Formation of alpha-AgI stabilized composites from AgI-Ag2O-B2O3 melts and glasses

The formation of alpha -AgI stabilized composites in the system AgI-Ag2O-B2 O3 was investigated on the basis of the relationship between the cooling co nditions in twin-roller quenching of melts and the microstructure of the pr oducts by means of X-ray diffraction (XRD) and field emission scanning elec tron microscopy (FE-SEM). A microstructure in which a-AgI microcrystals wer e dispersed in glass matrices was obtained during twin-roller quenching of 80AgI . 20(0.75Ag(2)O . 0.25B(2)O(3)) and 84AgI . 16(0.75Ag(2)O . 0.25B(2)O (3)) melts with the following process: (1) a phase separation of liquid occ urred to form dispersed particles of the AgI-rich amorphous phase, (2) the particles of the amorphous phase aggregated to form island regions, and (3) alpha -AgI microcrystals were formed from the island regions. A similar pr ocess of phase separation - aggregation - crystallization was also observed during the heating process up to around 120 degreesC in the 76AgI . 24(0.7 5Ag(2)O . 0.25B(2)O(3)) glass with a slightly smaller amount of AgI than th e alpha -AgI stabilized composites. By using the heating and cooling proces ses of the 78AgI . 22(0.75Ag(2)O . 0.25B(2)O(3)) glass up to 110 degreesC w e have successfully prepared the alpha -AgI stabilized composites, the micr ostructure of which was very similar to that of the composites prepared by twin-roller rapid quenching of melts. (C) 2001 Elsevier Science B.V. All ri ghts reserved.