Giant electrocaloric effect in PZT bilayer thin films by utilizing the electric field engineering

The enhancement of the electrocaloric effect (ECE) was achieved by the amplifying effect of applied electric field through devising the thin films' structure. The PbZr_0.95Ti_0.05O₃/PbZr_0.52Ti_0.48O₃ bilayer structured thin films were fabricated on a Pt(111)/Ti/SiO₂/Si substrate using sol-gel method. The ΔS = 20.5 J K^-1kg^-1 and ΔT = 24.8 K for bilayer thin films is achieved around 125 °C much below T_c, which is caused by the amplifying electric field induced phase transition of O_AFE/R_FE in PZr_0.95Ti_0.05O₃ layer. It is also worth mentioning that the films exhibit outstanding ECE at room temperature; ΔS = 11.9 J K^-1kg^-1 and ΔT = 10.7 K are observed, which are attributed to the effect of amplifying electric field in PbZr_0.95Ti_0.05O₃ layer and R_FE/T_FE at morphotropic phase boundaries (MPB) in PbZr_0.52Ti_0.48O₃ layer. This result indicates that to amplify the local electric field engineering and to maximize the number of coexisting phases in heterostructures or multilayer thin films may be an effective way for cooling applications.