Piezoelectric and Ferroelectric Properties of Li‐Doped (Bi 0.5 Na 0.5 )TiO 3 –(Bi 0.5 K 0.5 )TiO 3 –BaTiO 3 Lead‐Free Piezoelectric Ceramics

The piezoelectric and ferroelectric properties of 0.852[Bi 0.5 (Na (1− x ) Li x ) 0.5 ]TiO 3 –0.110(Bi 0.5 K 0.5 )TiO 3 –0.038BaTiO 3 ( x =0, 0.02, 0.05, 0.10, 0.15, and 0.30, abbreviated as BNKLBT x ) lead‐free piezoelectric ceramics were prepared by conventional ceramic processing. X‐ray diffraction on the samples revealed that Li + ions diffused into the Bi 0.5 Na 0.5 TiO 3 lattices (A‐site) and formed a solid solution with a single perovskite structure. All the samples could be sintered at 1160°–1180°C, with the density being on the order of >95% of the theoretical. The ceramics with x =0.10 exhibited the highest properties, with the piezoelectric coefficient being on the order of d 33 =235 pC/N, while the electromechanical coupling factors were found to be k p =0.30 and k t =0.45, respectively. The dielectric, pyroelectric, electromechanical, and ferroelectric behaviors were investigated as a function of temperature. It was found that the depolarization temperature T d showed a strong dependence on the content of Li + addition, shifting to a lower temperature with increasing Li + dopant.