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

Abstract

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 °C for 1–5 h and 1100 to 1140 °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 °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 µm when the sintering temperature increased from 1100 to 1140 °C. The density of the BNBKL ceramics increased as the sintering temperature increased up to 1120 °C, after that it decreased. The highest density (6.05 g/cm3) and dielectric constant (5855), were obtained at the sintering temperature of 1120 °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.