Phase formation and stability in reactively sputter deposited yttria-stabilized zirconia coatings

Yttria-stabilized zirconia (YSZ) coatings were produced by reactively cospu ttering metallic zirconium and yttrium targets in an argon and oxygen plasm a using a system with multiple magnetron sputtering sources. Coating crysta l structure and phase stability, as functions of Y2O3 content, substrate bi as, and annealing temperature, were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM), Results demonstrated that high ly (111)-oriented tetragonal and cubic zirconia structures were formed in 2 and 4.5 mol% Y2O3 coatings, respectively, when the coatings were grown wit h an applied substrate bias, Conversely, coatings deposited with no substra te bias had random tetragonal and cubic structures. XRD analysis of anneale d coatings showed that the cubic zirconia in 4.5 mol% Y2O3 coatings exhibit ed structural stability at temperatures up to 1200 degreesC, Transformation of the tetragonal to monoclinic phase occurred in 2 mol% Y2O3 coating duri ng high-temperature annealing, with the fraction of transformation dependen t on bias potential and annealing temperature.