Greatly enhanced energy storage and discharge properties of AgNbO3 ceramics with a stable antiferroelectric phase and high breakdown strength using hydrothermally synthesized powders

AgNbO3 lead-free antiferroelectric (AFE) material is one of the most promising candidates for fabricating dielectric capacitors due to its near-zero remnant polarization and good environmental friendliness. However, current AgNbO3 ceramics are commonly prepared by solid-state reaction methods, which results in high probability of decomposition of Ag2O with thermodynamic instability and enlarged grain sizes due to high sintering temperatures. This leads to reduced AFE phase stability and breakdown strength (E-b), and thus, poor capacitive properties. Here, novel AgNbO3 AFE ceramics with fine grains are fabricated by hydrothermal methods, and exhibit an ultra-high recoverable energy density (W-rec) of 3.34 J cm(-3) and large energy efficiency (eta) of 54.5%, being respectively 1.67 and 1.36 times as high as those of AgNbO3 ceramics obtained by solid-state methods. Their outstanding discharge properties with a discharge time of 0.032 mu s and power density of 118.64 MW cm(-3) outperform those of the latest lead-free dielectric ceramics. Finite element simulations demonstrate decreased grain sizes and increased grain boundary numbers in hydrothermally synthesized AgNbO3 ceramics make the local electric field distribution more uniform and increase electrical tree evolving branches, resulting in improved E-b and W-rec. Furthermore, the synthesis time of AgNbO3 powders is decreased from 20 h to 6 h via microwave-assisted hydrothermal methods.