Fabrication and electrical properties of Sc-doped (K, Na) NbO₃ multilayer ceramics with Ni internal electrodes

Abstract To develop low-cost, lead-free multilayer piezoelectric ceramics with Ni internal electrodes, we investigated Sc doping effects on (K, Na)NbO 3 -based ceramics. Acting as an acceptor, Sc enhanced the piezoelectric constant and, by suppressing semiconduction during sintering, improved the insulation resistance. However, excessive Sc doping accelerated degradation via oxygen vacancy formation and migration ( E a = 1.3 eV). Prototype 0.3 mol% Sc-doped multilayer ceramics with Ni interlayer electrodes exhibited a volume resistivity of 3 × 10 9 Ω m and a piezoelectric constant of 131 pm V −1 . These findings demonstrate that defect chemistry principles derived from Ni-BaTiO 3 multilayer ceramic capacitors are effective for designing Ni-cofired KNN multilayer ceramics.