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) A0.7x La0.2 Ti O3, 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) Ca0.7x La0.2 Ti O3 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. © 2006 American Institute of Physics.