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

Electron energy-loss spectrometry was employed to measure the white lines at the L_2.3 absorption edges of the 3d transition-metal oxides and lithium transition-metal oxides. The white-line ratio (L₃/L ₂) was found to increase between d⁰ and d⁵, and decrease between d⁵ and d¹⁰, 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 Li_1-xNi_0.80Co _0.2O₂ 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.