Firing Temperatures Effect on Phase Formation, Microstructure and Electrical Properties of BNBKL Ceramics Fabricated via the Solid-State Combustion Technique

Lead-free 0.85Bi0.5Na0.475Li0.025TiO3-0.11Bi0.5K0.5TiO3-0.04BaTiO3 (BNBKL) ceramics were prepared by the solid-state combustion technique. The BNBKL powders and ceramics were calcined and sintered between 650 to 850 degrees C for 1-5 h and 1100 to 1140 degrees C for 2 h, respectively. The effect of firing temperatures on the phase structure, microstructure, and electrical properties of BNBKL ceramics was investigated. X-ray diffraction patterns of BNBKL powders showed a pure perovskite phase structure at a calcination temperature of 800 degrees C for 3 h. The BNBKL ceramics sintered at different temperatures possessed coexisting rhombohedral (R) and tetragonal (T) phases. The ceramic grains showed a polyhedral shape with directionless growth. The average grain size of the BNBKL ceramics increased from 0.80 to 1.26 mu m when the sintering temperature increased from 1100 to 1140 degrees C. The density of the BNBKL ceramics increased as the sintering temperature increased up to 1120 degrees C, after that it decreased. The highest density (6.05 g/cm3) and dielectric constant (5855), were obtained at the sintering temperature of 1120 degrees C. As the sintering temperature increased, the polarization hysteresis loops (P-E loops) of the BNBKL ceramics exhibited less saturation and were more pinched, indicating more relaxor behavior.