Physical properties and electrochemical performance of molybdenum–lead-germanate glasses and glass ceramics

Glasses and glass ceramics of the xMoO3(100−x)[7GeO2·3PbO] system where x=0–30 mol% MoO3 were synthesized and characterized in order to obtain information about the structural correlations and the relationship between structure and physical properties in these materials. Changes of the FTIR, UV–vis and EPR data are discussed in view of the glass network structural changes determined by the evolution of molybdenum ions state, glass composition and MoO3 concentration. The spectroscopic studies indicate that with increasing of MoO3 content a fraction of the Mo6+ ions convert Mo3+ and Mo5+ ions. Accordingly, these modifications cause the depolymerization of the host network, the increase of the structural disorder and formation of GeO2 and PbMoO4 crystalline phases. The shape of EPR spectra is modified by the increase of the MoO3 concentration indicating that molybdenum ions exists in glass and glass ceramics in more than one valence state. The EPR spectra contain a broad line located at g∼5.2 and, for the samples with a MoO3 content up to x≥15 mol%, the presence of the hyperfine structure characteristic for the Mo5+ ions can be observed, too. The electrochemical performances of the glass and glass ceramics samples with x=10 and 30 mol% MoO3 were demonstrated by cyclic voltammetry.