J. Phys. IV France 7 (1997) C2-1171-C2-1172
X-Ray Absorption Spectra and the Local Structure of Nickel in Some Oxycompounds and FluoridesA.N. Mansour1 and C.A. Melendres2
1 Naval Surface Warfare Center, Carderock Division, Code 684, 10901 New Hampshire Avenue, Silver Spring, MD 20903-5640, U.S.A.
2 Argonne National Laboratory, Materials Science and Chemical Technology Divisions, 9700 South Cass Avenue, Argonne, IL 60439-8111, U.S.A.
X-ray absorption spectra were measured for a number of nickel oxycompounds and fluorides which contain nickel with valencies in the range of 2 to 4. Information on the local structure and nature of bonding of nickel were derived using theoretical standards generated with the FEFF code. The energies of the main Ni K-edge and the pre-edge peak were found to shift to higher values by about 1.5 and 0.6 eV, respectively, per unit increase in the valency of nickel. The average Ni-O and Ni-F bond length within the octahedron decreased linearly with increase in nickel valency from 2 to 4. The local structure parameters for the higher valency nickel oxycompounds are consistent with a multi-phase model in which up to three phases corresponding to Ni2+, Ni3+, and Ni4+ could be present in different proportions depending on preparation procedures.
© EDP Sciences 1997