Comparison Of Lattice Parameters Research Articles

Investigation on Relationship between the Amount of Ni4+ Ion and Thermal Stability in Ni-Rich Layered Cathode Materials

Recently, the lithium ion batteries (LIBs) have applied to electric vehicle (EV), energy storage system (ESS) as a part of smart grids, and various electronic devices. However, LIBs was faced with deficiency of cyclability and demand for improved energy and power density due to the development of advanced applications. The electrochemical performance of LIBs has been enhanced through the Ni-rich layered cathode materials, such as LiMO2 (M = Ni, Co, Mn, and Al, etc.) [1]. However, these cathode materials are exposed to the risk of combustion and performance degradation in a little thermally harsher environment, due to the inherent thermal instability [2]. To develop thermally enhanced Ni-rich cathode material, therefore, it is the significant challenge to explore how the primary factor determines the thermal stability of Ni-rich cathode materials for the safety and credibility of LIBs. The primary reason for the thermal instability in Ni-rich cathode materials was often noted as the reduction of Ni4+ ion, which occurs in the course of the exothermic reaction [3,4]. However, there was no deep discussion on how the reduction of Ni ions influences the thermal stability of cathode materials due to the ambiguity of interpretation and the uncertainty of equipment. In this study, the relationship between the amount of Ni4+ ion and thermal stability of LixNi0.5+yCo0.2Mn0.3-yO2 (x= 0.33, 1, y= 0, 0.1, 0.2) was investigated through synchrotron-based X-ray techniques; Time-resolved X-ray diffraction (TR-XRD), high-resolution powder diffraction (HRPD), and X-ray absorption spectroscopy (XAS) combined with differential scanning calorimeter (DSC). We observed that delithiated Ni-rich cathode material had a high degree of thermal expansion and a high possibility in formation of oxygen vacancy during heating process. They were identified through the comparison of lattice parameter and the k-weight (k = 1, 2, 3) dependent fitting using Ni K-edge EXAFS spectrum. Also, we specified the effect of amount of Ni4+ ion on the thermal expansion and formation of oxygen vacancy. Based on the results and well-known phase transition mechanism [5], we presented a complemented mechanism of 1st phase transition during heating process. Through the discussion, we will deliver how the primary factor determines the thermal stability of Ni-rich cathode materials. More details will be discussed in the meeting. Reference s : [1] Z. Liu, A. Yu and J. Y. Lee, Journal of Power Sources, 1999, 81, 416-419. [2]W.-S. Yoon, K. Y. Chung, M. Balasubramanian, J. Hanson, J. McBreen and X.-Q. Yang, Journal of power sources, 2006, 163, 219-222. [3] S.-M. Bak, K.-W. Nam, W. Chang, X. Yu, E. Hu, S. Hwang, E. A. Stach, K.-B. Kim, K. Y. Chung and X.-Q. Yang, Chemistry of Materials, 2013, 25, 337-351. [4] Y. Makimura, C. Okuda, T. Nonaka, Y. F. Nishimura, T. Sasaki and Y. Takeuchi, ECS Electrochemistry Letters, 2014, 3, A66-A68. [5] J. Reed and G. Ceder, Chemical reviews, 2004, 104, 4513-4534.

Thermodynamic properties of nuclear material uranium carbide using density functional theory

To understand the thermal behavior of superhard uranium carbide (UC), in the present work thermodynamic properties of UC in rock-salt structure are investigated using first-principles plane-wave pseudopotential method within the density functional theory. Thermodynamic functions such as specific heat, entropy, internal energy and enthalpy as a function of temperature have been calculated using the phonon dispersion curves and phonon density of states within quasi-harmonic approximation. The variation of lattice specific heat with temperature is also compared with available experimental data. The dependence of selected observations of UC compounds on the effective U parameter has also been investigated. The DFT + U calculation is performed in order to describe precisely the strong on-site Coulomb repulsion incorporation of Hubbard parameter U = 3.0 eV that leads to better comparison of lattice parameter and elastic constants with experimental and available theoretical data. The calculated phonon frequencies and elastic constants show that the UC in rock-salt structure is dynamically and mechanically stable at ambient condition as indicated by their positive values. The temperature dependence of thermal and electrical conductivities has also been calculated and compared with the available experimental data and discussed. The possible use of UC in thermoelectric devices using thermal conductivity and resistivity is also discussed, and the present study suggests that the UC can be a potential candidate for the thermoelectric application at higher temperatures. We hope that the present study should stimulate further studies of this material.

