Zhang Guochun

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.

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.