Dissertations / Theses on the topic 'SrFeO'
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Kleveland, Kjersti. "Preparation, microstructure and mechanical properties of LaCoO₃ and SrFeO₃ based ceramics." Doctoral thesis, Norwegian University of Science and Technology, Department of Chemistry, 2000. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-1931.
Full textGlenne, Rita. "Preparation and Transport Properties of SrFeO. Based Materials with controlled Microstructure." Doctoral thesis, Norwegian University of Science and Technology, Department of Chemistry, 2001. http://urn.kb.se/resolve?urn=urn:nbn:no:ntnu:diva-463.
Full textThis work consists of mainly two parts. The first part deals with the sintering behaviour and the microstructural stability of SrFe1-xCrxO3-δ, and the second with transport properties of membranes of the same compositions. The most important experimental tools have been dilatometry and oxygen permeability measurements. Supplementary tools were x-ray diffraction analysis (XRD), scanning electron microscope (SEM) and particle size distribution analysis.
Schmidt, Marek Wojciech, and Marek Schmidt@rl ac uk. "Phase formation and structural transformation of strontium ferrite SrFeOx." The Australian National University. Research School of Physical Sciences and Engineering, 2001. http://thesis.anu.edu.au./public/adt-ANU20020708.190055.
Full textRizki, Youssef. "Structure et propriétés physiques d’oxydes de fer à valence mixte SrFe1-x(Sc,Sn)xO3-d." Rouen, 2011. http://www.theses.fr/2011ROUES048.
Full textIn this thesis, the relationship between structure and physical properties of new transition-metal oxides of the SrFe1-x(Sc,Sn)xO3-d (M = Sc, Sn) type has been investigated. The structural characterization was performed by X-ray diffraction and transmission electron microscopy. Mössbauer spectrometry has been used to investigate both the oxidation state of iron and its local environment. The physical properties of the compounds were characterized by resistivity measurements with and without applied magnetic field, magnetic susceptibility measurements, magnetization measurements as a function of magnetic field or temperature. The substitution of iron by a nonmagnetic trivalent ion such as Sc3+ leads to a decrease in the oxygen content without affecting the crystalline structure of the compound. However, the substitution is limited and the SrFe0,5Sc0,5O2,5 limit compound can also be chemically synthesized in a brownmillerite ordered structure. Although transport and magnetic properties are strongly affected by such substitution, magnetoresistivity is not significantly altered. The substitution of iron by a tetravalent ion such as Sn4+ cannot maintain constant oxygen content, which increases with the substitution rate. Substitution is not limited, and a structural change is observed for a substitution rate higher than 0. 5. All the physical properties investigated (transport, magnetism, magnetoresistivity) are significantly influenced by the substitution
Hernandez, José Luis Valenzuela. "Obtenção e caracterização de filmes de perovskitas do tipo SrFeO3≠” para uso em spintrônica baseada em seleção aumentada de spins." reponame:Biblioteca Digital de Teses e Dissertações da UFRGS, 2018. http://hdl.handle.net/10183/184662.
Full textInspired by results that showed great ability of chiral systems to select spins in electronic transport, we produced films of SrFeO3− perovskite-type oxides that present helical magnetic structure. We used a chemical method starting from Fe(NO3)3.9H2O, SrCO3 and citric acid as precursors. Due to the complexity of production, the manufacturing route has been extensively explored and described. Electronic transport measurements were made by applying currents with controlled frequencies to the deposited film. Two transport mechanisms were found. Apparently they depend on the thickness of the sample, with a possible transition near 700 nm. The transport mechanism for temperatures above the magnetic transition is more sensitive to both frequency and temperature. On the other hand, two transitions attributed to magnetic phases were found around the temperatures of 105 K and 135 K. The temperatures coincide with the transitions corresponding to the helical magnetic transition. Through the use of the Mott and small Polarons models we can determine two magnetic phases separated by a transition (crossover) that is possibly antiferromagnetic. It is concluded that films of the perovskite that present transactions corresponding to those reported as helical, were manufactured successfully.
