DIELECTRIC AND PIEZOELECTRIC PROPERTIES OF Mn DOPED (K, Na)0.96Sr0.02NbO3 CERAMICS

Dense lead free ceramics with composition of (K0.5Na0.5)0.96Sr0.02Nb1-x MnxO3 (x = 0,0.01,0.02,0.03,0.04) were successfully prepared by conventional mixed oxide method, and their dielectric and piezoelectric properties have been investigated. The X-ray diffraction patterns indicated phase transition from peroveskite structure with orthorhombic symmetry to pseudo-tetragonal symmetry with increasing Mn content. Low loss tangent and relative high planar electromechanical coupling factor were obtained at x = 0.02 by the introduction of Sr and Mnion. The main parameters for the composition of x = 0.02 are: ϵ33 T/ϵ0 = 479, d33 = 121 kp = 41%, Qm = 298, tanδ = 1.6%, Tc = 391°C. The rates of resonant frequency variation, αfr, and planar coupling factor variation, αkp, with temperature 80°C are −1.85% and +1.19%, respectively. This material may be suitable for applications in ultrasonic transducers.