Langasite microstructure etching and characterization method for high temperature devices

Assessing the health of large industrial components such as aircraft engine blades is essential in high-temperature environments; however, conventional pressure sensors do not function at temperatures above 1100 °C. In this paper, a new Langasite (LGS) fabrication method, which enables the manufacturing of microstructures from high-melting, hard-brittle, and difficult-to-machine materials, is proposed. An HCl and H3PO4 mixed solution is used to achieve micron-level precision, allowing rapid and accurate manufacturing of microstructure equipment and technology. The etched surface was analyzed by X-ray photoradiation spectroscopy, energy-dispersive X-ray spectroscopy, and high-resolution transmission electron microscopy. The results showed that the etching did not affect the crystal's structure and properties. Moreover, a hot-pressing direct bonding method was used to seal the cavity, avoiding the thermal stress mismatch between indirect materials in high-temperature applications. A sealed 1-cm-in-diameter and 200-μm-thick diaphragm pressure sensor was fabricated by wet etching and hot-pressing bonding microstructures. The test results showed that the device can withstand pressures of 1 MPa at 1100 °C with an average sensitivity of 404 Hz/kPa. Therefore, the proposed method provides a simple and low-cost solution for the manufacturing of small and precisely-controlled structures made of high-temperature resistant, hard and brittle materials that are difficult to process.