MnO2 doping enhances energy storage performances in lead-free BiFeO3-based ceramics

BiFeO3-based ferroelectric ceramics as promising candidates for energy storage devices have attracted a great deal of interest owing to the large ferroelectric polarization and high Curie temperature. However, the Bi volatilization induced oxygen vacancy and Fe2+/Fe3+ ionic hopping limit its energy storage performances (ESP). A charge compensated method by introducing multivalent oxide is proposed to inhibit the oxygen vacancy and Fe2+/Fe3+ ionic hopping, aiming to improve dielectric breakdown strength (BDS), polarization saturation and ESP. Here, we prepared a series of MnO2-modified Bi0.83Sm0.17Fe0.95Sc0.05O3-0.85BaTiO3-0.15Bi(Mg0.5Zr0.5)O3 [BSFS-BT-BMZ-x wt%MnO2] ceramics by traditional solid state sintering. It revealed that a large reversible energy storage density (Wrec) of ∼ 4.1 J/cm3 and a great efficiency (η) of ∼ 88% can be achieved at x = 2.1 ceramics. The improved ESP could be attributed mainly to the effective inhibition of Fe2+ by multi-fold valence states of Mn ions accompanying with the decreasing of oxygen vacancy and Fe3+/Fe2+ ionic hopping, leading to the refinement of grain size, and the enhancement of BDS and ferroelectric polarization. Moreover, the optimized ceramics exhibit the good frequency/thermal stability, excellent fatigue resistance and high powder density. These results demonstrate that a charge compensated method pays a route of improving ESP for dielectric ceramic capacitors.