ferroelectric hysteresis loop shows typical characteristics of ferroelectrics.

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48

Zhang, Sa, Baishun Yang, Zijiang Liu, Xiaotao Zu, David O. Scanlon, Bing Huang, Liang Qiao, and Haiyan Xiao. "Tunable interface states driven by ferroelectric polarization discontinuity in BiFeO₃-based superlattice." Applied Physics Letters 121, no. 22 (November 28, 2022): 221601. http://dx.doi.org/10.1063/5.0098699.

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Interfacial electronic reconstruction is one of the central topics in condensed matter research as it brings in new physics and novel material properties. Typically, it is induced by dipole, valence, or lattice discontinuities near the interfaces. However, ferroelectric polarization discontinuity (FPD) can also induce electronic reconstruction, which is not well understood, particularly in perovskite oxide interfaces. Here, we demonstrate that FPD plays critical roles in determining the electronic properties of ferroelectric superlattices and creates coexisted two-dimensional hole gas (2DHG) and two-dimensional electron gas (2DEG). We further unravel that FPD competes the traditional polar discontinuity, thus, can lead to various final interface states. The present work opens a special door to achieve 2DEG and 2DHG in the ferroelectric perovskite heterostructure via ferroelectric polarization discontinuity and provides a guidance to achieve emergent interfacial phenomena.

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49

Pandey, Dhananjai. "The World of Perovskites: Phase Transitions and Exotic Properties." Acta Crystallographica Section A Foundations and Advances 70, a1 (August 5, 2014): C11. http://dx.doi.org/10.1107/s2053273314099884.

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Oxide perovskites with a general chemical formula ABO3 constitute an important class of technologically significant materials widely used in commercial capacitors, sensors, actuators and optical devices. The upper part of the earth's lower mantle extending from 670 to 2990 km deep is also predominantly composed of perovskite type (Mg,Fe)SiO3. The perovskite compounds and their solid solutions exhibit many exotic phenomena such as ferroicity, antiferroicity, multiferroicity, piezoelectricity, electrostriction, superconductivity, colossal magnetoresistance, many types of magnetic and cationic orderings and quantum critical point. They owe these phenomena to a rich variety of phase transitions that can be induced by a wide range of variables, such as composition, temperature, pressure, magnetic field, electric field, external stresses and particle size. The main focus of this lecture would be on recent developments on phase transition studies in materials like CaTiO3, SrTiO3, PbTiO3, PbZrO3, NaNbO3, BaTiO3, Pb(Fe1/2Nb1/2)O3, Pb(Mg1/2Nb1/2)O3, BiFeO3and their solid solutions. The examples to be covered in this presentation would include (i) antiferrodistortive tilt transitions (ii) ferroelectric, antiferroelectric, ferrielectric, quantum paraelectric, quantum ferroelectric and relaxor ferroelectric transitions, (iii) morphotropic phase transitions, (iv) isostructural phase transitions, (v) antiferromagnetic and spin reorientation transitions, (vi) tricritical transitions, (vii) stress-induced structural transitions and (vii) size induced transitions. The need for complimentary diffraction techniques (X-ray, neutron and electron diffraction) in conjunction with physical property measurements in capturing the signatures of these phase transitions will be highlighted. The results of group and Landau theory considerations will also be presented. The origin of exotic functional properties of the perovskite compounds and their solid solutions will be discussed.

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Chen, Bo, Jian Shi, Xiaojia Zheng, Yuan Zhou, Kai Zhu, and Shashank Priya. "Ferroelectric solar cells based on inorganic–organic hybrid perovskites." Journal of Materials Chemistry A 3, no. 15 (2015): 7699–705. http://dx.doi.org/10.1039/c5ta01325a.

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Abstract:

Ferroelectric solar cells were fabricated by using the inorganic–organic hybrid perovskite materials, and power conversion efficieny as high as 6.7% had been obtained based on the MAPbI_3−xCl_xthin film. This work provides an alternative avenue for high-performance ferroelectric solar cells beyond inorganic ferroelectric oxides.

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Journal articles on the topic 'Ferroelectric perovskite'

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