Compositional dependence of optical band gap and refractive index in lead and bismuth borate glasses

Abstract

A B S T R A C TWe prepared a series of lead and bismuth borate glasses by varying PbO/Bi 2 O 3 content and studied refractive index and optical band gap as a function of glass composition. Refractive indices were measured very accurately using a Brewster's angle set up while the optical band gaps were determined by analyzing the optical absorption edge using the Mott-Davis model. Using the Lorentz-Lorentz method and the effective medium theory, we calculated the refractive indices and then compared them with the measured values. Bismuth borate glasses show better agreement between the calculated values of the refractive index and experimental values. We used a differential method based on Mott-Davis model to obtain the type of transition and optical band gap (E opt ) which in turn was compared with the value of E opt obtained using the extinction coefficient. Our analysis shows that in both lead and bismuth borate glasses, the optical band gap arises due to direct forbidden transition. With increasing PbO/Bi 2 O 3 content, the absorption edge shifts toward longer wavelengths and the optical band gap decreases. This behavior can be explained in terms of changes to the Pb-O/Bi-O chemical bonds with glass composition. We obtained a new empirical relation between the optical band gap and the refractive index which can be used to accurately determine the electronic oxide polarizability in lead and bismuth oxide glasses.

Effect of B2O3 addition on thermal and optical properties of TeO2–ZnO–Bi2O3–TiO2 glasses

“…For the investigated samples, their values are 1.74615, 2.65687, 0.13139 and 0.00667, respectively. This typical change of refractive index versus band gap energy has also been reported in other papers but expressed in different approaches [48][49][50][51][52][53]. Moss's formulation [52] for this relation is expressed as:…”

Influences of copper–potassium ion exchange process on the optical bandgaps and spectroscopic properties of Cr3+/Yb3+ co-doped in lanthanum aluminosilicate glasses

“…where a is the absorption coefficient, A is a constant, m is the power depending on the nature of transition (m ¼ 1/2 for direct transition, and m ¼ 2 for indirect transition). [61][62][63] From formula (2), the values of both types (direct and indirect) of the optical bandgap in SALBK glasses are calculated and detailed in Table 5. For the sake of demonstration, we also present the plot of (hn) versus both (ahn) 2 and (ahn) 1/2 for estimating E g of all the considered samples in Fig.…”

The tungsten oxide within phosphate glasses to investigate the structural, optical, and shielding properties variations

“…In addition to, determining semiconducting features of materials used for opto-electronic and photocatalyst devices. The width of the localized states in the band gap which created as a result to the disorder inside the material can also be estimated from the study of the optical absorption spectrum for such material [25].…”