Electrocaloric effect and pyroelectric performance in (K,Na)NbO 3 ‐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 )K 0.5 Na 0.5 NbO 3 ‐ x Bi 0.5 Na 0.5 ZrO 3 (KNN‐ x BNZ) ceramics. The adiabatic temperature change (∆ T ) of 0.22 K at 100°C, 0.14 K at 70°C and 0.16 K at 30°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 × 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.