Structural investigation of Sr2LiReO6. Evidence for a continuous tetragonal-cubic phase transition

The presence of a continuous and reversible Fm3-barm-I4/m phase transition in a polycrystalline sample of the ordered double perovskite Sr2LiReO6 is described. The transition that occurs near 300 deg. C is a consequence of in-phase tilting of the BO6 octahedra. The temperature dependence of both the lattice parameters and the spontaneous strains are consistent with a second order phase transition as would be expected for a soft mode transition. - Graphical Abstract: The crystal structure of polycrystalline Sr2LiReO6 from room temperature 30 to 500 deg. C is described. The sample undergoes a continuous and second order I4/m to Fm3-barm phase transition. This transition is reversible and the tetragonal structure is formed upon re-cooling the cubic form.