Optimization and thermal cycling behavior of La₂Ce ₂O₇ thermal barrier coatings

The La₂Ce₂O₇ (LC) coating with the La/Ce ratio close to 1 was obtained by atmospheric plasma spraying, using La ₂Ce_2.5O₈ as a feedstock powder and optimized spray parameters. The spray distance plays a significant role in terms of phase composition, phase stability, as well as porosity of the LC coating, while keeping other spray parameters constant. The plasma-sprayed coatings were prepared and thermally cycled by gas-burner tests to evaluate thermal cycling lifetime. The thermal cycling lifetime of the LC/YSZ double-layer coating was more than three times the lifetime of a single-layer LC coating and comparable to the YSZ coating at operating temperature of ∼1230 °C. The thermal cycling lifetimes of the LC/YSZ coating were ∼40% longer at operating temperature of ∼1320 °C, but much lower at operating temperature of ∼1350 °C compared to the optimized YSZ coating. The failure mechanisms for the LC and LC/YSZ coatings thermally cycled under different conditions were also established in this work.