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Determination of the valence state of copper in cubic CuMn2O4 spinel by X-ray absorption edge measurements

1968; Elsevier BV; Volume: 29; Issue: 4 Linguagem: Inglês

10.1016/0022-3697(68)90032-2

1879-2553

Arthur R. Miller,

X-ray Diffraction in Crystallography

It cannot be determined from stoichiometry and electroneutrality considerations alone whether copper in CuMn2O4 is univalent or divalent. In order to resolve this ambiguity, the energy of the X-ray K absorption edge for copper was measured in the following three compounds: CuCr2O4 which is known to contain Cu2+; Cu2O, which is known to obtain Cu+ and CuMn2O4. The excitation energies measured in the solids were corrected by taking into account their electron affinities and the Coulomb potentials of copper in the solids. If it is assumed that CuMn2O4 contains divalent copper, then the measurements on CuMn2O4, and CuCr2O4 yield corrected values for the absorption edge which are consistent with each other within the limits of experimental error. On the other hand, if it is assumed that CuMn2O4 contains univalent copper, then the measurements on CuMn2O4 and Cu2O4 yield values which are discrepant by several times the estimated error. It is concluded that in the sample of CuMn2O4 investigated, copper is predominantly divalent. New expressions for the Coulomb potentials at the ionic sites in the spinel and cuprite structures are also reported.