Structural, microstructure and electrical properties of La2O3-doped Bi0.5(Na0.68K0.22Li0.1)0.5TiO3 lead-free piezoelectric ceramics synthesized by the combustion technique

Abstract The effect of firing temperatures on phase formation, microstructure and physical properties of [Bi 0.5 (Na 0.68 K 0.22 Li 0.1 ) 0.5 TiO 3 ] doped with La 2 O 3 at 0.1 wt% (BNKLLT) ceramics prepared by the combustion method was studied. Glycine was used as fuel and the ratio of raw material (corresponding oxidant metal nitrate) with fuel was about 1:0.56. The samples were calcined at 600–900 °C for 2 h and sintered at 1075–1150 °C for 2 h. The single rhombohedral peroveskite phase of BNKLLT powders was observed from the sample calcined at 750 °C for 2 h. The BNKLLT ceramics exhibited a pure peroveskite phase in all samples. The microstructures of the BNKLLT powders exhibited an agglomerated form while the grain ceramics exhibited a square shape. The average particle size and average grain size increased with increasing firing temperatures. The density, dielectric constant ( e r and e m ), P r and d 33 tended to increase with increasing sintering temperatures up to 1100 °C and then decreased. The maximum density (5.73 g/cm 2 ), maximum dielectric constant ( e r ~2572 and e m ~5536), good ferroelectric properties ( P r ~35.78 µC/cm 2 and E c ~22.42 kV/cm) and highest d 33 (210 pC/N) were obtained by the sample sintered at 1100 °C for 2 h.