Y4Al2O9 ceramics as a novel thermal barrier coating material for high-temperature applications

Considerable efforts are being invested to explore new alternative thermal barrier coating (TBC) materials to yttria stabilized zirconia (YSZ) for applications above 1473 K. In this work, Y4Al2O9 (YAM) ceramics were prepared by solid state reaction at 1873 K for 12 h. The phase stability, thermophysical properties and sintering-resistance behavior of the material were investigated. XRD results reveal that single monoclinic phase YAM is synthesized and no new phase appears after long-term annealing. The thermal conductivities of YAM ceramic decrease gradually with increase of temperature ranges from room temperature to 1273 K. The minimum value is similar to 1.81 W m(-1) K-1, which is lower than that of YSZ. Meanwhile, YAM shows moderate thermal expansion coefficient, about 8.91 x 10(-6) K-1 in the temperature range of 300-1473 K. Compared with YSZ, YAM has lower density and higher sintering-resistance ability, which is very favorable for TBC applications. These results imply that YAM can be a promising candidate material for the ceramic layer in TBC system. (C) 2014 Elsevier B.V. All rights reserved.