Low-temperature zirconia oxygen gauges based on RuO₂ electrode

Abstract

A low temperature oxygen gauge based on zirconia electrolyte has been developed. It makes use of RuO₂ as electrode material in place of platinum in conventional gauges. The low interfacial impedance of the RuO₂ electrode makes it possible to keep the cell resistance below 10⁶ ω even at low temperatures. Nernst's law tests indicate that this cell can give theoretical outputs down to 498 K campared to 923 K for gauges with platinum electrodes. Faraday's law tests confirm its good performance over a wide range of oxygen concentrations. High electronic conductivity, single oxide phase, slight non-stoichiometry and good adherence are responsible for the good performance of RuO₂ as electrode. An activation energy of 90.95 kJ/mole observed for the interface shows that the vacancy movement in the electrolyte is the rate controlling step. The evaporation of RuO₂ as RuO₄ gives rise to flow dependent output. This can be overcame by operating the cells at low temperatures though at the cost of speedy response. The low operating tempratures lead to a compact gauge with good stability.