UV-visible and infrared absorption spectra of Bi_2O_3 in lithium phosphate glasses and effect of gamma irradiation

摘要

Ultraviolet and visible absorption spectra of prepared undoped lithium phosphate glass and samples of the same nominal composition with additional Bi_2O_3 contents were measured before and after being subjected to gamma doses of 3 and 6 Mrad. The base undoped lithium phosphate glass exhibits strong charge transfer ultraviolet absorption bands, which are related to unavoidable presence of trace iron impurities within the raw materials for the preparation of this glass. Bi_2O_3-containing glasses show the extension of UV absorption beside the resolution of visible bands at 400,450, and 700 nm with the increase of Bi_2O_3 content due the sharing of absorption of Bi~(3+) ions. Gamma irradiation of the base glass reveals extended induced bands; the UV bands are related to the conversion of some Fe~(2+) to Fe~(3+) through photochemical reactions during the irradiation process. The visible induced bands are related to the formation of positive hole centers from the host phosphate glass. Glasses containing Bi_2O_3 are observed to show some shielding behavior, which is attributed to the presence of heavy weight and large atomic number of Bi~(3+) ions. Infrared absorption spectral measurements of the base lithium phosphate glass show characteristic vibrational modes which are related to specific phosphate groups. The addition of Bi_2O_3 in measurable percent produces additional vibrational bands due to the introduction of Bi-O groups such as BiO_3 and BiO_6.