Enhanced electrocaloric effect in compositional driven potassium sodium niobate-based relaxor ferroelectrics

Lead-free ferroelectric electrocaloric ceramics that could convert electrical energy into heat are the promising candidate for environment-friendly cooling devices. For refrigeration devices, a large temperature change (Delta T) and good temperature stability are required, which are highly related to the phase structure and the applied electric field. In this work, a diffused ferroelectric-paraelectric (FP) phase transition is formed in (K, Na)NbO3 (KNN) by using appropriate composition engineering. The relaxor ferroelectrics in this work present both a large Delta T of 1.24 K and a high Delta T/Delta E of 0.19 K mm/kV. In addition, a wide temperature span exceeds 55 degrees C at the high electrocaloric effect (ECE) criterion (Delta T >= 0.5 K) could also be observed. This work not only opens a new strategy for obtaining high-performance ceramics for refrigeration devices but also extends the application area of the KNN-based lead-free ferroelectrics from sensors, actuators and energy harvesting to solid-state cooling applications.

Automated summary

This study presents diffused ferroelectric-paraelectric phase transition in (K, Na)NbO3 (KNN) through appropriate composition engineering, resulting in relaxor ferroelectrics with large temperature change and high electrocaloric effect. These materials exhibit a wide temperature span exceeding 55 degrees Celsius at the high electrocaloric effect criterion, providing high-performance lead-free ferroelectric ceramics for refrigeration devices.