Abstract
Potassium niobate (KNbO3) ceramics are usually porous due to their poor sinterabilty under ordinary firing in air, although the single crystal exhibits a large amount of piezoelectricity. We found a marked improvement in the sinterability of KNbO3 ceramics on substituting a small amount of Pb for K. However, the amount of piezoelectricity of the ceramics was small due to their fine grains (< 0.2 µm). In order to realize large grains, we substituted Na and Pb for K, and fired the ceramics for long periods of time.