Electrical conductivity anomaly in silver vadadium-tellurite glasses at temperatures higher than a characteristic temperature: evidence for an ionic-nonadiabatic polaronic mixed conduction

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Abstract:

Electrical conduction anomaly was observed in the mixed ion-polaron regime for xAg2O-40TeO2-(60-x)V2O5 glassy system with 0 ≤x≤ 50 mol%, which were prepared by common melt quenching method. For the understudied glasses, the temperature dependence of dc electrical conductivity was measured from a characteristic temperature to 380 K, which certified their semiconducting nature. The measured conductivity values at a typical temperature of 300 K were within the range of 5.88×10-7-3.33×10-3 Scm-1, which indicate the decreasing trend of electrical conductivity with increasing of silver oxide content for x=0- 30 and an increasing trend for x=40-50. With increase of Ag2O content within the range of 20 ≤x≤ 50, and especially for x≥40 mol%, the conduction mechanism changes from polaronic to ionic-polaronic, which is an evidence for the anomaly in conduction mechanism. For the present samples, at temperatures above a characteristic temperature, the electrical conduction mechanism obeys the non-adiabatic small polaron hopping (NASPH) between the vanadium ions, and the values of charge carrier mobility and charge carrier density, as important parameters in electrical investigations, were determined in NASPH regime. Also, the study of the density of non-bridging oxygens (NBOs) indicates the effect of Ag2O on the glass thermal stability and fragility, implying on the sample with critical x=20as the highest thermal stable glass.

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