Pressure-induced phase transitions of hexagonal perovskite-like oxides

We have stabilized two new cubic (3C structured) A2BʹBʹʹO6-type double-perovskite phases, Ba2CoSbO6 and Ba2ZnTeO6, by means of a high-pressure heat-treatment of corresponding hexagonal (6H and 12R structured, respectively) non-perovskite phases at 4 GPa and 1000 °C. Similar treatments on hexagonal Ba2TiMnO6 (12R) and Ba2NiTeO6 (12R) phases did not yield the 3C double-perovskite structure but converted the 12R structure to the 6H structure. The pressure-induced phase conversion in each A2BʹBʹʹO6 system apparently goes from the 12R structure towards the 6H and 3C structures with increasing pressure, where the pressure ranges required most likely depend (among other possible factors) on the tolerance factor for the particular combination of A, Bʹ and Bʹʹ. We foresee that yet a number of novel B-site ordered double-perovskite compounds are to be discovered through the high-pressure high-temperature treatment.

High-pressure (HP) heat-treatment is an efficient tool to synthesize novel B-site ordered double-perovskite materials. This is demonstrated for two new cubic (3C structured) perovskite phases, Ba2CoSbO6 and Ba2ZnTeO6, obtained through a HP conversion of corresponding hexagonal (6H and 12R structured, respectively) non-perovskite phases at 4 GPa and 1000 °C. Similar treatments on hexagonal Ba2TiMnO6 (12R) and Ba2NiTeO6 (12R) phases yield the intermediate 6H structure.Figure optionsDownload as PowerPoint slide