Enhancing the properties of ZrO2(MgO)/CaO–Al2O3 bilayer structure by doping CeO2 for application in metallurgical electrochemical sensor

Abstract

The bilayer structure of ZrO2(MgO)/CaAl2O4+CaAl4O7 used as high temperature ion-conducting ceramic for industrial applications in electrochemical sensor was fabricated by screen-printing technology using ZrO2(MgO) electrolyte as the substrate and CaAl2O4+CaAl4O7 complexes doped with CeO2 as the coating materials. The effect of the CeO2 doped in the CaAl2O4+CaAl4O7 complex on the properties of the bilayer structure was investigated in terms of the phase composition, microstructure, ionic conductivity and application in sulfur and phosphorus determination. It was demonstrated that there was a transition layer between the electrolyte substrate and the CaAl2O4+CaAl4O7 coating when CeO2 added, forming a structure of electrolyte substrate/transition layer/coating, which made the CaAl2O4+CaAl4O7 coating adhere to the ZrO2(MgO) electrolyte more firmly compared with that of without CeO2 addition. A considerable increase in total ionic conductivity was observed with increasing the temperature and the amount of CeO2 addition. The bilayer structure of ZrO2(MgO)/CaAl2O4+CaAl4O7 could be used as a bifunctional electrolyte for preparation of sulfur sensor and phosphorus sensor at different measurement conditions. Furthermore, the electrochemical sensor had been assembled by the bilayer structure of ZrO2(MgO)/CaAl2O4+CaAl4O7 doped 3.0 wt% CeO2 and achieved good effect in sulfur and phosphorus determination in the liquid iron at 1773 K.