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) Å for Ti-O, 1.98(1) Å for Nb-O and 2.65(1) Å 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) = αu2/2 + βu3/3, were evaluated and the potential coefficients α and β for the Ti-O bond in La0.63Ti0.92Nb0.08O3 are 6.6(1) eV/Å2 and −42(3) eV/Å3, 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.
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