Chapter 13 - Photoacoustic studies on neutron irradiated RE oxide powders and γ-irradiated Nd-doped glasses

Abstract

Optical properties of rare earth (RE) ions in different matrices are very useful because of its application as a lasing medium in solid-state lasers. Any change in the optical property of RE ions affects the power of the laser in the presence of a radiation environment. The effects of neutron and gamma irradiation on RE oxide powders and RE-doped phosphate glasses, respectively, are presented. The effect of neutron irradiation on the photoacoustic spectra of Er2O3 and Nd2O3 powders is described in detail. A quenching effect on photoacoustic signals is observed, which regains intensity with time after the irradiation at room temperature. The effect of irradiation is to change the oxidation state of the RE ions from M3+ to M2+. The half-life of the recovery process from Er2+ to Er3+ in the irradiated Er2O3 is found to be 46h. Generation of some other types of defects due to irradiation is also expected. These results are compared with the results of the optical properties of gamma-irradiated Nd-doped phosphate glasses. Optical properties of these glasses change depending on the composition of the glass matrix. Differential absorption spectra (UV-Vis. and FTIR) of glasses before and after gamma irradiation show generation of some new absorption band below 700nm along with a decrease in the intensity of main Nd3+ absorption lines. This is attributed to the generation of different types of defects in the glass matrix such as change in the valence state of Nd3+ to Nd2+, generation of oxygen vacancies, and trapping of free electrons in the vacancies.