Microstructure, dielectric and piezoelectric properties of lead-free Bi_(o.5)Na_(0.5)TiO_3-Bi_(0.5)K_(0.5)TiO_3-BiMnO_3 ceramics

摘要

To improve the piezoelectric properties of Bi_(0.5)Na_(0.5)TiO_3-based ceramics, a new perovskite-type lead-free piezoelectric (1 - x -y) Bi_(0.5)Na_(0.5)TiO_3— xBi_(0.5)K_(0.5)TiO_3—yBiMnO_3 system has been fabricated by a conventional solid-state reaction method and their microstructure, dielectric and piezoelectric properties have been investigated. The results of X-ray diffraction (XRD) analysis reveal that the addition of small amounts of BiMnO_3 did not cause a remarkable change in crystal structure, but resulted in an evident evolution in microstructure. An obvious secondary phase was observed in samples with high Bi_(0.5)K_(0.5)TiO_3 content. It is found from dielectric constant curves that low-temperature hump disappeared with increasing y and it appeared again with increasing x. The piezoelectric properties significantly increase with increasing Bi_(0.5)K_(0.5)TiO_3 and BiMnO_3 content. The piezoelectric constant and electromechanical coupling factor attain maximum values of d_(33) = 182 pC/N at x = 0-21(y = 0-01) and k_p = 0-333 at x= 018 (y = 001), respectively.