Giant negative electrocaloric effect over a wide temperature region (263–373 K) in lead-free BiFeO3/B4Ti3O12 composite films

Abstract

A giant negative electrocaloric effect is found in lead-free BiFeO3/Bi4Ti3O12 composite films with ΔT = −5.717 K under a relatively suitable working applied field of ΔE = 305 kV/cm. More importantly, the negative electrocaloric effect is achieved over a wide temperature range (263–373 K). The strong electrocaloric effect is due to the BiFeO3 layer and Bi4Ti3O12 layer combined action to decrease thermal entropy in relatively modest electric fields. The negative electrocaloric effects allow a new type of solid-state refrigeration equipment to gradually become possible, which can make more effective use of energy and gain hope to enhance the cooling efficiency by combining with the ideal positive electrocaloric effect.