Effects of Sb-doping on the formation of (K, Na)(Nb, Sb)O3 solid solution under hydrothermal conditions

(K, Na)(Nb, Sb)O3 (KNNS) lead-free peizoceramic powders were successfully synthesized by hydrothermal treatment at 240 °C for 8 h using the KOH, NaOH, Nb2O5 and Sb2O3 as raw materials. Effects of Sb-doping on the crystal structure and morphology of the as-prepared powders were investigated by powder X-ray diffraction (XRD), Raman spectra (Raman), scanning electron microscope (SEM), transmission electron microscopy (TEM) and selected area electron diffraction (SAED). The Sb element was successfully doped into the alkaline niobate perovskite structure to form crystalline (K0.7Na0.3)(Nb0.95Sb0.05)O3 lead-free piezoelectric ceramic powder, which has a hexagonal morphology due to the aggregation growth of small grains. Phase and morphology evolutions with the reaction time were also studied, and a possible formation mechanism was proposed.