Reversible redox and clusterization of silver in glasses by X-ray irradiation and heat treatment: Mechanism of photochromic behavior of halogen-free silver-doped glass

► Mechanism of photochromic behavior of halogen-free Ag-doped glass is investigated. ► X-ray irradiation generates atomic Ag and small size Ag clusters in glasses. ► Post-heat-treatment temporarily forms Ag nanoparticles in soda-lime silicate glass. ► In aluminosilicate glasses, however, the nanoparticles are not generated. ► The difference is explained on the basis of the network structure of these glasses.