Fig. 7. Fitting of CGP 3466B coefficient (α) with Hydrogenic excitonic model ( Eq. (7)) for (70B2O3–29Li2O–1Dy2O3)–xBT glass system.Figure optionsDownload full-size imageDownload as PowerPoint slide
Values of band gap (Eg), excitonic binding energy (R), line widths for m=1 state (Γ1) and continuum (Γc), absorption strength parameter (Co), and best fit parameter (R2) obtained from the fitting of experimental data of absorption coefficient spectrum with Hydrogenic excitonic model ( Eq. (5)) for (70B2O3–29Li2O-1Dy2O3)-xBT glass system for different values of x.SampleEg(eV)R(eV)Γ1(eV)Γc(eV)Co(V1/2/cm)R2x=04.4370.0070.0250.101661.0730.921x=54.2150.0670.0860.0254156.6980.996x=104.0880.0840.0870.06475.4680.998x =154.0330.0730.0880.076699.9600.998x=203.9280.0520.1050.026170.9690.997Full-size tableTable optionsView in workspaceDownload as CSV
The amorphous materials such as glasses exhibit band tailing in the forbidden energy gap which emerges due to the random fluctuations of internal disorder in the amorphous materials. The extent of band tailing is helpful in characterizing the degree of disorder in the materials and is estimated using Urbach?s Empirical Rule  and equation(8)α(ν)=Bexp(hν/ΔE)where ΔE is the width of the band tail of electron states and B is a constant.