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

The formation of alpha -AgI stabilized composites in the system AgI-Ag2O-B2O3 was investigated on the basis of the relationship between the cooling conditions in twin-roller quenching of melts and the microstructure of the products by means of X-ray diffraction (XRD) and field emission scanning electron microscopy (FE-SEM). A microstructure in which a-AgI microcrystals were 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 occurred 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 process of phase separation - aggregation - crystallization was also observed during the heating process up to around 120 degreesC in the 76AgI . 24(0.75Ag(2)O . 0.25B(2)O(3)) glass with a slightly smaller amount of AgI than the alpha -AgI stabilized composites. By using the heating and cooling processes of the 78AgI . 22(0.75Ag(2)O . 0.25B(2)O(3)) glass up to 110 degreesC we have successfully prepared the alpha -AgI stabilized composites, the microstructure 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 rights reserved.