K0.5Na0.5NbO3Bi4−xPrxTi3O12 relaxation ferroelectric capacitor with piezoelectric unit inserted into Bi4Ti3O12 matrix

A layered perovskite structure K0.5Na0.5NbO3Bi4−xPrxTi3O12 lead-free relaxation ferroelectric capacitor was fabricated by inserting piezoelectric K0.5Na0.5NbO3 unit into Bi4Ti3O12 matrix. Pr element doping induced lattice distortion assists the matching between inserting unit and matrix. K0.5Na0.5NbO3Bi2.6Pr1.4TiO12 capacitor has aroused the large energy storage density (Ure) 69.7 J/cm3 and high efficiency (η) 78.13% at room temperature. The well performances can be captured by the randomly dispersed polar nano-regions. The inserted piezoelectric unit hosts regulate the long-range ferroelectric order, which leads to the disturbed ferroelectric order by Pr3+ doping and further forms the polar nano-regions. Raman spectra evolution is well documented to the polar nano-regions. What’s more, the energy capacitors exhibit excellent thermal stability in a temperature range of −20 ℃–140 ℃ and fatigue stability with charge/discharge cycling reaching 1 × 108. Inserting piezoelectric unit provides a strategy to design dielectric energy capacitors. •A piezoelectric unit is inserted into layered perovskite matrix.•Pr element doping induced lattice distortion assists the matching between inserting unit and matrix.•Piezoelectric unit hosts regulate the long-range ferroelectric orders.•The capacitors exhibit excellent thermal and durable stability.