Composition, mechanical properties and thermal cycling performance of YSZ toughened La2Ce2O7 composite thermal barrier coatings

Poor fracture toughness of La2Ce2O7 (LC) seriously prevents its practical applications as thermal barrier coatings. In this study, 8 wt% yttria stabilized zirconia (YSZ) was introduced to toughen the plasma-sprayed LC coatings. The mechanical performance, thermophysical properties and thermal shock resistance of the coatings were improved significantly, although a solid solution reaction between LC and YSZ occurred during spraying. For instance, the toughness, adhesion and thermal conductivity at 1273 K for 20 mol% YSZ doped LC coating achieved similar to 1.25 MPa.m(1/2), similar to 60 MPa and similar to 0.49 W/(m.K), respectively. Moreover, the thermal contraction was suppressed effectively. The enhanced toughness could be attributed to the increased fracture energy resulted from the reaction of LC with YSZ. The chipping spallation, caused by the high thermal stress as well as low fracture toughness, appeared within the ceramic top coat near the bond coat during cycling. These findings lay a theoretical foundation for the toughening of brittle coatings.