Nature of mixed electrical transport in Ag2O–ZnO–P2O5 glasses containing WO3 and MoO3

Highlights: • Electrical transport studied from 303 to 513 K depends on type of TMO. • In WO₃ glasses. clustering of WO₆ structural units is observed at high WO₃ content. • In MoO₃ glasses dominance of MoO₄ tetrahedra is observed at high MoO₃ content. • Change in transport mechanism reflects on the shape of the complex impedance plot. • Ag⁺ ions show significantly higher mobility then Li⁺ and Na⁺ ions. This study reports on the nature of electrical transport and role of structural changes induced by different type and content of TMO in Ag–containing glasses of xTMO–(30–0.5x)Ag₂O–(30–0.5x)ZnO–40P₂O₅ (TMO = MoO₃/WO₃, 0 ≤ x ≤ 60 mol%) composition. Raman spectra show clustering of WO₆ units in glasses with high WO₃ content while the addition of MoO₃ induces a gradual change of MoO₆ octahedra to MoO₄ tetrahedra both being cross-linked with phosphate units without clustering. For WO₃ glasses, minimum in DC conductivity is observed at 30–40 mol% of WO₃ for temperatures from 303 to 513 K, followed by an increase in conductivity with further WO₃ addition due to an increase in polaronic contribution. Observed turnover suggests a distinct transition from predominantly ionic to predominantly polaronic transport. On the contrary, for MoO₃ glasses, conductivity decreases in the whole mixed compositional range indicating that the nature of transport is dominated by ionic component throughout the measured temperature range. A comparative study of Ag⁺, Li⁺, Na⁺ transport in MoO₃/WO₃ glasses reveals a strong correlation between pre-exponential factor and activation energy, which allows detection of the prevalence of conduction mechanism. Finally, the results demonstrate that Ag₂O–WO₃–ZnO–P₂O₅ glass system is a promising electrically tunable material with significant contributions of ionic or polaronic conductivity depending on composition.