Antiferroelectric-ferroelectric phase transition and negative electrocaloric effect in alkaline-earth element doped PbZrO₃ thin films

Electrocaloric effect (ECE) in dielectric materials has attracted much attention due to its promising applications in solid-state cooling devices. In this work, alkaline-earth doped PbZrO₃ antiferroelectric thin films (Pb_0.9A_0.1ZrO₃ (A=Ca, Sr, and Ba)) were deposited by a sol-gel method and its antiferroelectric-ferroelectric phase competition as well as the negative ECE were studied. It is found that Ca²⁺ and Sr²⁺ expand the antiferroelectric phase region while Ba²⁺ reduces it, due to the different ion radii of these alkaline-earth elements. As a result, the Pb_0.9Sr_0.1ZrO₃ thin film exhibits an enhanced negative ECE with ΔT of around − 10.6 K under 450 kV/cm whereas the Pb_0.9Ba_0.1ZrO₃ thin film shows a decreased negative ECE with ΔT of around − 2.5 K under 200 kV/cm, as compared with the pristine PbZrO₃ thin films (with ΔT of around −7.3 K under 300 kV/cm). This work provides an effective method to enhance the negative ECE of antiferroelectrics in electrical cooling applications by adjusting their antiferroelectric to ferroelectric phase transition.