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The layered oxides LiNi 12x Mn x O 2 (x ~0.1-0.5) were synthesized and characterized using synchrotron X-ray diffraction, TOF neutron diffraction, SQUID magnetometry, ICP spectroscopy, XAFS, and electrochemical measurements. All the samples were single-phase and adopted the a-NaFeO 2 structure; LiNi 12x Mn x O 2 can be represented as Li (Ni 21 x Ni 31 122x Mn 41 x )O 2 . Structural analysis using synchrotron and neutron diffraction data demonstrated that the lattice parameters of LiNi 0.5 Mn 0.5 O 2 are a ~2.892 A ˚and c ~14.302 A ˚and that the chemical composition can be expressed by referring to the Wyckoff positions 3a and 3b as [Li 0.91 Ni 0.09 ] 3a [Li 0.09 Mn 0.5 Ni 0.41 ] 3b O 2 . The lattice parameters a and c and the fraction of Ni at the 3a site of LiNi 12x Mn x O 2 increased with Mn content up to the x ~0.4 composition and then showed little change between x ~0.4 and 0.5. An increase in the Ni-O distance was observed with increasing x. The appearance of ferromagnetism was clearly observed at x ~0.4-0.5 as the Ni 21 and Mn 41 content increased. The discharge capacity of the Li/LiNi 12x Mn x O 2 cell decreased from 190 mAh g 21 (x ~0.1) to 140 mAh g 21 (x ~0.5).

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Abstract. The electrical conductivity in the ZrO2-Ln203 and ZrO2-MO2-Ln203(M = Hf, Ce, Ln = lanthanides) systems has been examined.The highest conductivity of 0.3 S/cm at 1000 ~ was found in the ZrO2-Sc203 system. The addition of MO2 into the ZrO2-Ln203(Ln = Sc, Y, Yb) systems showed the conductivity decreasing. The conduction mechanism in the zirconia based oxide ion conductors was discussed in view of the dopant ionic radius. The aging effect of the conductivity in the ZrO2-Ln203 systems has been measured in a temperature rang 800-1000 ~ ZrO2 with a high content of Ln203 showed no significant conductivity degradation.

Synchrotron X-ray diffraction and XAFS measurement have been employed to investigate structural change and the charging process of a layered LiNi0.5Mn0.5O2 cathode material. The structure of charged Li1−xNi0.5Mn0.5O2 (x=0.5), which corresponds to the composition for showing rechargeable capacity, was determined. The results showed that divalent nickel metal was oxidized to trivalent after charging, in association with the phase transition from hexagonal (R3-m) to monoclinic (C2/m) resulting from the ordering of cations in the layered structure.