Ab initio study on influence of dopants on crystalline and amorphous Ge2Sb2Te5

The pronounced effects of dopants such as Si, N, and O atoms, on material properties of Ge2Sb2Te5 are investigated at the atomic level using ab initio calculations. In the crystalline phase, stable doping sites are determined by characteristic chemical bonds such as Ge–N and Ge–O. The comparison of lattice parameters between theory and experiment supports the existence of dopants at vacant or interstitial positions. The electronic density of states indicate that the localization at the valence top increases with N- or O-doping, explaining the increase of resistivity in experiments. The amorphous structures of doped Ge2Sb2Te5 are obtained by melt-quench simulations and they are well understood by selective bonds between dopants and host atoms. The chemical bonds around dopants are more favorable in the amorphous phase than in the crystalline state, accounting for increased amorphous stability of doped Ge2Sb2Te5. The atomic and electronic structures of amorphous Ge2Sb2Te5 do not support a viewpoint that the bonding nature is changed toward the covalent character upon doping. The recrystallization of doped Ge2Sb2Te5 is also simulated and it is directly confirmed that the crystallization process of doped Ge2Sb2Te5 is slowed down by dopants.

Phase formation in rapidly solidified R2T17 intermetallics

Abstract Rapid solidification was utilized to produce a series of light and heavy rare earth-transition metal intermetallics in the R H –Co, R L –Co/Fe, and Sm–Co(Fe) systems with R H = Dy and Tb and R L = Pr and Sm. The influence of Nb–C and Zr–C additions on phase formation in the binary and ternary alloys has also been investigated. The X-ray diffraction patterns obtained with synchrotron radiation were refined by the Rietveld method for structural phase determination and analysis. It was found that the ability to create disorder strongly depended on the rare earth element, with light rare earth systems possessing more disorder, and rapid solidification effectively suppressed the development of long-range order in these compounds. Cobalt in contrast to iron favored the formation of disordered structures. Replacement up to two out of the three of the cobalt atoms with iron in the Sm–Co–Fe system has retained the establishment of the disordered TbCu 7 -variant and exhibited complete cobalt–iron solubility. Additions of Nb–C and Zr–C have also greatly influenced the order formation. The comparison of lattice parameters of the intermetallic compounds obtained by rapid solidification to the parameters of equilibrium 2–17 phases summarized in the literature revealed that formation of partially ordered and disordered structures was associated with expansion of the both a - and c -axes in Th 2 Zn 17 - and Th 2 Ni 17 -type phases for all binary compounds.

Electrical and optical properties of the mixed-valence misfit-layer compound (YbS) 1.25CrS 2

The crystals of the new misfit-layer compound (YbS) 1.25CrS 2 were grown by chemical transport reaction in a closed silica ampoule. This compound is built up of alternately stacking of YbS and CrS 2 layers. The dimensions of a unit cell are a 1 = 5.31 Å, b 1 = 5.75 Å, and c 1 = 10.63 Å for the YbS sublattice and a 2 = 3.32 Å, b 2 = 5.75 Å, and c 2 = 10.63 Å for the CrS 2 sublattice. Both layers are incommensurate along the a-axis and the incommensurability parameter, which is defined by α = a 2/ a 1, is about 0.625. It is found from the comparison of lattice parameters among a series of lanthanide misfit-layer compounds and lanthanide monosulfides that Yb is in an intermediate valence state close to trivalency rather than divalency due to charge transfer to CrS 2 layers. Temperature-dependent electrical resistivity shows that the compound is a semiconductor with the activation energy of about 0.31 eV. This activation energy almost agrees with that of the acceptor levels in nonstoichiometric YbS samples. A reflectivity spectrum reveals small peaks at 0.8 and 1.1 eV, whereas an absorption spectrum exhibits a large peak at 1.1 eV. The results obtained suggest that valence fluctuation happens for Yb-like Eu in (EuS) 1.173NbS 2.

