Mixed ionic and electronic conductivity in the quaternary V2O5–Na2O–ZnO–P2O5 glass system

Abstract

The melt quenching method was adopted to synthesize glasses with the formula xV2O5–(0.4-x) Na2O–0.35ZnO–0.25P2O5 (x = 0.05, 0.1, 0.15, 0.2, and 0.25). X-ray diffraction patterns for the x = 0.05 sample showed the complete amorphous structure, whereas other composites revealed the development of nanocrystallites over the amorphous glassy networks. DSC measurement showed that glass transition temperature reduced as V2O5 concentration rose, and values were consistent with modified CBH model theoretical (fitting) data. DC conductivity for x = 0.05 and 0.1 composites followed an Arrhenius-type relation and linearity against the reciprocal of temperature, revealing ionic conductivity. On the contrary, the electronic or small polaron hopping mechanism was responsible for DC conductivity for all other composites. AC conductivity mechanism was described by the modified correlated barrier hopping model, and ideal glass transition temperatures were predicted (361 °C (x = 0.05) to 412 °C (x = 0.25)). It was observed that with rising V2O5 content (x), there was blockage of ionic pathways of Na+ ions, causing the ionic conductivity to decline and the electronic or small polaronic conductivity to enhance, as the radius of small polaron reduces. AC conductivity scaling property established that the time-temperature superposition principle and the BNN relation did not hold for the systems.