Selection and optimization of Sb and Ta co-doped (K 0.41 Na 0.59 )(Nb 1-x-y Sb x Ta y )O 3 lead-free ceramics

Lead-(K 0.41 Na 0.59 )(Nb 1-x-y Sb x Ta y )O 3 (abbreviated as KNNST) ceramics with x = 0.0–0.15 and y = 0.0–0.2 were successfully synthesized and thoroughly investigated. The analysis of the XRD patterns recorded for KNNST ceramics revealed the presence of orthorhombic, tetragonal, and rhombohedral perovskite phases. The nature of the phase formed was influenced by the concentration of Sb or Ta. Good physical, dielectric, ferroelectric, and piezoelectric properties were recorded for the Sb-doped (K 0.41 Na 0.59 )NbO 3 ceramics when the Sb content was 0.06 M ( ε r = 945, k p = 0.33, k t = 0.39, d 33 = 145 pC/N, and tan δ = 0.15). The co-doping of KNN ceramics with Sb and Ta significantly affects the structure, density, and electromechanical properties of the materials. When the rhombohedral and tetragonal ( R – T ) phases of (K 0.41 Na 0.59 )(Nb 0.79 Sb 0.06 Ta 0.15 )O 3 coexisted, the ceramics exhibited improved electrical characteristics with d 33 = 170 pC/N, k p = 0.47, k t = 0.41, T C = 315 °C, and P r = 12.6 μC/cm 2 . Additionally, with the Ta content was 0.15 M and the Sb content was 0.06 M, the value of S max (0.086%) and d 33 * (356 pm/V) increased significantly.