Effect of Titanium Dioxide Doping on Optical Properties of Borosilicate Photochromic Glasses

Abstract

Glasses with composition (SiO₂)₄₅(B₂O₃)₃₅ ${\mathrm {(}{\text {Al}}_{\mathrm {2}}\mathrm {O}_{\mathrm {3}}\mathrm {)}}_{\mathrm {7.5}}\left ({\text {Na}}_{\mathrm {2}}\mathrm {O} \right )_{\mathrm {12.5}}$ doped with $\left (\text {AgBr} \right )\!,\mathrm {\thinspace }\left ({\text {Cu}}_{\mathrm {2}}\mathrm {O} \right )\mathrm {~and~}$ (TiO₂)_x, in which, x=0, 1.1, 2.2,4.5 and 6.5 atom%, were prepared. The amorphous nature of these glass samples was established and confirmed using X-ray diffraction analysis. Densities of the prepared samples were measured and compared with theoretical ones. The absorption measurements in the infrared region of the spectrum were recorded in the wavenumber range 4000-400 cm^-1. Spectral reflectance and transmittance at normal incidence of the prepared glasses were recorded with a double beam spectrophotometer in the spectral range 200-2500 nm. Analytical expressions were used to deduce the real and imaginary parts of the refractive indices. Dispersion parameters such as single oscillator energy, dispersion energy and Abbe’s number were deduced and compared. Absorption dispersion parameters such as optical energy gap for direct and indirect transitions, Urbach energy and steepness parameter were extracted. Effects of doping with titanium dioxide (TiO₂) as a transition metal on the linear and the predicted nonlinear optical parameters were investigated and discussed. Density increases with increasing TiO₂ concentration, according to doping with large quantity from 1.1-6.5 atom %. Glasses prepared showed high reflectance and low transmittance in the UV region, which confirms the photochromic behavior. Indirect band gap values and direct band gap decreased from 4.64 to 1.63 eV and 3.34-1.85 eV respectively with the increase in the TiO₂ doping concentration.