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Phase and Valence Transitions in Ba^2^LnSnxNb1-xO6-δ



Paul J. Saines, Brendan J. Kennedy, Bernt Johannessen, Sarah Poulton


The structures of compounds in the perovskite series Ba2LnSnxNb1−xO6−δ (Ln=Pr and Tb and x=0, 0.1, 0.2, ..., 1.0) have been examined using synchrotron X-ray and neutron diffraction. It was found that niobate members of both series feature full B-site cation ordering but that this order is lost with increasing x. X-ray absorption near-edge structure (XANES) and near-infrared spectroscopies indicate that the oxidation state of the lanthanide cations gradually changes from Ln3+ to Ln4+ with increased Sn4+ doping. This is believed to be the cause of the loss of B-site ordering. Least squares analysis of the XANES spectra suggests that the rate of the transformation of Ln3+ cations to the tetravalent state is such that the Pr series contains no oxygen vacancies while the Tb series may contain a very small amount of vacancies, with δ≈0.02.
Journal of Solid State Chemistry


Perovskites , phase transitions, citation ordering, oxygen vacancy, lanthanum oxidation states


Saines, P. , Kennedy, B. , Johannessen, B. and Poulton, S. (2008), Phase and Valence Transitions in Ba^2^LnSn<sub>x</sub>Nb<sub>1-x</sub>O<sub>6-&#948;</sub>, Journal of Solid State Chemistry, [online], (Accessed April 17, 2024)
Created November 1, 2008, Updated March 18, 2024