High-temperature alkali corrosion of Kyocera SN282 silicon nitride

• The role of Cs in corrosion of SN282 Si3N4 sintered with Lu2O3 was examined at 1200 °C.
• Cs accelerates SN282 oxidation.
• Adversity on Si3N4 corrosion resistance is stronger for Cs2O dissolving SiO2 than other alkali oxides.
• SN282 oxidation kinetics remain parabolic, but the oxides were thick, uneven, heterogeneous, cracked.

The role of Cs in corrosion of SN282 Si3N4 with 5.35 wt.% Lu2O3 was examined at 1200 °C for up to 20 h in oxygen with 220 ppm CsNO3 to determine particulars of SN282 corrosion under Cs, and high-temperature Cs+ behavior in glass silicate hosting 137Cs. Cs accelerates SN282 oxidation. The pronounced adverse effect of Cs on Si3N4 corrosion resistance is predicted thermodynamically more strongly for SiO2 dissolution in Cs silicate than in other alkali silicates. While oxidation kinetics remained parabolic, Cs oxide layers were thick, uneven, heterogeneous and cracked.