Effects of composition on the structure, thermal and some physical characteristics of Bi2O3-B2O3-ZnO-SiO2 glasses

Abstract

The influence of composition on the structure, thermal, and some physical characteristics of bismuth borate glasses, formulated as 55Bi2O3–(35-x-y)B2O3–(5+x)ZnO–(5+y)SiO2 (where 0 ≤ x, y ≤ 15 mol%), was investigated. Comprehensive analyses were conducted using techniques such as X-ray Diffraction (XRD), Scanning Electron Microscopy (SEM), Fourier-Transform Infrared Spectroscopy (FTIR), Differential Thermal Analysis (DTA), and Dilatometry. XRD confirmed the amorphous nature of the glass samples, while FTIR spectroscopy revealed that the glasses are primarily composed of BO4, BO3, BiO6, BiO3, ZnO4, and SiO4 structural units. DTA provided further evidence of the samples' glassy state and insights into key temperatures like glass transition (Tg), crystallization (Tc), and melting (Tm). The study finds that substituting B2O3 with SiO2 increases all characteristic temperatures, whereas replacing it with ZnO decreases Tg and Tc but increases Tm. The maximum thermal stability, indicated by a ΔT of 99°C, was observed in the glass with a 55Bi2O3–20B2O3–20ZnO–5SiO2 composition. Dilatometric measurements showed that the investigated glasses have a high coefficient of thermal expansion (10.0–10.7 ppm/°C) values, a low glass transition temperature (345–376°C), and a low dilatometric softening temperature (364–392°C). Additionally, the density and molar volume of the samples were accurately determined.