Abstract: 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. In the present paper, the structure of PbBr₂-PbF₂-P₂O₅ glasses was characterised 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 60mol%, most of Pb²⁺ ions act as network modifier. When P₂O₅ content decreases to 50mol%
and even 40mol%, some Pb²⁺ ions could enter glass network and form [PbO₄] tetrahedron or P--O--Pb linkage with decreasing P_₂O_₅ 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.

Key words: PbBr₂-PbF₂-P₂O₅ glasses, FTIR, XPS, structure