Color Centers in Aluminoborate Glass

Abstract

Different types of color centers are present in aluminoborate glass. Some of these are related to impurities, others are possibly due to defects in the glass structure. Radiation induced bands at 520 and 340 mμ are attributed to hole centers. The Fe³⁺ and Pb²⁺ ions present as impurities in a normal melt of aluminoborate glass act as electron traps, while Fe²⁺ ions and Pb⁰ (atoms) present in a reduced glass act as hole traps. The reduction of Fe³⁺ ions to Fe²⁺ ions results in decrease of uv absorption around 220 mμ. On heating the irradiated glass thermoluminescence along with bleaching of color centers were observed and the relation between the two processes was investigated. Glow peaks were observed at 60°±5°C, 165°±10°C, and 210°±5°C. The high‐temperature glow peak is observed only at high gamma‐ray exposures (∼10⁷ R).