Possibility of cofiring a nickel inner electrode in a (Na _0.5K_0.5)NbO₃-LiF piezoelectric actuator

Multilayer (Na_0.5K_0.5)NbO₃ (NKN) ceramics are considered promising candidates for lead-free piezoelectric actuators. The possibility of cofiring a nickel inner electrode in an NKN-LiF ceramic was investigated by evaluating the electrical properties and microstructures. The fabricated Ni inner electrode multilayer actuator sintered in a reduced atmosphere exhibited comparable dielectric properties to those of bulk NKN ceramics. The electric-field-induced strain was approximately 210 pm/V. Analysis based on the Rayleigh model showed that the extrinsic non-180° domain wall motion was suppressed in the multilayer structure. The microstructure of the NKN ceramic was not affected by cofiring with nickel, and the NKN/ Ni interface was both compositionally and structurally sharp. These results imply that the NKN-LiF ceramic can be cofired with nickel without any deterioration of its properties.