Enhanced ferroelectric and electrocaloric properties in CuO-modified lead-free (Na0.5K0.5)NbO3 ceramics for solid-state cooling application

Abstract Lead-free (Na0.5K0.5)NbO3: x mol. % CuO (abbreviated as NKN-xCu) ferroelectric ceramics with x = 0, 0.5, 1.0 and 2.0 were synthesized by the conventional solid-state reaction method and the correlation of structure, dielectric, ferroelectric, and electrocaloric (EC) properties was investigated. The orthorhombic‐tetragonal and tetragonal–cubic transition temperatures of NKN-xCu ceramics decreased with an increase in CuO doping level. The ferroelectric loops and saturation polarization values were improved with the CuO addition. A large adiabatic temperature change (ΔT) of ~1.98 K and corresponding EC strength (ΔT/ΔE) of ~0.49 K.mm/kV were achieved at the electric field of 40 kV/cm at 450 K for x = 2.0. The higher EC response makes NKN-xCu ceramics highly promising for environmentally-friendly electrocaloric effect (ECE) based solid-state cooling application.