Dieletric anomalies in Pb 0.7 ( 1-x) Ca 0.7x La 0.2 Ti O 3

Abstract

Transitions from ferroelectric to relaxorlike and then to quantum paraelectriclike behavior occur in Pb0.7 (1-x) Ca0.7x La0.2 Ti O3 (PCLT) with increasing x from 0.05 to 0.60. The relaxorlike behavior, which can be well fitted to the Vogel-Fulcher relation, is clearly demonstrated by the frequency dispersions of permittivity. More interestingly, a thermal hysteresis of ∼5 K was observed in the temperature dependences of real and imaginary permittivity (ε′ and ε″) for PCLT with x=0.40 under both zero-field cooling and zero-field heating conditions. The compositional dependence of transition temperature Tmax vanished with a finite slope, contrary to that of the quantum ferroelectric relation Tmax ∝ (x- xc) 0.5. © 2005 American Institute of Physics.