Electrocaloric effect and pyroelectric performance in (K,Na)NbO3-based lead-free ceramics

The issue of how to achieve an electrocaloric effect (ECE) and pyroelectric effect in a material simultaneously remains to be a challenge for developing practical solid-state cooling devices and RF-detectors. Here, we structure a polymorphic phase transition (PPT) region by doping modification in KNN-based ceramics, which are developed to achieve the ECE. The direct measured ECE and pyroelectric properties are investigated in lead-free (1-x)K0.5Na0.5NbO3-xBi(0.5)Na(0.5)ZrO(3) (KNN-xBNZ) ceramics. The adiabatic temperature change ( increment T) of 0.22 K at 100 degrees C, 0.14 K at 70 degrees C and 0.16 K at 30 degrees C can be obtained under an electric field of 35 kV cm(-1) for x = 0.03, 0.04 and 0.05, respectively. In addition, the temperature dependence of pyroelectric coefficient (p) is established for all compositions via the Byer-Roundy method. A large p of 454.46 x 10(-4) C m(-2) K-1 is detected at Curie temperature (T-C) in the ceramics with x = 0.03. Achieving electrocaloric effect and pyroelectric performance simultaneously may shed light and provide a feasible design scheme for developing practically useful electrocaloric and pyroelectric materials.