Characterization of Ln4Al2O9 (Ln = Y, Sm, Eu, Gd, Tb) rare-earth aluminates as novel high-temperature barrier materials

A family of cuspidine-type rare-earth (RE) aluminates with the general formula Ln(4)Al(2)O(9) (Ln = Y, Sm, Eu, Gd, Tb) was prepared for potential use as thermal-barrier coating (TBC) materials with appropriate properties. Various trivalent lanthanides were applied to tailor the properties of the oxides for use as ceramic top coat (TC) materials intended for high-temperature applications. Following various heat treatments, the X-ray diffraction (XRD) results obtained demonstrated that Eu4Al2O9 (EuAM) possessed the greatest structural stability of all the samples at 1200 and 1300 degrees C. Moreover, Y4Al2O9 (YAM) had a long lifetime at 1000 degrees C, and was stable at 1100 degrees C. At 1200 degrees C, Sm4Al2O9 (SmAM) and Gd4Al2O9 (GdAM) were more stable than Tb4Al2O9 (TbAM). However, at 300-1000 degrees C, the TbAM exhibited the highest thermal expansion coefficient (TEC) of all the samples. At 600 degrees C, the thermal diffusivity values of the five compositions were favourable, and were lower than that of yttria-stabilised zirconia (YSZ) oxides.