Study of nickel inner electrode lead-free piezoelectric ceramics

A (K,Na)NbO₃ (KNN)-based multilayer piezoelectric ceramic with nickel inner electrodes was successfully fabricated by co-firing in a reducing atmosphere. We studied the compositional modification of KNN in order to increase reducing resistance in the sintering process, and obtained a good composition by using a solid solution with CaZrO₃. A multilayer ceramic specimen had a ratio between the strain and induced electric field S/E of 360 pm/V, which is close to the highest value of KNN-type non-textured ceramics ever reported. Nickel is a suitable electrode material for multilayer structures with thinner ceramic layers, because of a high electro-migration resistance and low material cost. Thus, nickel inner electrode multilayer ceramics with KNN are good candidates as lead-free materials to replace PZT for several piezoelectric applications.