Wan Song-Ming

High temperature Raman spectroscopic study of the micro-structure of a caesium triborate crystal and its liquid

Raman spectra of a caesium triborate (CBO) crystal at different temperatures up to the melting temperature have been recorded. All of the peaks of corresponding to the crystal broaden and decrease in wavenumber with increasing temperature. The vibrational modes of the CBO crystal, in which the basic structural unit is the triborate group (B3O7)5−, have been simulated using a plane-wave pseudopotential method. An isomerization reaction from four-coordinated boron to a three-coordinated species was observed during the melting process. The continuous three-dimensional network of the crystal collapsed and transformed into spiral chains that consist of (B3O6)3−groups during the melting process. Detailed spectral analysis is also competently explained by applying quantum chemistry ab initio calculations.

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 50 μm.

Preparation and Characterization of Y3Sc2Ga3O12 Nano-Polycrystalline Powders by Co-Precipitation Method

Abstract In order to grow high-quality gallium garnet crystals, polycrystalline materials were used as starting materials. YSGG precursor was synthesized by co-precipitation method using aqueous ammonia as a precipitator, and the precursor was then sintered at different temperatures. The results showed that the feasible pH range was 8.3 ∼ 9.84 in the process of co-precipitation reaction. The YSGG precursor and the powders sintered at different temperatures were characterized by IR, XRD and TEM methods. It was found that the precursor transformed to pure YSGG polycrystalline phase at 800 °C. YSGG nano-polycrystalline powders sintered at 800 ∼ 1000 °C were well dispersed and the sizes of the YSGG grains were about 40 ∼ 100 nm.

Investigation of the Cr:LiSrAlF6 crystal by high-temperature Raman spectroscopy

In this paper, Cr-doped LiSrAlF6 crystals are investigated using high-temperature Raman spectroscopy and the single-crystal Raman spectra of Cr:LiSrAlF6 are analysed by factor group theory and comparison with other fluorides. The results indicate that Cr:LiSrAlF6 is stable below its melting point; Raman peaks located at 561, 322 and 250 cm−1 are assigned to the A1g modes of AlF6, SrF6 and LiF6 octachdra, respectively; with temperature increasing, Raman peaks associated with AlF6 octahedra shift towards low frequencies, while LiF6 and SrF6 octahedra are temperature-insensitive; around the crystal melting point, three new Raman peaks occur, which are associated with the AlF6 octahedral chain structure. Finally, the microstructural evolution of Cr:LiSrAlF6 from room temperature to its melting point is discussed based on its Raman spectra.

High-Temperature Raman Investigation on Phase Transition of LBO Crystal

The high-temperature Raman spectroscopy technique is applied to investigate the phase transition of LiB3O5 crystal. The result shows that the crystal is stable in the range of 293–893 K. When the temperature increases up to above 1107K, the phase transition occurs. In the liquid phase, Li2B4O7 crystal precipitates out. Up to 1173K, the Li2B4O7 crystal disappears in the melt.

Study on the growth and luminescence characterization of Cr/Nd:GLSAG crystal

The Cr/Nd:GLSAG crystal were grown by Czochralski method, its structure and luminescence properties were studied, which show that the luminescence properties of Nd³⁺ ions were improved by co-doping Cr³⁺ ions and adjusted by mixed garnet.