| Summary: | In this study, non-stoichiometry lead-free piezoelectric ceramic Li<sub>0.058</sub>(K<sub>0.48</sub>Na<sub>0.535</sub>)<sub>0.966</sub>(Nb<sub>0.9</sub>Ta<sub>0.1</sub>)O<sub>3</sub> (LKNNT) thick films were deposited on Pt/Ti/Si substrates using spin-coating method technology to form a LKNNT/Pt/Ti/Si structure of the micro-pressure thick films. Additionally, the influence on the crystalline properties, surface microstructure images, and mechanical properties, and the piezoelectric properties of the non-stoichiometry lead-free piezoelectric ceramic Li<sub>0.058</sub>(K<sub>0.48</sub>Na<sub>0.535</sub>)<sub>0.966</sub>(Nb<sub>0.9</sub>Ta<sub>0.1</sub>)O<sub>3</sub> (LKNNT) thick films were observed, analyzed, and calculated using X-ray diffraction (XRD), field-emission scanning electron microscopy (FE-SEM), focused ion beam (FIB) microscopy, nano-indention technology, and other instruments. This study was divided into two parts: The first part was the investigation into the fabrication parameters and properties of the bottom layer (Pt) and buffer layer (Ti). The Pt/Ti/Si structures were achieved by the DC sputtering method, and then the rapid thermal annealing (RTA) post-treatment process was used to re-arrange the grains and reduce defects in the lead-free Li<sub>0.058</sub>(K<sub>0.48</sub>Na<sub>0.535</sub>)<sub>0.966</sub>(Nb<sub>0.9</sub>Ta<sub>0.1</sub>)O<sub>3</sub> (LKNNT) thick films. In the second part, lead-free Li<sub>0.058</sub>(K<sub>0.48</sub>Na<sub>0.535</sub>)<sub>0.966</sub>(Nb<sub>0.9</sub>Ta<sub>0.1</sub>)O<sub>3</sub> (LKNNT) powder was prepared by the solid-state reaction method, and then acetic acid (C<sub>2</sub>H<sub>4</sub>O<sub>2</sub>) solvent was added to form a slurry for spin-coating technology processing. The fabrication parameters, thick film micro-structure, crystalline properties, nano-indention technology, and the piezoelectric coefficient characteristics of the developed lead-free Li<sub>0.058</sub>(K<sub>0.48</sub>Na<sub>0.535</sub>)<sub>0.966</sub>(Nb<sub>0.9</sub>Ta<sub>0.1</sub>)O<sub>3</sub> (LKNNT)/Pt/Ti/Si structure of the micro-pressure thick film devices a were investigated. According to the experimental results, the optimal fabrication processing parameters of the lead-free Li<sub>0.058</sub>(K<sub>0.48</sub>Na<sub>0.535</sub>)<sub>0.966</sub>(Nb<sub>0.9</sub>Ta<sub>0.1</sub>)O<sub>3</sub> (LKNNT) were an RTA temperature of 500 °C, a Ti buffer-layer thickness of 273.9 nm, a Pt bottom electrode-layer thickness of 376.6 nm, a theoretical density of LKNNT of 4.789 g/cm<sup>3</sup>, a lattice constant of 3.968 × 10<sup>−8</sup> cm, and a d<sub>33</sub> value of 150 pm/V. Finally, regarding the mechanical properties of the micro-pressure devices for when a microforce of 3 mN was applied, the thick film revealed a hardness of 60 MPa, a Young’s modulus of 13 GPa, and an elasticity interval of 1.25 μm, which are suitable for future applications of micro-pressure devices.
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