Electronic to ionic conductivity of glasses in the Li 2O–V 2O 5–TeO 2 system

Abstract

Glasses in the 3TeO 2 xLi 2O(1− x)V 2O 5 system have been synthesised for 0≤ x≤1. Conductivity data obey an Arrhenius type behaviour between room temperature and the glass transition temperature. The isothermal conductivity curves exhibit a sharp minimum near x=0.5. Values of activation energies and pre-exponential factors in the V 2O 5 rich region are lower compared to those in the alkali oxide rich region implying that the conductivity mechanisms in these two regions are different. Experimental values suggest that an electronic conductivity by polaron hopping between V VI and V V cations would prevail in the first region. In the alkali oxide rich region, ionic conductivity would operate by an interstitial pair mechanism between non-bridging oxygens. The very low conductivity expected for x=0.5 could be explained by assuming that, for this composition, both ionic and electronic paths would not percolate any more.