New quaternary oxides with both families of second-order Jahn-Teller (SOJT) distortive cations: Solid-state synthesis, structure determination, and characterization of YNbTe2O8 and YNbSe2O8

Abstract

Two novel quaternary mixed metal tellurite and selenite, YNbTe2O8 and YNbSe2O8, respectively, have been synthesized through standard solid-state reactions using Y2O3, Nb2O5, TeO2 or SeO2 as reagents. Single crystal X-ray and powder neutron diffraction analyses have been utilized to determine the structures of the reported materials. YNbTe2O8 and YNbSe2O8 are isostructural to each other and crystallize in the monoclinic centrosymmetric space group, C2/m (No. 12). Due to the two families of constituent second-order Jahn-Teller (SOJT) distortive cations, i.e., Nb5+ and Te4+/Se4+, local asymmetric environments occur from the three-dimensional frameworks. Intra-octahedral distortions along the local C-4 direction and asymmetric trigonal pyramidal coordination moieties generated by stereoactive lone pairs are observed from the NbO6 octahedra and TeO3 (or SeO3) polyhedra, respectively. Thermogravimetric analysis, infrared and UV-vis diffuse reflectance spectroscopies, elemental analysis, out-of-center distortions, dipole moment calculations, and electronic structure calculations for the reported materials are presented. (C) 2015 Elsevier B.V. All rights reserved.