Achieving high energy storage performance in Na0.5Bi0.5TiO3‒based ceramics via Li+ substitution

In the search for dielectric material with high energy storage density, a ceramic system of 0.8Na 0.5 Bi 0.5 TiO 3 –0.2K 1- x Li x TaO 3 (NBT-KLT- x , x  = 0.1–0.5) is proposed in this work. The addition of Li 2 CO 3 is conducive to the decrease of sintering temperature of ceramics. Moreover, the XRD diffraction data of sintered ceramics indicate that pure perovskite phase showing the pseudo-cubic structure can be achieved when x  = 0.1–0.3 while the excessive addition of Li 2 CO 3 leads to the formation of pyrochlore phase. Based on the Rietveld refinement and Raman results, the Li + doping in the NBT-KLT- x solid solutions ( x  = 0.1–0.3) can improve the phase content of P 4bm, induce the lattice expansion and structural change towards a higher-symmetry phase. TEM observation also demonstrates the reduction in the size of polar nanoregions. With increasing x from 0.1 to 0.5, both the oxygen vacancy concentration and grain size display a tendency to decrease first and then increase. For the x  = 0.2 ceramics with the lowest oxygen vacancy concentration and grain size, the largest electrical breakdown strength and lowest polarization hysteresis are achieved, giving an excellent recoverable energy storage density of 4.86 J/cm 3 under 32 kV/mm, accompanied by a high efficiency of 90.46 %. Additionally, the recoverable energy density achieves a high level of ∼3.5 J/cm 3 and energy storage efficiency is larger than 80 % over 28–160 °C, suggesting the outstanding temperature stability.