PNNL

Abstract

We studied the ultraviolet – visible spectrum of the Nd-O local environment with Na2O/(Na2O+Al2O3) in the range from 0 to 1 for the system: 60SiO2•15B2O3•xNa2O•(25-x)Al2O3•yNd2O3 [x from 0 to 25 mol% and y at the solubility limits depending on x/(25-x) or Na2O/(Na2O+Al2O3)]. By use of the Judd-Ofelt theory, we determined the oscillator strength parameters ?2 (sensitive to asymmetry and bond covalence) and ?6 (sensitive to bond covalence) for the electronic transitions of the trivalent lanthanides (Ln). Our previous study showed that Nd-induced micro-phase separation existed over 0.35 Na2O/(Na2O+Al2O3) > 0.8. In the current study, a similar trend was found for the ?2/?6. Additional tests were performed with the same baseline glasses at a fixed, low Nd2O3 concentration. We found that the corresponding ?2/?6 was generally lower and remained constant. Based on literature data and our previous results from optical, Raman, and EELS studies of Ln cations (Nd, Gd and La) in similar sodium alumino-borosilicate glasses with Na2O/(Na2O+Al2O3) = 0 and 0.75, we expected a stable Ln-metal borate local structure, 1BO4 : 1Nd : 2BO3. Accordingly, we expect that the ?2/?6 trends are consistent with Nd cations partitioning to the borate-rich or silicate-rich environments.