The impact of anion ordering on octahedra distortion and phase transitions in SrTaON and BaTaON.

In this work we synthesized BaTaON and SrTaON using a two-step high-temperature solid-state reaction method and analysed the structural distortions, relative to the ideal cubic perovskite structure, according to group theory. From a complete distortion analysis/refinement using high-resolution neutron diffraction data in the temperature range 8 to 613 K, we identified tetragonal structures for BaTaON [P4/mmm (No. 123)] and SrTaON [I4/mcm (No.