Characterization of structural, thermal and mechanical properties of bismuth silicate glasses

•Reduction in hydrogen leads to formation of layer on the glass surface.•Layer is formed by granules of metallic bismuth embedded in a glass matrix.•Metallic bismuth melts during heating of a previously reduced glass sample.•Reduction in hydrogen prevents the glass softening.

The influence of heating and reduction processes on the structural, thermal and mechanical properties of bismuth-silicate glasses has been investigated. Two compositions of glasses: 40Bi2O3–60SiO2 (Bi0.57Si0.43Ox) and 27Bi2O3–73SiO2 (Bi0.43Si0.57Ox) were fabricated by a typical melt quenching technique. Then the reduction in hydrogen at 380 °C for 20, 42 or 67 h was performed. It was found that a 50 μm-thick layer was formed on the glass surface after reduction process. It was confirmed that this layer is formed by granules of metallic bismuth embedded in a glass matrix. The DSC measurements confirmed that melting of metallic bismuth takes place during heating of a previously reduced glass sample. It was also found that heat treatment process influences hardness and Young modulus of Bi–Si–O glass.