Composition-tailor induced electrocaloric effect near room temperature in (Pb,Ba)HfO3 films

Abstract

More and more researchers start to pay attention to the electrocaloric temperature change (ΔT) in polar materials, which is caused by an applied electric field. In this paper, Ba-doped PbHfO3 (PBH) films were prepared by sol-gel method. Their components, microstructures, dielectric polarization and electrocaloric effects (ECEs) were investigated. With the addition of Ba2+, PBH films went from antiferroelectric (AFE) to ferroelectric (FE). At the same time, their dielectric peaks shifted toward lower temperature. The maximum ΔT obtained in Pb0.8Ba0.2HfO3 FE film is 41.1 K, which is an order of magnitude larger than PbHfO3 film (ΔT ∼ −4 K at 50 °C) and Pb0.9Ba0.1HfO3 film (ΔT < 4 K at 120 °C). In order to explain this phenomenon, the Landau-Devonshire theory was adopted. Our analysis shows that the rapid variation of energy barrier height near the phase transition temperature is beneficial to obtain large polarization change and high △T, which is needed in solid-state cooling devices.