The nature of the orthorhombic to tetragonal phase transition in Sr1−xCaxMnO3

The orthorhombic–tetragonal phase transition in the perovskite series Sr1−xCaxMnO3 0.4⩽x⩽0.6 has been studied by synchrotron X-ray powder diffraction. At room temperature the Ca rich oxides x⩾0.45 have the orthorhombic Pbnm superstructure whereas Sr0.6Ca0.4MnO3 is two phases with both tetragonal I4/mcm and orthorhombic Pbnm. Analysis of the octahedral tilts suggest the co-existence of these two phases is a consequence of a first-order I4/mcm to Pbnm transition. The evolution of the structure of Sr0.5Ca0.5MnO3 with temperature is also described and this is found to evolve from orthorhombic to tetragonal and ultimately cubic.

The temperature dependence of the lattice parameters for Sr0.5Ca0.5MnO3.Figure optionsDownload as PowerPoint slide