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

Abstract

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.