Dielectric study on relaxor-like phase transition of lanthanum doped bismuth layer-structured ferroelectrics

Lanthanum doped bismuth layer-structured ferroelectrics and its intergrowth type, SrBi4-xLaxTi4O15, Sr2LaxBi4-xTi5O18, and (Bi, La)(4) Ti3O12-Sr(Bi, La)(4)Ti4O15, have been prepared by solid-state reaction method. The dielectric properties of those materials are measured. The results show that SrBi4-xLaxTi4O15 (x = 1.0), Sr2LaxBi4-xTi5O18 (x greater than or equal to 0.5), (Bi, La)(4) Ti-3 O-12-Sr (Bi, La)(4)Ti4O15 (x = 1.50) exhibit typical relaxational characteristics. The degree of diffuseness and relaxation increased with increasing La3+ content. The origin of relaxation is the microdomain induced by La3+ doing. The micromechanism corresponding to the transition between normal ferroelectrics and relaxors is explained as the transition from the macrodomain of normal ferroelectrics to the microdomain of relaxors.