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Cerium Dioxide

Crystal: CeO2

Structure: Fluorite

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Cohesive energy:

eV

Lattice parameter:

2.35 Å

Density:

g/cm3

 

Stiffness constants: in 1011 dynes/cm2, at room temperature

 

c11:40.3

c12:10.5

c44:6.0

Nakajima et al, Phys. Rev. B 50, 13297 (1994)

Compressibility (in 1011 dynes/cm2):

Poisson ratio:

 

Debye temperature: 410 K at 30K.

630 K at 350K.

Melting temperature: 2730 ° C

Neel temperature: K

 

Phonon spectrum discussed by: Resthral, Phys. Stat. Sol. 10, k1-4 (1982)

 

Transverse optic phonon T0 (k=0): cm-1

Longitude optic phonon L0 (k=0): cm-1

 

Gruneissen constant:

Ratio e*/e:

 

Photoelastic constants:

p11:

p12:

p44:

 

 

Band gap:

direct: 3.78 eV. (Ref.1)

indirect: eV.

 

Gap: eV.

First exciton: eV.

 

Band structure discussed by:

 

Static dielectric constant: 16-20 at 1 Mhz. (Ref.2)

Optic dielectric constant:

CeO2:

e 0= 24.5

e (¥ )= 5.31

Main peaks: 272 cm-1, weaker: 424 cm-1

Ref.: J.Phys., April 1972

 

Electron mobility:

Hole mobility:

Polaron coupling constant: a = ( for m*=1 )

Effective mass:

conduction band:

valence band:

 

Electron affinity: ( in eV., from bottom of conduction band under vacuum)

 

Spin-orbit coupling: ( valence band)

 

Cation polarisation: Å-3

Anion polarisation: Å-3

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Other information:

 

 

 

 

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References:

 

1. T.R. Griffiths, M.J. Davies, H.V. Hubbard, Spectroscopic studies on single crystals having the Fluorite lattice, J. Chem. Soc. Farad II 4, 765 (1976)

 

2. V.M. Koleshko, N.V. Babushkina, Properties of rare earth oxides films, Thin Sol. Films 62, 1 (1979)

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Supplementary information on CeO2:

 

Powder diffraction analysis of Cerium Dioxide at high pressure:

L. Gerward, J.Staun Olsen, Powder diffraction, 1993

CeO2 transforms to an orthorhombic PbCl2-type structure at a pressure of about 31 GPa. The phase transition is accompanied by a 9.8% volume contraction. The bulk modulus of the low-pressure fluorite type structure is 236(4) GPa. Comparisons are made with the high-pressure behaviour of UO2 and ThO2.

 

 

Raman Study of CeO2: Second-order scattering , lattice dynamics, and particle-size effects.

W.H. Weber, K.C. Hass, J.R. McBride, (Phys Rev B, 1993)

Polarized Raman-scattering spectra are obtained from oriented single crystals of CeO2. Second-order features are assigned to phonon overtones from the X and L points on the Brillouin-zone boundary on the basis of selection rules and by analogy to another fluorite structure compound, BaF2, in which the phonon dispersion curves are known. Complete selection rules for second-order scattering from these high-symmetry points are determined. A rigid-ion model is constructed for the phonon dispersion curves by fitting several of these features and the known zone-centre optical modes. The F(2g) Raman-active mode at 465 cm-1 in CeO2 shifts are broaden with decreased particle size (cf. G.W. Graham, J. Catalysis 130, 310 (1991)). It is shown using the calculated dispersion curves that this particle-size effect cannot be explained with the spatial-correlation model.

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