B5.3 - Selectivity Improvement of High-Temperature Resonant Gas Sensors using Micromachined Membrane Arrays
- SENSOR+TEST Conferences 2009
2009-05-26 - 2009-05-28
Congress Center Nürnberg
- Proceedings SENSOR 2009, Volume I
- B5 - Gas Sensors
- D. Richter, J. Sauerwald, H. Fritze - Clausthal University of Technology, Goslar, Germany
- 239 - 244
Different types of piezoelectric langasite (La3Ga5SiO14) membranes are manufactured using wet chemical etching. The membranes show thicknesses as low as 25 µm, leading to a resonance frequency of 60 MHz. Arrays of membranes are coated with platinum electrodes and different metal oxide sensor films such as CeO2 and SnO2 using pulsed laser deposition.
The sensor arrays are tested at 600 °C at different oxygen partial pressures in hydrogen and carbon monoxide containing gas mixtures. In comparison to conventional bulk acoustic wave resonators with larger thickness, i.e. lower fundamental frequency, the frequency shift caused by stoichiometry changes of the sensor films is increased by one order of magnitude, thereby enabling improved distinction between the above mentioned gases. CeO2 coated resonators show large changes of its resonance frequency at oxygen partial pressures below about 10E-15 bar, while SnO2 can be used to monitor gas mixtures
at oxygen partial pressures above about 10E-12 bar.