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Academic literature on the topic 'Polarisation ferroélectrique'
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Journal articles on the topic "Polarisation ferroélectrique"
Er-Raha, Brahim, Ahmed Toumanari, Driss Khatib, Abdallah Boukhris, and Wataru Kinase. "Étude théorique des polarisabilités électroniques et de la polarisation spontanée du composé KD2PO4 (DKDP) dans la phase ferroélectrique." Comptes Rendus de l'Académie des Sciences - Series IIB - Mechanics-Physics-Astronomy 327, no. 10 (September 1999): 1083–88. http://dx.doi.org/10.1016/s1287-4620(00)87021-0.
Full textToumanari, Ahmed, Brahim Er-Raha, Lahsèn Lifsal, Driss Khatib, and Wataru Kinase. "Calcul de la polarisation spontanée dans les phases ferroélectriques de BaTiO." Comptes Rendus de l'Académie des Sciences - Series IV - Physics 2, no. 5 (July 2001): 781–86. http://dx.doi.org/10.1016/s1296-2147(01)01187-8.
Full textDissertations / Theses on the topic "Polarisation ferroélectrique"
Rault, Julien. "Structure chimique et électronique des interfaces métal/ferroélectrique en fonction de la polarisation ferroélectrique." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2013. http://tel.archives-ouvertes.fr/tel-00840865.
Full textDuclere, Jean-René. "Croissance épitaxiale par ablation laser et caractérisations de couches minces du matériau ferroélectrique SrBi2Nb2O2." Rennes 1, 2002. http://www.theses.fr/2002REN10072.
Full textChmielowski, Radoslaw. "Bicouche oxyde ferroélectrique / oxyde conducteur Bi3. 25La0. 75Ti3O12 / Sr4Ru2O9 : élaboration par ablation laser, caractérisations structurales et propriétés électrique." Toulon, 2007. http://www.theses.fr/2007TOUL0007.
Full textBilayers ferroelectric oxide / conductive oxide, Bi3. 25La0. 75Ti3O12 (BLT) / Sr4Ru2O9 / Si[100] were elaborated by pulsed laser deposition. Structural characterizations were done by electron microscopy and X-ray diffraction; electrical properties were measured by impedance spectroscopy and Van der Pauw’s method. It is the first time that Sr4Ru2O9 is elaborated as thin films. We have shown that Sr4Ru2O9 is a conductive oxide at high temperature and has a semiconductor behavior at low temperature. The BLT thin films have polarization out of the substrate plane. Thick films of the BLT have polarization in the plane, which corresponds to a preferential orientation (00l). An intermediate layer, based on SrTiO3, between the substrate oxide Sr4Ru2O9 and the layer of BLT, was highlighted by electron microscopy. This phase grows at the cost of the ferroelectric material
Dubois, Frédéric. "Elaboration et caractérisations électro-optique et diélectrique de composites à cristaux liquides ferroélectriques dispersés dans une matrice polymère." Phd thesis, Université du Littoral Côte d'Opale, 2004. http://tel.archives-ouvertes.fr/tel-00009656.
Full textCe travail concerne l'élaboration et l'étude des propriétés structurales, diélectriques et électro-optiques de composites PDFLC. L'objectif principal est d'étudier l'influence de la nature dispersée et confinée du cristal liquide sur les propriétés des composites. Pour cela, deux cristaux liquides ferroélectriques présentant respectivement un pas d'hélice faible et élevé par rapport à la taille des gouttelettes ont été utilisés pour élaborer ces composites.
Une étude comparative des propriétés des cristaux liquides et des films PDFLC a été réalisée. Les composites étudiés présentent des propriétés électro-optiques intéressantes, tels que l'existence d'un ancrage bistable, des temps de réponse et des tensions de commutation relativement faibles. La caractérisation des mécanismes de relaxation observés pour les composites montrent qu'ils sont liés à la ferroélectricité des cristaux liquides utilisés. Les caractéristiques de ces mécanismes, à savoir leur amplitude et leur fréquence critique, diffèrent fortement de celles observées pour les cristaux liquides purs. Ces différences ont été attribuées à l'hétérogénéité diélectrique des composites PDFLC.
Xu, Qian. "Perovskite ferroelectric nanostructures for photo(electro)catalysis." Electronic Thesis or Diss., université Paris-Saclay, 2024. http://www.theses.fr/2024UPASF025.
Full textPhoto(electro)catalysis, which can directly harvest energy from solar illumination and convert it into chemical energy, has brought light to the depletion of fossil fuels and concerns about environmental issues. Significant attention has been dedicated to promoting charge separation and transport dynamics to enhance solar energy conversion to reach the requirements for practical applications. Ferroelectric and piezoelectric polarization that can trigger spatial charge redistribution and promote bulk or surface charge-carrier separation has been demonstrated as a promising strategy for designing highly efficient photocatalytic systems. In this PhD project, BaTiO₃ (BTO) has been selected as a typical ferroelectric semiconductor, with its ferroelectric and piezoelectric properties being employed to enhance directional charge carrier transfer and lifetime, explored through PEC water oxidation and Rhodamine B (RhB) degradation, respectively. More specifically, the principles and applications of piezo/ferroelectric-assisted photo(electro)catalysis were thoroughly discussed. We then developed core-shell BTO/TiO₂ nanostructures, deposited with Ni(OH)₂ oxygen evolution cocatalysts (OEC), as photoanodes for photoelectrochemical water oxidation. The relationship between ferroelectric polarization and charge separation and transport of TiO₂ was investigated by BTO crystalline phases and external electric fields. In addition, the role of piezoelectric polarization delivered by BTO in charge transport dynamics during the photocatalytic process was explored through the degradation of Rhodamine B (RhB), and was further discussed in detail based on the insights drawn from experimental characterizations and theoretical calculations
AYDI, Abdelhedi. "Elaboration et caractérisations diélectriques de céramiques ferroélectriques et/ou relaxeur de formule MSnO3-NaNbO3(M=Ba,Ca)." Phd thesis, Université Sciences et Technologies - Bordeaux I, 2005. http://tel.archives-ouvertes.fr/tel-00009068.
