Correlation between multi-factor phase diagrams and complex electrocaloric behaviors in PNZST antiferroelectric ceramic system
Junjie Li, Ruowei Yin, Jianting Li, Xiaopo Su, Yanjing Su, Lijie Qiao, Yang Bai
Abstract
Ferroelectric (FE) phase transition with a large polarization change benefits to generate large electrocaloric (EC) effect for solid-sate and zero-carbon cooling application. However, most EC studies only focus on the single-physical factor associated phase transition. Herein, we initiated a comprehensive discussion on phase transition in Pb<sub>0.99</sub>Nb<sub>0.02</sub>[(Zr<sub>0.6</sub>Sn<sub>0.4</sub>)<sub>1−<i>x</i></sub>Ti<sub><i>x</i></sub>]<sub>0.98</sub>O<sub>3</sub> (PNZST100<i>x</i>) antiferroelectric (AFE) ceramic system under the joint action of multi-physical factors, including composition, temperature, and electric field. Due to low energy barrier and enhanced zero-field entropy, the multi-phase coexistence point (<i>x</i> = 0.12) in the composition–temperature phase diagram yields a large positive EC peak of maximum temperature change (Δ<i>T</i><sub>max</sub>) = 2.44 K (at 40 kV/cm). Moreover, the electric field–temperature phase diagrams for four representative ceramics provide a more explicit guidance for EC evolution behavior. Besides the positive EC peaks near various phase transition temperatures, giant positive EC effects are also brought out by the electric field-induced phase transition from tetragonal AFE (AFE<sub>T</sub>) to low-temperature rhombohedral FE (FE<sub>R</sub>), which is reflected by a positive-slope boundary in the electric field–temperature phase diagram, while significant negative EC responses are generated by the phase transition from AFE<sub>T</sub> to high-temperature multi-cell cubic paraelectric (PE<sub>MCC</sub>) with a negative-slope phase boundary. This work emphasizes the importance of phase diagram covering multi-physical factors for high-performance EC material design.