Li, Jianlin. "SrCeO₃₋based protonic conductors for hydrogen production and separation by water gas shift, steam reforming, and carbon dioxide reforming reactions." [Gainesville, Fla.] : University of Florida, 2009. http://purl.fcla.edu/fcla/etd/UFE0024942.
Full textMaity, Avishek. "Etude des mécanismes de diffusion de l’oxygène dans SrFeO3-x et Pr2NiO4+d, réalisée par diffraction du rayonnement synchrotron in situ sur monocristal." Thesis, Montpellier, 2016. http://www.theses.fr/2016MONTT188/document.
Full textUnderstanding fundamental aspects of oxygen diffusion in solid oxides at moderate temperatures, down to ambient, is an important issue for the development of a variety of technological devices in the near future. This concerns e.g. the progress and invention of next generation solid oxygen ion electrolytes and oxygen electrodes for solid oxide fuel cells (SOFC) as well as membrane based air separators, oxygen sensors and catalytic converters to transform e.g. NOx or CO from exhaust emissions into N2 and CO2. On the other hand oxygen intercalation reactions carried out at low temperatures present a powerful tool to control hole doping, i.e. the oxygen stoichiometry, in electronically correlated transition metal oxides. In this aspect oxides with Brownmillerite (A2BB’O5) and K2NiF4-type frameworks, have attracted much attention, as they surprisingly show oxygen mobility down to ambient temperature. In this thesis we investigated oxygen intercalation mechanisms in SrFeO2.5+x as well as Pr2NiO4+x by in situ diffraction methods, carried out on single crystals in especially designed electrochemical cell, mainly exploring synchrotron radiation. Following up oxygen intercalation reactions on single crystals is challenging, as it allows to scan the whole reciprocal lattice, enabling to obtain valuable information as diffuse scattering, weak superstructure reflections, as well as information of the volume fraction of different domains during the reaction, to highlight a few examples, difficult or impossible to access by powder diffraction. Both title systems are able to take up an important amount of oxygen on regular and interstitial lattice sites, inducing structural changes accompanied by long range oxygen ordering. For SrFeO2.5+x the uptake of oxygen carried out by electrochemical oxidation yields SrFeO3 as the final reaction product. The as grown SrFeO2.5 single crystals we found to show a complex defect structure, related to the stacking disorder of the octahedral and tetrahedral layers. During the oxygen intercalation we evidenced the formation of two reaction intermediates, SrFeO2.75 and SrFeO2.875, showing complex and instantly formed long range oxygen vacancies. Due to the specific twinning with up to totally twelve possible twin individuals, we directly follow up the formation and changes of the specific domain and related micro-structure. We thus observed a topotactic reaction mechanism from SrFeO2.5 to SrFeO2.75, while further oxidation lead to important rearrangements in the dimensionality of the oxygen defects in SrFeO2.75, implying the formation of an additional twin domain in course of the reaction. The electrochemical reduction of orthorhombic Pr2NiO4.25 yields stoichiometric Pr2NiO4.0 as the final reaction product with the same symmetry, while tetragonal Pr2NiO~4.12 appears as a non-stoichiometric intermediate phase. Using a single crystal with 50µm diameter, the reaction proceeded under equilibrium conditions in slightly less than 24h, implying an unusually high oxygen ion diffusion coefficient of > 10^-11cm2*s-1 at already ambient temperature. From the changes of the associated twin domain structure during the reduction reaction, the formation of macro twin domains was evidenced. Heating up Pr2NiO4.25 single crystals in air revealed a complex series of phase transition, evidencing the true symmetry of the starting phase to be in fact monoclinic. Beside exploring the complex phase diagrams of SrFeO2.5+x and Pr2NiO4+d we were able to investigate detailed changes in the micro-structure using in situ single crystal diffraction techniques, impossible to access by classical powder diffraction methods. The importance of changes in the domain structure goes far beyond the investigated title compounds and has utmost importance of the performance, stability and lifetime of e.g. battery materials
Karim, Abid [Verfasser], and Christine A. [Akademischer Betreuer] Kuntscher. "Electronic correlations in SrFe2-xCoxAs2 pnictides and EuB6 probed by infrared spectroscopy under high-pressure and low-temperatures / Abid Karim. Betreuer: Christine A. Kuntscher." Augsburg : Universität Augsburg, 2014. http://d-nb.info/1077704267/34.
