Phase structure and defect engineering in (Bi0.5Na0.5)TiO3-based relaxor antiferroelectrics toward excellent energy storage performance

Dielectric ceramics with outstanding energy storage performance are urgently expected for energy storage capacitors. In this work, high energy storage density were achieved by deliberately designing a (1-x)Bi0.5Na0.5TiO3-xAgNb0.5Ta0.5O3 (100xANT) relaxor antiferroelectrics, associating with defect engineering. Both relaxor behaviour and evident antiferroelectric characteristic were successfully realized through phase structure engineering to an antiferroelectric tetragonal (T) dominant structure. Furthermore, defect engineering was also adopted by sintering in a flowing oxygen atmosphere to eliminate various defects (such as metal silver and oxygen vacancies), which significantly improved the breakdown strength and reduced the hysteresis loss. As a consequence, ultrahigh recoverable energy storage density of 6.6 J/cm3 and good efficiency of 72% were achieved in O2-sintered 15ANT ceramics, accompanying with excellent frequency stabilities and outstanding low field performance. This work not only provides a promising dielectric material for energy storage applications, but also proves that phase structure and defect engineering are effective ways for designing new high-performance Bi0.5Na0.5TiO3-based dielectric material.