Thermodynamic Properties and Thermal Cycling Lifetimes of LaMeAl11O19/YSZ Thermal Barrier Coatings

LaMeAl11O19 ceramics is a kind of thermal barrier coating（TBC） material with promising application prospect due to its unique crystal structure, excellent thermodynamic properties, low thermal conductivity, and high temperature phase stability. Here, LaMeAl11O19/YSZ（Me=Mg, Cu, Zn） thermal barrier coatings were prepared by atmospheric plasma spraying（APS）. Failure analysis of the coating was carried out by burner rig test and other analysis techniques. The results show that LaMgAl11O19（LMA）, LaZnAl11O19（LZA） and LaCuAl11O19（LCA）powders are decomposed during the plasma spraying, resulting in different contents of magnetoplumbite phase in the coatings, which may be an important factor responsible for their distinction of thermal cycling lifetimes. The LaMeAl11O19 layer is delaminated upon YSZ layer due to mismatch of thermal expansion coefficient between LaMeAl11O19 layer and YSZ layer and volume shrinkage caused by recrystallization of amorphous phase. Then the YSZ layer is exposed high temperature, accelerating sintering and TGO growth, and promoting the delamination of the YSZ layer from the bond coat. At low temperature, with the increase of the atomic number of the divalent Me2+,the thermal conductivity of the LaMeAl11O19 decreases. At high temperature, LCA coating has better infrared emissivity（0.88, 600 ℃） than both LMA and LZA, which weakens the contribution of photon conduction to thermal conductivity and leads to the reduction of thermal conductivity. Therefore, LCA coating has potential application in high temperature infrared radiation coating.