Investigation On The Refrigeration Performance Of Antiferroelectric Thick Films Originated From Electrocaloric Effect

With the rapid development of the modern industry, micron-electric devicesincreasingly becomes microminiature and multifunctional. However, produced heat isharmful to the operational stability of the devices. Maintaining these devices operating atlow temperature played a key role in the development of micron-electric devices. Thus, therefrigeration based on electrocaloric effect (ECE) is believed to be a more promisingcandidate in micron-electric cooling devices. PbZrO3is a typical antiferroelectric (AFE).The dipoles in PbZrO3are alternatively aligned in the opposite directions and thus no netspontaneous polarization exists. Under an external field high enough, AFEs could beconverted to a ferroelectric (FE) state. This phase switching process is accompanied by alarge entropy change and a giant ECE. In this paper, PbZrO3-based AFE thick films weresuccessfully fabricated via a sol-gel method, and the ECE was investigated.Firstly,(Pb0.97La0.02)(Zr0.75Sn0.18Ti0.07)O3thick film was prepared via a PVP-modifiedsol-gel method. The microstructure, dielectric properties, ECE and leakage currentbehavior of the thick films were investigated in detail. The maximum ECEs of T=53.8oCand S=63.9J·K-1·kg-1at5oC at900kV/cm was obtained in the PLZST AFE thick film,and a large T of above30oC was observed in the temperature range of5oC to25oC.Secondly, the effects of the chemical composition and compositionally gradientsequences for AFE thick films on the microstructure, dielectric properties, ECE andleakage current behavior were investigated. It is found that the saturation polarization,dielectric constant, Curie temperature and leakage current density of(Pb1-3x/2Lax)(Zr0.85Ti0.15)O3AFE thick film decrease with the La content increase, and themaximum ECE of T=25.0oC at990kV/cm was obtained in the films with the La contentof8mol%. With the increase of the molar ratios of Zr/Sn, the saturation polarization, Curietemperature and leakage current density of the (Pb0.97La0.02)(Zr1-xSnxTi0.05)O3AFE thickfilms increase, and the dielectric constant decrease. The maximum ECE of T=33.0oC at900kV/cm was obtained in the film with the molar ratio of Zr/Sn of75/20. Moreover, ascompared to the single-composition (Pb1-3x/2Lax)(Zr0.85Ti0.15)O3AFE thick film, the compositionally graded thick films exhibited the significant enhancement in dielectricproperties and ECE. The largest ECE of T=28oC at room temperature were alsoachieved in the up-graded film.Finally, the effects of different oxide buffer layer and different oriented(Pb0.97La0.02)(Zr1-xSnxTi0.05)O3on the microstructure, dielectric properties, ECE andleakage current behavior were investigated. It can be seen that the saturation polarization,dielectric constant and ECE of the films were improved by introduced the oxide bufferlayer. The largest ECE of T=37.1oC at room temperature were also achieved in the filmwith ZrO2buffer layer. Moreover,(111)-oriented (Pb0.97La0.02)(Zr0.73Sn0.22Ti0.05)O3AFEthick film possesses the maximum ECE of T=28.1oC.