Enhanced energy storage and charge-discharge capability of (1-x)K0.5Na0.5NbO3 - xSr(Zn1/3Nb2/3)O3 ceramics

With high power density and energy storage density, lead-free ceramics are urgently needed for the pulsed power capacitors. Here, we adopted grain size engineering strategy, to develop a series of (1 - x)K0.5Na0.5NbO3 - xSr(Zn1/3Nb2/3)O-3 [(1 - x)KNN - xSZN] lead-free relaxor ferroelectric ceramics with both high recoverable energy storage density (W-rec) and charge-discharge properties. The heterovalent occupation of the A/B-site hinders ferroelectric ordering and form polar nanodomains regions (PNRs), results in the relaxor characteristics and submicron scale grain synergistically contribute to the high energy storage density (W), approximately of 6.8 J cm(-3), and W-rec, approximately of 2.75 J cm(-3) for 0.92KNN-0.08SZN ceramics under fairly low applied electrical field (220 kV cm(-1)). Satisfactorily, current density (C-D) and power density (P-D) of 0.92KNN-0.08SZN ceramics reached 2197 A cm(-2) and 208.7 MW cm(-3), which is exceeds the most of the value ever reported for relaxors FEs. Moreover, it also possesses a high discharge energy density, approximately of 2.2 J cm(-3) which remaining steady over a wide range of 20-130 degrees C under 170 kV cm(-1). Results demonstrate that KNN-SZN ceramics not only accelerate the developing of pulsed power devices owing to their high energy storage and superior discharge capability at wider temperature, but also provide a counsel for fostering other KNN-based energy storage ceramics.