Electromechanical Properties of Acceptor‐Doped Lead‐Free Piezoelectric Ceramics

We have studied the processing and electromechanical properties of Mn and Fe‐doped 0.88[Bi 0.5 Na 0.5 TiO 3 ]–0.08[Bi 0.5 K 0.5 TiO 3 ]–0.04[Bi 0.5 Li 0.5 TiO 3 ] 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°C–1150°C) to achieve the highest density and mechanical quality factor. Mn or Fe doping resulted in a considerable enhancement of Q m in both planar and thickness resonance modes. In 1.5 mol% Mn‐doped ceramics sintered at 1100°C, a planar Q m of about 970 and tanδ of 0.88% were obtained. In Fe‐doped ceramics, a planar Q m as high as 900 was achieved. Acceptor dopants also resulted in decreasing the coupling coefficients, the piezoelectric charge coefficient, and the dielectric constant.