Fast response solid electrolyte oxygen sensors with porous thin film electrodes

A novel solid electrolyte sensor with considerably improved response times is presented. The new so-called eFIPEX [etched flux (Φ) probe experiment] is based on the FIPEX [flux (Φ) probe experiment] sensor applied for the measurement of molecular and atomic oxygen concentrations. A main application is the measurement of atmospheric atomic oxygen aboard sounding rockets up to altitudes of 250 km. eFIPEX employs a new manufacturing technique for its electrodes combining two manufacturing steps-the deposition of platinum films with a polyol process and electrochemical etching to carve out the electrode geometry. Selectivity toward atomic oxygen is achieved through gold plating. All work steps can be completed in ambient air. Electrodes with thicknesses of 200 nm to 1.5 μm are manufactured and characterized with optical and electron microscopy as well as with energy dispersive x-ray spectroscopy. It is shown that the significantly faster response times are related to pores in the platinum film reaching down to the substrate. The new eFIPEX were flown in comparison with conventional FIPEX sensors on the PMWE-2 sounding rocket flight showing significantly improved performance. Due to the easier fabrication and the superior transient behavior, this new sensor system will be preferentially used in future missions.