Physical and electric properties of lead-free (Na0.5K0.5)NbO3-Ba(Zr0.04Ti0.96)O3 ceramics

Extending the investigations on (Na0.5K0.5)NbO3-based solid solution for lead-free piezoelectric ceramics, this paper consider the complex solid-solution system (Na0.5K0.5)NbO3-Ba(Zr0.04Ti0.96)O-3 [NKN-BZT]. (Na0.5K0.5)NbO3 with 0-10 mol% Ba(Zr0.04Ti0.96)O-3 has been prepared following the conventional mixed oxide process. X-ray diffraction analysis revealed that, during sintering, all of the Ba(Zr0.04Ti0.96)O-3 diffuses into the lattice of (Na0.5K0.5)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(Zr0.04Ti0.96)O-3 exhibit relatively good physical and electric properties. For 0.98 (Na0.5K0.5)NbO3-0.02Ba(Zr0.04Ti0.96)O-3 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 degrees C for 2 h. The ratio of thickness coupling coefficient to planar coupling coefficient is 2. For 0.98(Na0.5K0.5)NbO3-0.02Ba(Ti0.96Zr0.04)O-3 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 degrees C for 5 h. With suitable Ba(Zr0.04Ti0.96)O-3 concentration and sintering condition, good physical and electric properties were obtained. Our results show that 0.98(Na0.5K0.5)NbO3-0.02Ba(Zr0.04Ti0.96)O-3 solid solution ceramics are one of the promising lead-free ceramics for high frequency electromechanical transducer applications. (C) 2009 The Ceramic Society of Japan. All rights reserved.