Electronic conductivity and structural chemistry in Li–Te–V5+,4+ oxide glasses

Abstract The electronic conductivity of the Li2O–Te2V2O9 glass system reveals that, even for high lithium content, electron hopping occurs between V4+ and V5+. The study of the V4+ content versus various syntheses shows that more than lithium content, the nature of the counter ion used in Li+ reagent and its decomposition behavior are responsible for the efficiency of the spontaneous V5+ reduction via a ‘sprouting’ phenomenon. The electron hopping process implies interconnection of VOn polyhedra which are accessible for both V4+ and V5+ species. Such fact gives information about short and medium range ordering in the glasses. On the basis of the LiVTeO5 crystal structure and in agreement with wide angle X-ray scattering experiments, a possible rearrangement bringing together VO5 square pyramids is proposed to explain the electron hopping. Such proposal corresponds to a lithium network forming effect. It could explain why for Li/V>1 the electronic conductivity increases with lithium content while the V4+ amount remains low.