Energy storage properties of NaNbO3-based lead-free superparaelectrics with large antiferrodistortion

NaNbO3-based 3-based lead-free energy storage ceramics are essential candidates for next-generation pulsed power capacitors, especially under the background of energy saving and environmental protection. However, the room- temperature antiferroelectric P phase of pure NaNbO3 3 ceramics limits its further development in energy storage owing to the irreversible antiferroelectric to ferroelectric phase transition under electric fields. In this work, CaZrO3 3 was introduced to NaNbO3 3 ceramics to destroy the long-range polarization ordering but keep large antiferrodistortion, causing the formation of superparaelectric state with macrodomains, which can be identified by the refinement results of high-energy synchrotron X-ray diffraction, neutron diffraction and TEM results. Combined with the fine grains, dense and homogeneous microstructure, ergodic relaxation behaviors, and delayed polarization saturation, a high recoverable energy storage density of-5.4 J/cm3 3 and efficiency of-82% can be realized in 0.85NaNbO3-0.15CaZrO3 3-0.15CaZrO 3 ceramics at an ultrahigh breakdown electric field of-68 kV/mm. The results found in this work suggest that the supersparaelectric with non-cubic phase would be a good candidate for generating excellent dielectric energy storage properties.