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Abstract: Borate glasses with basic composition xR2O.(100−x)B2O3 where R=Na, K, were colored by doping with one of transition metal ions Ni, Cr, Fe or doping with mixing of them. The effect of glass composition and gamma ray irradiation on the optical and infrared absorption spectra was studied and interpreted in terms of structural concepts. A resolution of the observed absorption spectra showed the existence of each transition metal ion in the possible coordination state according to the composition of the glass. The IR measurements reveal characteristic absorption bands due to various groups of triangular and tetrahedral borate network. The introduction of trace amounts of mixed dopants Cr2O3, Fe2O3 and NiO has no major effect on the structure of the studied glasses. The induced absorption spectra exhibit the characteristic absorption bands caused by the intrinsic base borate glass and the respective transition metal ions. The response of the doped glasses to gamma ray irradiation is assumed to be related to the formation and annihilation of the induced color centers. [Copyright &y& Elsevier]

Abstract: Pristine lithium phosphate, lead phosphate and zinc phosphate glasses and glasses of the same compositions containing TiO2 (0.25→2.5%) were prepared. UV–visible and infrared absorption spectra of the prepared samples were measured before and after gamma irradiation. Optical spectra of these prepared glasses reveal strong UV absorption bands which are attributed to the presence of trace iron impurities in lithium and zinc phosphate glasses while the broad UV bands in lead phosphate glasses were related to absorption of both trace iron impurities and divalent lead ions. The TiO2-containing glasses reveal an extra two visible bands at about 550–580 and 680–740nm due to the transitions 2B2g →2B1g and 2B2g →2A1g of distorted octahedral Ti3+ ions. The effects of gamma irradiation reveal variations, extended in the UV–visible region in the lithium phosphate while with lead phosphate and zinc phosphate samples the variations are restricted to UV spectra. The response to gamma irradiation on optical absorption has been analyzed for both the sharing of all glass constituents including trace iron impurities. Lead and zinc phosphate glasses reveal only induced UV bands from photochemical effect of trace iron impurities while lithium phosphate shows extra induced visible band due to positive holes. The effects of gamma irradiation on the IR spectra are limited to a slight decrease of the intensities for some IR bands. The IR spectra are observed to be slightly affected by the increase of TiO2 indicating the stability of the main phosphate network units and the shielding behavior of titanium ions. [Copyright &y& Elsevier]