Photoluminescence behavior in MgTiO3 powders with vacancy/distorted clusters and octahedral tilting

MgTiO3 powders were prepared by the complex polymerization method and heat treated at different temperatures for 2 h. These powders were analyzed by X-ray diffraction (XRD), Rietveld refinements, micro-Raman (MR) spectroscopy, X-ray absorption near edge spectroscopy (XANES), ultraviolet–visible (UV–vis) absorption spectroscopy and photoluminescence (PL) measurements. XRD patterns and MR spectra showed that the crystalline powders have a rhombohedral structure. XANES spectra indicated that the local structure of crystalline MgTiO3 powders is composed only by [TiO6] clusters, while the disordered exhibit the simultaneous presence of both [TiO5] and [TiO6] complex clusters into the lattice. UV–vis spectra revealed different optical band gap values as a function of heat treatment temperature. This result can be an indicative of intermediary energy levels within the band gap of this material because of structural defects into the perovskite-type structure. PL behavior was attributed to the structural order–disorder and/or distortions on the [TiO6]–[TiO6] complex clusters.