Enhancing comprehensive energy storage properties in Pb-free relaxor AFE/FE system via heterogeneous structure tuning and defect engineering

Multi-phase NaNbO ₃ (NN) exhibits high adjustability on the ordering of both polarization and oxygen octahedral tilt, becoming a perfect carrier to design heterogeneous structure for boosting comprehensive energy storage properties. To balance the energy storage density and efficiency, the coexistence of the relaxor antiferroelectric (AFE) with high polarization capability and the relaxor ferroelectrics (RFE) with high efficiency is designed in this work by introducing Sr _0.7Bi _0.2□ _0.1Ti _0.75Ta _0.2□ _0.05O ₃ (SBTT) into NaNbO ₃-BiFeO ₃. As a result, an outstanding capacitive energy density ( W_rec) of 12.25 J cm ⁻³ with a high η of 83 % can be achieved in NN-BF-SBTT ceramic, which can be identified as a novel heterogeneous coexisting structure with the crossover of high polarization capability in relaxor AFE and high efficiency in RFE in terms of high-resolution TEM. Furthermore, grain refinement and the dense structure inhibit the leak current, suppress the concentration of oxygen vacancy defects and raise the activation energy ( E_a), thus enhancing the E_B. These excellent energy storage properties overcome the trade-offs between the two sets of parameters ( W_rec- η, Δ P- E_B), offering a refreshing strategy for the development of high-performance ceramic capacitors.