Dynamic characterization of structural relaxation in V2O5–P2O5 bulk oxide glass

Abstract

In oxide glasses, the microscopic hidden flow and the structural origin of the glass-to-liquid transition (GLT) are unclear due to the lack of detailed structural information. Herein, we investigate the evolution of the microscopic localized flow during GLT in a V₂O₅–P₂O₅ bulk oxide glass (BOG) by combining differential scanning calorimetry, temperature- and frequency-dependent bending experiments and stress relaxation spectra. The characteristic changes, their intrinsic correlations with the GLT process and the complete relaxation process are discussed in detail. We have observed three relaxation stages in the V₂O₅–P₂O₅ bulk oxide glass. Stage (I) corresponds to the nano-scale liquid-like movement with reversible activation of flow units. Stage (II) refers to the cooperative interaction of α and β relaxation, whereas stage (III) represents the glass transition process. In the frequency spectra, we have obtained a different result with metallic glasses by using a quasi-point defect model. When T < 480 K (T_β), the correlation factor χ related to the quasi-point defect concentration is low and nearly constant, whereas, for T > 480 K (T_β), χ shows a linear relationship with temperature. The present study provides useful insights to describe the relationship between the architecture of local atomic arrangements and mechanical properties of oxide glass.