Synthesis of lead-free (K, Na)(Nb, Ta)O ₃ nanopowders using a sol-gel process

Lead-free (K _0.5Na _0.5)(Nb _0.7Ta _0.3)O ₃ piezoelectric material was successfully synthesized via a sol-gel process. Crystalline (K _0.5Na _0.5)(Nb _0.7Ta _0.3)O ₃ nanopowders were obtained after heat treatment at 700 °C. The particle size was estimated to be 87nm±23 nm. The transmission electron microscopy images showed that individual nanoparticles were single crystalline and had a pseudo-cubic structure with a lattice parameter of ∼3.96 Å. Both X-ray diffraction and scanning electron microscopy studies consistently showed that the crystallization of the (K _0.5Na _0.5)(Nb _0.7Ta _0.3)O ₃ occurred slightly above 500 °C. The samples have an appropriate stoichiometry as found via energy dispersive X-ray spectroscopy. The demonstration of the synthesis of (K _0.5Na _0.5)(Nb _0.7Ta _0.3)O ₃ via a sol-gel process as presented in this paper can provide an important foundation for the development of a synthetic route towards (K _0.5Na _0.5) (Nb _0.7Ta _0.3)O ₃ doped with various other elements for high performance piezoelectric devices.