Via incorporation of Sr2+ into (Pb,La)(Zr,Sn,Ti)O-3, high recoverable energy density (U-re) is achieved in (Pb,Sr,La)(Zr,Sn,Ti)O-3 (PSLZST) ceramics. All Sr2+ modified ceramics exhibit orthorhombic antiferroelectric (AFE) characteristics, and have higher ferroelectric-AFE phase switching electric field (E-A, proportional to U-re) than the base composition with a tetragonal AFE phase. By properly adjusting the Sr2+ content, the U-re of PSLZST ceramics is greatly improved. This is attributed to the substitution of Pb2+ by Sr2+ with a smaller ion radius, which decreases the tolerance factor leading to enhanced AFE phase stability and thus increased E-A. The best energy storage properties are achieved in the PSLZST ceramic with a Sr2+ content of 0.015. It exhibits a maximum room-temperature U-re of 5.56 J/cm(3), the highest value achieved so far for dielectric ceramics prepared by a conventional sintering technique, and very small energy density variation (< 12%) in the range of 30-90 degrees C. The high Ure (>4.9 J/cm(3)) over a wide temperature range implies attractive prospects of this material for developing high power capacitors usable under various conditions. Published by AIP Publishing.