Interaction of gamma rays with some sodium phosphate glasses containing cobalt

Undoped and cobalt-doped sodium phosphate glasses of various compositions and with varying cobalt contents were prepared. UV-visible absorption spectra were measured before and after successive gamma irradiation. Experimental results indicated that the undoped base glass reveals strong ultraviolet absorption which is related to the presence of unavoidable trace iron impurities in the raw materials. Cobalt-doped glasses show characteristic visible absorption bands which are related to the presence of Co2+ ions mostly in the tetra-coordination state. The generated induced color centers in the UV and visible regions by gamma irradiation are characterized in relation to intrinsic defects from the host base sodium phosphate glass and the extrinsic defects from both trace iron impurities and added doped cobalt ions. Infrared absorption measurements were carried out for some selected samples to identify the structural building groups in the studied glasses. Cobalt ions showed a shielding behavior towards the effects of progressive gamma irradiation especially in the visible spectral region. (C) 2009 Elsevier B.V. All rights reserved.