Enhancement of electrical conductivity in lithium vanadate glasses by nanocrystallization

Abstract

Electronically conducting nanomaterials were prepared by annealing glasses of the Li 2O–V 2O 5–P 2O 5 system at crystallization temperature T c. The electrical conductivity was measured for initial glassy samples and during the thermal treatment up to 400 °C. The presence of crystalline V 2O 5 grains formed after annealing at T c 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 T c 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 T c=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 V 2O 5 nanocrystals and on their surfaces. Further annealing at higher temperature T=398 °C leads to considerable growth of V 2O 5 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.