The change of the local environment of MnO incorporated in the lead-germanate glassy network

Abstract InfraRed, UltraViolet–visible and Electron Paramagnetic Resonance Spectroscopies were employed to investigate the xMnO ∙(100 − x)[7GeO2 ∙ 3PbO2] vitreous system, where x = 0–50 mol% MnO, in order to obtain valuable information about the competitive role played by the manganese ions in manganese-lead-germanate network formation. Our results evidenced that the local environment of the manganese ions was modified depending on the MnO content of samples. As a result of this fact, the presence of manganese cations in these samples increases the structural disorder by breaking some of the Ge–O bonds and formation of non-bridging oxygen ions. Variations in optical gap energy and resonance EPR lines are also attributed to the structural modifications of the local environment of the manganese ions. This compositional evolution can be explained considering that the addition of MnO to the host matrix causes a progressive conversion of lead-germanate glassy network leading to the formation of non-bridging oxygen ions and further, to the decrease of the strength of the glass structure by the interconnection of the new structural units.