Order-degree-modulated ferroic response and an unconventional electrocaloric effect in B-site complex systems: a case study in Pb[(Yb1/2Nb1/2)0.84(Mg1/3Nb2/3)0.16]O3 ceramic

Abstract

The order-degree-modulated ferroic response and electrocaloric effect (ECE) in Pb(B1,B2)O3-type B-site complex antiferroelectrics (AFEs) are explored in this work. The results show that local/phase structure and dielectric/ferroic properties are strikingly dependent on the degree of order (high, intermediate and low for samples S1, S2 and S3, respectively). A decrease in the content of the AFE orthorhombic phase and an increase in the weakly polar disorder phase is observed from S1 to S3, accompanied by an enhanced relaxation behavior with a smearing of the AFE-to-paraelectric phase transition. Ferroic and EC responses in the three samples present distinct features. Antiferroelectricity wakes-up significantly in sample S1, which boosts the ECE to ∼0.95 K and is almost three times that of S3 (∼0.23 K). An abnormal ECE [negative ECE with a hop–hop character and asymmetrical electrocaloric (EC) response] is unexpectedly found in sample S1. The underlying mechanism is unveiled by dipolar relaxation and phenomenology analysis, which states that the AFE coupling strength dominates the EC performance in this AFE. This work not only presents a refreshing method for order-degree regulation of the ECE in B-site complex AFEs, but also clarifies the possibility that AFEs with robust dipolar coupling strength have an unconventional ECE.