Lead-free AgNbO₃ anti-ferroelectric ceramics with an enhanced energy storage performance using MnO₂ modification

Dielectric ceramic materials have been actively studied for advanced pulsed power capacitor applications. Despite the good properties obtained in lead-based ceramics, lead-free counterparts are highly desired due to environmental regulations. This study revealed the potential of AgNbO₃ to be a promising lead-free ceramic for energy storage applications. AgNbO₃ ceramics fabricated using a conventional solid-state reaction method under an O₂ atmosphere show a characteristic anti-ferroelectric (AFE) double hysteresis loop at an electric field of >130 kV cm^-1, with a peak recoverable energy storage density (W_rec) of 1.6 J cm^-3 at 140 kV cm^-1. In addition, the incorporation of MnO₂ into AgNbO₃ can further increase W_rec, exceeding 2.3 J cm^-3 at 150 kV cm^-1 by the reduction of the remnant polarization, which is due to the enhanced AFE stability induced by the addition of MnO₂. Of particular importance is that the 0.1 wt% MnO₂-doped AgNbO₃ ceramics were found to possess a good thermal stability with W_rec = 2.5-2.9 J cm^-3 over a temperature range of 20-180 °C at 150 kV cm^-1 and 1 Hz.