Electrical properties of Ni-particle-dispersed alkaline niobate composites sintered in a protective atmosphere

Co-firing of piezoceramics with metals is drawing ever-increasing attention. This article reports Ni-particle-dispersed [Li0.06(K0.5Na0.5)0.94]NbO3 (LKNN/Ni) lead-free piezoelectric composites that were sintered in a protective atmosphere of nitrogen gas. The base metal Ni was not oxidized and the piezoelectric LKNN preserved the perovskite structure. The microstructure observations show that Ni particles were uniformly dispersed in LKNN ceramics matrix. With increasing Ni content from 0 to 20 vol%, the piezoelectric constant d33 of the LKNN/Ni composites decreased from 165 to 23 pC/N, and the corresponding dielectric constant ɛr greatly increased. The 95%LKNN-5%Ni composite still exhibited a typical ferroelectric loop; however, the P-E curves measured for Ni > 5 vol% composites demonstrated some metallic characteristics. The LKNN/Ni composites could find applications in piezoelectric actuators with functionally graded microstructure (FGM).