Oxygen octahedron framework design for large energy capacitive relaxors

Lead-free dielectric capacitors commonly rely on chemical disorder design to regulate relaxor behavior. In order to avoid the polarization sacrifice caused by non-ferroactive cations while maintaining a strong enough local random field, an oxygen octahedron tilt framework design strategy is introduced in this work. Based on the Bi_0.5Na_0.5TiO₃-AgNbO₃ system with high-content ferroactive cations, slush-like heterogeneous polar nanoregions enable a large polarization response. Meanwhile, besides the local random electric and elastic fields caused by the heterovalence and different cation radii, the additional local random elastic field caused by the randomly disordered distribution of the BO₆ tilt mode and angle not only slows polarization reorientation and growth but also provides a restoring force to reset polarization during charging, enabling the slim hysteresis loop with delayed polarization saturation as well as excellent energy storage properties. This work provides a feasible avenue for high-performance lead-free relaxors with low tolerance factor.