Download CENTENNIAL HONORS COLLEGE Western Illinois University Undergraduate Research Day 2016

CENTENNIAL HONORS COLLEGE Western Illinois University Undergraduate Research Day 2016 PosterPresentation
VariationofOpticalBandGapinLeadandBismuthBorateGlasses
TylerJ.Czarnecki
FacultyMentor:P.K.BabuandSaisudhaMallur
Physics
The study of variation of optical band gap with composition in oxide glasses gives information regarding
the structure and the nature of bonds in the matrix. The width of the localized states in the band gap which
arises due to the disorder in the matrix can also be determined. We studied the variation of optical band
gap as a function of glass composition in lead and bismuth borate glasses. Glasses are prepared by the
usual melt quench method for various amounts of lead and bismuth oxides. The prepared glass samples
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are then annealed at 400 C for 3 hours to remove thermal strains. They are then polished using a felt pad
sander. Optical absorption measurements are carried out on these samples using a UV-VIS absorption
spectrometer. The experiment is done in the absorption mode, where the polished glass sample is placed
in the path of electromagnetic radiation from the excitation source. The absorption edge data is then
analyzed in detail to obtain the optical band gap of the glass samples. The experimental value of the band
gap is used to determine the type and nature of the optical transition. Overall the band gaps of the Bi2O3
glasses were smaller. Our results show that in both glasses, the optical band gap decreases with
increasing concentration. Our analysis also showed that these are indirect allowed transitions (n = 2).
Variations in band gaps can be attributed to the structural and chemical changes that accompany the
variation in glass composition.