Thermal and mechanical properties of Ta2O5 doped La2Ce2O7 thermal barrier coatings prepared by atmospheric plasma spraying

摘要

La2Ce2O7 (LC) is a new promising thermal barrier coating (TBC) material for high-temperature applications. However, the sudden decrease of thermal expansion coefficient (TEC) at similar to 623 K limits its application. In this study, the plasma-sprayed La2Ce1.7Ta0.3O7.15 (LCT) coating was developed by partial substitution of Ce4+ in LC with Ta5+. LCT coating shows lower thermal conductivity between 298 K and 1273 K (0.54-0.71 W/(m.K)) than LC coating (0.65-0.85 W/(m.K)) and the traditional yttria partially stabilized zirconia (YSZ) coating (1.53-1.72 W/(m.K)). It also exhibits excellent thermal stability at least up to 1573 K for 1000 h. What is more, the sudden TEC drop is suppressed owing to the reduced oxygen vacancy concentration governed by Ta5+ -substitution content. As a result, LCT TBC shows an improved thermal cycling lifetime in an air furnace as compared to LC TBC.