Enhanced energy storage properties in Nb-modified Bi0.5Na0.5TiO3-SrTiO3 lead-free electroceramics

Lead-free (1-x)Bi0.5Na0.5TiO3-xSrTiO(3)+ywt%Nb2O5 electroceramics were synthesized using the conventional method to investigate the influences of SrTiO3 content and Nb2O5 doping on the material's phase structure, microstructure, and energy storage properties. All the investigated compositions possessed a single perovskite phase structure of pseudocubic symmetry. The introduction of SrTiO3 and Nb2O5 led to a weakened relaxor characteristic and a decrease of T-m. The microstructure was refined by Nb2O5 doping, and the average grain size of the 0.6Bi(0.5)Na(0.5)TiO(3)-0.4SrTiO(3) sample decreased drastically from similar to 10 to similar to 1 mu m when 2.5wt% Nb2O5 was added. Enhanced electrical breakdown and polarization were achieved for the samples with the refined microstructure. Among the various Bi0.5Na0.5TiO3-based ceramics, 0.6Bi(0.5)Na(0.5)TiO(3)-0.4SrTiO(3)+2.5wt%Nb2O5 ceramic exhibited excellent energy-storage properties with thermal stability, in which large recoverable energy-storage density W-rec similar to 1.82J/cc and efficiency similar to 81% were both achieved. Our results indicate that this ceramic is a promising material for lead-free energy storage applications.