Elaboration and Characterizations of Glasses/Glass‐Ceramics in the Na ₂ O–V ₂ O ₅ –TeO ₂ System for Energy Storage Applications

ABSTRACT Glasses and corresponding glass‐ceramics were studied in the Na ₂ O–V ₂ O ₅ –TeO ₂ (NVT) system. The thermal and electrical properties, as well as the structure of parent glasses, were determined by differential scanning calorimetry (DSC), electrochemical impedance spectroscopy measurements (EIS), and pair distribution function (PDF), respectively. The V ⁴⁺ /V ⁵⁺ ratio in the parent glasses was estimated by X‐ray photoelectron microscopy (XPS). While only one crystalline phase has already been discovered in the NVT system, this thorough experimental study evidences the stabilization of several novel crystalline phases through the glass crystallization process. An attempt to solve one of these structures, (Te _0.66 Na _0.34 ) ₂ V ₂ O ₈ , is described in the present study. The glass‐ceramics were produced by the spark plasma sintering (SPS) technique and characterized by X‐ray diffraction (XRD) and scanning electron microscopy (SEM). An overall increase in the electrical conductivity from the parent glass to its corresponding glass‐ceramic is observed up to five orders of magnitude for some compositions, to be related to the microstructure and the nature of the stabilized crystalline phase.