SiCN–Sc 2 Si 2 O 7 environmental barrier coatings were fabricated on the surface of C/SiC composites at low temperatures by adding Li 2 CO 3 as sintering aids. With this addition, the fabrication temperature could be lowered about 100–200°C. The shrinkage of the polysilazane–Sc 2 Si 2 O 7 bars with and without Li 2 CO 3 was tested by dilatometer. The results indicate that the shrinkage speed of the polysilazane–Sc 2 Si 2 O 7 bar with Li 2 CO 3 is faster than the one without Li 2 CO 3 , indicating that the Li 2 CO 3 greatly promotes the sintering of polysilazane–Sc 2 Si 2 O 7 . Water-vapor corrosion behavior of the SiCN–Sc 2 Si 2 O 7 coated C/SiC composites was carried out at 1250°C. The results reveal that the SiCN–Sc 2 Si 2 O 7 coatings can effectively protect the C/SiC composites. The corrosion resistance of SiCN–Sc 2 Si 2 O 7 coatings is not degraded by adding Li 2 CO 3 .