Formation of Ag nanoparticles in transparent mica glass-ceramics

Transparent or translucent mica glass-ceramics containing metallic Ag nanoparticles could be prepared by heating the 1-40 mol% Ag2O added parent glasses at 700-850 °C. A part of Ag+ ions added to the parent glasses as Ag2O was reduced to metallic Ag by the evolution of fluorine from the parent glasses during heating above 700 °C, and then the specimens were colored in yellow or brown. At 700-800 °C, the size of metallic Ag particles was < 10 nm and became smaller slightly with an increase in additive amount of Ag2O. The shape was spherical while the rod-like Ag nanoparticles sandwiched between layers of micas were also observed in the specimens to which a smaller amount of Ag2O was added. The spherical Ag nanoparticles formed in mica structure at ≤ 800 °C grew preferentially to the parallel direction to the layer of micas at 850 °C together with the remarkable growth of micas to the parallel direction to the layer and then the shape varied to the rod-like. The rod-like Ag nanoparticles with width of 1-2 nm and length of < 40 nm were sandwiched between layers of micas and oriented to the parallel direction to the layer.