Positive and Negative Electrocaloric Effect in Lead-Free Silver Niobate Antiferroelectric Ceramic Depending on Affluent Phase Transition

Abstract

We prepared a dense AgNbO3 ceramic using a conventional solid-state reaction method. The phase structure, electrical properties and electrocaloric effect (ECE) were systematically investigated. Large negative and positive ECEs (−4.38 °C at 65 °C and 2.3 °C at 210 °C) under an external electric field of 180 kV·cm−1 were obtained in the eco-friendly AgNbO3 antiferroelectric (AFE) ceramic due to affluent phase transition and a high electric field. The large positive and negative ECEs originated from the phase transition between ferrielectric (FIE) phases (the orthorhombic space group (Pmc21) and AFE phases (Pbcm) tuned by an applied external field. Additionally, a probable mechanistic model was proposed to illustrate the generation of positive and negative ECEs. This study may provide guidelines for the design of high-efficiency solid-state cooling devices.