Lead-Free Piezoelectric Ceramic Micro-Pressure Thick Films

Abstract

In this study, non-stoichiometry lead-free piezoelectric ceramic Li0.058(K0.48Na0.535)0.966(Nb0.9Ta0.1)O3 (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 Li0.058(K0.48Na0.535)0.966(Nb0.9Ta0.1)O3 (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 Li0.058(K0.48Na0.535)0.966(Nb0.9Ta0.1)O3 (LKNNT) thick films. In the second part, lead-free Li0.058(K0.48Na0.535)0.966(Nb0.9Ta0.1)O3 (LKNNT) powder was prepared by the solid-state reaction method, and then acetic acid (C2H4O2) 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 Li0.058(K0.48Na0.535)0.966(Nb0.9Ta0.1)O3 (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 Li0.058(K0.48Na0.535)0.966(Nb0.9Ta0.1)O3 (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/cm3, a lattice constant of 3.968 × 10−8 cm, and a d33 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.