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

Abstract

Lead-free (K _0.48 Na _0.48 Li _0.04 )(Nb _0.95 Sb _0.05 )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 °C presented a pure perovskite phase with an orthorhombic phase. The particle size was in the range of 0.1–0.4 μ m. The two-step sintering temperature (range: 950 to 1100 °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 °C (density ( ρ ): 4,35 g cm ^−3 ; electromechanical coupling factor ( k _p ): 0.33, k _t : 0.35; dielectric constant ( ε _r ): 849; dielectric loss (tan δ ): 0.073; maximum dielectric constant ( ε _max at T _C ): 6659; piezoelectric constant ( d _33 ): 195 pC N ^−1 ; remanent polarization ( P _r ): 16.1 μ C cm ^−2 ; energy storage density ( W _rec ): 0.36 J cm ^−3 ; energy storage efficiency ( η ): 48.1%; t _2 = 4 h), proving the efficacy of the two-step sintering technique.

Keywords

• lead-free ceramics
• KNLNS
• the two-step sintering method
• energy storage efficiency