Relaxor ferroelectric 0.94Na(0.5)Bi(0.5)TiO(3)-0.06BaTiO(3)-modified antiferroelectric Pb0.99Nb0.02[(Zr0.57Sn0.43)(0.94)Ti-0.06](0.98)O-3 ceramics, (1-x)PNZST-x(BNT-6BT), were prepared to acquire high energy storage and thermal stability properties. X-ray diffraction and element mapping revealed that a solid solution between PNZST and BNT-6BT occurs, and Ti cations enter the PNZST lattice, partly extruding Sn cations and leading to the formation of isolated SnO2 particles at the grain boundaries and a 0-3 type composite structure. Such a composite structure helps to create deviatoric stress in the solid solution component. The BNT-6BT content significantly influences the energy storage capacity, and thex = 0.2 composition renders optimal performance. The room-temperature-recoverable energy density and energy efficiency are 2.23 J/cm(3)and 78%, respectively, at 260 kV/cm. Both parameters vary less than 6% within a temperature range of 25 degrees C and 125 degrees C. The improved energy storage and temperature stability indicate that the ceramics can potentially be applied in pulse power capacitors and that this relaxor-modified antiferroelectric ceramic preparation method is a valuable reference for further optimizing the functional properties.