Mn-modified (K_(0.5)Na_(0.5))_(0.96)Sr_(0.02)NbO_3 Lead-free Piezoelectric Ceramics

Dense lead free ceramics of (K0.5Na0.5)0.96Sr0.02Nb1-xMnxO3 (x=0,0.01,0.02,0.03,0.04) were successfully prepared by a conventional mixed oxide method. The X-ray diffraction patterns revealed pure peroveskite structure after Mn doping as compared to the original composition. This was attributed to the inhibition of K+ volatility during sintering process. Dielectric anomaly was observed and explained by multiple-cell structure resulting from Mn-induced lattice distortion. Low loss tangent and relatively high planar electromechanical coupling factor were obtained at x=0.02. The main parameters for the composition of x=0.02 are:e33 T/e0=479, d33=121pC/N Kp=41%, Qm=298, tan5=1.6%, Tc=391℃. The rates of resonant frequency variation,αfr, and planar coupling factor variation,αKp, with temperature are -1.85% and 1.19% at 80℃, respectively. This material may be suitable for applications in ultrasonic transducers.