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

Abstract

Electron energy-loss spectrometry was employed to measure the white lines at the L-2,L-3 absorption edges of the 3d transition-metal oxides and lithium transition-metal oxides. The white-line ratio (L-3/L-2) 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 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 Li1-xNi0.8Co0.2O2 in the range of 0less than or equal toxless than or equal to0.64. In these experiments the 3d occupancy of the nickel ion decreased upon lithium deintercalation, while the cobalt valence remained constant.

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