High-Pressure Synthesis and Structures of Perovskite-Type Oxyfluorides

Abstract

In this article, our recent researches on the crystal structure of the perovskite-type oxyfluorides were reviewed. Parts of these compounds were synthesized using the cubic-multi-anvil type high-pressure apparatus. In cubic oxyfluorides, the displacement from ideal positions of an anion or a cation was observed and the ion species displaced depended on the tolerance factor. The oxyfluorides containing Pb and/or Mn ions had a tetragonal structure and PbMnO₂F containing both ions exhibit very high tetragonality (c/a=1.10). In addition, the solid solutions between a perovskite-type oxide and an oxyfluoride or a fluoride were synthesized using high-pressure apparatus. As the result, it was revealed that one of these solid solutions, (1−x)BaTiO₃-xKTiO₂F represented unique structures and interesting dielectric properties.