A planar gas sensor based on rf. sputtered yttria-stabilized zirconia

A planar electrochemical potentiometric CO sensor, composed of three electrodes on a sputtered yttria stabilized zirconia film, has been fabricated and studied. The working and counterelectrodes were made with Pt, while the reference electrode was made with Au. The counterelectrode was covered with a thin layer of the catalyst. The catalytical oxidation of the CO in the mixture by CuO coupled with the diffusion resistance of the oxide layer result in a oxygen concentration gradient across the oxide layer and cell. An EMF (electromotive force) is thereby induced, and its value depends on the CO concentration in the gas. The experimental results obtained over the temperature range of 300-450°C are presented. The present study shows that this type of cell exhibits a measurable EMF (typically 100-200 mV at 300-400°C). The EMF response to CO injection (ΔEMF) was experimentally determined. High sensing accuracy was obtained at 340°C