Optical and magnetic characterization of pure and vanadium-doped Bi12TiO20 sillenite crystals

Visible and Infrared (IR) optical absorption, Raman scattering and Electron Paramagnetic Resonance (EPR) techniques were used for systematic characterization of sillenite type crystals: nominally pure Bi12TiO20 (BTO) and doped with vanadium (BTO:V). IR and Raman scattering results showed that the most conspicuous difference between BTO and BTO:V was the appearance of a band, at 767 cm(-1) and at 790 cm(-1), attributed to the (VO4)(-3). EPR, at 20 K, led us to suggest that the valence state of vanadium ions in BTO is 5+. In pure BTO samples, anisotropy of the EPR spectra at 20 K may be related to Fe3+ impurities coming from starting compounds plus the presence of the (Bi-M(3+)+h(O)(+)) intrinsic defect. Results obtained from these different techniques confirm the Oberschmid and Grabmaier model [R. Oberschmid, Phys, Stat. Sol. (a) 89 (1985) 263; B.C. Grabmaier, R. Oberschmid, Phys. Stat. Sol. (a) 96 (1986) 199]. (C) 1999 Elsevier Science B.V. All rights reserved.