Thermal expansion and cation disorder in Bi2InNbO7

The structure of the pyrochlore-type oxide Bi2InNbO7 has been investigated between room temperature and 700 °C using electron and synchrotron X-ray powder diffraction and at room temperature and 10 K using neutron diffraction methods. Bi2InNbO7 exhibits an A2B2O7 cubic pyrochlore-type average structure at all temperatures that is characterized by an apparently random mixing of the In3+ and Nb5+ cations on the octahedral B sites. The Bi cations on the eight-coordinate pyrochlore A sites are displacively disordered, presumably as a consequence of their lone pair electron configuration. Heating the sample does not alter this disorder.