Structural studies of the phases in Ba2LaIrO6—New light on an old problem

Accurate and precise structures for the cation-ordered double perovskite Ba2LaIrO6 at a number of temperatures are presented. Careful analysis of the synchrotron X-ray and neutron diffraction profiles of Ba2LaIrO6 suggests that, at room temperature, this is monoclinic in space group I2/m. Heating the sample to 375 K results in a transition to a rhombohedral phase in R3¯ with further heating resulting in the loss of the tilting of the octahedra, the structure being in Fm3¯m. Cooling the sample induces an additional phase transition to a triclinic structure in I1¯. Details of the various structures are presented.

Graphical abstract Text3Variable temperature neutron and synchrotron X-ray powder diffraction methods have been used to resolve the long standing question regarding the symmetry and structure of the cation-ordered perovskite Ba2LaIrO6. We show this is monoclinic in I2/m   at room temperature, with the sequence of phases I1¯→I2/m→R3¯→Fm3¯m.Figure optionsDownload full-size imageDownload as PowerPoint slide