Abstract:

Dense lead free ceramics of (K _0.5 Na _0.5 ) _0.96 Sr _0.02 Nb _1-x Mn _x O ₃ (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: ε^T₃₃/ε₀=479, d₃₃=121pC/N K_p=41%, Q_m=298, tanδ=1.6%, T_c=391℃. The rates of resonant frequency variation, α_fr, and planar coupling factor variation, α_Kp, with temperature are --1.85% and 1.19% at 80℃, respectively. This material may be suitable for applications in ultrasonic transducers.

Key words: lead free, piezoelectric ceramics, dielectric, transducer