High-Pressure Behavior of Ca 2 SnO 4 , Sr 2 SnO 4 , and Zn 2 SnO 4 .

The pressure-induced structural evolution of Ca 2 SnO 4 , Sr 2 SnO 4 , and Zn 2 SnO 4 has been characterized by powder X-ray diffraction up to 20 GPa using the ALBA synchrotron radiation source and density functional theory calculations. No phase transition was observed in Ca 2 SnO 4 and Zn 2 SnO 4 in the investigated pressure range. The observation in Zn 2 SnO 4 solves contradictions existing in the literature. In contrast, a phase transition was observed in Sr 2 SnO 4 at a pressure of 9.09 GPa. The transition was characterized as from the ambient-condition tetragonal polymorph (space group I 4/ mmm ) to the low-temperature tetragonal polymorph (space group P 4 2 / ncm ). The linear compressibility of crystallographic axes and room-temperature pressure-volume equation of state are reported for the three compounds studied. Calculated elastic constants and moduli are also reported as well as a systematic discussion of the high-pressure behavior and bulk modulus of M 2 SnO 4 stannates.