Residual strains and dielectric properties of Pb/sub 0.7/La/sub 0.2/TiO/sub 3/-based perovskites

A correlation between the local structural distortions and dielectric behaviors of Pb/sub 0.7/La/sub 0.2/TiO/sub 3/ (PLT-A20) was developed on the basis of XRD residual strain analyses. It was observed that A-site iso-valent substitutions with various ionic sizes, i.e. Ba/sup 2+/ and Sr/sup 2+/, generate tensile and compressive lattice mismatch strains, which are balanced delicately by the long-range Coulombic forces and short-range repulsions, leading to a breakdown in dipolar long-range order. Thus, both dielectric transition from normal ferroelectric to relaxor and enhancement in diffuse phase transition (DPT) are observed by increasing the level of Ba/sup 2+/ and Sr/sup 2+/ substitution in PLT-A20, respectively.