Order-degree-modulated ferroic response and an unconventional electrocaloric effect in B-site complex systems: a case study in Pb[(Yb_1/2Nb_1/2)_0.84(Mg_1/3Nb_2/3)_0.16]O₃ ceramic

Abstract

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. Results show that local/phase structure and dielectric/ferroic properties are strikingly dependent on order degree (high, intermediate and low order degree for S1, S2 and S3 sample, respectively). A decrease in AFE orthorhombic phase and increase in weakly–polar disorder phase content is observed from S1 to S3, accompanying by an enhanced relaxation behavior with a smearing of AFE-to-PE phase transition. Ferroic and EC responses in three samples present distinct features. Antiferroelectricity wakes–up significantly in S1 sample, which boosts ECE up to ~ 0.95 K and is almost three times that of S3 (~ 0.23 K). Besides, abnormal ECE (negative ECE with a hop–hop character and asymmetrical EC response) is unexpectedly found in S1. Underlying mechanism is unveiled by dipolar relaxation and phenomenology analysis, which states that AFE coupling strength dominates the EC performance in this AFE. This work not only presents a refreshing method for order degree regulating ECE in B–site complex AFEs, but also clarifies a possibility that AFEs with robust dipolar coupling strength procure unconventional ECE.