Fig. 36 (a-c) Cross-sectional morphology of γ-Y2Si2O7, β-Yb2Si2O7, and β-Sc2Si2O7 after CMAS corrosion at 1500 ℃; (d) Schematic diagram of the formation of “blister” cracks. Reproduced with permission from Ref. [116] for (a), © Elsevier 2018. Reproduced with permission from Ref. [115] for (b-d), © Elsevier 2018. summarizes representative studies on the CMAS corrosion of rare earth silicates. For RE2Si2O7, β-phases with smaller RE ionic radii (such as Yb2Si2O7 and Lu2Si2O7) demonstrate relatively lower corrosion resistance than γ- and δ-phases, which contain larger ions, exemplified by γ-Y2Si2O7 and δ-Gd2Si2O7. At high temperatures, the CMAS grain boundary infiltration occurs in RE2Si2O7 resulting in a lower corrosion resistance relative to that of the RE2SiO5 counterpart. Within RE2SiO5, the corrosion resistance of the X1 phase positively correlates with the RE ionic radius but remains inferior to that of the X2 phase. Notably, for X2-RE2SiO5, corrosion resistance inversely correlates with RE ionic radius at lower temperatures, while at elevated temperatures, it becomes less sensitive to variations in the RE element species.
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