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High-entropy(Y_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Er_(0.2))AlO_3: A promising thermal/environmental barrier material for oxide/oxide composites
Yttrium aluminum perovskite(YAl O_3) is a promising candidate material for environmental barrier coatings(EBCs) to protect Al_2 O_(3 f)/Al_2 O_3 ceramic matrix composites(CMCs) from the corrosion of high-temperature water vapor in combustion environments. Nevertheless, the relatively high thermal conductivity is a notable drawback of YAl O_3 for environmental barrier coating application. Herein, in order to make REAl O_3 more thermal insulating, a novel high-entropy rare-earth aluminate ceramic(Y_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Er_(0.2))AlO_3 was designed and synthesized. The as-prepared(Y_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Er_(0.2))AlO_3 ceramic possesses close thermal expansion coefficient(9.02 × 10~(-6)/oC measured from room temperature to 1200℃) to that of Al_2 O_3. The thermal conductivity of(Y_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Er_(0.2))AlO_3 at room temperature is 4.1 W·m~(-1)K~(-1), which is almost one third of the value of YAl O_3. Furthermore, to effectively prevent the penetration of water vapor from possible pores/cracks of coating layer, which are often observed in T/EBCs, a tri-layer EBC system REAl O_3/RE_3 Al_5 O_(12)/(Al_2 O_3 f/Al_2 O_3 CMCs) is designed. Close thermal expansion coefficient to Al_2 O_3 and low thermal conductivity of(Y_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Er_(0.2))AlO_3, as well as the formation of dense garnet layer at(Y_(0.2)Nd_(0.2)Sm_(0.2)Eu_(0.2)Er_(0.2))AlO_3/Al_2 O_3 interface, indicate that this new type of high-entropy ceramic is suitable as a candidate environmental barrier coating material for Al_2 O_3 f/Al_2 O_3 CMCs.
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Journal of Materials Science & Technology
2020年12期

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