Fabrication of lead-free piezoelectric (Na 0.5 K 0.5 )NbO 3 ceramics by a modified solid-state reaction method

Sodium potassium niobate, (Na 0.5 K 0.5 )NbO 3 , fine powder has been successfully synthesized at the low temperature of 550degC through a modified solid-state reaction method, in which urea [CO(NH 2 ) 2 ] plays an important role. High-density (Na 0.5 K 0.5 )NbO 3 ceramics could be obtained by conventional sintering of the synthesized (Na 0.5 K 0.5 )NbO 3 fine powder with the addition of 0.03 mol% Co 3 O 4 as a sintering additive. The crystal structure, microstructure, and dielectric and piezoelectric properties were characterized. The (Na 0.5 K 0.5 )NbO 3 ceramic showed a comparatively saturated P-E hysteresis loop. The (Na 0.5 K 0.5 )NbO 3 ceramic also displayed piezoelectricity with a piezoelectric constant d 33 of 126 pC/N and a planar electromechanical coupling factor k p of 33%.