The properties of rare-earth-containing oxynitride glasses in the Ln-Si-Al-O-N systems (Ln=Dy, Er, Gd, La, Nd, Sm, Y, Yb) were investigated and the following results were obtained.
(1) The glass transition temperature and the softening temperature in these glasses are in a range of 915-950°C and 960-1020°C, respectively.
(2) The correlation between the glass transition and softening temperatures of glasses and the radius of rare-earth ion is weak in these oxynitride glasses.
(3) The oxidation behaviors of the Ln-Si-Al-O-N glasses were analyzed by assuming that the weight change was proportional to the n-th power of oxidation time, and it was found that the oxidation exponent, n, tends to decrease and that the oxidation resistance tends to increase as the radius of rare-eath ion decreases.
(4) The Yb-Si-Al-O-N glass has the best oxidation resistance in the Ln-Si-Al-O-N glasses obtained in this work.
(5) In the oxidation process of the Yb-Si-Al-O-N glass, n equals 1 at the initial stage (interface reaction controlled oxidation), 1/2 at the middle stage (diffusion controlled oxidation) and 1/6 at the final stage of oxidation. In the stage of n=1/6, the oxidation rate is decelerated than that of the parabolic law, because many crystals grow from the interface to the inner parts of glass and the amount of glassy phase at the vicinity of interface are contracted during oxidation.