Soft Xray XANES of Glasses

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Soft X-ray XANES of Glasses

• Grant S Henderson
• Geology Department
• University of Toronto

Photo courtesy of the Canadian Light Source,
University of Saskatchewan
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• XANES (X-ray Absorption Near Edge Structure) 0 -
  40 eV - structural environment and coordination
  geometry of 1st and 2nd coordination sphere
• Soft X-rays 0-10 keV Mainly interested in lt 2
  keV.
• Si K-edge (1839 eV), Al L2,3-edge (73 eV), O
  K-edge (543 eV), B K-edge (193 eV), Ti L-edge
  (460 eV)

• High resolution (lt.1 eV)
• Structural information around atom
• Electronic information

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B K-edge XANES Glasses (Nuclear waste hosts) and
Minerals
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a
Little change in these features
b
c
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Peak b?
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• Ti 2p3/2 and 2p1/2 excitations to 2p53d1
• Split by t2g and eg
• Higher energy peak of pair split by distortion
• Sensitive to coordination of Ti

Henderson, G.S.,, LIU, X. FLEET, M.E. (2002),
Phys. Chem. Minerals 29, 32-42.
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Coordination of Ti4 in Ba2TiSi2O8 Glass
Ti-K XANES 60-80 5Ti4 20 4Ti4 20
6Ti4 (?)

F. Farges, J Non-Cryst Solids 204 (1996) 53.
Courtesy of Th. Hoche, IOM, Leipzig.
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Ti-L3 ELNES from Ba2TiGe2O8 Ba2TiSi2O8
Th. Höche et al. Philos. Mag. 84 (2004) 3117.
Ti - O7 1.717 Å Ti - O4 1.923 Å Ti - O1 1.965 Å
Ba2TiGe2O8
z2
xy
zx
yz
x2-y2
Ti - O4 1.698 Å Ti - O3 1.970 Å
Ba2TiSi2O8
z2
x2-y2
xy
yz, zx
Courtesy of Th. Hoche, IOM, Leipzig.
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Henderson, G.S., Liu, X. Fleet, M.E. (2003),
Mineral. Mag. 67, 597-607.
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• 4Ti and 5Ti indicated by peaks at 534 and
  533eV, respectively.
• No evidence for 6Ti.

5Ti
4Ti
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O K-edge XANES

• O 1s to O 2p ? antibonding states hybridized
  with cation s, p and d states
• Dominated by cation environment NOT oxygen
  environment

Wang, H.M. Henderson, G.S. (2004) Chem. Geol.,
213, 17-30. _____ _____ (2005) Phys. Chem.
Glasses, 46, 377-380. Cabaret, D., Mauri, F., and
Henderson G.S. (2007) Phys. Rev B, 75, 184205.
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Cabaret, D., Mauri, F., and Henderson G.S.
(2007) Phys. Rev B, 75, 184205.
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N2O-GeO2-P2O5 glasses
Cabaret, D., Mauri, F., and Henderson G.S.
(2007) Phys. Rev B, 75, 184205.

• Peak shift indirectly related to presence of
  Ge5
• Can discriminate between Ge4 and Ge5 and
  Ge6

Wang, H., Henderson, G.S., (2007), JNCS, in press.
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• Overall little effect on Si environment with
  addition of GeO2
• CRN model Homogeneous distribution

Henderson, G.S., Neuville, D.R., Cormier, L.,
(2007), in prep.
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Increasing GeO2
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Weigel et al., (2007), High resolution Al L2,3
XANES determination of Al surroundings in
minerals and glasses, in prep.
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• L3-L2 split is related to spin-orbit coupling
• Relative intensities different for different
  coordinations
• L3/L2 of mixed coordination states superimposed
• Relationship between edge position, bond
  electronegativity and Al coordination