Humidity Properties of Sintered MnWO4 with a Low Temperature Firing Frit

A low melting borosilicate glass frit was used as an adhesion promoter, which enables <TEX>$MnWO_4$</TEX>to be sintered with in a reasonable sintering temperature range (<TEX>$800∼1000^{\circ}C$</TEX>). The glass was evaluated for glass transition temperature (<TEX>$Τ_{g}$</TEX> X) and thermal expansion coefficient(<TEX>$\alpha$</TEX>). Mechanical property (Vickers hardness), grain growth, the comparison of lattice parameter and pore distribution of sintered <TEX>$MnWO_4$</TEX> with the frit were methodically discussed. As sintering temperature increased, a typical liquid phase sintering showed the rapid grain growth and high densification of X<TEX>$MnWO_4$</TEX>grain, improvement of hardness (until <TEX>$920^{\circ}C$</TEX>) and different pore size distribution. Resistance of sintered <TEX>$MnWO_4$</TEX>varied from 450k<TEX>$\Omega$</TEX> to 8.8M<TEX>$\Omega$</TEX> under the measuring humidify ranging from 30 to 90%. Thus, the results will contribute to the application of glass frit containing sensor materials and their future use.

New Methods for the Accurate Comparison of Lattice Parameters

AbstractTwo new methods of comparison of lattice parameters are described. The first method uses a double crystal diffractometer, fitted with a specimen rotation stage. Bragg peak positions of a silicon reference and the specimen crystal are recorded for the crystals at 0 and rotated 180° about the diffraction vector. From the mean Bragg positions the lattice parameters can, in principle, be compared to parts in 106. The second method is a variant on the above, using a triple axis diffractometer. It uses a beam conditioner and monochromator to define the incident wavevector ko, and an analyser crystal to define the diffracted wave vector kh. Only the analyser motion must be accurate and stable to the arc second level. We present a detailed error analysis for the case where reference and specimen Bragg angles differ significantly. Peak location to a confidence level of 1 arc second permits absolute, traceable lattice parameter determination to several parts in 106.

Experimental Comparison of Widely Differing Lattice Parameters

We report the implementation of two new methods of accurate comparison of lattice parameters against a silicon standard using a high resolution X-ray diffractometer. The double axis method uses a specimen rotation stage which set the limit of reproducibility (at 3 sigma) to 3 parts in 105. An application of the technique is illustrated in measurements of the zinc concentration in Cd1-xZnx Te to an accuracy of 0.1%. The triple axis technique uses beam conditioner and analyser crystals to define the incident and diffracted wave vectors. In measurement of the lattice parameters of InAs, we found a precision of 1 part in 105 and traceable accuracy of a several parts in 105.

The role of octacalcium phosphate in subcutaneous heterotopic calcification.

Comparison of lattice parameters and morphology of some of the microcrystallites in a subcutaneous heterotopic calcification reported by Daculsi et al. [1] with those of heat-treated octacalcium phosphate (OCP) suggests that OCP is one of the mineral phases in dense globules and one of the precursors for the apatite.

Studies on the formation of a solid solution compound in Li 2O impregnated CuAl 2O 4 catalyst

Li 2O impregnated CuAl 2O 4 samples were calcined at two temperatures (673 K and 1173 K). X-ray analysis showed that the lattice parameter of the spinel phase decreased with increasing calcining temperature. X-ray studies on the solid solution series Cu 1−x Li x 2 Al 2+ x 2 O 4 (x = 0, 0.1, 0.2, 0.3, 0.4 and 0.5) showed that the lattice parameter decreased with increasing concentration of lithium and from the comparison of lattice parameters it appears that Cu 0.84 Li 0.08 Al 2.08 O 4 is formed in the impregnated sample calcined at 673 K. Electrical resistivity measurements are consistent with the formation of a solid solution compound.

