Role of A- and B-site excess doping on the improvement of the piezoelectric properties of BaTiO3 lead-free piezoceramics

Excess Li, Al, and Si co-doped BaTiO 3 (BT) piezoceramics were synthesized using a conventional solid-state reaction sintering method. The influences of excess A- and B-site doping on the crystalline structure, dielectric, ferroelectric, and piezoelectric properties of BT ceramics were studied and discussed. While ceramics had a tetragonal crystal structure, weak secondary phases appeared with an increase in the doping content. Compared to pure BT ceramics, the dielectric constant of the Li/Al/Si-doped ceramics decreased, but the dielectric loss decreased and remained at a relatively low level of approximately 0.017 with a Li–Al content of x and 0.02 with an excess Si doping content of Δ. The remnant polarization 2 P r reached the maximum values of 12.55 μC/cm 2 at x = 0.07 for excess Li–Al doped ceramics and 18.58 μC/cm 2 at Δ = 1.6% for excess Si doped ceramics. The piezoelectric constant d 33 was significantly improved owing to the excess doping of Li–Al and Si without decreasing the Curie temperature, and its maximum value was approximately 212 pC/N at x = 0.032. The excess Si doping at the B-site helped to improve and stabilize the piezoelectric properties of the ceramics in a wide excess composition range.