钙铝榴石-钙铁榴石固溶体的拉曼光谱

Raman Scattering of Grossular-Andradite Solid Solution

为了研究Al3+-Fe3+离子替代对固溶体结构的影响,进行了钙铝榴石-钙铁榴石固溶体的拉曼光谱研究。结果表明:钙铝榴石、钙铁榴石端元分别观测到20和19个拉曼峰,多数峰位随成分呈连续、线性变化,光谱中未发现双模式振动;中频峰峰位变化较大,可能与结构联动或耦合振动有关;由于结构对称性降低,振动光谱中发现了额外峰;拉曼峰宽化现象与有序度降低及结构的畸变有关。通过单参数的Margules方程拟合半峰宽,预测了固溶体的混合焓特征。

The effects of Al3+-Fe3+substitution on 10 synthesized garnet samples along the grossularandradite binary were investigated using Raman spectroscopy.Twenty and nineteen peaks were observed in non-polarized Raman spectra for grossular and andradite end-members,respectively.The frequencies of most peaks were changed almost linearly with the composition.Two-mode behavior was not observed in this study.Differing from previous reports on other garnet solid solutions,the medium frequency modes,which are assigned to internal bending vibrations,have the largest average rate of change with the composition,which may be related to structural connectivity and coupled vibrations.Due to the reduction of symmetry,extra peaks appear in the Raman spectra of garnets with intermediate compositions.Peak broadening in intermediate compositions was also observed,which is related to disordering and distortion.One-parameter Margules equation was used to describe the full width at half maximum of peaks,and a relationship with enthalpy of mixing was proposed.