Optical spectra of doped Bi12TiO20 crystals

Abstract

Single crystals of Bi12TiO20. Both "pure" and doped with various concentrations of V, W, Mo, Nd and Cr, have been studied. Absorption spectra in the energy range 2.0-2.8 eV have been obtained from classical reflection and transmission measurements. The constant-photocurrent method has also been employed in order to study absorption spectra in a wider energy range (1.3-2.8 eV). A well expressed absorption decrease at energies hv>2.2 eV has been observed for Bi12TiO20: 0.056 wt% V and Bi12TiO20: 0.013 wt% Mo crystals. Also, a considerable absorption decrease has been measured at energies hv<2 eV for Bi12TiO20: 0.056 wt% V and Bi12TiO20: 0.008 wt% W. The origin of some new absorption bands observed in doped Bi12TiO20 crystals as well as some differences in the effect of impurities on the optical absorption of Bi12TiO20 and Bi12TiO20 crystals have been discussed.