Potassium doping of semiconducting vanadium tellurate glasses

dGlasses of the ternary system 2TeO(2)xK(2)O(1 - X)V2O5 have been prepared for x = 0.0, 0.2. 0.4, 0.6, 0.8 and 1.0mol%. For each composition only one glass transition T-g is observed in the temperature range 497-517 K. For each composition, the conductivity data were obtained in the temperature range 323-473 K, using impedance techniques. They obey an Arrhenius relationship with a composition independent pre-exponential factor. The isothermal conductivity curves exhibit a sharp minimum near x = 0.5. The experimental data suggest that a polaron hopping mechanism operates in the electronically conducting domain of 0 less than or equal to x < 5 and an interstitial pair mechanism operates in the ionically conducting domain of 0.5 < x less than or equal to 1. 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. (C) 2002 Elsevier Science B.V. All rights reserved.