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Introduction Strontium titanate (SrTiO 3 ) is a compound with perovskite structure, with a face-centred cubic symmetry [ 1 ] and stable over a wide temperature range between 104 and 2300 K [ 2 ]. Owing to its high dielectric

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Abstract  

The present work investigates the influence of milling and calcination atmosphere on the thermal decomposition of SrTiO3 powder precursors. Both pure and neodymium-modified SrTiO3 samples were studied. Milling did not significantly influence numerical mass loss value, but reduced the number of decomposition steps, modifying the profiles of the TG and DTA curves. On the other hand, milling increases the amount of energy liberated by the system upon combustion of organic matter. It was also observed that the milling process, associated to the calcination in an oxygen atmosphere, considerably decreases the amount of organic matter and increases the final mass loss temperature.

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Journal of Thermal Analysis and Calorimetry
Authors: A. Ianculescu, A. Brăileanu, M. Zaharescu, S. Guillemet, I. Pasuk, J. Madarász, and G. Pokol
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Journal of Thermal Analysis and Calorimetry
Authors: M. A. F. Souza, R. A. Candeia, S. J. G. Lima, M. R. Cassia-Santos, I. M. G. Santos, E. Longo, and A. G. Souza
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Journal of Thermal Analysis and Calorimetry
Authors: M. A. F. de Souza, A. G. Souza, R. A. Candeia, D. M. A. Melo, L. E. B. Soledade, M. R. C. Santos, I. M. G. Santos, S. J. G. Lima, and E. Longo
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Journal of Thermal Analysis and Calorimetry
Authors: Márcia Silva, Mary Alves, S. Lima, L. Soledade, Elaine Paris, E. Longo, A. Souza, and Iêda Santos

Abstract  

Sr(Ti,Nd)O3 was synthesized in order to evaluate the influence of the amount of neodymium on the thermal and structural properties of SrTiO3. The synthesis was carried out using the polymeric precursor method. A small mass gain was observed for the SrTiO3 and SrTi0.98Nd0.02O3 samples accompanied by an exothermic peak in the DTA curves. Other steps at higher temperatures are assigned to the combustion of the organic material and carbonate. Elimination of defects by previous calcination of the precursors is responsible by the short and long range ordering of the perovskite. Cubic phase was obtained for undoped and doped SrTiO3.

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Methods of DTA, TG, DSC, IR spectroscopy and X-ray phase analysis were used to study the thermal dehydration and decomposition of Ca2+ and Sr2+ peroxotitanates to the corresponding metatitanates. The stages of the process and the intermediate phases were identified. The information obtained was utilised to determine the optimum temperatures of heating of the initial peroxotitanates to yield metatitanates with a fairly high degree of crystallinity (for CaTiO3 680C, and for SrTiO3 650C).

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The sorption of uranium(VI) on the perovskite structure of strontium titanate in a 0.5M KNO3 solution is studied. SrTiO3 commercial material was characterized by XRD showing a tausonite face, with a specific area of 2.42 m2.g−1. The electrical surface characterization of the compound was performed by mass and potentiometric titrations. pHpzc in water was 8.5±0.3 and 9.1±0.2 in 0.5M KNO3 solution, showing a positively charged surface. FITEQL 4.0 program was used to calculate the sorption curves and the surface acidity constants by the constant capacitance model obtaining: log K 1 = 8.67 and log K 2 = −9.43. The sorption edge was fitted with two different uranium(VI) species sorbed, corresponding to bidentate complexes of UO2 2+ and UO2(OH)2H2O on the surface of strontium titanate.

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The fabrication method of superconducting thin films of compositions HgBa2Ca2Cu3O8+δ (Hg-1223) and Tl2Ba2CuOy (2201) on single-crystalline SrTiO3 and LaAlO3 substrates is reported. The highest obtained T c was 134 K and J c over 106 A cm–2 at 77 K. High pressure DTA(HP-DTA) was applied to grow mercury- and thallium-based high-temperature superconducting crystals and thin films, to identify melting points of particular phases within these oxide systems and determine suitable processing conditions. The DTA system operates at the: maximum temperature of 1200C, volume up to 5 cm3, working pressure up to 1.5 GPa and at a working atmosphere — inert gas with up to 25% oxygen.

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This work reports on the synthesis of a SrTi1−xFexO3 nanostructured compound (0.0 ≤ x ≤ 0.1) using a modified polymeric precursor method. The effect of the addition of iron on the thermal, structural and morphological properties of the nanoparticles was investigated by FT-IR spectroscopy, X-ray diffraction, and field emission scanning electron microscopy (FE-SEM). A thermogravimetric analysis indicated that the crystallization process preceded by three decomposition steps. Differential thermal analysis experiments showed that decomposition occurred in a broad range of temperatures from 400 to 600 °C. It was observed that iron ions acted as catalysts, promoting rapid organic decomposition and phase formation at a lower temperature than in SrTiO3. Moreover, the addition of iron decreased the crystallite size and increased the lattice parameter of the SrTi1−xFexO3 structure.

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