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

Abstract Glasses and glass ceramics of the x MoO 3 (100− x )[7GeO 2 ·3PbO] system where x =0–30 mol% MoO 3 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 MoO 3 concentration. The spectroscopic studies indicate that with increasing of MoO 3 content a fraction of the Mo 6+ ions convert Mo 3+ and Mo 5+ ions. Accordingly, these modifications cause the depolymerization of the host network, the increase of the structural disorder and formation of GeO 2 and PbMoO 4 crystalline phases. The shape of EPR spectra is modified by the increase of the MoO 3 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 MoO 3 content up to x ≥15 mol%, the presence of the hyperfine structure characteristic for the Mo 5+ ions can be observed, too. The electrochemical performances of the glass and glass ceramics samples with x =10 and 30 mol% MoO 3 were demonstrated by cyclic voltammetry.