Structure studies of PbBr₂-PbF₂-P₂O₅ glasses

Glasses in the system of PbBr₂-PbF₂-P₂O₅ have low melting temperature, good water durability and good optical properties, which can serve as the host materials of organic-doped scintillator. The structure of PbBr₂-PbF₂-P₂O₅ glasses was characterized by Fourier transfer infrared (FTIR) spectroscopy and X-ray photoelectron spectroscopy (XPS). Results show that lead ions play dual roles, network former and network modifier, in the structure of PbBr₂-PbF₂-P₂O₅ glasses. When P₂O₅ content is 60 mol%, most of Pb²⁺ ions act as network modifier. When P₂O₅ content decreases to 50 mol% and even 40 mol%, some Pb²⁺ ions could enter glass network and form [PbO₄] tetrahedron or P-O-Pb linkage with decreasing P₂O₅ content, while other Pb²⁺ ions still act as network modifier. The length of phosphate chains decreases with decreasing P₂O₅ content. Both Br^- and F^- ions could enter glass network and form [PO_4-nX_n](X=Br or F, n = 0-4) tetrahedron when they reach certain content, breaking [PO₄] tetrahedron and decreasing the length of phosphate chains. The P-O-P linkages content keep unchanged with the same P₂O₅ content. Decreasing P₂O₅ content and increasing lead halide content lead to the formation of P-O-Pb linkage through the delocalization of P=O and P-O^- bonds.