Silver stoichiometry engineering: an alternative way to improve energy storage density of AgNbO3-based antiferroelectric ceramics

Lead-free dielectric capacitor with high energy storage density is in great demand, but with the challenge of limited energy storage density. In this work, Ag(Nb0.85Ta0.15)O3-x wt% Ag2O (ANTAx) lead-free ceramics with nonstoichiometric Ag2O were fabricated, with the aim of improving energy storage density. The element concentration, phase structure, microstructure, dielectric property, and energy storage performance were investigated. Improved recoverable energy storage density (Wrec) of 4.8 J/cm3 were achieved for ANTA1 ceramics with 1 wt% Ag2O in excess, demonstrating obvious improvement compared with the stoichiometric counterpart. In addition, the ANTA1 ceramics also exhibited highly stable energy storage performance in the temperature range from room temperature to 150 °C, with variations less than 4% and 5% for Wrec and energy storage efficiency, respectively. The good properties may be associated with the dismissing of various defects by adding excess Ag2O. This work demonstrates that silver stoichiometry engineering is an effective method to improve energy storage properties of AgNbO3-based antiferroelectric ceramics.