Phase Boundary Design and Electrical Properties of Sb/Ta/Li Co-doped KNN-Based Pb-Free Piezoelectric Ceramics

Pb-free piezoelectric ceramic materials (K 0.48 Na 0.48 Li 0.04 )(Nb 0.92 Ta 0.08− x Sb x )O 3 (KNLNTS) were designed and prepared. The effects of varied Sb/Ta doping on the physical structure, surface morphology, and electrical characteristics of ceramics were also studied. The perovskite structure is present in all of the doped ceramic samples without any secondary phase (when x  < 0.05). All of the doped ceramic samples have a Curie temperature ( T C ) above 300°C. At the same time, the orthorhombic–tetragonal phase transition temperature ( T O–T ) is pushed closer to ambient temperature. Doping with Sb/Ta/Li changed the electrical characteristics of the samples and increased their piezoelectric properties. At x  = 0.03, the KNLNTS sample has the best piezoelectric properties: d 33  = 215 pC/N, Pr = 26.08 μC/cm 2 , T C  = 342.6°C.