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SUMMARY:Advanced Structural Characterisation Techniques for Amorphous Mate
 rials: Case Study of Rare-earth Phosphate Glasses - Dr Jacqui Cole (Cavend
 ish Laboratory\, Cambridge)
DTSTART:20081124T160000Z
DTEND:20081124T170000Z
UID:TALK14291@talks.cam.ac.uk
CONTACT:11283
DESCRIPTION:This seminar concerns the structural characterisation of rare-
 earth phosphate glasses\, materials that exhibit exotic optical and magnet
 ic properties. The high structural complexity of glasses and their highly 
 disordered nature means that little structural information can be gained f
 rom employing just one structural characterisation technique. We have ther
 efore used a wide range of structural probes\, conventional and anomalous 
 X-ray and neutron diffraction [1\,2]\, rare-earth LIII and K-edge EXAFS [3
 \,4]\, XANES [5]\, solid-state NMR [1\,2]\, FTIR [6]\, each of which revea
 l particular key structural information about the glasses\, which when pie
 ced together and combined with theoretical modelling techniques (e.g. Reve
 rse Monte Carlo routines)\, allow the realisation of an overall unified th
 ree-dimensional model of these glasses. To date\, we have characterised th
 e pair-wise structural correlations in these glasses out to a radial distr
 ibution of 4A\, and this is described in the introduction of the presentat
 ion.\nHowever\, one key atomic pair-wise correlation\, the closest R…R s
 eparation\, has proved particularly difficult to characterise\, and yet is
  of key importance from a materials-centred perspective\, given that this 
 separation dictates the optical and magnetic properties in these glasses. 
 Attempts to combat this have led us to undertake some complicated and nove
 l experiments. We report herein the descriptions and results of three such
  experiments: the world’s first successful magnetic difference neutron d
 iffraction experiment on an amorphous material\, using the GEM powder neut
 ron diffraction instrument at ISIS\, RAL\; the first example of a full ano
 malous neutron scattering experiment\, accessing both real and imaginary c
 omponent differences\, where data was collected on D4 at the ILL\, Grenobl
 e\, France\; and an anomalous X-ray scattering experiment\, undertaken on 
 1-ID\, APS\, USA. Results are presented and are shown to have important im
 plications on their physical properties. \n\nReferences\n\n1.	 J. M. Cole\
 , E. R. H. van Eck\, G. Mountjoy\, R. J. Newport\, T. Brennan\, G. A. Saun
 ders (1999). J. Phys. Cond. Matt.\, 11\, 9165-9178.\n\n2. 	J. M. Cole\, E.
  R. H. van Eck\, G. Mountjoy\, R. Anderson\, T. Brennan\, G. Bushnell-Wye\
 , R. J. Newport\, G. A. Saunders (2001). J. Phys. Cond. Matt.\, 13\, 4105-
 4122.\n\n3. 	R. Anderson\, T. Brennan\, J. M. Cole\, G. Mountjoy\, D. M. P
 ickup\, R. J. Newport\, G. A. Saunders\, (1999). J. Mater. Res. 14\, 4706-
 4714.\n\n4.	J. M. Cole\, A. C. Hannon\, R. A. Martin\, R. J. Newport\,  "D
 irect observation of R...R distances in rare-earth (R) phosphate glasses b
 y magnetic difference neutron diffraction"\, Phys. Rev. B. 73 (2006) 10421
 0-(1-5). \n\n5. 	J. M. Cole\, A. C. Wright\, R. J. Newport\, C.E. Fisher\,
  S. J. Clarke\, R. N. Sinclair\, H. E. Fisher\, G. J. Cuello\, “The stru
 cture of the rare-earth phosphate glass\, (Sm2O3)0.205(P2O5)0.795 studied 
 by anomalous dispersion neutron diffraction”\, J. Phys. Cond. Matt. 19 (
 2007) 056002(1-12).\n\n6.	J. M. Cole\, R. J. Newport\, "Direct observation
  of the R...R separation in rare-earth phosphate glasses"\, J. Non-Cryst. 
 Solids 353 (2007) 1773-1778.\n\n
LOCATION:Harker 2 lecture room\, Department of Earth Sciences\, Downing Si
 te
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