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

The formation of α-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 α-AgI microcrystals were dispersed in glass matrices was obtained during twin-roller quenching of 80AgI · 20(0.75Ag2O·0.25B2O3) and 84AgI · 16(0.75Ag2O·0.25B2O3) 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) α-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 °C in the 76AgI · 24(0.75Ag2O·0.25B2O3) glass with a slightly smaller amount of AgI than the α-AgI stabilized composites. By using the heating and cooling processes of the 78AgI·22(0.75Ag2O·0.25B2O3) glass up to 110 °C we have successfully prepared the α-AgI stabilized composites, the microstructure of which was very similar to that of the composites prepared by twin-roller rapid quenching of melts.