Giant negative electrocaloric effect and energy storage response in 0.94(K0.5Na0.5)NbO3-0.06SrMnO3 nanocrystalline ceramics

We report the electrocaloric (EC) effect investigation on lead-free 0.94(K0.5Na0.5)NbO3-0.06SrMnO(3) nanocrystalline ceramics by an indirect thermodynamic method using Maxwell's relations. The maximum value of the negative EC effect (Delta T-max = -1.66 K) was observed at 459 K near the transition temperature at the field of 50 kV/cm. The corresponding EC responsivity was calculated to be - 3.32 x 10(-7) K m/V under 50 kV/cm at 459 K whereas the coefficient of performance (COP) and recoverable energy density (W-rec) were found to be 1.03 and 0.17 J/cm(3), respectively under 50 kV/cm at 443 K. The observed values of negative EC effect, and EC responsivity are larger than any other lead-free ferroelectric ceramics with good COP and W-rec value. The results are interesting to improve the cooling efficiency and energy storage for device application.