Characterization of zirconia oxygen sensors with a molten internal reference for low-temperature operation

A miniature zirconia oxygen sensor with a molten internal reference was developed for low-temperature use. As the internal reference, In–In2O3, Sn–SnO2, and Pb–PbO were tested. Sensors with Sn–SnO2 and Pb–PbO worked well at low temperatures near 550 K, and were superior to one with In–In2O3. The sensor with a molten reference responded quickly to temperature changes. An advantage of using a molten reference instead of a solid reference is that the molten reference has good contact with the zirconia electrolyte due to its wettability.