Nonstoichiometric (K,Na)NbO3 ceramics: Densification and electrical properties

In order to clarify the influence of excess ions in A or B sites on perovskite (K,Na)NbO₃ ceramics, various compositions of (K_0.48Na_0.52)Nb_1+x%O₃ (ABO₃) ceramics where x is in the range of ±1 % were prepared by conventional solid state method and their densification, structure, dielectric and piezoelectric properties were investigated. Results showed that a small amount of excess A-site ions could compensate for the deficiency of K and Na ions in A-sites caused by volatilization resulting in good piezoelectric properties. The ceramics with x?=??0.1 exhibited optimum piezoelectric properties with d ₃₃?=?127pC/N and k _p?=?0.41. However, presence of too much alkali elements (x?<??0.5) led to deterioration of density, dielectric and piezoelectric properties, although the crystal structure was not changed. The electrical properties, on the other hand, were not sensitive to the B-site excess ions. These results are expected to be very useful for further designing of (K,Na)NbO₃-based ceramics as lead-free alternatives to piezoelectric materials.