Yttria-stabilized zirconia (YSZ) coatings were produced by reactively cosputtering metallic zirconium and yttrium targets in an argon and oxygen plasma using a system with multiple magnetron sputtering sources. Coating crystal structure and phase stability, as functions of Y2O3 content, substrate bias, and annealing temperature, were investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM), Results demonstrated that highly (111)-oriented tetragonal and cubic zirconia structures were formed in 2 and 4.5 mol% Y2O3 coatings, respectively, when the coatings were grown with an applied substrate bias, Conversely, coatings deposited with no substrate bias had random tetragonal and cubic structures. XRD analysis of annealed coatings showed that the cubic zirconia in 4.5 mol% Y2O3 coatings exhibited structural stability at temperatures up to 1200 degreesC, Transformation of the tetragonal to monoclinic phase occurred in 2 mol% Y2O3 coating during high-temperature annealing, with the fraction of transformation dependent on bias potential and annealing temperature.