磷酸钠结构的高温拉曼光谱研究

用高温拉曼光谱仪测定了固态和熔融态磷酸钠(Na3PO4)晶体的光谱,分析了磷酸钠晶体的结构及其随温度的变化。通过对从常温谱到高温谱的解析,得出主峰波数随温度的变化及主峰半高宽的变化,可以观察到在600 K附近及1773 K有两个相变产生。此外,磷酸钠晶体的相关高温DSC检测分析,也和拉曼谱中发现的两个相变符合。量子化学理论计算同时对该体系的P-O键振动和平均键长进行了模拟,随着键长的增加,对应的振动频率会降低。还确认了磷酸钠Raman光谱中各个峰的归属,938 cm-1波数处的峰属于(PO4)3-中P-O键的对称伸缩振动,是Na3PO4的特征峰,425及580 cm-1处峰属于磷氧四面体的弯曲振动。

High Temperature Raman Spectral Study of Sodium Phosphate Structure

The high temperature Raman spectra of Na3PO4 crystal and its liquid were measured. The structure of Na3PO4 crystal and its change with temperature were analyzed. From the resolution of the room and high temperature spectra, the temperature dependent Raman shifts and FWHH were observed. It was suggested that there were two phase transitions that occurred around 600 and 1 773 K respectively. The high temperature DSC results also indicated the two phase transitions. It is consistent with the results of the Raman spectra analysis. Gaussian 98W program was also applied to calcukting the Raman frequencies of vibrational modes and the average P-O bond length. And the calculation results were evaluated. When the bond length increased, the corresponding Raman shift decreased. This paper also generally concluded the assignment of the different peaks in the Raman spectra. Raman shift at 938 cm-1 wavenumber was assigned to the symmetry stretch mode of the P-O bond in the (PO4 )3- tetrahedra. It was the dominant peak in the Raman spectrum of the Na3PO4 crystal.