Reaction-Layer Controlled CMAS Resistance in Rare-Earth Mg-Al Ceramics under Sustained Melt Exposure

This is the authors' abstract. We don't add key points for this paper.

The interaction of molten calcium-magnesium-aluminosilicate (CMAS) with rare-earth magnetoplumbite-type hexaaluminate ceramics (REMgAl 11 O 19 , RE = La, Ce, Nd, Gd) was investigated at 1350°C for 10, 24, and 48 h under a sustained CMAS-excess environment. A dense, single-phase α-Al 2 O 3 was exposed to CMAS for 48 h under similar conditions and served as an alumina-rich reference. XRD analysis shows that La-, Nd-, and Gd- containing compositions predominantly form magnetoplumbite-type hexaaluminates, whereas the Ce-containing composition also includes stable Al-rich oxides, including CeAlO 3 , α-Al 2 O 3 , and MgAl 2 O 4 . Despite comparable surface anorthite formation at 48 h, the mean substrate Ca signal increased from La to Nd to Gd, following the decrease in rare-earth ionic radius. The Ce-containing composition developed a continuous reaction layer with Al-rich and Mg-rich local chemistry and minimal Ca-Si incorporation, as confirmed by quantitative EDS analysis, whereas the α-Al 2 O 3 reference formed discontinuous reaction-product islands. These findings suggest that the continuity and composition of the reaction layer are important in limiting CMAS infiltration.