Perovskite related phases in the Sr5Nb4O15 - SrTiO3 - Sr4Nb2O9 system
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Phase relations have been investigated within the Sr5Nb4O15−SrTiO3−Sr4Nb2O9 region of the SrO−Nb2O5−TiO2 system with a view to clarifying the occurrence of fully oxidised perovskite related phases. Overall phase analysis was carried out by powder X-ray diffraction and microstructures were clarified by transmission electron microscopy. There is only one main composition triangle in this area at 1350°C. The tie-line between Sr5Nb4O15 and SrTiO3 contains a homologous series of hexagonal layered perovskite phases including Sr6Nb4TiO18 and Sr7Nb4Ti2O21. The phase Sr4Nb2O9 is a nonstoichiometric phase with a disordered perovskite structure. There is some extension of this phase along the Sr4Nb2O9−SrTiO3 tie-line, but SrTiO3 does not show a significant composition range. Samples with a composition Sr4Nb2O9, when heated at 900°C show several ordered modifications. Samples along the Sr4Nb2O9−SrTiO3 tie-line which are annealed at 900°C contain these ordered materials together with samples showing considerable short range order which increases as the Ti content increases.
KeywordsPerovskite Diffuse Scattering Image Simulation Solid Solution Phase Phase Line
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