摘要:
采用固相烧结法制备了六方晶型结构的MgTiO3粉体.经高温原位X射线衍射分析（293—1473K）进行了表征与确认,获得了晶胞参数及其随温度的变化,测量了高温原位拉曼光谱（273—1623K）,并运用第一性原理理论计算方法对应核实了拉曼谱峰的归属.结果表明,随着温度升高,MgTiO3晶面间距和晶格常数增大,从而反映对于拉曼光谱较为敏感的键长和键角的变化;温致拉曼位移可以反映Ti—O,Mg—O等键长以及Ti—O—Ti,Ti—O—Mg与Mg—O—Mg等键角随温度的细微变化,相关关系则独立于温度,有效提升了原位拉曼光谱微探针诊断技术的分析能力;拉曼谱峰随温度升高而展宽,表明原子瞬间运动振幅加剧,弥散性增加,稳定性有所下降,但仍维持六方晶型.
Abstract:
Hexagonal MgTiO3 crystal powder is prepared by solid-phase sintering method and characterized by X-ray diffraction method.Temperature dependent crystal cell parameters（293—1473 K） are deduced from the results of in-situ X-ray diffraction measurement with temperature increasing.In-situ Raman spectra are recorded（293—1623 K） at various temperatures and all the vibrational modes were assigned with the aid of theoretical calculation of first principles.It is demonstrated that temperature dependent Raman spectra are sensitive and can show the delicate variations of different bond lengths and angles between various atoms of local structure.But the relationship between Raman shift and bond length and angle can be independent of temperature.Those observed Raman vibrational bands being wider and overlapped with the increasing temperature reveals the enhanced amplitude of atomic instantaneous movement,which leads atoms to diffuse more heavily and the stability of the crystal to decrease,although MgTiO3 remains hexagonal crystal type.
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