Comprehensive characterization of xV₂O₅-(0.3-x)Li₂O-0.35TeO₂-0.35P₂O₅ glasses: Influence of V₂O₅ concentration on thermal and dielectric properties

Glassy specimens with the composition xV₂O₅-(0.3-x)Li₂O-0.35TeO₂-0.35P₂O₅ (x = 0.05, 0.10, 0.15, and 0.20) were synthesized via the conventional melt-quenching technique. The structural, thermal, and dielectric properties were systematically analyzed to understand the influence of vanadium pentoxide (V₂O₅) concentration on the glass network. The results indicate that increasing V₂O₅ content enhances the glass transition temperature (T_g) and thermal stability due to the formation of VO₄ structural units, which strengthen cross-linking with phosphate chains, increasing the rigidity of the glass network. FTIR spectroscopy also affirms the depolymerization of the phosphate glass network by systematic conversion of metaphosphate chains with the inclusion of vanadium ions. Dielectric analysis reveals a significant rise in permittivity, attributed to small polaron hopping enabled by mixed-valence vanadium ions (V⁴⁺/V⁵⁺). Impedance spectroscopy confirms a transition from ionic to mixed ionic-electronic conduction, evidenced by decreasing bulk resistance at elevated temperatures. The incorporation of V₂O₅ facilitates polaron hopping conduction, influencing charge transport and energy storage capabilities. The composition-dependent permittivity enhancement and systematic bulk resistance reduction suggest tunable dielectric and electrical properties. These findings highlight the potential of these glassy systems for high-energy storage applications, solid-state electrolytes, and electrochemical capacitors.