Vanadium characterization in BTO: V sillenite crystals

Materials Research

J.f. Carvalho²  R.w.a. Franco¹  C. J. Magon¹  L.a.o. Nunes¹  F. Pellegrini²  A.c. Hernandes¹ 

[1] ,Universidade Federal de GoiásGoiânia GO ,Brazil

关键词: sillenite;    photorefractive;    defects;    BTO;   

DOI  :  10.1590/S1516-14391999000200008

来源: SciELO

【 摘 要 】

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 BiM3+ + 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.

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