Synthesis and characterization of novel high energy density capacitors for green energy

We have developed lead free high energy density capacitor materials, {\{}Ba(Zr$_{0.2}$Ti$_{0.8})$O$_{3}${\}}$_{(1-x)}$ {\{}(Ba$_{0.7}$Ca$_{0.3})$TiO$_{3}${\}}x [x = 0.10,0.15,0.20 (BZT$_{(1-x) }$BCT$_{x}$ ] with high dielectric constant and moderate breakdown voltage. The ceramic materials were prepared using high energy ball milling for 4 hours at 400 rpm. The ball milled powders were calcined at 1250$^{o}$C for 10hrs. Ceramic pellets having 13mm diameter were prepared using hydraulic press (2 ton) and sintered at 1400$^{o}$C-1500$^{o}$C for 4 hrs. X-ray diffraction studies of the sintered pellets revealed the rhombohedral/pseudo cubic crystal structure. The crystal structure was further confirmed by Raman spectra and TEM analysis. High dielectric constant and moderate polarization ($\sim $P$_{s}\sim $ 15-25 $\mu $C/cm$^{2})$ were obtained in the sintered pellets. The SEM images revealed monolithic grain growth in samples sintered at 1500$^{o}$C. Preliminary data show moderate breakdown field $\sim $ 15-20 kV/cm and energy density of 0.12-0.3 J/cm$^{3}$ for all compositions. Details of the results will be presented.