Figure 3

FESEM micrographs of glass-ceramics: (a) S1, (b) S2, (c) S3, (d) S4, (e) S5. The magnification of (a–c) is 1,000 times. The magnification of (d,e) is 10,000 times. The magnification of (f) is 500 times, and magnified the position of the spinel.