Vanadium characterization in BTO: V sillenite crystals


Visible and Infrared Optical Absorption and Electron Paramagnetic Resonance (EPR) techniques have been used to characterize the intrinsic defects in sillenite type crystals: nominally pure Bi12TiO20 (BTO) and doped with vanadium (BTO:V). Optical quality crystals, with the composition Bi12.04±0.08Ti0.76±0.07V0.16±0.02O20, have been grown. Results obtained by these different techniques have shown unambiguously the 5+ valence state of the vanadium ion in BTO:V crystals. In pure BTO samples, the EPR and optical spectra show strong evidence of the presence of the intrinsic defect BiM 3+ + ho +, which consists of a hole h+, mainly located on the oxygen neighbors of the tetrahedrally coordinated Bi3+ ion. After doping with vanadium, results have shown that the characteristic bands, associated to this hole defect center, disappear, suggesting its transformation in single Bi3+. Anisotropy of the EPR spectra , at 20 K, is related to Fe3+ impurities.



Sillenite, Photorefractive, Defects, BTO


CARVALHO, J. F.; FRANCO, R. W. A.; MAGON, C. J.; NUNES, L. A. O. ; PELLEGRINI, F.; HERNANDES, A. C. Vanadium characterization in BTO: V sillenite crystals. Materials Research, São Carlos, v. 2, n. 2, p. 87-91, 1999.