Dielectric and piezoelectric properties of Mn‐doped (K,Na) 0.96 Sr 0.02 NbO 3 ceramics

Dense, lead‐free ceramics with composition 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 the sintering process. A dielectric anomaly was observed and explained by a 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 T 33 / ε 0 = 479, d 33 = 121 pC/N, K p = 41%, Q m = 298, tan δ = 1.6%, T c = 391 °C. The rates of resonant frequency variation, α  f   r, and planar coupling factor variation, α  K   p, with a temperature of 80 °C are –1.85% and +1.19%, respectively. This material may be suitable for applica‐ tions in ultrasonic transducers. (© 2006 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)