Thermal stability of lanthanum zirconate plasma-sprayed coating

Lanthanum zirconate (La2Zr2O7, LZ) is a newly proposed material for thermal barrier coatings (TBCs). The thermal stability of LZ coating was studied i n this work by long-term annealing and thermal cycling. After long-term ann ealing at 1400 degreesC or thermal cycling, both LZ powder and plasma-spray ed coating still kept the pyrochlore structure, and a preferred crystal gro wth direction in the coating was observed by X-ray diffraction. A considera ble amount of La2O3 in the powder was evaporated in the plasma flame, resul ting in a nonstoichiometric coating. Additionally, compared with the standa rd TBC material yttria-stabilized zirconia (YSZ), LZ coating has a lower th ermal expansion coefficient, which leads to higher stress levels in a TBC s ystem.