Effects of Nb, Mn doping on the structure, piezoelectric, and dielectric properties of 0.8 Pb (Sn _0.46 Ti _0.54) O ₃-0.2 Pb (Mg _1/3 Nb _2/3) O ₃ piezoelectric ceramics

Nb and Mn were doped, respectively, to 0.8Pb(Sn_0.46Ti _0.54)O₃-0.2Pb(Mg_1/3Nb_2/3)O ₃ (PST-PMN) to improve electrical properties for meeting the requirement in various fields. The additions of Nb and Mn influence in a pronounced way the structure, and improve the densities of the ceramics. Nb-doped PST-PMN increased the piezoelectric coefficient d₃₃, planar electromechanical coupling k_p, and relative dielectric constant ε, indicating "soft" piezoelectric behavior. Mn doping played a "hard" part, which significantly enhanced the mechanical quality factor Q_m without deteriorating other piezoelectric properties. The most excellent properties of Nb-doped PST-PMN were obtained with doping amount of 0.75 mol%, specifically d₃₃, k_p, being on the order of 455 pC/N, 57.5% and 3560, respectively. The addition of 0.75 mol% Mn for PST-PMN presented the optimum electrical properties, with Q_m of 554, d ₃₃ of 430 pC/N, k_p of 57.0%, ε of 2770. It was proposed that the addition of Nb, Mn generated different defect dipoles involved in the domain walls motion and intrinsic piezoelectric responses, leading to different effects on electrical properties.