High temperature structural phase transitions in SrSnO3 perovskite

Three high temperature structural phase transitions have been identified in the perovskite-structured phase SrSnO3 using differential scanning calorimetry and dilatometry, and have subsequently been structurally characterised using high-resolution neutron powder diffraction. Between 298 and 905 K, SrSnO3 is orthorhombic, space group Pmcn before undergoing a continuous phase transition to a second orthorhombic phase in space group Incn. At 1062 K there is a first order phase transition to a tetragonal phase in space group I4/mcm before finally transforming to the aristotype phase at 1295 K. Using the magnitude of the anti-phase tilt as a measure of the order parameter for the transition from I4/mcm to Pm3¯m suggests this transition is tricritical in nature. Crystal structures are reported for the three hettotype phases.