Effects of K4CuNb8O23 on the structure and electrical properties of lead-free 0.94(Na0.5K0.5)NbO3–0.06LiNbO3 ceramics

Dense K4CuNb8O23-modified (K0.5Na0.5)0.94Li0.06NbO3 ceramics were prepared by normal sintering. The effects of K4CuNb8O23 on the phase structure, microstructure and electrical properties of the ceramics were studied. Results showed that K4CuNb8O23 induced a perovskite structure transition from coexistence of orthorhombic and tetragonal phases to orthorhombic symmetry. The addition of K4CuNb8O23 promoted the sintering of (K0.5Na0.5)0.94Li0.06NbO3 ceramics and simultaneously caused the grain growth. Moreover, K4CuNb8O23-doping changed the (K0.5Na0.5)0.94Li0.06NbO3 to “hard” ceramics and significantly enhanced the mechanical quality factor Qm. It was found that the (K0.5Na0.5)0.94Li0.06NbO3 ceramics doped with 0.60 mol% K4CuNb8O23 exhibited a high mechanical quality factor (Qm ∼ 983) as well as relatively large d33 (136 pC/N) and kp (35.9%), suggesting that this material is a promising candidate for lead-free piezoelectric ceramics for high-frequency applications.