Ultrahigh energy density and excellent discharge properties in Ce4+ and Ta5+ co-modified AgNbO3 relaxor antiferroelectric ceramics via multiple design strategies

Silver niobate (AgNbO3) has been recently regarded as one of the best candidates for developing high-performance dielectric capacitors on account of its large maximum polarization and near-zero remnant polarization, but its room-temperature ferrielectric (FIE) behavior and large electric hysteresis impede further improvement of energy storage properties. In order to solve this issue, herein, we design Ce4+ and Ta5+ co-modified (Ag0.96Ce0.01)(Nb1-xTax)O3 relaxor antiferroelectric (AFE) ceramics. The introduction of Ce4+ and Ta5+ decreases the tolerance factor, reduces the B-site cation polarizability, and enhances A- and B- site cation disorder, leading to suppressed FIE characteristic, improved AFE stability, and enhanced relaxor degree. Besides, the co-doping strategy causes the decrease of the grain size, and the experimental results and finite element simulations both indicate that this is fairly effect on the improvement of the breakdown strength. Consequently, an ultrahigh recoverable energy density of 7.37 J/cm3, which far exceeds those of the latest AgNbO3-based ceramics, and a large efficiency of 75.66% are simultaneously achieved in (Ag0.96Ce0.01)(Nb0.7Ta0.3)O3 ceramics. More encouragingly, the ceramic exhibits excellent actual discharge capacity with ultrafast discharge time of 23 ns and ultrahigh power density of 294.28 MW/cm3, which outperforms many recently reported lead-free dielectric ceramics, and the discharge properties are fairly stable during a wide temperature range of 20–180 °C. This work sheds light on designing and developing high-performance lead-free dielectric capacitors applicable in harsh environment.