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

Abstract

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 (η) 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 μs 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.