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 Li2CO3 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 P4bm, 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-degrees, suggesting the outstanding temperature stability.