Gas detecting langasite membranes by wet chemical etching

Piezoelectrically actuated membranes in lanthanum gallium silicate (langasite) were fabricated. The membranes have shown operating temperatures up to 850 degC and are applied as high temperature gas detecting devices by means of CeO₂ sensor films. The measurements show, that gas sensing with membranes is feasible and results in even higher frequency shifts as for thick plan-parallel resonators. A multi-step wet chemical etching process has been developed and was used to structure the langasite. Furthermore, membranes have been fabricated by using the different etch characteristics of doped and undoped langasite