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Title: Multiple rare-earth ion environments in amorphous ( G d 2 O 3 ) 0.230 ( P 2 O 5 ) 0.770 revealed by gadolinium K -edge anomalous x-ray scattering

A Gd K-edge anomalous X-ray scattering (AXS) study is performed on the rare-earth (R) phosphate glass, (Gd 2O 3) 0.230(P 2O 5) 0.770, in order to determine Gd…Gd separations in its local structure. The minimum rare-earth separation is of particular interest given that the optical properties of these glasses can quench when rare-earth ions become too close to each other. To this end, a weak Gd…Gd pairwise correlation is located at 4.2(1) Å which is representative of a meta-phosphate R…R separation. More intense first neighbor Gd…Gd pairwise correlations are found at the larger radial distributions, 4.8(1) Å, 5.1(1) Å and 5.4(1) Å. These reflect a mixed ultra-phosphate and meta-phosphate structural character, respectively. A second neighbor Gd…Gd pairwise correlation lies at 6.6(1) Å which is indicative of meta-phosphate structures. Meta- and ultra-phosphate classifications are made by comparing the R…R separations against those of rare-earth phosphate crystal structures, R(PO 3) 3 and RP 5O 14 respectively, or difference pair distribution function (ΔPDF) features determined on similar glasses using difference neutron scattering methods. The local structure of this glass is therefore found to display multiple rare-earth ion environments, presumably because its composition lies between these two stoichiometric formulae. These Gd…Gd separations are wellmore » resolved in the ΔPDFs that represent the AXS signal. Indeed, the spatial resolution is so good that it also enables the identification of R…X (X = R, P, O) pairwise correlations up to r ~ 9 Å; their average separations lie at r ~ 7.1(1) Å, 7.6(1) Å 7.9(1) Å, 8.4(1) Å and 8.7(1) Å. This is the first report of a Gd K-edge AXS study on an amorphous material. Its demonstrated ability to characterize the local structure of a glass up to such a long-range of r, heralds exciting prospects for AXS studies on other ternary non-crystalline materials. However, the technical challenge of such an experiment should not be underestimated, as is highlighted in this work where probing AXS signal near the Gd K-edge is found to produce inelastic X-ray scattering that precludes the normal AXS methods of data processing. Furthermore, it is shown that AXS results are not only tractable but they also reveal local structure of rare-earth phosphate glasses that is important from a materials-centered perspective and which could not be obtained by other materials characterization methods.« less
 [1] ;  [2] ;  [3] ;  [2] ;  [4]
  1. Univ. of Cambridge, Cambridge (United Kingdom); STFC Rutherford Appleton Lab., Oxfordshire (United Kingdom); Argonne National Lab. (ANL), Argonne, IL (United States)
  2. Univ. of Cambridge, Cambridge (United Kingdom)
  3. Argonne National Lab. (ANL), Argonne, IL (United States)
  4. Univ. of Kent, Canterbury (United Kingdom)
Publication Date:
Grant/Contract Number:
Accepted Manuscript
Journal Name:
Physical Review Materials
Additional Journal Information:
Journal Volume: 2; Journal Issue: 4; Journal ID: ISSN 2475-9953
American Physical Society (APS)
Research Org:
Argonne National Lab. (ANL), Argonne, IL (United States)
Sponsoring Org:
Engineering and Physical Sciences Research Council (EPSRC); USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22). Scientific User Facilities Division
Country of Publication:
United States
OSTI Identifier:
Alternate Identifier(s):
OSTI ID: 1434822