Effect of Mixed Transition Metal Ions on DC conductivity in Lithium Bismuth Borate Glasses.

The DC conductivities of glasses having composition x(2NiO·V₂O₅)·(30-x)Li₂O·20Bi₂O₃·50B2O₃ (with x=0, 2, 5, 7 and 10, i.e. NVLBB glasses) and glass samples having composition 7NiO·23 Li₂O·20Bi₂O₃·50B2O₃ and 7V₂O₅·23Li₂O·20Bi₂O₃·50B2O₃ (NLBB and VLBB respectively) are investigated as a function of temperature. Conductivity for glasses containing higher percentage of lithium ions is predominantly ionic and in glasses containing higher percentage of transition metal (TM) ions is predominantly electronic. The observed increase in conductivity with x and peak-like behavior at x=7 in NVLBB glasses due to competitive transport of small polaron contributing to a significant structural change in NVLBB glasses. Variation of molar volume and density was also observed with x. In NVLBB glasses, as x increases density increases except a slight decrease at x=7. Also density increases in NLBB whereas in case of VLBB it decreases in comparison to NVLBB1 glass composition. Mott's small polaron hopping (SPH) model has been applied to analyze the high temperature conductivity data and activation energy. [ABSTRACT FROM AUTHOR]