Effect of Co 2 O 3 Additive on Structure and Electrical Properties of 85(Bi 1/2 Na 1/2 )TiO 3 –12(Bi 1/2 K 1/2 )TiO 3 –3BaTiO 3 Lead‐Free Piezoceramics

In this paper, Co 2 O 3 ‐added‐85(Bi 1/2 Na 1/2 )TiO 3 –12(Bi 1/2 K 1/2 )TiO 3 –3BaTiO 3 (BNKB) lead‐free piezoceramics were fabricated by the conventional solid oxide routine. By the use of X‐ray photonic spectra, X‐ray diffraction, and scanning electronic microscope, the valence state of Co cations, lattice distortion, and microstructures were investigated. It is revealed that the Co 2 O 3 addition affects the concentration of Co 3+ cations and changes the tetragonality c / a of the perovskite lattice. The variation in tetragonality and microstructure, combined with the acceptor doping behavior of Co 2 O 3 , play a determinant role in the depolarization temperature T d , mechanical quality factor Q m , and other electrical properties of the ceramics. The T d is elevated to 157°C for 0.5 mol% Co 2 O 3 addition; and the Q m reaches a maximum of 626 at 1.5 mol% Co 2 O 3 addition, which is in the highest flight compared with other BNKB ceramics reported until now.