Optimization of the calcination and two-step sintering temperatures of (K0.48Na0.48Li0.04)(Nb0.95Sb0.05)O3 ceramics

Lead-free (K0.48Na0.48Li0.04)(Nb0.95Sb0.05)O-3 (KNLNS) ceramics have been successfully optimized for the calcination and two-step sintering temperatures. The experimental results reveal that the KNLNS powder calcined at 850 or 900 degrees C presented a pure perovskite phase with an orthorhombic phase. The particle size was in the range of 0.1-0.4 mu m. The two-step sintering temperature (range: 950 to 1100 degrees C) significantly affects the structure, microstructure, and electrical properties of KNLNS ceramics. The presence of a pure perovskite phase with good crystallization is observed in all samples. The microstructure was researched by varying the two-step sintering temperature to obtain a dense microstructure and a clear grain boundary in order to optimize their piezoelectric properties. The best electrical properties of KNLNS ceramics were recorded at the optimized temperature of 1050 degrees C (density (rho): 4,35 g cm(-3); electromechanical coupling factor (k(p)): 0.33, k(t): 0.35; dielectric constant (epsilon(r)): 849; dielectric loss (tan delta): 0.073; maximum dielectric constant (epsilon(max) at T-C): 6659; piezoelectric constant (d(33)): 195 pC N-1; remanent polarization (P-r): 16.1 mu C cm(-2); energy storage density (W-rec): 0.36 J cm(-3); energy storage efficiency (eta): 48.1%; t(2) = 4 h), proving the efficacy of the two-step sintering technique.