8wt% Yttria stabilized zirconia(8YSZ) thermal barrier coatings were fabricated by atmospheric plasma spraying. The coatings were exposed to high temperatures and phase evolution of 8YSZ coatings was investigated by a combination of X-ray powder diffraction and Rietveld refinement. The results show that,8YSZ powder mainly consistes of stable tetrgonal phase structure,while the as-sprayed coating mainly containes metastable tetragonal phase. The phase composition changes signific-antly in the first 10 h and t...