Effect of monovalent ions on the piezoelectric properties of (Na0.5K0.5)NbO3–(M)TaO3 ceramics

Sodium potassium niobate (NKN) ceramics modified by lithium or silver tantalates were prepared in order to compare the effect of monovalent additives and then their crystal structure, sinterability, and dielectric and piezoelectric properties were investigated with varying the amount of additives. It was clearly seen for the silver tantalate added NKN ceramics that dielectric constant, kp and d33 were dependent on the density and microstructure. While NKN ceramics added with lithium tantalate exhibited strong dependence on the existence of morphotrophic phase boundary and second phase formation rather than the density. These results were explained in terms of the phase formed and microstructure and sinterability.