Annealing Effect on Copper-Doped Sodium Borate Glasses (Na2O.4B2O3)

The annealing effect of an alkali borate type glass below its softening point was investigated according to the Na2O-B2O3 binary system. The samples were doped by introducing different amounts of copper oxide (CuO). The properties of elaborate glasses before and after annealing were studied. X-ray diffraction (XRD) as well as optical and infrared spectroscopy were used in this study. The results obtained show that annealing, that is, a heat treatment process, affects the structure of this type of glass by redistributing its structural units and partially correcting any defects, thereby reinforcing the structure. It was noticed that the BO3 units were reformed while the number of BO4 ones decreased, leading to an increase in the coefficient of thermal expansion, a decrease in both the refractive index and optical dispersion, the weakening of mechanical properties as well as a reduction in thermal conductivity and electric permittivity.