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.