Structure, Optical Absorption and Photochromic Effect in Rb0.95Nb1.375Mo0.625O5.79

The compound with beta-pyrochlore structure with rare for structure type symmetry (orthorhombic, Pnma) has been prepared recently. In polycrystalline sample Rb0.95Nb1.375Mo0.625O5.79 with beta-pyrochlore structure type prepared by solid-state reaction, the diffuse reflection and transmission spectra have been studied. The spectral dependence of the photochromic effect and the temperature dependence of its kinetics have been investigated. It was found that Rb0.95Nb1.375Mo0.625O5.79 is an indirect-gap semiconductor with band gap of 3 eV. A study of the transmission spectrum and a detailed investigation of the photochromic effect made it possible to determine some characteristics of the deep impurity defect level and make a conclusion about the energy ranges in which the Fermi level can be localized in a band gap.