Enhanced dielectric breakdown strength and energy storage density in lead-free relaxor ferroelectric ceramics prepared using transition liquid phase sintering

Abstract

Lead-free relaxor ferroelectric ceramics have been widely explored for high power energy storage applications because of their high polarization saturation and low remnant polarization. However, lead-free relaxor ceramics with the bulk form exhibit low recoverable energy storage density (W_rec < 2 J cm⁻³) owing to low dielectric breakdown strength (DBS <200 kV cm⁻¹). Here we use a strategy (the transition liquid phase sintering) to decrease the porosity and increase DBS of lead-free relaxor ferroelectric ceramics. This is achieved by introducing ZnO into 0.8(K_0.5Na_0.5)NbO₃–0.2Sr(Sc_0.5Nb_0.5)O₃ (0.8KNN–0.2SSN) ceramics. A dense microstructure (a low porosity) and submicron sized grains were found for 0.8KNN–0.2SSN–x mol%ZnO ceramics, which is responsible for a large DBS (400 kV cm⁻¹). Both a large W_rec (2.6 J cm⁻³) and high energy storage efficiency (73.2%) were achieved for 0.8KNN–0.2SSN–0.5 mol%ZnO ceramics. The W_rec of 2.6 J cm⁻³ exceeds all the other reported results of lead-free bulk ceramics. The 0.8KNN–0.2SSN–0.5%ZnO ceramics are believed to be an attractive material for high power energy storage applications.