Thermal aging and CMAS corrosion behaviors of Y2SiO5 ceramic for environmental barrier coatings

Yttrium silicate (Y2SiO5) is considered as one of the most promising candidate materials for environmental barrier coatings. In this paper, Y2SiO5 powder with a single phase were successfully prepared by hightemperature solid phase reaction method. The influence of sintering behavior on the microstructure, phase composition and mechanical properties of Y2SiO5 ceramics was studied at 1400 degrees C. In addition, the corrosion behavior and mechanism of Y2SiO5 against CMAS at 1250 degrees C and 1350 degrees C were also investigated. The results showed that the grain size of the prepared Y2SiO5 ceramic was about 1.28 mu m with relatively uniform, and there were many pore structures. Although Y2SiO5 was still the main phase, a new small amount of Y4.67(SiO4)3O phase was formed in Y2SiO5 ceramics after sintering at 1400 degrees C for 25 h. The sintering phenomenon of Y2SiO5 ceramics occurred at 1400 degrees C: the porosity decreased and the grain size grew. With the increase of sintering time, fracture toughness first increased and then decreased. The maximum fracture toughness was 4.84 MPa m1/2 after 50 h sintering. Part of Y2SiO5 was dissolved in CMAS melt and Ca4Y6(SiO4)6O rare-earth oxyapatite phase was generated after CMAS corrosion for 24 h. The corrosion zone could be divided into loose corrosion area (about 93 mu m thickness) and dense reaction layer with Ca4Y6(SiO4)6O phase (about 16 mu m thickness) at 1250 degrees C for 24 h. With the increase of corrosion time and corrosion temperature, both the corrosion depth of CMAS and the thickness of dense reaction layer increases. The dense Ca4Y6(SiO4)6O layer can effectively resist the further corrosion of CMAS melt.