Experimental Observation of Possible Pressure-Induced Phase Transformation in GdAlO3 Perovskite Using In Situ X-ray Diffraction

Gadolinium aluminate perovskite (GdAlO3) was studied at high pressures of up to 23 GPa in a diamond anvil cell (DAC) using monochromatic synchrotron X-ray powder diffraction. Evidence pressure-induced phase transformation from orthorhombic (Pbnm) rhombohedral (R3¯c) structure observed 21 and further proved by DFT calculations. Before transition, the volumetric ratio polyhedron A B (i.e., VA/VB for ABX3 general notation) Pbnm continuously increased towards ideal value five indicating decrease structural distortion as opposed trend many other perovskites (e.g., CaSnO3, CaGeO3, MgSiO3 NaMgF3). Pressure–volume data were fitted third-order Birch–Murnaghan equation state yielding bulk modulus (Ko) 216 ± 7 with pressure derivative (Ko′) 5.8 (fixed). This work confirms higher symmetry previously predicted GdAlO3 perovskite.