Study of the correlation between optical properties and the variations of nano-scale free volume in bismuth borate glasses

Abstract

Positron annihilation lifetime spectroscopy (PALS) has been applied to prove the amorphous and defect structure of Bi2O3 –B2O3 glasses as a function of Bi2O3 content. A fast-fast coincidence system with a time resolution (FWHM) of 200-260 ps has been used. A positron came from the radioactive source 22NaCl which, was sandwiched between two identical samples. The lifetime spectra have been analyzed after source and background corrections. Furthermore, the physical properties have been studied such as density, molar volume and oxygen packing density. Also, the glass transition temperature (Tg) of these samples have been studied in the temperature range 0°C to 600°C with heating flow 10°C/min. by Differential Thermal Analysis (DTA). The optical properties have been investigated by the Fourier Transform Infrared spectroscopy (FTIR). Optical band gap energy (Eg) and basicity are deduced.