Enhancement of electrical conductivity in lithium vanadate glasses by nanocrystallization

Electronically conducting nanomaterials were prepared by annealing glasses of the Li2O–V2O5–P2O5 system at crystallization temperature Tc. The electrical conductivity was measured for initial glassy samples and during the thermal treatment up to 400 °C. The presence of crystalline V2O5 grains formed after annealing at Tc was confirmed by X-ray diffractometry (XRD). The average size of these grains was estimated to about 30 nm. The nanomaterials obtained by annealing at Tc exhibit much higher conductivity (up to 10−1 S/cm at 360 °C) and much lower activation energy (E=0.27 eV) than the initial glasses. Moreover, such nanomaterials are thermally stable up to Tc=360 °C whereas the initial glasses of that composition are stable only to T=260 °C. This considerable enhancement of electrical conductivity after nanocrystallization is ascribed to formation of extensive and dense network of electronic conduction paths which are situated between V2O5 nanocrystals and on their surfaces. Further annealing at higher temperature T=398 °C leads to considerable growth of V2O5 crystallites (up to 1 μm) and formation of other crystalline phase. These phenomena lead to disappearance of aforementioned “conduction tissue” for electrons and substantial reduction of electronic conductivity.