Large electrocaloric and pyroelectric energy harvesting effect over a broad temperature range via modulating the relaxor behavior in non-relaxor ferroelectrics

Abstract

Designing dielectric materials displaying a large electrocaloric temperature change over a wide temperature window is still challenging for developing electrocaloric cooling devices. Relaxor materials could be good candidates because of their sluggish phase transition and good temperature stability. However, the polarization of relaxor materials is usually low. Normal ferroelectrics can have higher magnitude of polarization, while they suffer from sharp phase transition and poor temperature stability. Herein, we introduce a novel method through compositionally modulating the relaxor behavior in normal ferroelectrics to simultaneously realize large and temperature-stable electrocaloric performance. After large amount of Ba substitution in the A-site, the normal ferroelectric material PbLa(ZrSnTi)O₃ shows relaxor phase transition with elimination of the antiferroelectric phase upon heating and no evident reduction of polarization. As a result, a large electrocaloric temperature change of more than 1.20 K was achieved over a rather broad temperature range of 28–140 °C (temperature span of 112 K). And the modulated PbLaBa(ZrSnTi)O₃ relaxor ferroelectric materials demonstrate a maximum electrocaloric temperature change of 1.58 K and entropy change of 1.65 J K⁻¹ kg⁻¹ at near room temperature. Moreover, a pyroelectric energy of 0.89 J cm⁻³ was obtained per cycle in PbLaBa(ZrSnTi)O₃ ceramics, showing a great potential for pyroelectric energy harvesting application. This work provides a new method to enhance the electrocaloric and pyroelectric energy harvesting performance via modulating relaxor phase transition in non-relaxor ferroelectric materials.