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Abstract  

Perovskites belong to the great group of the inorganic pigments and thanks to their excellent properties they have been widely used in an industry. CaTiO3, BaTiO3 and SrTiO3 with the perovskite structure were prepared in this work. These compounds were synthesized with using the solid state reaction by calcination in temperature region 1000–1200°C. The thermal analysis was used for characterization of thermal behaviour and formation of tested perovskites. The main aim of this work was studied the influence of calcination temperature on colour properties of perovskites. Colour properties of powdered compounds and samples applied into ceramic transparent glaze P 07491 were also studied. The tested compounds can be described by different light colour hues and that depending on calcining temperature. The structures of the powdered compounds were studied by X-ray diffraction analysis.

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Abstract  

La0.8 A'0.2 MnO3+δ (A'=Sr, Ba, K, Cs) perovskites were studied by temperature-programmed reduction. The amount of non-stoichiometric oxygen was found to decrease from δ=0.16 for LaMnO3+δ to δ=0.07 (Sr-), 0.06 (Ba-), 0.07 (K-) and 0.03 (Cs-) substituted manganites. The reducibility at low and mean-temperatures (t<500C) increased in the sequence La<(La, Sr)≈(La, Ba)<(La, Cs)<(La, K).

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Abstract  

A thermogravimetric method has been used for the determination of the oxygen chemical diffusion coefficients in La1–xSrxMnO3+δ; x=0; 0.05; 0.10; 0.15 (LSM). A temperature range of 700–1000C was studied. The chemical diffusion coefficient varies between 1.6⋅10–13 and 1.8⋅10–10cm2s–1 for the samples in the temperature range studied. The activation energy for oxygen chemical diffusion was determined to be 190–280 kJ mol–1 for the LSM samples. The magnitude of the chemical diffusion coefficients of the LSM samples does not depend on the strontium site occupation factor.

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Abstract  

The synthesis of strontium-doped lanthanum chromite, La1−xSrxCrO3 (x=0.1 and 0.3), used as an interconnect material for solid oxide fuel cells (SOFC), was investigated using two unconventional synthesis methods: (1) organic precursors’ method based on the thermal conversion of complex combination resulted in the oxidation reaction of 1,2-ethanediol by La3+, Sr2+ and Cr3+ nitrates; (2) combustion synthesis based on the exothermic redox reaction of La3+, Sr2+ and Cr3+ nitrates with urea and glycine as fuels. We also used a mixture of urea and glycine as fuel. The samples were characterized by means of thermal analysis and X-ray diffraction.

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Abstract  

This paper presents possible applications of thermal analysis and sorptomatic methods to study physico-chemical properties of the high-T csuperconductor Y1Ba2Cu3O7-x and perovskite LaCoO3. It is shown that both Y1Ba2Cu3O7-x and perovskite phase are highly sensitive to water vapour. Mechanism of adsorption of water on LaCoO3depends largely on time activation (t act). When the time of water vapour saturation was 0<t act<180 s, physisorption process was observed. In the case of longer times water vapour action, t act>180 s, chemical decomposition was observed.

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Journal of Radioanalytical and Nuclear Chemistry
Authors: Z. Németh, Z. Homonnay, F. Árva, Z. Klencsár, E. Kuzmann, J. Hakl, K. Vad, S. Mészáros, K. Kellner, G. Gritzner, and A. Vértes

Abstract  

In this paper we present 57Co emission Mössbauer and AC magnetic susceptibility studies of La0.8Sr0.2CoO3-δ perovskite. The observed coexistence of paramagnetic and magnetic subspectra in the 57Co emission Mössbauer spectra, as well as the difference of their isomer shifts support the existence of electronic phase separation in this perovskite, in good agreement with the double exchange based cluster model.

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Abstract  

CaSnO3 was synthesized by the polymeric precursor method, using different precursor salts as (CH3COO)2CaH2O, Ca(NO3)24H2O, CaCl22H2O and CaCO3, leading to different results. Powder precursor was characterized using thermal analysis. Depending on the precursor different thermal behaviors were obtained. Results also indicate the formation of carbonates, confirmed by IR spectra. After calcination and characterization by XRD, the formation of perovskite as single phase was only identified when calcium acetate was used as precursor. For other precursors, tin oxide was observed as secondary phase.

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The reversible cycling of the oxygen content in layered Co-substituted perovskites of type YBaFeCuO5+δ was investigated applying thermoanalytical methods. For the system YBaCoCu1−xFexO5+δ an increasing amount of oxygen incorporation into the oxygen deficient lattice was found by thermogravimetry for an increasing iron content ofx=0.4 to 0.8. With a cycle of subsequent heating and cooling the reversible incorporation of oxygen on account of redox active cations with mixed valencies could be demonstrated. The combination of several cycles under different gas atmospheres confirmed the reversibility of the oxidation processes suggesting the application for catalytical processes.

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Abstract  

Synthesis of perovskite-type oxides Ln1-xAxBO3 (Ln: lanthanoid; A: alkaline earth; B: transition metal) by heating at low temperature with large ratio of alkaline earth element, especially barium, easily involves impurity of alkaline earth carbonate. We succeeded to prepare the precursor without the formation of barium carbonate even at a large content of barium. The chemical state and structure of Ln1-xAxBO3- d (Ln: La, Eu; A: Ca, Sr, Ba: B: Fe, Mn) perovskite-type oxides prepared by using those precursors have been studied by Mössbauer spectroscopy and X-ray powder diffraction. The X-ray powder patterns showed many types of crystal system depending on x.

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Journal of Thermal Analysis and Calorimetry
Authors: V. Balek, H. Mitamura, T. Banba, M. Beneš, Z. Málek, I. N. Beckman, I. M. Bountseva, H. Haneda, and T. Mitsuhashi

Summary Emanation thermal analysis (ETA) was used to characterize thermal behaviour of the perovskite ceramics designed as a matrix for the encapsulation of high level radioactive waste. The perovskite ceramics (composition CaTiO3 where small admixtures of Nd and Ce simulated the radioactive elements Cm and Pu, respectively) was prepared from sol-gel precursors by hot pressing at 1250°C/29 MPa for 2 h. The chemical durability of the ceramics was tested by leaching in the solution with pH 2 at 90°C/2 months. ETA results of ‘as-leached’ and ‘as-prepared’ perovskite ceramics samples were compared and evaluated by means of a mathematical model. Three temperature ranges of the annealing of structure defects in the ‘as-prepared’ sample were determined from the decrease of radon release rate in the ranges 280-560, 800-960 and 960-1200°C, respectively. One annealing step was determined for the ‘as-leached’ sample from the decrease of radon release rate in the range of 800-950°C.

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