Optical absorption spectra of reduced transition-metal ion-doped SrTiO₃

The optical absorption spectra of SrTiO3 doped with V, Cr, Mn, Fe, Co, and Ni have been measured as a function of reduction temperature. The high-temperature reduced state was frozen in the crystal by rapid quenching to room temperature. Low-temperature reduction ≲ 1100°C generally produces low valency states of the dopants, but at higher reduction temperatures totally different absorption spectra are produed. These spectra are thought to be intimately related to some aggregation of the high density of oxygen vacancies produced upon high-temperature reduction. © 1984.