Influence of PbO molar fraction and Se doping on borate glasses

Glasses of xPbO(1-x)B2O3 composition, with x = 0.2, 0.4, 0.5 and 0.6, and doped with  Se (0.01, 0.02, and 0.03 mol) were synthesized from H3BO3, PbO, Pb3O4 and Se  powders, homogenized and then fused at about 700 - 800 oC. The fused mixing was  annealed at temperatures lower than the glass transition one, about 400 oC and during 3  hours. Samples were then slowly cooled down to room temperature. PbO concentration  correlates with an increase on the color intensity of the samples. Final glasses were cut,  mechanical etched and then characterized by spectrometry in the 400 - 830 nm range  and by differential scanning calorimetry (DSC) and thermal gravimetry (TG). The  influence of PbO and Se concentrations on the spectra was confirmed studying the  correlation between molar fraction and intensity of the 435 nm and 610 nm peaks. TG  results indicate that, when heated up to 800 oC, samples with Se decompose. However,  sample color as far as increases for the 435 nm absorption peak, indicating the possible  incorporation of Se to the glass structure. DSC diagrams show a glass transition in the  443-436 oC temperature range. DSC also indicate the glasses have up to three crystalline  phases. Future work will confirm these phases and Se incorporation by X-ray  diffraction.