Mullite as an electrochemical probe for the determination of low oxygen activity in liquid iron

Oxygen activities in liquid iron deoxidized with aluminium were measured at 1873 K, using a mullite electrolyte having a Cr-Cr₂O₃ reference mixture. These results were compared with those obtained using commerical tube-type ZrO₂-8 mol% MgO and plug-type ZrO₂-9 mol% MgO probes, along with oxygen activities calculated from analysis. Oxygen activities from EMF measurements using mullite and plug-type probes were found to be in agreement with those calculated from the Al/Al₂O₃ equilibrium and those estimated from analyzed oxygen contents. Polarization effect due to electrochemical oxygen transport was observed in a commerical tube-type ZrO₂-based probe. Supersaturation in liquid iron deoxidized with aluminium was also measured at 1873 K.