Full textWattiaux, Alain. "Etude du comportement électrocatalytique relatif au dégagement de l'oxygène des pérovskites non-stoechiométriques La1-xSrFe1-zCOzO3-y." Phd thesis, Université Sciences et Technologies - Bordeaux I, 1985. http://tel.archives-ouvertes.fr/tel-00574567.
Full textDarracq, Stéphane. "Contribution à l'étude des corrélations entre stoechiométrie, structure, liaison chimique et propriétes physico-chimiques de perovskites oxygénées renfermant un élément 3d a un degrè d'oxydation inusuel (Cu(III), Cu(IV), Fe(IV))." Phd thesis, Université Sciences et Technologies - Bordeaux I, 1993. http://tel.archives-ouvertes.fr/tel-00136172.
Full textDamljanović, Vladimir [Verfasser]. "Raman scattering, magnetization and magnetotransport study of SrFeO3-δ, [SrFeO 3-delta], Sr3Fe2O7-δ [Sr 3 Fe 2 O 3-delta] and CaFeO3 / vorgelegt von Vladimir Damljanović." 2009. http://d-nb.info/993271472/34.
Full textSchmidt, Marek Wojciech. "Phase formation and structural transformation of strontium ferrite SrFeOx." Phd thesis, 2001. http://hdl.handle.net/1885/48187.
Full textZhong, Yu-Jie, and 鍾雨潔. "Spin Waves in SrFeO3." Thesis, 2013. http://ndltd.ncl.edu.tw/handle/83776472587581403332.
Full text國立臺灣大學
物理研究所
101
We calculate the self-energy and dispersion relation of magnons in the spiral spin state of SrFeO3. Our model consists of the superexchange (SE) interaction and the itinerant ferromagnetic (SD) interaction with or without external magnetic field. The SE interaction part comes from the electrons in the t2g orbitals, and the SD part comes from the itinerant electrons which reside mostly in the eg orbitals. For the SE part, we start with treating spins as classical vectors and then considered the quantum fluctuation with the Holstein-Primakoff transformation. Then Bogoliubov transformation is used to diagonalize the Hamiltonian. For the itinerant ferromagnetic part, we use a projection operator method to simplify the Hamiltonian. Finally the self-energy and the dispersion of magnons are calculated and they give a linear relation between frequency and wavevector.
Huang, Tsai-Hung, and 黃在宏. "Characterization and gas monitory analysis ofperovskite type SrFeO3-x." Thesis, 1993. http://ndltd.ncl.edu.tw/handle/42796973931569285486.
Full text國立臺灣大學
化學工程研究所
81
Sensors have been widely used recently in various areas such as automatical exhaust monitor, poisonous gas detector and reaction on controlling device. P-type perovskite SrFeO3-x oxide is a good sensor material because of its durability and stability properti- es. In this work, the perovskite materials were prepared by sol- gel method and coprecipitation method, and their physical proper- ties were studied by means of XRD, TPD/TPR, TEM, and TGA/DTA. It is found that the sol-gel method is superior than the coprecipit- ation method in preparation and physical properties . We former yields thematerials of smaller particle size, and higher oxygen desorption and hydrogen consumption. The TPDand TPR results show that their oxidizing and reducing abilities are better. When the SrFeO3-x madeby sol-gel method is used as CO gas sensor, The re- sistance of material decreases with increasing temperature. The- refore, tends to decrease the η(response ratio). The reason may be ascribed to thereduction of oxygen adsorption with the incre- ase in temperature. The hole numbers increase at higher tempera- ture. The sensor resistance is found toincrease with increasing CO concentration, showingthe reaction of holes in the sensor with CO is deeper. The experimental result, shows that the optimum temperature for CO detecting is in the rangeof 280-340℃. Resist- ance variance is large enough,and detceting time is short too. reproducibility of response after several oxidation and reduction cycle is better, Finally the elementary sensorial kinetics are proposed.
