High‐temperature stability of YSZ and MSZ ceramic materials in CaF 2 –MgF 2 –MgO molten salt system

The high‐temperature stability of YSZ and MSZ specimens was investigated in CaF 2 –MgF 2 –MgO molten salt at 1200°C. YSZ was mostly composed of m‐ZrO 2 and a small part of YF 3 in the early stages. The formation of YF 3 was attributed to the chemical reaction between Y 2 O 3 and MgF 2 , which can lead to the leaching of Y 2 O 3 from YSZ . With an increase in exposure time, the degraded surface was coarser, and considerable amount of cracks, pores, and spallations were formed. Furthermore, no Y 2 O 3 was found up to 120 μm of the YSZ bulk in the early stages. MSZ was composed of t‐ZrO 2 after 24 hours. However, the volume fraction of m‐ZrO 2 was 72% after 72 hours, and CaZrO 3 was formed by the chemical reaction between CaO and ZrO 2 after 168 hours. In addition, the volume fraction of m‐ZrO 2 was 60% in 2.5 wt% MgO and 49% in 10 wt% MgO. In 5 wt% MgO, CaZrO 3 was formed. We demonstrate that the high‐temperature stability of MSZ was better than that of YSZ , and that 10 wt% MgO was much more stable than the other concentrations of MgO.