Fabrication of lead-free piezoelectric KNbO3 ceramics by modified solid state reaction method

Potassium niobate (KNbO3) fine powder has been successfully synthesized at a low temperature of 500 degrees C through a modified solid state reaction, in which urea [CO(NH2)(2)] plays an important role. High-density KNbO3 ceramics can be obtained by the conventional sintering of the synthesized KNbO3 fine powder with the addition of 1 mol % Co3O4, which is a sintering additive. Their crystal structure, microstructure, and dielectric and piezoelectric properties were characterized. The KNbO3 ceramics show a comparatively saturated P-E hysteresis loop. The remnant polarization and coercive field are 14 mu C/cm(2) and, 16 kV/cm, respectively. The KNbO3 ceramics also show piezoelectricity with a planar electromechanical coupling factor, k(p), of 16%.