Magnetic properties of partially devitrified B2O3-MnFe2O4 glass

Crystallization processes of partially devitrifled glass obtained by rapid quenching of 0·175 MnO + 0·175. Fe2O3 + 0·65 B2O3 melt were studied by DTA and X-ray analyses and the temperature regions of nucleation, crystallization and decompozition of the spinel phase were established. The magnetization curves measured between 4·2 and 250 K in magnetic fields up to 42 kOe divided the samples into two groups: the original as cast glass and those annealed below the crystallization temperature, as well as above the decomposition temperature showed essentially paramagnetic behaviour, whereas those annealed closely above the crystallization temperature displayed a spontaneous magnetic moment. The former ones could not be classified as superparamagnetic but the temperature dependence of their susceptibility could be explained by interactions of the antiferromagnetic type. The comparison of lattice parameter and Curie temperature of the latter one with crystalline Mn x Fe3-x O4, system indicated pronounced iron enrichment of the spinel phase formed during heat treatment.

Comparison of Lattice Parameter and Resistivity Change in Electron‐Irradiated Copper

AbstractLattice parameter and residual resistivity measurements were performed on high‐purity copper samples irradiated simultaneously with 2.6 MeV electrons at 6 K up to defect concentrations of about 0.1%. Lattice parameter changes could be measured with a resolution of Δa/a = 5 × 10−6. In six irradiations the ration η = (Δa/a)/Δϱ was determined as a function of defect concentration and thermal recovery. During defect production the ratio η amounts to (1.75 ± 0.10) × 103 (Ωcm)−1 and is independent of the defect concentration. Furthermore, the ratio η stays constant throughout the recovery stages I, II, and III.

Phase equilibria in the high magnesia corner of the system MgO-ThO2-B2O3 at 1200° C

Phase equilibria in the high magnesia corner of the system MgO-ThO2-B2O3 were investigated at 1200°C using X-ray powder diffraction techniques. The two magnesium borates reported previously at this temperature were confirmed, but no magnesium thorate and no ternary phases were found. Solid solution effects were investigated; for the binary phases by comparison of patterns, for magnesium oxide and thorium oxide by comparison of lattice parameters. No solid solutions were detected.

Comparison of Lattice-Parameter and Resistivity Change in Electron-Irradiated Aluminum

Lattice-parameter and residual-resistivity measurements were performed on high-purity aluminum samples irradiated simultaneously with 3-MeV electrons at 4.5 \ifmmode^\circ\else\textdegree\fi{}K. For the latticeparameter measurements, a rotating single-crystal backreflection x-ray technique with monochromatic radiation ($\mathrm{Cu} K{\ensuremath{\alpha}}_{1}$) was used with a resolution of $\frac{\ensuremath{\Delta}a}{a}\ensuremath{\approx}6.5\ifmmode\times\else\texttimes\fi{}{10}^{\ensuremath{-}6}$. In four runs the ratio $\ensuremath{\eta}=\frac{(\frac{\ensuremath{\Delta}a}{a})}{\ensuremath{\Delta}\ensuremath{\rho}}$ was determined as a function of defect concentration and of thermal recovery. During defect production the ratio $\ensuremath{\eta}$ amounts to (1.61 \ifmmode\pm\else\textpm\fi{} 0.10) \ifmmode\times\else\texttimes\fi{} ${10}^{3}$ ${(\mathrm{\ensuremath{\Omega}}\phantom{\rule{0ex}{0ex}}\mathrm{c}\mathrm{m})}^{\ensuremath{-}1}$ and remains unaffected by the radiation annealing processes up to defect densities of about 2 \ifmmode\times\else\texttimes\fi{} ${10}^{\ensuremath{-}3}$. Furthermore, the ratio $\ensuremath{\eta}$ stays constant throughout the recovery stages I, II, and III. This behavior suggests that the rearrangement in the local distribution of the interstitials and vacancies accompanying the radiation annealing and thermal recovery processes - especially the interstitial clustering processes - does not appreciably affect the lattice-parameter expansion and the electrical resistivity per unit of Frenkel-defect concentration.