Composition and strain engineered AgNbO3-based multilayer capacitors for ultra-high energy storage capacity

Abstract

Antiferroelectric (AFE) materials owing to their double-loop-shaped electric-field (E) dependent polarization (P) are considered quite promising for energy-storage capacitors. Among the large family of AFE materials, the AgNbO₃ composition is attractive not only because it is environmentally friendly, but also because it has high recoverable energy storage density (W_rec). However, the reported values of W_rec < 4 J cm⁻³ in Ag(Nb_0.85Ta_0.15)O₃ multilayer capacitors are lower than that of the corresponding monolithic ceramic. This is attributed to high leakage current density (J) and inferior breakdown strength (BDS) in multilayer structures. Here we demonstrate that MnO₂ doping not only effectively reduces the J value and results in slim P–E loops, but also enhances the breakdown strength (BDS). Multilayer capacitors with composition Ag(Nb_0.85Ta_0.15)O₃ + 0.25 wt% MnO₂ (ANT + Mn) demonstrated an excellent W_rec = 7.9 J cm⁻³ and efficiency η = 71%. Extensive investigations were conducted on ANT + Mn multilayer capacitors to demonstrate the role of strain engineering in enhancing the maximum polarization (P_max) and ΔP values. Results reveal the effect of built-in stress in the active layers of multilayer capacitors on the magnitude of P_max, remanent polarization (P_r) and W_rec, and provide guidance towards the development of high energy storage density in multilayer capacitors.