Raman Spectrum Analysis on the Solid--Liquid Boundary Layer of BGO Crystal Growth

We study the Raman spectra of Bi₄Ge₃O₁₂ crystal at different temperatures, as well as its melt. The structure characters of the single crystal, melt and growth solid--liquid boundary layer of BGO are investigated by their high-temperature Raman spectra for the first time. The rule of structure change of BGO crystal with increasing temperature is analysed. The results show that there exists GeO₄ polyhedral structure and Bi ion independently in BGO
melt. The bridge bonds Bi--O--Bi and Bi--O--Ge appear in the crystal and at the boundary layer, but disappear in the melt. The structure of the growth solid--liquid boundary layer is similar to that of BGO crystal. In the melt, the long-range order structure of the crystal disappears. The thickness of the growth solid--liquid boundary layer of BGO crystal is about 50μm.