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 Ba 0.85 Ca 0.15-x Sr x Zr 0.1 Ti 0.9 O 3 (BCZT-xSr, 0.01 ≤ x ≤ 0.10) thin films are successfully prepared on the substrates (Pt/Ti/SiO 2 /Si) via sol-gel route, and the effect of the Sr substitution on the structure, electric properties and ECE of the films were investigated. The dielectric analyses show that the rhombohedral-tetragonal phase transition temperature (T R-T ) move to a higher temperature and the tetragonal-cubic phase transition temperature (T m ) shift to a lower temperature with increasing Sr content, and finally the T R-T peaks merge into the T m peaks at room temperature. The BCZT-0.05Sr film presents a giant ECE with ΔT = 27.1 K and ΔS = 30.6 J K −1 kg −1 at 800 kV cm -1 near room temperature (301 K). The giant ΔT 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.
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