STUDIES ON GAMMA – IRRADIATED SODIUM TETRABORATE GLASSES CONTAINING YTTERBIUM

Abstract

A series of glass samples of (Na₂B₄O₇)_100-x – (Yb₂O₃)_x were prepared by the usual melt quenching technique, where x varied from 0 to 5 mol.%. Optical absorption spectra were measured before and after gamma- irradiation of the glasses. Gamma-irradiation causes a shift of the fundamental absorption edge to longer wavelengths and induces a new absorption band around 550 nm for all glass compositions. The position of this band remains unaltered by increase in either the Yb₂O₃ content or the gamma-dose. A second band at 360 nm only appears for glasses doped with Yb₂O₃; its position remains unaffected by a storage time of 2500 h. The radio-thermoluminescence (RTL) curve for the base glass (Na₂B₄O₇) shows two peaks around 90 ^°C and 200 ^°C. The inclusion of Yb₂O₃ in the base glass causes a gradual suppression of the low temperature peak with increasing Yb₂O₃ concentration. At 4 mol.% Yb₂O₃, it disappears and the RTL curve subsumes a single well-defined peak at high temperatures. The RTL peaks tend to shift to higher temperatures with increase in Yb inclusions.