Electromechanical Properties of Acceptor-Doped Lead-Free Piezoelectric Ceramics

We have studied the processing and electromechanical properties of Mn and Fe-doped 0.88[Bi0.5Na0.5TiO3]-0.08[Bi0.5K0.5TiO3]-0.04[Bi0.5Li0.5TiO3] piezoelectric ceramics prepared by the mixed oxide route. Different amounts of Mn (0.01, 0.014, 0.015, 0.016, 0.017, 0.02, 0.022) or Fe (0.0125, 0.015, 0.0175) were doped to this lead-free piezoelectric composition. Ceramics were sintered at different temperatures (1075 degrees C-1150 degrees C) to achieve the highest density and mechanical quality factor. Mn or Fe doping resulted in a considerable enhancement of Qm in both planar and thickness resonance modes. In 1.5mol% Mn-doped ceramics sintered at 1100 degrees C, a planar Qm of about 970 and tan of 0.88% were obtained. In Fe-doped ceramics, a planar Qm as high as 900 was achieved. Acceptor dopants also resulted in decreasing the coupling coefficients, the piezoelectric charge coefficient, and the dielectric constant.