Abstract
The temperature dependence of EXAFS Debye-Waller factors in La0.63Ti0.92Nb0.08O3 perovskite with cation deficiency was investigated with the cumulant expansion method. The measurements of the Ti and Nb K-edge and La L3-edge EXAFS spectra were carried out in the transmission mode at temperatures up to 800 K. The obtained local bond distances of 1.95(1) angstrom for Ti-O, 1.98(1) angstrom for Nb-O and 2.65(1) angstrom for La-O are significantly smaller than the expected values on Shannon's radii. This characteristic is attributable to the presence of the cation deficiency. The effective pair potentials, V(u) = alpha u(2)/2 + beta u(3)/3, were evaluated and the potential coefficients alpha and beta for the Ti-O bond in La0.63Ti0.92Nb0.08O3 are 6.6(1) eV/angstrom(2) and -42(3) eV/ angstrom(3), respectively. The Ti-O bond in the A-site-deficient La0.63Ti0.92Nb0.08O3 has relatively larger anharmonic and soft potential coefficient than that in ordinary CaTiO3 perovskites.