New Lead-free Piezoelectric Ceramics in Ternary AgNbO3-NaNbO3-KNbO3 Solid Solutions

0.2AgNbO(3)-0.8(xNaNbO(3)-yKNbO(3)) powders were synthesized by using the solid state reaction method under an air atmosphere. In order to suppress the direct reaction between AgNbO3 and KNbO3, we prepared the AgNbO3-NaNbO3 compound as a first priority. The AgNbO3-NaNbO3 compound was then reacted with KNbO3 at 850 degrees C similar to 1050 degrees C for 5 h. Due to the replacement of Na+ ions by K+ ions, a perovskite structure with an orthorhombic symmetry was revealed, but no major structural changes were observed for all investigated compositions. The electromechanical coupling factors (k(p)) and the piezoelectric constants (d(33)) were in the range of 37 similar to 40% and 110 similar to 123 pC/N, respectively. We observed no drastic increase of the properties due to coexistence of two phases as Pb(Zr,Ti)O-3.