Chen, Jung-Fu, and 陳榮富. "Study of the charge ordering in SrFeO3-δ using X-ray scattering." Thesis, 2012. http://ndltd.ncl.edu.tw/handle/97078957939075504316.
Full text淡江大學
物理學系碩士班
100
We report the study of the magnetoresistance behavior and the charge/spin modulations in a high quality single crystal of SrFeO3-δ using magnetization, conductivity, and x-ray scattering. The crystal displays a sharp magnetic transition at T ≈ 60 K and a nonlinear conductivity behavior at about T ≈ 110 K, suggesting a 3-δ of about 2.81. In addition, there exists the hysteresis phenomenon with a transition width of about 10 K at T ≈ 60 K. A charge modulation was located at (0, 0, L ± q), q ≈ 0.36 to have a transition temperature of T ≈ 110 K by the use of x-ray scattering with x-ray energy of 10 keV and 12 keV. This is in accord with the nonlinear transport transition as observed by conductivity measurement. By the means of resonant soft x-ray diffraction around the Fe L-edge, we also observed the spin modulation (from paramagnetic to antiferromagnetic states) in agreement with the formation of spin ordering doubling the c-axis.
Lin, Yi-Shiuan, and 林意軒. "Study of the charge and spin ordering in SrFeOx using X-ray scattering." Thesis, 2014. http://ndltd.ncl.edu.tw/handle/57034261056795234786.
Full text淡江大學
物理學系碩士班
102
We report the study of charge/spin-ordering in single crystal SrFeOx using resonant soft x-ray scattering. Probing the charge and spin ordering using x-rays is difficult due mainly to the very weak diffraction intensity. However, this difficulty can be overcome by the use of resonant x-ray diffraction. In this study, we performed the resonant soft x-ray diffraction at the Fe L-edge and O K-edge, and observed a huge enhancement from the spin and charge ordering reflections. The wave vectors of charge- and spin-ordering in SrFeOx were observed to be Qco ≈ (0, 0, 0.64) and Qso ≈ (0, 0, 0.5) with transition temperatures at Tco ≈ 107 K for charge ordering and Tso ≈ 65 K for spin. These reflections were also further confirmed to originate from charges and spins, respectively, using the different polarized x-rays.
TANG, LIAO JUNG, and 廖榮堂. "(一)Preparation of SrFeO3-x precursors (二)Preparation of Ru-Pt(Pd) binary precursors." Thesis, 1999. http://ndltd.ncl.edu.tw/handle/73594360374956415667.
Full textHsieh, Shang-Hsien, and 謝尚憲. "The Electronic and Magnetic Structures of SrFeO3-δ and Ni0.4Mn0.6TiO3 Single Crystals Studied by X-ray Spectroscopy and Neutron Scattering." Thesis, 2018. http://ndltd.ncl.edu.tw/handle/64p4sv.
