Nobuyuki Itakura

Crystallization of α-AgI from AgI–Ag2O–MxOy (MxOy=B2O3, GeO2, WO3) melts and glasses

Abstract Crystallization behavior of α-AgI was investigated by means of XRD, DSC, and FE–SEM from the melts and glasses of AgI–Ag 2 O–M x O y (M x O y =B 2 O 3 , GeO 2 , WO 3 ). α-AgI microcrystals were formed by rapid quenching of melts with around 80 mol% AgI and also by heating of glasses with around 75 mol% AgI. In any system, α-AgI fine particles of about 20–40 nm in diameter were dispersed in the composites from the melts; there were no marked differences in microstructure among the samples in those systems. The α-AgI microcrystals included in the composites obtained from the melts had a large heterogeneous lattice strain at room temperature. The samples of those systems showed almost the same degree of lattice strain at room temperature. On the other hand, AgI-rich amorphous particles with 40–60 nm in diameter were dispersed in the twin-roller quenched glasses of any system with 75 mol% AgI, for which no X-ray crystalline peaks were observed. In those glasses being heated up to 95–120°C, island regions of several hundreds of nanometers were observed; the island regions contained finely dispersed α-AgI particles of about 20–30 nm in diameter. It is noteworthy that the crystallization temperatures of α-AgI are much lower than the α–β phase transformation temperature (147°C). The crystallization of α-AgI from the glass below the α–β phase transformation temperature supports the possibility of the existence of α-AgI nuclei in the AgI rich amorphous particles in the as-quenched glasses with 75 mol% AgI.

Microstructure of AgI–Ag2O–B2O3 fast ion conducting glasses with large amounts of AgI

Abstract The microstructure of twin-roller quenched glasses in the system AgI–Ag 2 O–B 2 O 3 (Ag 2 O/B 2 O 3 =3) has been investigated by means of a field emission type scanning electron microscope (FE-SEM). Fine particles, 40–60 nm in diameter, were dispersed in twin-roller quenched glasses with 75 mol% AgI, for which no X-ray diffraction peaks due to crystalline phases were observed. The particle size observed in the glass with 75 mol% AgI was larger than that of the α-AgI particles 20–30 nm in diameter) observed in the α-AgI-stabilized composite with 82 mol% AgI. The larger particles observed in the glass with 75 mol% AgI were probably an AgI rich amorphous phase. The AgI rich amorphous particles aggregated to form island regions, several hundreds of nanometers in size when the AgI content was increased from 75 to 80 mol%. Such island regions were shown to be composed of finely dispersed α-AgI particles of 20–30 nm in diameter and an amorphous part. Similar island regions were also observed when the glass with 75 mol% AgI was heat-treated up to 120 ∘ C. In both cases α-AgI nuclei present in the AgI rich amorphous phase grow to form α-AgI microcrystals in the quenching process of a melt containing 80–82 mol% AgI or in the reheating process on a glass with 75 mol% AgI.

Coloration and decoloration of glasses by photo-irradiation and heat treatment for easily recycled glass products

We have been developing a technique of coloration and decoloration of glasses by photo-irradiation and heat-treatment for application to easily recyclable colored glass products. The mechanisms of the photo-induced coloration of glasses used in this research are a) the photo-induced defects (color centers) formation, b) the photo-induced change in oxidation state of ions, and c) the photo-induced formation of nanoparticles in glasses. The subjects for application of these phenomena to recyclable colored-glass products are presented. The research examples for each mechanism are presented in this paper as follows: 1) the effect of the doped Fe ions on the optical density and stability of coloration due to color centers, 2) the coloration by the change in oxidation state, (formula available in paper) and 3) the reversible coloration and decoloration for an Ag single-doped glass.