Linear-like lead-free relaxor antiferroelectric (Bi0.5Na0.5)TiO3-NaNbO3 with giant energy-storage density/efficiency and super stability against temperature and frequency

摘要： A novel lead-free polar dielectric ceramic with linear-like polarization responses was found out in (1-x)(Bi0.5Na0.5)TiO3-xNaNbO3 ((1-x)BNT-xNN) solid solutions, exhibiting giant energy storage density/efficiency and super stability against temperature and frequency. High-resolution transmission electron microscopy, Raman scattering and Rietveld refinements of x-ray diffraction data suggest that these property characteristics be derived from temperature and electric field insensitive large permittivity as a result of relaxor antiferroelectricity (AFE) with polar nanoregions. Additionally, this feature intrinsically requires high driving field for AFE to ferroelectric (FE) phase transitions due to large random fields. Measurements of temperature-dependent permittivity and polarization versus electric field hysteresis loops indicate that high-temperature AFE P4bm phase in BNT was gradually stabilized close to room temperature, accompanying a phase transition from relaxor rhombohedral FEs to relaxor tetragonal AFEs approximately at x=0.15-0.2. A record high for recoverable energy-storage density W~7.02 J/cm3 as well as a high efficiency η~85% was simultaneously achieved in the x=0.22 bulk ceramic, which challenges the existing fact that W and η must be seriously compromised. Furthermore, desirable W (?3.5 J/cm3) and η (?88%) with a variation of less than 10% can be accordingly obtained in the temperature range of 25-250 oC and frequency range of 0.1-100 Hz. These excellent energy-storage properties would make BNT-based lead-free AFE ceramic systems be a potential candidate applied for pulsed power systems.