Affiliation: | aCAS Key Laboratory of Rare Earths on Advanced Materials and Valuable Utilization of Resources, Changchun Institute of Applied Chemistry, Chinese Academy of Sciences, Changchun 130022, Jilin, China bGraduate School of the Chinese Academy of Sciences, Beijing 100049, China cBeijing Institute of Aeronautical Materials, Beijing 100095, China |
Abstract: | Lanthanum magnesium hexaluminate (LaMgAl11O19, LMA) is an attractive material for thermal barrier coatings (TBCs), and the failure of its coating was studied in this work by thermal cycling, X-ray diffraction, dilatometric measurement and thermal gravimetric-differential thermal analysis. The dilatometric measurement indicates that even though the bulk material of LMA has a higher sintering-resistance than the typical TBC material, i.e. yttria-stabilized zirconia (YSZ), the plasma sprayed coating of LMA has two serious contractions due to the re-crystallization of LMA and phase transitions of alumina. LMA has similar thermal expansion behaviour with alumina, leading to a good thermal expansion match between LMA and the thermally grown oxide layer. On the other hand, the plate-like structure of LMA not only results in a low thermal conductivity, low Young's modulus, but also a high stress tolerance, and these are believed to be the reasons for the long thermal cycling life of LMA coating. |