Full textDionot, Jelle. "Topology of ferroelectric polarization at the BaTiO3(001) surface from ab initio calculations and electron microscopy-spectroscopy." Thesis, Paris 11, 2015. http://www.theses.fr/2015PA112182/document.
Full textAt a surface or interface of a ferroelectric material, the polarization can be destabilized and even suppressed by the depolarizing field which arises from uncompensated polarization charge. In the absence of external (adsorbates, electrodes) or internal (defects, dopants) screening mechanisms, domain ordering is the most natural way for a system to remain ferroelectric and minimize its electrostatic energy. This thesis focuses on the study of the stability of various possible domain configurations, and on how it depends and interplays on size, chemical and elastic factors, at the (001) surface of BaTiO3.First-principles calculations, based on density functional theory, have been performed to enlighten the influence of surface terminations, in-plane strain, system thickness and domain size in ultrathin films on the polarization in different ferroelectric phases. The effect of surface oxygen vacancies on the polarization and electronic structure has also been investigated. Low Energy electron microscopy (LEEM) and photoemission electron microscopy (PEEM) have been used to study the surface properties of ferroelectric polarization in reduced BaTiO3 single crystals, allowing to address the influence of oxygen vacancies on the ferroelectric polarization from experimental approaches, supporting the calculations results
Marlec, Florent. "Nouveaux matériaux perovskites ferroélectriques : céramiques et couches minces issues de la solution solide (Sr₂Ta₂O₇)₁₀₀₋ₓ(La₂Ti₂O₇)ₓ." Thesis, Rennes 1, 2018. http://www.theses.fr/2018REN1S024/document.
Full textThis research focuses on the study of a new material resulting from the combination of two ferroelectric perovskite oxides Sr2Ta2O7 and La2Ti2O7; the resulting solid solution is formulating according to (Sr2Ta2O7)100 x(La2Ti2O7)x (STLTO). Our study includes the synthesis of powders, the realization of ceramics, thin film deposition and their structural, morphological, elemental, optical, dielectric and ferroelectric characterizations. The medium-term objective for this material is its integration into miniature and reconfigurable microwave devices. For this, high permittivity, variable under electric field, is required in order to achieve a tunability of the material, then a reconfigurability of the antennas, for example. Structural analysis by X-ray diffraction confirmed, by the linear variation of the cell parameters, the formation of the solid solution for the compositions x ∊ [0-5]. The dielectric analyzes carried out at low frequencies (1 - 100 kHz) on STLTO ceramics showed maximum values of permittivity (375) and tunability (55% at 3 kV/cm), associated with weak loss tangents (0,01), for the composition x = 1.65. The measurements at high frequencies (200 MHz – 18 GHz) are in agreement with the results obtained at low frequencies. The deposition of thin film by reactive sputtering, made from a target of composition x = 1.65, produces films similar at Sr2.83Ta5O15 phase, which denotes a loss of strontium. However, at low frequencies, the films have relatively high permittivity (130) for low losses (0.01) with moderate tunability (A= 14.5% at 340 kV/cm at f = 100 kHz). Deposition of oxynitride thin film (Sr,La)(Ta,Ti)O2N, carried out in Ar + N2 reactive atmosphere, leads to coloured samples having high permittivity (up to about 3000), but with equally high losses (up to 2) and without tunability. Moreover, the study of SrTaO2N showed that these compounds are suitable for the decomposition of water under visible light
Chanthbouala, André. "Jonctions tunnel magnétiques et ferroélectriques : nouveaux concepts de memristors." Phd thesis, Université Pierre et Marie Curie - Paris VI, 2013. http://tel.archives-ouvertes.fr/tel-00932584.
Full textLebon, Alexandre. "Influence de la direction de polarisation sur la coexistence de phases et la structure en domaines du ferroélectrique - relaxeur Pb(Zn1/3Nb2/3)O3 : une étude sur monocristal par diffraction des rayons X et diffusion Raman." Châtenay-Malabry, Ecole centrale de Paris, 2001. http://www.theses.fr/2001ECAP0707.
Full textPb(Zn1l3Nb2/3)03 (PZN) is a complex lead based perovskite. This ferroelectric relaxor exhibits remarkable electromechanical properties that make necessary a study as a function of the direction of polarisation. In fact, even though the spontaneous polarisation is parallel to a <111> direction, its piezoelectric properties are optimised when the crystal is polarised along [001]. Spontaneously, the cubic → rhombohedral phase transition that occurs at Tc = 385 ± 5 K is diffuse in temperature. Rhombohedral microdomains appear within the cubic phase, as their number increases, they occupy all the crystal around 330 K. Below Tc, the application of an electric field along [111] induces a complex structure of rhombohedral macrodomains. These macrodomains of a few tens of microns are separated by regions that diffuse light and that belongs to {11O} plans. As the [001] direction of the applied electric field is concerned, a Monoclinic tetragonal phase coexistence is induced. In a field cooling process, a structure of 4 monoclinic microdomains is ordered symmetrically with respect to the direction of the electric field. All , our data enabled to build an electric field - temperature diagram (E-T) along [001]. At last, on the basis of structural data, a tetragonal symmetry is proposed for the nanopolar regions that give way to dielectric relaxation