Miniaturized piezoelectric structures for application temperatures up to 1000 °C

Miniaturized piezoelectric structures based on the material langasite are fabricated and characterized. Single crystalline langasite is a high-temperature stable material and can be excited using the piezoelectric effect up to temperatures above 1000 °C. The scope of our research is to design and realize small piezoelectric structures to serve as resonant sensors or active electronic components at high temperatures. Wet chemical etch processes are developed which enable isotropic and anisotropic etching with rates up to 90 μm/h. Small structures such as membranes as well as cantilevers are prepared. Electrical and optical characterization provides information about the electromechanical properties of those structures. Resonance properties are determined with electrical impedance measurements in-situ at temperatures close to 1000 °C. The temperature dependent frequency shift and the resonator quality factor are determined for membranes, cantilevers and tuning forks. In addition, investigations with a laser interferometer are obtained. Thereby, the spatial distribution of the vibration displacement is observed for several piezoelectric devices.

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