Ferroelectric crossovers triggered by isovalent A-site substitution in Pb0.7La0.2TiO3

Abstract

A -site isovalent substitutions trigger ferroelectric transitions in Pb0.7(1−x)A0.7xLa0.2TiO3, where A=Ca, Sr, or Ba. The transitions are dependent on the type and amount of substitutions such as Ca2+, Sr2+, and Ba2+. A transition from normal ferroelectric (FE) to relaxor FE (RFE) is induced by Ca2+, Ba2+, and Sr2+ substitutions at x=0.30, 0.40, and 0.60, respectively. Interestingly, a further crossover to quantum paraelectriclike behavior occurred in Pb0.7(1−x)Ca0.7xLa0.2TiO3 with x=0.60, in addition to the transition from FE to RFE. The observed ferroelectric crossovers and temperature dependence of relative permittivity ε′(T) can be correlated to the structural parameters and breakdown in long-range polar order brought by the A-site isovalent substitution.