A study on optical characteristics of amorphous structure (Vitreous) including oxides of main and transitional elements in binary system B2O3 a?? CaO

摘要

Amorphous Structures have specific characteristics including semi-conductivity. Boron trioxide can form the vitreous structure with other oxides. Addition of certain oxides to boron trioxide modifies the properties of these glasses. In our investigation B2O3 - CaO binary was studies and it was appeared that the system of (100 – x) B2O3 – x CaO is able to form the vitreous structure and the range of x was determined experimentally. For better understanding the electronic structure and study on the edge-absorption, we can use optical absorption. By using a UV - Visible spectrophotometer the absorption spectrums were obtained. Studying these spectrums and by using Urbach and Mott-Davis theories, the absorption coefficient, α(ω), have calculated according to Bir-Lambert relation. By tracing (α?§ω)1 against ?§ω plot, the amount of n was determined. For B2O3 - CaO binary system n = 1/2 was obtained. Extrapolating (α?§ω)2 against ?§ω plot, we can determine optical gap energy, Eopt , at (α?§ω)2 = 0. Obtaining results show that, Eopt increase with CaO percentage increasing. The coefficient B, also, is calculated by using Mott-Davis relation. By determining the slop of ln α(ω) against ?§ω diagram, the width of localized states in the energy of bonds, E, can be obtain.