Physical and electric properties of lead-free (Na_0.5K_0.5)NbO₃-Ba(Zr_0.04Ti_0.96)O₃ ceramics

抄録

Extending the investigations on (Na_0.5K_0.5)NbO₃-based solid solution for lead-free piezoelectric ceramics, this paper consider the complex solid-solution system (Na_0.5K_0.5)NbO₃-Ba(Zr_0.04Ti_0.96)O₃ [NKN-BZT]. (Na_0.5K_0.5)NbO₃ with 0-10 mol% Ba(Zr_0.04Ti_0.96)O₃ has been prepared following the conventional mixed oxide process. X-ray diffraction analysis revealed that, during sintering, all of the Ba(Zr_0.04Ti_0.96)O₃ diffuses into the lattice of (Na_0.5K_0.5)NbO₃ to form a solid solution. Only a orthorhombic phase with a perovskite structure was found in this system. It was found that the samples with a low content of Ba(Zr_0.04Ti_0.96)O₃ exhibit relatively good physical and electric properties. For 0.98 (Na_0.5K_0.5)NbO₃-0.02Ba(Zr_0.04Ti_0.96)O₃ ceramics, the electromechanical coupling coefficients of the planar mode k_p and the thickness mode k_t reach 0.26 and 0.52, respectively, at the sintering of 1100°C for 2 h. The ratio of thickness coupling coefficient to planar coupling coefficient is 2. For 0.98(Na_0.5K_0.5)NbO₃-0.02Ba(Ti_0.96Zr_0.04)O₃ ceramics, the electromechanical coupling coefficients of the planar mode k_p and the thickness mode k_t reach 0.3 and 0.55, respectively, at the sintering of 1100°C for 5 h. With suitable Ba(Zr_0.04Ti_0.96)O₃ concentration and sintering condition, good physical and electric properties were obtained. Our results show that 0.98(Na_0.5K_0.5)NbO₃-0.02Ba(Zr_0.04Ti_0.96)O₃ solid solution ceramics are one of the promising lead-free ceramics for high frequency electromechanical transducer applications.