Development of an oxygen sensor for molter 44.5% lead-55.5% bismuth alloy

A potentiometric sensor for measuring oxygen activity in molter 44.5% lead-55.5% bismuth alloy is under development. Three parts form this sensor: an In/In₂O₃ reference electrode, a ZrO₂/Y₂O₃ solid electrolyte, and a molybdenum working electrode. The oxygen partial pressure in the melt is calculated applying the Nernst equation to the potential difference measured by the sensor. The minimum oxygen partial pressure detected by this sensor is 10⁻⁴⁰ bar. The sensor has been calibrated with the following metal/metal oxide mixtures: Pb-Bi/PbO, Pb/PbO, Sn/SnO₂, and Bi/Bi₂O₃. Reproducible measurements of the oxygen pressure of PbO formation have been obtained. The sensor performance has been evaluated in 99.999% N₂ and air (20% O₂) environments.