Microstructure of superionic glassy composites with stabilized α-AgI

Abstract

Microstructures of twin-roller quenched samples in the system AgI-Ag 3BO 3 were investigated by means of a field-emission-type scanning electron microscope. A 66.7AgI · 33.3Ag 3BO 3 glass sample with typical X-ray diffraction halo patterns exhibited homogeneous morphology. Small amounts of fine particles, 20–40 nm in diameter, were observed in the 85.6AgI · 14.4Ag 3BO 3 sample, for which no X-ray crystalline peaks were observed. Large amounts of fine particles (about 40 vol.%) of α-AgI of about 20–40 nm diameter in a glass matrix were dispersed in the 90.1AgI · 9.9Ag 3BO 3 sample, for which the peaks of α-AgI were only observed at room temperature in the X-ray diffraction pattern. However, large grains of β-AgI, several hundreds nm in diameter, were observed in the 92.5AgI · 7.5Ag 3BO 3 sample. The microstructure of the 90.1AgI · 9.9Ag 3BO 3 composite heated at 120 °C, which was higher than the glass-transition temperature of the matrix glass, was analogous to that of the quenched 92.5AgI · 7.5Ag 3BO 3 sample with the large grains of β-AgI originally observed.