EXAFS and x-ray structural studies of (Tb2O3

A study of low energy magnetic excitations in terbium metaphosphate glass

“…Even if somewhat smaller distances cannot be excluded as a consequence of the disordered topology, a mean Tb-Tb first-neighbour distance of about 0.6 nm appears to suggest that there is no clustering of rare earth ions within the sample. We should emphasise that such a conclution is also supported by the results of independent EXAFS [4] and magnetisation studies on the same glass: taken together these results suggest that eventual effects of local clustering, if present, are limited to very small number of Tb ions.…”

“…[3]) have been subtracted from those of the materials containing magnetic Tb-ions. For the glasses this is acceptable because they each have very similar structures and vibrational characteristics [4,19]. Hence subtraction of the results for the La-glass from those of Tb-glass provides an estimate of the magnetic contribution C M to the specific heat; this is also true for the single crystals.…”

“…Onedimensional (1D) and two-dimensional (2D) 31 P MAS NMR studies in alkaline [6,7] and alkaline earth phosphate glasses [8] proved that Q 1 and Q 2 units are formed from the depolymerization of Q 3 tetrahedra due to the addition of the metallic oxide. These general findings concerning the structural arrangement of the phosphate network can be extended to terbium glass, where EXAFS study [4] showed that Tb 3þ ions are situated within the PO 4 skeleton, surrounded by 5.8 ± 0.2 non-bridging oxygen atoms at a distance of 2.27 ± 0.005 A A and evidenced no clustering for terbium ions on the length scale probed by EXAFS. Comparing the R-O distance with the correlation distances calculated using the tables of ionic radii [9] shows that the results of the structural studies are in accord with a co-ordination number of 6 and a valency of 3 þ corresponding to electronic configuration 4f 8 .…”

“…The trivalent Tb 3þ ion has J ¼ 6 in its ground-state multiplets and an energy-level diagram that is somewhat more complex than for Pr 3þ . The local structure of terbium metaphosphate glass has already been examined using the complementary probs of X-ray diffraction and EXAFS [4,5], although details of the longer range structure are lacking. There is a wide consensus, however, that the network of phosphate glasses is formed from chains, rings and branched polymeric units of interconnected PO 4 tetrahedra, the metallic cations being hosted in the interstices of the skeletal structure.…”

Structure of rare-earth phosphate glasses by X-ray and neutron diffraction

“…Initial studies of single samples provided information about R-O coordination numbers, N RO , and R-O distances, r RO [7][8][9][10][11]. Since it is well known that the ionic radii of the lanthanides decrease with the increasing atomic numbers, studies of such series attract special interest.…”