Fabrication of ZrO2(MgO)/CaAl2O4+CaAl4O7 Bilayer Structure Used for Sulfur Sensor by Laser Cladding

The ZrO2(MgO)/CaAl2O4+CaAl4O7 bilayer structure used for sulfur sensor was fabricated by the laser powder cladding (LPC) method using the MgO partially stabilized zirconia (2.7 wt% MgO-PSZ) as the substrate and the CaAl2O4 + CaAl4O7 composites as the coating material. The microstructure, phase composition and ionic conductivity of this bilayer structure were investigated for better application in the sulfur determination. The results indicated that the structure of the coating was dense and well-distributed with a thickness of 100 μm. The ionic conductivity of the ZrO2(MgO)/CaAl2O4+CaAl4O7 bilayer structure was up to 2.06 × 10−3 S·cm−1 at 850 °C that met the required ionic conductivity of ionic conductor for solid electrolyte sulfur sensor. Furthermore, the sulfur sensor Mo|Cr+Cr2O3| ZrO2(MgO)| CaAl2O4+CaAl4O7|[S]Fe| Mo was assembled used this bilayer structure and tested in carbon-saturated liquid iron at 1773 K and 1823 K. The stability and reproducibility of the sulfur sensor were satisfactory and could be used for sulfur determination in the liquid iron.