钨酸铅晶体及其熔体结构的高温拉曼光谱研究

High Temperature Raman Spectra and Structure Study of Stolzite-Structured PbWO_4 Crystals and Its Melt

测量了升温条件下(298～1473K)钨铅矿型钨酸铅(PbWO4)晶体及其熔体的拉曼光谱,确定了各振动模的归属,其中波数902.7cm-1的最强拉曼峰为[WO4]四面体的内振动光学模式ν1(Ag),属于对称伸缩振动。同时,随温度上升,谱峰展宽并伴随强度减弱,体系内无序化程度增加。至1398K晶体初步熔化,并且在1473K完全熔融,高温熔体谱中自由[WO4]2-结构单元的内振动模式显现,同时发生了由晶体固定晶胞的S4型对称性向熔体中[WO4]2-结构单元的Td型对称性的结构转化,表明PbWO4的熔体中存在相对孤立的[WO4]2-结构单元。

Raman spectra of stolzite-structured PbWO4 crystal were recorded from 298 to 1 473 K.All the appearing vibrational modes were interpreted and assigned.The most intense mode at 902.7 cm^-1,which is identified as the internal mode ν1（Ag）of symmetrical stretching attributed to the vibration of [WO4]^2-tetrahedron.Temperature dependent characteristics of the Raman spectra of the crystal were investigated.Band half-widths widened accompanied by the relative intensity decreased,and the lattice became more disorder with the increase in temperature.As being heated up to 1 398 K,PbWO4 crystals began to be melting and have completely transformed to liquid state at 1 473 K,while the internal vibrational modes of isolated [WO4]^2-tetrahedron have appeared and the symmetry of vibrational modes transformed from S4 in crystal into Td of [WO4]^2-in melt.It suggested that the isolated [WO4]^2-structure unit exists in the melt.