Temperature dependent Raman spectra and micro-structure study of hexagonal MgTiO3 crystal

Hexagonal MgTiO3 crystal powder is prepared by solid-phase sintering method and characterized by X-ray diffraction method. Temperature dependent crystal cell parameters (2931473 K) are deduced from the results of in-situ X-ray diffraction measurement with temperature increasing. In-situ Raman spectra are recorded (2931623 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.