Lead containing oxides with perovskite structure are widely used as sensors and actuators. Among those materials lead titanate zirconate PbZr_1-xTi_xO₃ (PZT) and lead magnesium niobate-lead titanate, PMN-PT are the most prominent ones. The possible environmental hazard connected with lead has driven research of novel materials with comparable electrical and mechanical properties as PZT. Lead-free piezoelectric ceramics (1-x-y)Bi_0.5Na_0.5TiO₃-xBaTiO₃-yK_0.5Na_0.5NbO₃ (0.05 ≤ x ≤ 0.07 and 0.01 ≤ y ≤ 0.03) have been synthesized by the mixed oxide route and sintering. Preliminary electromechanical characterization revealed a remarkable strain of approximately 0.4 % at an electric field of 8 kV/mm close to the boundary between two compositions with dominant ferroelectric and anti-ferroelectric properties [1, 2, 3]. Room temperature powder neutron diffraction at the SPODI diffractometer at the FRM II TU Munich showed superstructure reflections which were indexed based on the tetragonal space group P4bm [4] and the rhombohedral one R3c [5]. As no superstructure reflections were detected on a synchrotron powder run the preliminary conclusion leads to a displacement of the oxygen atoms of their positions in the cubic system. No prominent domain structure as commonly seen in PZT polycrystals was observed in TEM experiments. In contrast, electron dif-fraction revealed weak superlattice reflections in prominent zone axes. Further investigations within the composition range given above are in progress.

[1]   S.-T. Zhang, A. B. Kounga, E. Aulbach, H. Ehrenberg, J. Rödel, Appl. Phys. Lett. 91 112906 (2007).

[2]   S.-T. Zhang, A. B. Kounga, E. Aulbach, T. Granzow, Wook Jo, H.-J. Kleebe, J. Rödel, J. Appl. Phys. 103 034107 (2008).

[3]   S.-T. Zhang, A. B. Kounga, E. Aulbach, Wook Jo, T. Granzow, H. Ehrenberg, J. Rödel, J. Appl. Phys. 103 034108 (2008).

[4]   G.O. Jones, P.A. Thomas, Acta Cryst. B 56, 426 (2000).

[5]   G.O. Jones, P.A. Thomas, Acta Cryst. B 58, 168 (2002).

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