Firing Temperature Effects on Phase Formation, Microstructure and Electrical Properties of BNKLT-Sm Ceramics

Lead-free Bi-0.5(Na0.68K0.22Li0.10)(0.5)TiO3 + 0.003 mol Sm2O3 (BNKLT-Sm) ceramics were synthesized via the solid-state combustion technique with calcination temperatures between 750 and 850 degrees C and sintering temperatures between 1025 and 1100 degrees C for 2 h. The results showed that increasing the calcination temperature caused the percentage of perovskite phase and the particle size of the BNKLT-Sm powders increased. The BNKLT-Sm powder calcined at 800 degrees C displayed a pure perovskite structure without any impurity phases. The influence of the sintering temperature on the phase formation, microstructure and electrical properties of the ceramics was then investigated. All samples sintered at different temperatures possessed coexisting rhombohedral (R) and tetragonal (T) phases and the R phase became dominant when the sintering temperature increased. The microstructure of all ceramics showed a rectangular shape and anisotropic growth. The average grain size increased with increasing sintering temperature. Dielectric and ferroelectric behavior displayed relaxor characteristics in all samples. The maximum dielectric constant at T-m (epsilon(m) ) of 4777 and the highest remnant polarization (P-r ) of 5.03 mu C/cm(2) were obtained by the densest ceramics (5.85 g/cm(3)), which was sintered at 1075 degrees C for 2 h.

Automated summary

The lead-free BNKLT-Sm ceramics were synthesized using solid-state combustion technique with varying calcination and sintering temperatures. Increasing the calcination temperature resulted in increased perovskite phase percentage and particle size. The ceramics exhibited coexisting rhombohedral and tetragonal phases with the dominance of R phase at higher sintering temperatures, showing anisotropic growth in microstructure. Relaxor characteristics were observed in dielectric and ferroelectric behavior, with the densest ceramics sintered at 1075 degrees C for 2 hours showing the highest dielectric constant and remnant polarization.