Full text淡江大學
物理學系博士班
106
The synchrotron radiation based spectroscopic techniques provide element-specific information of electronic and atomic structures for fundamental researches, material studies and industrial applications. Techniques include X-ray diffraction (XRD) for lattice structure, X-ray absorption near edge structure (XANES) and X-ray linear dichroism (XLD) for electronic and orbital structures, X-ray emission spectroscopy (XES) and resonant inelastic X-ray scattering (RIXS) for information of the occupied states and inherent elementary excitations, extended X-ray absorption fine structure (EXAFS) for local atomic structure. In addition, neutron scattering related techniques provide direct evidence and texture of magnetic structure, such as elastic and inelastic neutron scattering (ENS and INS) for spatial correlations and dynamics of spin moments, small angle neutron scattering (SANS) for spatial correlations of magnetic clusters. These techniques are considerable and powerful techniques for the study of various complex couplings in novel single crystal materials with special magnetic structure. In the first part of this thesis, the local electronic and atomic structures of the high-quality single crystal of SrFeO3-δ were studied using temperature-dependent x-ray absorption (XAS) and valence-band photoemission spectroscopy (VB-PES) to investigate the origin of anisotropic resistivity in the ab-plane and along the c-axis close to the region of thermal hysteresis (near temperature for susceptibility maximum, Tm~78 K). All experiments herein were conducted during warming and cooling processes. The Fe L3,2-edge XLD results show that during cooling from room temperature to below the transition temperature, the unoccupied Fe 3d eg states remain in persistently out-of-plane 3d3z2-r2 orbitals. In contrast, in the warming process below the transition temperature, they change from 3d3z2-r2 to in-plane 3dx2-y2 orbitals. The nearest-neighbor (NN) Fe-O bond lengths also exhibit anisotropic behavior in the ab-plane and along the c-axis below Tm. The anisotropic NN Fe-O bond lengths and Debye-Waller factors stabilize the in-plane Fe 3dx2-y2 and out-of-plane 3d3z2-r2 orbitals during warming and cooling, respectively. Additionally, a VB-PES study further confirms that a relative band gap opens at low temperature in both the ab-plane and along the c-axis, providing the clear evidence of the charge-density-wave nature of SrFeO3-δ single crystal. In the second part, ENS and INS experiments were performed on a single crystal of Ni0.4Mn0.6TiO3 (NMTO) to study the spatial correlations and dynamics of spins in the XY-like spin-glass (SG) state. Magnetization measurements reveal signatures of SG behavior in NMTO with a freezing temperature of TSG ~ 9.1 K. The ENS experiments indicated that the intensity of magnetic diffuse scattering starts to increase around 12 K, which is close to TSG. Also, spin-spin correlation lengths (ξ) at 1.5 K are approximately 21.05±0.6 and 72.99±1.6 Å in the interlayer and the in-plane directions, respectively, demonstrating that magnetic correlations in NMTO exhibit quasi two-dimensional-like antiferromagnetic order. INS results show quasi-elastic neutron scattering (QENS) profiles below TSG. The life-time of dynamic correlations (τ), obtained from the QENS profiles, are approximately 16.27±0.8 and 15.88±1.9 psec at 10 K for two positions (0.00, 0.00, 1.52) and (0.01, 0.01, 1.50), respectively. Therefore, our experimental findings demonstrate that short-range-ordered antiferromagnetic clusters with short-lived spin correlations are present in the XY-like SG state of NMTO at a temperature of approximately TSG. In final part, SANS, RIXS, and XAS experiments on the single crystal of NMTO have been carried out to study the role of electronic and atomic properties in the XY-like SG state. SANS presents the texture of toroidal glass and phase diagram of NMTO. RIXS experiments provide the evidence of crystal field (d-d) excitations at Ni and Mn L3-edge. However, spin-flip excitations are only observable which are prominent at Ni L3-edge RIXS. Using temperature dependent XANES, XLD and EXAFS studies along with RIXS, it has been shown that symmetry breaking/ lattice distortion occurs at low temperature near SG phase transition due to the local disorder in Ni-O bond lengths, and further induced the orbital preference occupation charge from out-of-plane state (3d3z2-y2) to in-plane state (3dx2-y2). We therefore believe that XY-like SG state of NMTO is associated with the unoccupied in-plane (3dx2-y2) states.
Ho-Pan, Lin, and 林禾弁. "The Visible-Light-Driven Photocatalysts of The Magnetic and Mesoporous SrFeO3-x/g-C3N4 and BiOBr/PbBiO2Br Nano-Composites: Synthesis, Characterization, Photocatalytic Activity, and Degraded Mechanisms." Thesis, 2015. http://ndltd.ncl.edu.tw/handle/61880728636873037308.
