Ultrahigh energy storage in multilayer BiFeO3-BaTiO3-NaTaO3 relaxor ferroelectric ceramics

The rising challenge of high-density electric energy storage has accelerated the research of electric energy-storage capacitors due to their high power density and voltage resistance, excellent temperature stability, and environmental friendliness. However, lead-free ferroelectric capacitors generally have a low discharge energy density. This study used a multilayer ceramic capacitor (MLCC) design with active ceramic layers of relaxor ferroelectric NaTaO3-modified BiFeO3-BaTiO3 co-sintered with 90Ag/10Pd interlayer electrodes. Superb recoverable energy densities of Wrec similar to 2.8 J cm-3 with an energy efficiency of eta similar to 73% at 400 kV cm-1 and Wrec similar to 4.5 J cm-3 with an energy efficiency of eta similar to 77% at 450 kV cm-1 were attained, respectively, in 9-active-ceramic-layer and 24-active-ceramic-layer MLCCs. Excellent thermal stability and fatigue resistance of energy storage capability were achieved up to 180 degrees C and exceeding 1 x 104 cycles. The ultrahigh energy-storage properties can be linked to the synergistic effects of multiple local lattice distortions, nanoscale structures, and interfacial E fields at grain boundaries. This report demonstrates an efficient scheme to utilize ternary BiFeO3-BaTiO3-based ceramics via the MLCC technology for ultrahigh-energy-density electrostatic energy storage.