Role of Heavy Metal Ions in the Formation of Oxyfluoride Glasses and Glass Ceramics

In order to investigate the influence of different heavy metal ions on the formation of the oxyfluoride glasses and glass ceramics, samples with different PbF2/CdF2 ratios have been prepared by the melting quenching and thermal treatment method. The different effects of Pb2+ and Cd2+ on the glass network structure are investigated by FTIR and Raman spectra. During the formation of glass network structure, Pb2+ prefers to break the Si-O-Si bond and subsequently bond to F- for charge compensation, and Cd2+ prefers to break the Si-O-Al bond and is surrounded by O2-. Pb2+ and F- gather together and form the fluoride nanocrystals, while Cd2+ remains in oxide matrix after thermal treatment. Introduction of proper CdF2 is important to adjust and control the glass network structure and crystallization process in the fabrication of the transparent glass ceramics.