Y2O3 coatings were prepared on aluminum substrates using plasma spraying with argon as primary gas. Structure and morphology were characterized by using X-ray diffraction, scanning electron microscopy and metallographic analysis. Results show that Y2O3 coating’s porosity is 5.6%. Coatings prepared with helium as secondary gas are purely white. However, there are black spots when hydrogen is used as secondary gas. A phase transformation from cubic to monoclinic tends to take place during the spraying operation under argon and hydrogen atmosphere. However this prejudicial transformation can be suppressed by using helium instead of hydrogen.