Effect of heat treatment in the electrical properties of bismuth-vanadium oxide glasses

With the aim of elucidating the reasons for the change in the electrical properties of bismuth-vanadium oxide glasses under the action of heat treatment, this paper discusses some data on the effect of heating on the temperature dependence of the electrical conductivity and integrated intensity of the ESR signal for glasses of the composition 78.33V2O5-5.74Bi /SUB 2O/ <3-15.88CaO (mole %). The heat treatment includes heating the specimens of untreated glass in air for 15 minutes at various temperatures. The ESP was measured using a standard RE-1306 radiospectrometer. It is shown from the experimental ESR data that after heat treatment the concentration of V4+ ions increases in the experimental glass. It is proposed that the increase in the electrical conductivity of the Bi2O3-V2O5-CaO system after heat treatment is explained by the increase in the concentration and size of the CaV12O30 crystallites. The latter is confirmed by an increase in the integrated intensities of the ESR signal after the glass has been heated