Defect engineering via BiMnO3 doping in AgNbO3: Achieving high energy storage density under moderate electric fields

In this work, relaxor antiferroelectric (1−x) AgNbO3−xBiMnO3 ceramics were synthesized by solid-state processing. The analysis of electron paramagnetic resonance and x-ray photoelectron spectroscopy confirmed the coexistence of Mn2+ and Mn3+ states. Positron annihilation lifetime measurements revealed that BiMnO3 doping promoted the formation of cation vacancies VAg′, while effectively suppressing oxygen vacancy VO·· concentration. The resultant reduction in the tolerance factor stabilized the antiferroelectric phase at room temperature. Simultaneously, hybridization between the 6s of Bi3+ and the 2p orbitals of O2− and the generation of VAg′ enhanced the maximum polarization from 39.97 μC/cm2 in undoped AgNbO3 to 62.89 μC/cm2 in the 0.995AgNbO3-0.005BiMnO3 composition. Furthermore, the incorporation of BiMnO3 led to decreased grain size and enhanced breakdown strength. Specifically, the 0.5 mol. % BiMnO3-modified AgNbO3 ceramic achieved a recoverable energy density of 6.87 J/cm3 and a recoverable energy storage intensity of 26.02 × 10−3 J kV−1 cm−2 under a moderate electric field of 264 kV/cm, demonstrating its potential for environmentally compatible energy storage applications.