Valency

About: Valency is a research topic. Over the lifetime, 1632 publications have been published within this topic receiving 26141 citations.

X-ray absorption studies of high-Tc YBa2Cu3Ox

Abstract: The a Cu valency and local structure in high-Tc YBa2Cu3Ox have been analyzed by X-ray absorption near-edge structure (XANES) and by extended X-ray absorption fine structure (EXAFS) techniques. The Cu valency is predominantly divalent. The evidence for trivalent Cu has not been observed. The radial distribution function around Cu ions indicates that an average of 4.1 oxygen atoms are present at 1.915 A.

Electronic and optical properties of CeO under pressure

Abstract: The volume behaviour of cerium monoxide (CeO) is interesting as a function of pressure. The volume decreases rapidly up to 3 GPa and decreases more slowly above 3 GPa. The authors present the fully self-consistent band structure of CeO for four different values of lattice constant corresponding to four different pressures, using the linearised augmented plane-wave method. The local density formulation has been assumed for the exchange and correlation part of the potential. From the band-structure results, they have calculated the valency of Ce in CeO. The calculated valency increases from 3.0 to 3.26 with increase in pressure. From the band-structure results, the density of states, the coefficient of linear specific heat and the optical absorption spectra have been calculated.

Impact of Surface Layer Formation during Cycling on the Thermal Stability of the LiNi0.8Co0.1Mn0.1O2 Cathode.

Abstract: In this study, the effects of charge/discharge cycling on the thermal stability of LiNi0.8Co0.1Mn0.1O2, a high-Ni cathode material, are systematically investigated. X-ray diffraction measurements show that there is almost no change in the bulk structure of the cathode after cycling. However, X-ray absorption fine structure measurements indicate that Ni in the surface layer is reduced and stable rock-salt structures are formed. Differential scanning calorimetry (DSC) measurements show that the heat generation at the lowest temperature, which can trigger thermal runaway in batteries that use high-Ni cathodes, decreases significantly with the formation of rock-salt structures on the active material surface. This finding indicates that the rock-salt layer on the surface enhances the thermal stability of a high-Ni cathode. The change in the total heat generation with degradation, indicated by DSC measurements, is similar to that in the K-edge of Ni (i.e., the Ni valency), suggesting a strong correlation between the heat generation and crystal structure changes during cycling.