Yttrium aluminum perovskite(YAl O3)is a promising candidate material for environmental barrier coatings(EBCs)to protect Al2 O3 f/Al2 O3 ceramic matrix composites(CMCs)from the corrosion of high-temperature water vapor...Yttrium aluminum perovskite(YAl O3)is a promising candidate material for environmental barrier coatings(EBCs)to protect Al2 O3 f/Al2 O3 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 O3 for environmental barrier coating application.Herein,in order to make REAl O3 more thermal insulating,a novel high-entropy rare-earth aluminate ceramic(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 was designed and synthesized.The as-prepared(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 ceramic possesses close thermal expansion coefficient(9.02×10-6/oC measured from room temperature to 1200℃)to that of Al2 O3.The thermal conductivity of(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 at room temperature is 4.1 W·m-1K-1,which is almost one third of the value of YAl O3.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 O3/RE3 Al5 O12/(Al2 O3 f/Al2 O3 CMCs)is designed.Close thermal expansion coefficient to Al2 O3 and low thermal conductivity of(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3,as well as the formation of dense garnet layer at(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3/Al2 O3 interface,indicate that this new type of high-entropy ceramic is suitable as a candidate environmental barrier coating material for Al2 O3 f/Al2 O3 CMCs.展开更多
Structural and dielectric properties of Ce-doped BaTi_(0.97)Y_(0.03)O_(3)powders,with the chemical formulation(Ba_(1−x)Ce_(x))(Ti(_(0.97−x/4))-Y_(0.03))O_(3)such as x=0%,1%,3%,5%,7%and 9%,produced by the sol-gel metho...Structural and dielectric properties of Ce-doped BaTi_(0.97)Y_(0.03)O_(3)powders,with the chemical formulation(Ba_(1−x)Ce_(x))(Ti(_(0.97−x/4))-Y_(0.03))O_(3)such as x=0%,1%,3%,5%,7%and 9%,produced by the sol-gel method,have been investigated.X-ray diffraction analysis showed that Ce^(3+)ions incorporated Ba sites until x=7%indicating that this concentration represents a solubility limit of Ce^(3+)ions in BaTi_(0.97)Y_(0.03)O_(3)matrix.Scanning electron microscopy(SEM)analysis showed a decrease in grain size down to the same concentration of 7%.Raman spectroscopy analysis showed the appearance of A_(1g) mode,which we attributed to the effect of incorporation of Ce^(3+)and Y^(3+)in BaTiO_(3)matrix.Dielectric measurements revealed that doping with cerium lowers the temperature of permittivity maximum at the ferroelectric-to-paraelectric transition(FPT)of the BaTi_(0.97)Y_(0.03)O_(3)sample,and reaches a value that should be below 40℃ for x=9%.Moreover,the phenomenon of dielectric resonance was observed on all Ce-doped samples,which was not the case with other dopants as reported in the literature.展开更多
基金financial supported by the National Natural Science Foundation of China(Nos.51672064 and 51972089)。
文摘Yttrium aluminum perovskite(YAl O3)is a promising candidate material for environmental barrier coatings(EBCs)to protect Al2 O3 f/Al2 O3 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 O3 for environmental barrier coating application.Herein,in order to make REAl O3 more thermal insulating,a novel high-entropy rare-earth aluminate ceramic(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 was designed and synthesized.The as-prepared(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 ceramic possesses close thermal expansion coefficient(9.02×10-6/oC measured from room temperature to 1200℃)to that of Al2 O3.The thermal conductivity of(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3 at room temperature is 4.1 W·m-1K-1,which is almost one third of the value of YAl O3.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 O3/RE3 Al5 O12/(Al2 O3 f/Al2 O3 CMCs)is designed.Close thermal expansion coefficient to Al2 O3 and low thermal conductivity of(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3,as well as the formation of dense garnet layer at(Y0.2Nd0.2Sm0.2Eu0.2Er0.2)AlO3/Al2 O3 interface,indicate that this new type of high-entropy ceramic is suitable as a candidate environmental barrier coating material for Al2 O3 f/Al2 O3 CMCs.
文摘Structural and dielectric properties of Ce-doped BaTi_(0.97)Y_(0.03)O_(3)powders,with the chemical formulation(Ba_(1−x)Ce_(x))(Ti(_(0.97−x/4))-Y_(0.03))O_(3)such as x=0%,1%,3%,5%,7%and 9%,produced by the sol-gel method,have been investigated.X-ray diffraction analysis showed that Ce^(3+)ions incorporated Ba sites until x=7%indicating that this concentration represents a solubility limit of Ce^(3+)ions in BaTi_(0.97)Y_(0.03)O_(3)matrix.Scanning electron microscopy(SEM)analysis showed a decrease in grain size down to the same concentration of 7%.Raman spectroscopy analysis showed the appearance of A_(1g) mode,which we attributed to the effect of incorporation of Ce^(3+)and Y^(3+)in BaTiO_(3)matrix.Dielectric measurements revealed that doping with cerium lowers the temperature of permittivity maximum at the ferroelectric-to-paraelectric transition(FPT)of the BaTi_(0.97)Y_(0.03)O_(3)sample,and reaches a value that should be below 40℃ for x=9%.Moreover,the phenomenon of dielectric resonance was observed on all Ce-doped samples,which was not the case with other dopants as reported in the literature.
