Thermal expansion and cation disorder in Bi2InNbO7

The structure of the pyrochlore-type oxide Bi(2)InNbO(7) has been investigated between room temperature and 700 degrees C using electron and synchrotron X-ray powder diffraction and at room temperature and 10K using neutron diffraction methods. Bi(2)InNbO(7) exhibits an A(2)B(2)O(7) cubic pyrochlore-type average structure at all temperatures that is characterized by an apparently random mixing of the In(3+) and Nb(5+) 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. Crown Copyright (c) 2004 Published by Elsevier Inc. All rights reserved.