Full text國立臺中教育大學
科學教育與應用學系科學教育碩士班
103
The mixing and heating method and the hydrothermal method are applied to synthesizing two visible-light-driven (VLD) photocatalysts, SrFeO3-x/g-C3N4 and BiOBr/PbBiO2Br, respectively. X-ray diffractometer, Field Emission-Scanning Electron Microscopy-Energy Dispersive Spectroscopy, Field Emission-Transmission Electron Microscopy-Energy Dispersive Spectroscopy, Fourier Transform Infrared Spectroscopy, UV-vis diffuse reflectance spectra, Surface Area and Porosity Analyzer, and Ultraviolet Photoelectron Spectroscopy are utilized for distinguishing the synthesized samples. SrFeO3-x/g-C3N4 and BiOBr/PbBiO2Br degraded crystal violet dye and chloramphenicol solution are used for simulating the environmental target pollutants. From the reaction rate constant of the degraded crystal violet dye solution, the 4wt.% SrFeO3-x is added g-C3N4 for the calcination at 500℃ for 2 hours. The acquired SrFeO3-x/g-C3N4 0.0997h-1 is higher than g-C3N4 0.0209h-1 and SrFeO3-x 0.0014h-1, and the degradation efficiency constant of BiOBr/PbBiO2Br appears 0.0601h-1 which apparently enhances the photocatalytic efficiency in comparison to BiOBr 0.0207h-1 and PbBiO2Br 0.0017h-1. The distinguishing with reactive species and Electron Paramagnetic Resonance shows the important roles of free radicals, ․OH and․O2— , in the photocatalytic reaction. In order to understand the pathway of the crystal violet dye and chloramphenicol degradation, the reactive intermediate in the HPLC-PDA-ESI-MS separation process is used for predicting the possible photocatalytic degradation mechanism for the research basis of crystal violet dye and chloramphenicol degradation.
Marques, Vânia Alexandra Morgado. "Síntese e caracterização de compostos da série SrTi1-xFexO3." Master's thesis, 2015. http://hdl.handle.net/10400.6/5940.
Full textThe development of nano-structured materials has been of great interest in the scientific, technological and innovation areas, particularly regarding advanced ceramic materials. Materials constituted from perovskite-type oxide (ABO3) are developed for various types of applications, such as catalytic or photocatalytic films, and electrodes, as cathodes or as anodes. The SrTiO3 oxide, SrFeO3 and SrTi0,5Fe0,5O3 were synthesized by solid route with the ceramic method, and the final synthesis temperature reached 1200ºC. The structural characterization of the compounds, which were obtained in the form of powders, was prepared by XRD, and the morphological characterization by SEM and TEM. Films were prepared from the synthesized compounds in nickel foam substrate by using the slurry-paint method and the Triton X-100 was used as a dispersant. The morphological characterization of the films was made by SEM. Films were also prepared by immobilizing commercial TiO2 particles in order to compare the photocatalytic performance of the synthesized powders with the perovskite structure, with the most popular photocatalyst in scientific literature – the TiO2. All of the films were used as photocatalysts, by using 254 nm UV radiations for the degradation of the Acid Orange 7 dye solution (AO7). The degradation was monitored by the action of ultraviolet and visible spectrophotometry. SrFeO3 showed the highest absorbance removal, within the synthesized perovskite - type structure compounds, after 6 hours of assays. However, the best result was obtained with the commercial TiO2 compound. In the perovesquites series studied, the results indicate an increase of photocatalytic effect with an increase of the Fe content. The percentages of absorbance removal for the azo dye, after 6 hours of assays, for the compounds SrTiO3, SrTi0,5Fe0,5O3, SrFeO3 and TiO2, , were 84.8; 90.0; 95.4 and 96.8 % respectively.