Local distortion around the guest ion in perovskite oxides

In transition metal (M) oxides, partial substitution of guest (Mg) for host (Mh) elements causes local distortion via the difference in the ionic radius (r). Here, we systematically investigated the local structures in the pure (x = 0.0) and mixed (x = 0.1) perovskite oxides, LaM^h _1-x,M^g _x O₃, by means of extended X-ray absorption fine structure (EXAFS) analysis. We found that the local distortion [ϵ≡√(1/3)Σ_x,y,z(Δd^h _ad)² where Δd^h _adis the variation in the adjacent Mh-O bond length] in a mixed compound, was smaller than that in the virtual compound, in which the M^h-O bond length had an ideal value. This empirical relation is useful for designing a functional material by partial substitution.