PROBLEM TO BE SOLVED: To prevent the formation and dissipation of a gaseous Si compd. from a substrate under a high-temp. environment containing moisture by forming a barrier layer contg. Y2O3 or the like and having a thermal expansion coefficient approximate to that of the substrate into a specified thickness on a substrate consisting of Si-contg. ceramics, an Si-contg. alloy or the like. SOLUTION: On the Si-contg. substrate consisting or ceramics such as SiC and an Mo-Si alloy, a barrier layer for environmental and thermal protection is formed. As this barrier layer, the one contg. Y2O3, Y2SiO5 or the like is preferable, e.g. it is consisting of about 66 to 78 wt.% Y2O3, and the balance SiO2, and its thermal expansion coefficient is controlled to be ±3.0 ppm/ deg.C of that of the substrate, and its thickness is controlled to about 0.0127 to 0.127 mm. If necessary, an intermediate layer having about 0.0762 to 0.762 mm thickness and consisting of SiO2, mullite or the like and a bond layer having about 0.0762 to 0.152 mm thickness and consisting of Si, SiO2 or the like are formed between the substrate and the barrier layer. The barrier layer is formed preferably by thermal spraying after applying grit blasting at need.