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SUMMARY:XAFS study of zirconium oxides modified by yttrium and magnesium
DTSTART;VALUE=DATE-TIME:20200713T141600Z
DTEND;VALUE=DATE-TIME:20200713T141700Z
DTSTAMP;VALUE=DATE-TIME:20261008T190752Z
UID:indico-contribution-1866@indico.inp.nsk.su
DESCRIPTION:Speakers: Vladimir Kriventsov ()\nToday the mixed oxides with 
 a fluorite structure of the composition (Zr\, Y) O2-x are widely used to h
 arden ferritic steels used as fuel element cladding materials for the new 
 generation of fast neutron reactors operating under irradiation and high t
 emperatures. This work is devoted to study of the state and local structur
 e of samples of zirconium oxides modified by yttrium and magnesium\, prepa
 red by coprecipitation and calcined at a temperature of 1250 °C. XAFS (XA
 NES/EXAFS) spectra (Y-K\, Zr-K edges) of studied samples were recorded at 
 SSTRC\, Novosibirsk. It was shown that from the yttrium side\, the XANES s
 pectra of both samples were almost identical. On the zirconium side\, the 
 XANES spectra have minor differences. It can be assumed that the charge st
 ate and the nearest environment of yttrium also practically does not chang
 e depending on the composition of the samples. For zirconium\, with the ch
 arge state unchanged\, some changes in the nearest oxygen environment appe
 ar to occur due to the composition of the samples. It was found out that t
 he curves of the radial distribution of atoms (RDFs) obtained from the EXA
 FS spectra of the studied samples have a number of characteristic features
 . Only the first coordination spheres of the Me-O and Me-Me types are obse
 rved\, but long-range coordination spheres (more than ~0.45 nm) are practi
 cally absent\, which may indicate distortions of the long-range order in t
 he structures. The local yttrium arrangement is stable when the compositio
 n of the samples changes\, which may indicate the formation of clusters th
 at include only Y and O elements. The local zirconium arrangement depends 
 on the composition of the samples\, since there are some differences in th
 e RDFs curves. Thus\, the amplitudes of the peaks assigned to the coordina
 tion spheres Zr-O and Zr-Me are significantly reduced (by more than 25%) f
 or the Y\,Mg- modified sample in comparison with those for the Y- modified
  sample\, which indicates distortions of the original fluorite structure. 
 The observed changes in the Zr-O and Zr-Me distances (more than 0.05) are 
 greater than the changes due to differences in the cell parameters for the
  compared samples. Using the model of statistical solid solution with a fl
 uorite structure\, it is suggested that the presence of Y-O clusters preve
 nts refinement of structures.\nThe work was carried out in the framework o
 f the RFBR project no. № 19-03-00530. The work was done at the shared re
 search center SSTRC on the basis of the Novosibirsk FEL/VEPP-4-VEPP-2000 c
 omplex at BINP SB RAS\, using equipment supported by project RFMEFI62119X0
 022.\n\nhttps://indico.inp.nsk.su/event/24/contributions/1866/
LOCATION:
URL:https://indico.inp.nsk.su/event/24/contributions/1866/
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