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White lines and d -band occupancy for the 3 d transition-metal oxides and lithium transition-metal oxides

2004; American Physical Society; Volume: 69; Issue: 23 Linguagem: Inglês

10.1103/physrevb.69.235103

1550-235X

Jason Graetz, Channing C. Ahn, Hao Ouyang, Peter Rez, Brent Fultz,

Transition Metal Oxide Nanomaterials

Electron energy-loss spectrometry was employed to measure the white lines at the L23 absorption edges of the 3d transition-metal oxides and lithium transition-metal oxides. The white-line ratio (L3/L2) was found to increase between d^0 and d^5 and decrease between d^5 and d^10, consistent with previous results for the transition metals and their oxides. The intensities of the white lines, normalized to the post-edge background, are linear for the 3d transition-metal oxides and lithium transition-metal oxides. An empirical correlation between normalized white-line intensity and 3d occupancy is established. It provides a method for measuring changes in the 3d-state occupancy. As an example, this empirical relationship is used to measure changes in the transition-metal valences of Li_{1-x}Ni_{0.8}Co_{0.2}O_2 in the range of 0 < x < 0.64. In these experiments the 3d occupancy of the nickel ion decreased upon lithium deintercalation, while the cobalt valence remained constant.