Preparation and characterization of Bi2O3–SiO2–Al2O3 based glasses of good transparency with high Bi2O3 content

Bi2O3–SiO2–Al2O3 based glasses of good transparency with high Bi2O3 content (~ 36 mol%) have been obtained by using melting method. Glass transition, crystallization and phase reaction temperatures of as-synthesized glass have been characterized by differential scanning calorimetry (DSC). The X-ray diffraction (XRD) analysis confirms the amorphous structure of the glass samples before and after the annealing. Ultraviolet and visible transmittance spectra show that the transmittance of as-synthesized glasses (0.6 mm thickness) can reach up to 80.1% in the visible region (above 550 nm), with the cutoff wavelength at 386 nm. The linear absorption coefficient (α), optical mobility gap (Eopt) as well as Urbach energy (ΔE) are calculated from optical transmittance. After annealing at 550 °C, the transmittance increases slightly near the absorption edge which shifts itself towards shorter wavelength. The roles of composition, heating and annealing profile on the transmittance of glasses have been discussed. For Bi2O3–SiO2–Al2O3 glasses with high Bi2O3 content, the Hruby factor is about 0.26, suggesting good stability.