High-temperature phase transitions inSrZrO3

The high-temperature phase transitions of ${\mathrm{SrZrO}}_3$ have been studied using powder neutron diffraction and the Rietveld method. The material is tetragonal $\mathrm{}(I4/mcm)\mathrm{}$ between ∼1020 and 1360 K. At higher temperatures (>1360 K) the structure was found to be the ideal cubic perovskite $\left(Pm3\mathrm{}¯m\right).\mathrm{}$ From the neutron-diffraction data and the space-group assignments, the transition from the tetragonal to cubic phase is consistent with a continuous phase transition. The angle of tilt of the oxygen octahedron in the tetragonal phase is taken to be the order parameter and its temperature variation is typical of a tricritical phase transition.