  Polycrystalline lead-free Ba$_{0.85}$Ca$_{0.15}$Zr$_{0.10}$Ti$_{0.90}$O$_3$
(BCZT), BaTi$_{0.89}$Sn$_{0.11}$O$_3$ (BTSn) and
0.4Ba$_{0.85}$Ca$_{0.15}$Zr$_{0.10}$Ti$_{0.90}$O$_3$-0.6BaTi$_{0.89}$Sn$_{0.11}$O$_3$
(0.4BCZT-0.6BTSn) ferroelectric ceramics were prepared via sol gel process and
their structural, dielectric and energy storage properties were studied. Pure
perovskite structure was confirmed by X ray diffraction analysis. The evolution
of energy storage performances with temperature was studied. A Significant
recoverable energy storage density of 137.86 mJ/cm$^3$ and high energy-storage
efficiency of 86.19% under a moderate electric field of 30 kV/cm were achieved
in the composite 0.4BCZT 0.6BTSn ceramic at 353 $^\circ$K. Moreover, excellent
temperature stability (70-130 $^\circ$C) of the energy storage efficiency (less
than 3%) was achieved.
