Synergistically optimizing electrocaloric effect and temperature span in KNN-based ceramics utilizing relaxor multiphase boundary
A combination of large adiabatic temperature change (∆T) and wide temperature span (Tspan) in lead-free ceramics is highly desired to develop eco-friendly and high-efficient solid-state refrigeration based on electrocaloric effect. However, the unsuccess in synergistically optimizing both large ∆T and wide Tspan in one material impedes practical applications of electrocaloric refrigeration technology. Here, a relaxor multiphase boundary (RMPB) is structured in (1-x)(K0.49Na0.49Li0.02)(Nb0.8Ta0.2)O3–xCaZrO3 (KNLNT–xCZ) ceramics through intentional composition engineering, successfully achieving a region of multiphase coexistence accompanied by diffuse phase transition. A moderate ∆T (0.63 K under 80 kV cm–1) with wide Tspan (43 K within 90% ∆T attenuation) is obtained in relaxor KNLNT–5CZ ceramic with coexistence of R-O-T phase. Results indicate that a coupling effect original from multi-directional polarization and polar nano-regions (PNRs) in RMPB contributes to the excellent performance combining large ∆T and wide Tspan. This work not only expands the applications of KNN-based ceramics from electric energy storage and piezoelectric applications to refrigeration field, but also opens up a new design avenue for the development of high performance electrocaloric materials with broad temperature ranges.
- This article is part of the themed collection: Journal of Materials Chemistry C HOT Papers