Morphology and thermal conductivity of La2(Ce0.3Zr0.7)2O7-3Â wt.%Y2O3 coatings

The La2(Ce0.3Zr0.7)2O7-3 wt%Y2O3 coating was deposited by electron beam physical vapor deposition (EB-PVD). In order to reveal the structure evolution of the coating with the deposition parameter, the selected rotation rates of the substrate were 0 rpm, 5, 15 and 25 rpm, while the substrate temperature was fixed at 870 °C based on the structure zone model of 0.3 < Tsub/Tmp < 0.5. The microstructure of the column tips ranged from a 'triangular pyramid' (branch tips at 5 rpm and column tips at 0 rpm) to a 'roof top', then to a 'pyramid' with increasing the rotation rate. Under stationary deposition, the columnar crystals grew along the < 110 > direction. The tips of the 'roof top' or the pyramids were covered by four {111} planes. During rotation deposition, the columnar crystal grew along the < 100 > direction. If one assumes that the pore fraction has little effect on the thermal conductivity, the 'C' shaped Type I pores reduced the thermal conductivity, the straight Type I pores increased the thermal conductivity, the lamellar Type II pores significantly reduced the thermal conductivity. The minimum thermal conductivity was 0.761 W/(m K) at the rotation rate of 15 rpm. This gives an approach to optimize the structure of the La2(Ce0.3Zr0.7)2O7-3 wt%Y2O3 coatings.