A new family of high temperature stability and ultra-fast charge-discharge KNN-based lead-free ceramics

Dielectric ceramic capacitors have been widely used in pulse-power technology because of their good performance of high power density and fast discharge speed. A series of lead-free relaxor ceramics (1-x)K0.5Na0.5NbO3-xLa(Mn0.5Ni0.5)O-3 (KNN-xLMN) featuring with considerable charge-discharge behavior and energy storage properties were designed and prepared in this work. The grain size of ceramics decreases to 180 +/- 20 nm, and the dispersion coefficient is > 1.6, both of which are beneficial to obtain slender P-E loops and improve the energy storage performance in K0.5Na0.5NbO3 ceramics upon La(Mn0.5Ni0.5)O-3 doping. Consequently, acceptable dielectric properties (maximum permittivity epsilon(r) of 1693, Delta epsilon/epsilon(100 degrees C) <= +/- 15% from 33 degrees C to 309 degrees C, minimum dielectric loss tan delta of 0.028, 50 kHz) and a high recoverable energy storage density (W-rec similar to 1.65 J/cm(3)) accompanied by high energy storage efficiency (eta similar to 76%) were obtained simultaneously in 0.97KNN-0.03LMN ceramics. Meanwhile, 0.97KNN-0.03LMN composition exhibited satisfactory charge-discharge performance (P-D similar to 155 MW/cm(3), t(0.9) similar to 55 ns) and temperature stability (30 similar to 110 degrees C). This work not only proposes an efficient strategy to realize high energy storage and ultra-fast charge-discharge performance in lead-free KNN based ceramics, but also provide an candidate material for application of advanced pulsed power capacitors.