Coexistence of Large Negative and Positive Electrocaloric Effects and Energy Storage Performance in LiNbO3 Doped K0.5Na0.5NbO3 Nanocrystalline Ceramics

The electrocaloric effect (ECE) has been investigated in (1 - x)K0.5Na0.5NbO3-xLiNbO(3) (KNN-xLiN) nanocrystalline ceramics with compositions in the range of 0.01 <= x <= 0.05 by the indirect measurement using Maxwell's approach. The coexistence of the negative and positive ECEs has been achieved in all samples. The maximum values of negative and positive ECE were found to be -0.40 and 0.24 K for x = 0.01, -0.23 and 0.18 K for x = 0.03, and -0.13 and 0.29 K for x = 0.05, respectively. The maximum recoverable energy densities were found to be 0.12, 0.13, and 0.128 J/cm(3) with energy storage efficiencies of 30, 50, and 51% at an electric field of 45 kV/cm for x = 0.01, 0.03, and 0.05, respectively. The coexistence of the negative and positive ECEs with a high recoverable energy density in one material makes it a promising candidate for highly efficient, environmentally friendly cooling devices and energy-storage device applications.