Weigel et al., (2007), High resolution Al L2,3
XANES determination of Al surroundings in
minerals and glasses, in prep.
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Weigel et al., (2007), High resolution Al L2,3
XANES determination of Al surroundings in
minerals and glasses, in prep.
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Weigel et al., (2007), High resolution Al L2,3
XANES determination of Al surroundings in
minerals and glasses, in prep.
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Henderson, G.S., Neuville, D.R., Cormier, L.,
(2007), An O K-edge XANES study of glasses in the
CaO-Al2O3-SiO2 (CAS) system, submitted to Chem.
Geol.
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• Here I compare your XANES with my EELS (CaAl2O4).
  There are two differences.
• Peak A in XANES is not seen in EELS.
• Peak B (relative to peak C) is stronger in EELS.
• Jiang, 2006, J. Applied Physics, 100, 013703

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p
d
Henderson, G.S., Neuville, D.R., Cormier, L.,
(2007), Canadian Journal of Chemistry, 85,
801-805.
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Henderson, G.S., Neuville, D.R., Cormier, L.,
(2007), Canadian Journal of Chemistry, 85,
801-805.
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Decrease in Ca9
Increase in Ca6
Q2
Q4Q3
Q4
Q4
Edge shift as Q species changes
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• Acknowledgements
• Thomas Hoche- IOM Leipzig
• Nan Jiang-ASU
• G. Calas, L. Galoisy, L. Cormier, D. Cabaret and
  C. Weigel- IMPMC
• D. Neuville, P. Richet- IPG
• H. Wang, S. Dong, L. Soltay, J. Reeves- U of T.
• SGM/PGM beamline staff CLS

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Henderson, G.S., Neuville, D.R., Cormier, L.,
(2007), An O K-edge XANES study of Calcium
Aluminates, Canadian Journal of Chemistry, 85,
801-805..
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B K-edge XANES Glasses (Nuclear waste hosts) and
Minerals
3B
3/4B
4B
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Hörkner and Muller-Büschbaum (1976), J. Inorg.
Nucl. Chem., 38, 983. Monoclinic P21/n
CaAl2O4 viewed down b axis Ca6 (blue) Ca9
(red). AlO4 tetrahedra Q4.
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Goodwin and Lindop, (1970), Acta Cryst, B26,
1230, monoclinic C2/c
CaAl4O7 viewed down 010. Ca7 (blue). Oxygen
tricluster (red)
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Mondal and Jeffery (1975), Acta Cryst, B31, 689.
Cubic Pa-3
Ca3Al2O6 viewed down 111. Ca6 (blue) and
Ca8 (red). AlO4 tetrahedra Q2.
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Figure 4. O K-edge spectra of glasses along the
CaO-SiO2 join CA50, CA56 CA60. The ratio of
CaOSiO2 is indicated on the plots.
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Figure 5. O K-edge spectra for glasses along the
CaSiO3-Al2O3 join. The shoulder at 536.6 eV
increases in intensity and can be attributed to
the addition of Al2O3 to the glass.
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Figure 6. O K-edge spectra for glasses along the
join labelled CA in Figure 1 and whose
compositions are given in BLUE. This corresponds
to the join R1 of Neuville et al. (2004). The
spectra have been separated into compositions
before 33.3 mol SiO2 and composition after 33.3
mol SiO2. The SiO2 contents of each composition
are indicated on the plot.
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Figure 7. O K-edge spectra for glasses along the
join labelled C2A in Figure 1 and whose
compositions are given in RED. This corresponds
to the join R2 of Neuville et al. (2004). The
SiO2 contents of each composition are indicated
on the plot.
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Figure 8. O K-edge spectra for glasses along the
join labelled C3A in Figure 1 and whose
compositions are given in GREEN. This corresponds
to the join R3 of Neuville et al. (2004). The
SiO2 contents of each composition are indicated
on the plot.
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Figure 9. O K-edge spectra for glasses with
increasing mol Al2O3 along the join representing
11 CaO/SiO2 ratio. The mol Al2O3 is indicated
on the plots.
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Energy Scheme and Coordination
free Ti4
Electron Structure 1s22s22p63s23p63d0 Ti-L2,3
edge 2p ? 3d
Courtesy of Th. Hoche, IOM, Leipzig.
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• Experimental O K-edge XANES reproduced well by
  simulations
• Peak positions and intensities reproduced well
  for T-GeO2 and K2Ge8O17

Cabaret, D., Mauri, F., and Henderson G.S.
(2007) Phys. Rev B, 75, 184205.