The varying temperature- and pressure-induced phase transition pathways in hybrid improper ferroelectric SrSnO.

A variable-temperature and pressure single-crystal diffraction study of hybrid improper ferroelectric SrSnO is reported. In combination with symmetry analysis, we reveal that the application of pressure and temperature induce distinct phase transition pathways, driven by a differing response of the octahedral rotations to these stimuli. Contrary to what has been previously predicted, we observe the ferroelectric to paraelectric phase transition between 10.17(18) and 12.13(14) GPa, meaning the hybrid improper ferroelectric phase remains stable to significantly higher pressures than expected.