Supercritical Relaxor Nanograined Ferroelectrics for Ultrahigh-Energy-Storage Capacitors

Supercritical relaxor nanograined ferroelectrics are demonstrated for high-performance dielectric capacitors, showing record-high overall properties of energy density approximate to 13.1 J cm(-3) and field-insensitive efficiency approximate to 90% at approximate to 74 kV mm(-1) and superior charge-discharge performances of high power density approximate to 700 MW cm(-3), high discharge energy density approximate to 6.67 J cm(-3), and ultrashort discharge time <40 ns at 55 kV mm(-1). Ex/in situ transmission electron microscopy, Raman spectroscopy, and synchrotron X-ray diffraction provide clear evidence of the supercritical behavior in (Na,K)(Sb,Nb)O-3-SrZrO3-(Bi0.5Na0.5)ZrO3 ceramics, being achieved by engineering the coexistence of multiple local symmetries within the ergodic relaxor zone. The vanished difference between the ground relaxor state and the high-field supercritical state eliminates polarization hysteresis. The supercritical evolution with electric field enables a highly delayed polarization saturation with continuously increased polarization magnitudes. The results demonstrate that such a design strategy of compositionally induced and field-manipulated supercritical behavior can be generalizable for developing desirable energy-storage dielectrics for applications in ceramic/film capacitors.