Excellent energy storage and mechanical performance in hetero-structure BaTiO3-based relaxors

BaTiO 3 -based lead-free ceramics are mainstays of electrical functional materials in industry with mature technology and relatively low cost. However, the huge challenge of low recoverable energy storage density ( W rec ) has long restricted their development in solid-state energy storage capacitors. Here, an ultrahigh W rec of ∼9.04 J cm −3 and a large efficiency ( η ) of ∼87.2% are realized in BaTiO 3 -based relaxor ceramics via designing heterostructure formed by coexisting rhombohedral-tetragonal multiphase ergodic polar nanoregions. Encouragingly, outstanding mechanical properties (Vickers hardness ∼9.7 Gpa, compressive strength ∼500 MPa) are also achieved and the structural correlation between the energy storage and mechanical properties has been established, which are linked to the synergistic mechanisms of solid solution strengthening, denseness strengthening, grain boundary strengthening, and twin boundary strengthening. It is particular significance that this work provides an effective strategy to design new high-performance dielectric materials, accelerating the development of BaTiO 3 -based lead-free capacitors used in advanced energy-storage devices.