Phase stability and thermal insulation of YSZ and erbia-yttria co-doped zirconia EB-PVD thermal barrier coating systems

In order to cope with the ever-increasing operating temperature of aero gas turbines, new thermal barrier coatings are being investigated. Among the different solutions, erbia-yttria co-doped zirconia coatings made by electron-beam physical vapour deposition (EB-PVD) show promising results in terms of thermal insulation enhancement. Annealing of these coatings was performed at 1100 °C in air in order to investigate their stability in comparison with that of standard 8 wt% yttria-stabilized zirconia (8YSZ). Their thermal transport properties were measured using the laser-flash technique. The results show that the as-deposited co-doped coatings offered lower heat conduction than the standard ones in the studied temperature range (from room temperature to 1100 °C). However, the microstructural and phase transformations of the co-doped coatings after annealing were significantly greater than those of the standard coatings, hence strongly modifying their thermal insulation potential.