Raman spectroscopy study of sillenites. II. Effect of doping on Raman spectra of Bi12TiO20

Raman spectra of single crystals of Bi12TiO20 doped with various cations, X (X = Al, P, V, Cr, Mn, Cu, Cd, Co, W, Mo, Nd, Ag), were measured. The resu lts show that doping of Bi12TiO20 changes the ratio between the intensities of the transverse and the longitudinal components of the anti-symmetric Ti -O stretching mode. Doping with Ag, Cu and V, generates an additional peak at about 792 cm(-1) resulting from the local symmetric stretching mode of X O4 tetrahedra. Doping with P shifts, the peaks sensitive to the geometry of the BiOn polyhdera, which indicates that the Bi-O framework in Bi12TiO20:P rearranges, in order to embed the second type of tetrahedral cations of a much smaller ionic radius. (C) 1999 Elsevier Science Ltd. All rights reserv ed.