Synthesis and phase stability of scandia, gadolinia and ytterbia co-doped zirconia for thermal barrier coating application

摘要

Scandia, gadolinia and ytterbia co-doped zirconia (SGYZ) ceramic powder was synthesized by chemical coprecipitation and calcination processes for application in thermal barrier coatings to promote the durability of gas turbines. The ceramic powder was agglomerated and sintered at 1150°C for 2 hours, and the powder exhibited good flowability and apparent density to be suitable for plasma spraying process. The microstructure, morphology and phase stability of the powder and plasma sprayed SGYZ coatings were analysed by means of scanning electron microscope and X-ray diffraction. Thermal conductivity of plasma sprayed SGYZ coatings was measured. The results indicated that the SGYZ ceramic powder and the coating exhibit excellent stability to retain single non-transformable tetragonal zirconia even after high temperature (1400°C) exposure for 500 hours and do not undergo a tetragonal-to-monoclinic phase transition upon cooling. Furthermore, the plasma sprayed SGYZ coating also exhibits lower thermal conductivity than yttria stabilized zirconia coating currently used in gas turbine engine industry. SGYZ can be explored as a candidate material of ultra-high temperature thermal barrier coatings for advanced gas turbine engines.