Enhanced electrocaloric effect in Sr-doped Ba0.85Ca0.15Zr0.1Ti0.9O3 lead-free thin films near room temperature

Ferroelectric thin films with giant room-temperature electrocaloric effect (ECE) could be very useful in design of solid-state refrigeration devices. Here, lead-free Ba0.85Ca0.15-xSrxZr0.1Ti0.9O3 (BCZT-xSr, 0.01 <= x <= 0.10) thin films are successfully prepared on the substrates (Pt/Ti/SiO2/Si) via sol-gel route, and the effect of the Sr sub-stitution on the structure, electric properties and ECE of the films were investigated. The dielectric analyses show that the rhombohedral-tetragonal phase transition temperature (TR-T) move to a higher temperature and the tetragonal-cubic phase transition temperature (Tm) shift to a lower temperature with increasing Sr content, and finally the TR-T peaks merge into the Tm peaks at room temperature. The BCZT-0.05Sr film presents a giant ECE with AT = 27.1 K and AS = 30.6 J K-1 kg-1 at 800 kV cm-1 near room temperature (301 K). The giant AT benefits from a multiphase coexisting region with successive R-T and T-C phase transition character near room temperature. These results indicate that the lead-free Sr-doped BCZT thin film is an attractive material for application in ECE refrigeration devices.

Automated summary

Lead-free Sr-doped BCZT thin films were successfully prepared and their structure, electric properties and ECE were investigated. The results show that the phase transition temperatures of the films change with increasing Sr content and merge at room temperature. The BCZT-0.05Sr film exhibits a giant ECE near room temperature.