Effects of K_4CuNb_8O_(23) on the structure and electrical properties of lead-free 0.94(Na_(0.5)K_(0.5))NbO_3-0.06LiNbO_3 ceramics

摘要

Dense K_4CuNb_8O_(23)-modified (K_(0.5)Na_(0.5))_(0.94)Li_(0.06)NbO_3 ceramics were prepared by normal sintering. The effects of K_4CuNb_8O_(23) on the phase structure, microstructure and electrical properties of the ceramics were studied. Results showed that K_4CuNb_8O_(23) induced a perovskite structure transition from coexistence of orthorhombic and tetragonal phases to orthorhombic symmetry. The addition of K_4CuNb_8O_(23) promoted the sintering of (K_(0.5)Na_(0.5))_(0.49)Li_(0.06)NbO_3 ceramics and simultaneously caused the grain growth. Moreover, K_4CuNb_8O_(23)-doping changed the (K_(0.5)Na_(0.5))_(0.94)Li_(0.06)NbO_3 to "hard" ceramics and significantly enhanced the mechanical quality factor Qm. It was found that the (K_(0.5)Na_(0.5))_(0.94)Li_(0.06)NbO_3 ceramics doped with 0.60 mol% K_4CuNb_8O_(23) exhibited a high mechanical quality factor (Q_m ～ 983) as well as relatively large d_(33) (136 pC/N) and k_p (35.9%), suggesting that this material is a promising candidate for lead-free piezoelectric ceramics for high-frequency applications.