Diffuse dielectric behaviors in non-stoichiometric sodium niobate-based ceramics via Bi-substitution

Systematic investigation on the phase transition, dielectric behavior, and ferroelectric property of non-stoichiometric sodium niobate-based antiferroelectric (AFE) ceramics is carried out via Bi-substitution. Doping Bi3+ is capable of adjusting phase transition temperature meanwhile accelerating the formation of polar nanoregions instead of the long-range order structure. The phase transition is identified by the structural Rietveld refinement from the orthorhombic P phase to the pseudo-cubic phase consisting of the P and orthorhombic R phase as Bi3+ dopant increases. The composition regulation shifts the dielectric anomaly to a lower temperature and effectively enhances the relaxor nature. Specifically, associated with the diffuse dielectric relaxation aroused by oxygen vacancy defect, excellent thermal stability is achieved in a wide temperature range from −82 °C to 408 °C. Additionally, the simultaneously significant improvement of the recoverable energy density and efficiency is gained at moderate electric fields. This work makes it an alternative AFE strategy for the application of high-temperature capacitor.