Fabrication and evaluation of lead-free piezoelectric ceramic LF4 thick film deposited by aerosol deposition method

(K0.44Na0.52Li0.04)(Nb0.86Ta0.10Sb0.04)O-3 (LF4) thick films were directly prepared on glass, stainless-steel and Pt/Ti/ZrO2 substrates at room temperature by the aerosol deposition method (ADM). The effects of moisture content in the starting powder and postdeposition annealing temperature on the dielectric properties of LF4 film were investigated. The LF4 film prepared using preheated powder (moisture content of 0.006%) has dielectric properties with high stability at increasing frequencies, whereas the LF4 film prepared with non-preheated powders (0.21%) has a dielectric constant that decreases abruptly at higher frequencies. When the postdeposition annealing temperature of the film was 600 degrees C, the dielectric constant increased from 200 to 343 at 1 MHz with increasing preheating temperature from 150 to 1100 degrees C. Also, the dielectric constant of the film increased from 231 to 559 with increasing annealing temperature from 400 to 1000 degrees C. These results strongly indicate that moisture elimination in starting powders through preheating and postdeposition annealing for ADM plays an important role in realizing good dielectric properties of LF4 film for practical application as lead-free Piezoelectric ceramics. Also, the Curie temperature (T-c) of the deposited LF4 film was 250 degrees C.