Flux growth of crystals of MNb2O6 (M = Ni,Co, Mn,Fe)

The growth of crystals of MNb₂O₆ (M = Ni, Co, Mn, Fe) from fluxed melts is described. With M = Ni and Co, platinum crucibles were used, but with M = Mn and Fe, growth was carried out under nitrogen in molybdenum and iron crucibles respectively.     

Low-temperature preparation of some perovskites La2MM′O6 (M,M′=Cr,Mn, Fe,Co, Ni,M≠M)

The low-temperature preparation of some La₂MM′O₆ compounds (M,M′=Cr, Mn, Fe, Co, Ni, M≠M′) by the decomposition of coprecipitated basic carbonates is described. Single phase compounds are formed. The stability of physical properties of these phases towards further heating depends on the M and M′ ions. The results are interpreted in terms of the stability of the M-M′ oxidation states. Communication No. 122 from the Solid State and Structural Chemistry Unit     

锂离子电池正极材料LiM0.1Ni0.4Mn1.5O4(M:Co,Cr,Fe)纳米纤维的制备与电化学性能

利用高压静电纺丝技术与溶胶凝胶法相结合制备出了锂离子电池正极材料LiM_(0.1)Ni_(0.4)Mn_(1.5)O_4(M:Co,Cr,Fe)纳米纤维。采用X射线衍射(XRD)、场发射扫描电镜(FESEM)对材料的晶体结构和表面形貌进行了表征,并采用恒流充放电手段研究了材料在室温下的循环稳定性和倍率特性。结果表明:LiFe_(0.1)Ni_(0.4)Mn_(1.5)O_4材料以0.5C充放电循环100周后容量保持率高达95.5%,显示了良好的循环稳定性;而LiCr_(0.1)Ni_(0.4)Mn_(1.5)O_4材料以10C放电比容量仍高达120mAh/g,显示出了极好的倍率特性。     

Preparation and Dielectric Properties of Bi1.5MNb1.5O7 (M = Cu, Mg, Mn, Ni, Zn) Pyrochlore Oxides

Bi_1.5MNb_1.5O₇ (M = Cu, Mg, Mn, Ni, Zn) oxides are prepared by solid-state reactions and are shown, by x-ray diffraction, to have cubic pyrochlore structure with lattice parameters in the range a= 10.495–10.570 Å. The phases with M = Cu, Mg, Mn, and Ni are prepared and characterized for the first time. The 1- and 10-kHz dielectric permittivity and loss tangent of Bi_1.5MNb_1.5O₇ are measured from 80 to 300 K. For M = Mg, Ni, and Zn, exhibits a maximum at 130, 150, and 90 K, respectively.     

Über die systeme BaRu1−xMxO3−y (M = Rh,Ir, Mn,Fe, Co,Ni)

In the systems BaRu_1?xM_xO_3?y (M = Rh, Ir, Mn, Fe, Co, Ni) several perovskite stacking polytypes are present. The influence of the crystal structure and Ru/M-ratio on the electrical conductivity and catalytic activity is investigated.     

Comparative study on the doping effect of 3d elements in Bi1.5Pb0.2Sr2Ca2Cu2.8M0.2O y (M=Sc,Ti, V,Cr, Mn,Fe, Co,Ni, or Zn)

With XRD,R-T, and acχ measurements a comparative study on the doping effects of 3d elements in Bi_1.5Pb_0.2Sr₂Ca₂Cu_2.8M_0.8O _y (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, or Zn) has been carried out. The effects of the former five members are significantly different, both on phase formed and onT _c , from the latter four. It seems that the effect on phase stabilization correlates with the valency of the doped cation. In connection with the instability of the 2223 phase, the correlation has been discussed.     

The effect of Cu-sites doping on electrical properties of La2CuO4 as thermoelectric material

The electrical conductivity and thermoelectric power for solid solutions of La₂Cu_0.9M_0.1O₄ (M = Mn, Fe, Co and Ni) prepared by polymeric precursor synthesis were measured between 300 and 1173 K to test its suitability as a thermoelectric material. Fe-, Mn-and Ni-doped compositions exhibited a metal-semiconductor transition with decreasing temperature, whereas Co doping showed a semiconducting behaviour in the entire temperature range of measurement. With Cu-sites doping in La₂CuO₄, power factors were not enhanced.     

Comparative study on the doping effect of 3d elements in Bi1.5Pb0.2Sr2Ca2Cu2.8M0.2Oy (M=Sc, Ti, V, Cr, Mn, Fe, Co, Ni, or Zn)

With XRD,R-T, and ac measurements a comparative study on the doping effects of 3d elements in Bi_1.5Pb_0.2Sr₂Ca₂Cu_2.8M_0.8O _y (M = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, or Zn) has been carried out. The effects of the former five members are significantly different, both on phase formed and onT _c , from the latter four. It seems that the effect on phase stabilization correlates with the valency of the doped cation. In connection with the instability of the 2223 phase, the correlation has been discussed.     

Structural characterization of mixed conducting perovskites La(Ga,M)O3−δ (M=Mn, Fe, Co, Ni)

Comparative analysis of the structure refinement results of perovskite-like LaGa_0.5M_0.5O_3−δ (M=Mn, Fe, Co, Ni) and data on other LaGaO₃-based phases, heavily doped with transition metal cations, shows that on doping the structural changes in these oxides follow common trends for the perovskite-type systems. The maximum ionic conductivity, observed in various perovskites when the tolerance factor values are approximately 0.96-0.97, was found to correlate with the transition from orthorhombic to rhombohedral structure and maximum lattice distortion. The perovskite unit cell distortion near the orthorhombic-rhombohedral phase boundary may hence play a positive role in the ionic transport processes.     

Standard Gibbs' energy of formation of LaFeO3 and comparison of stability of LaMO3 (M = Mn,Fe, Co or Ni) compounds

The thermodynamic stability of LaFeO₃ at high temperatures is of interest in materials technology. For evaluating the thermodynamic data of LaFeO₃, the e.m.f. of the following galvanic cell was studied over the range 1094 to 1299 K: Pt, LaFeO₃, Fe, La₂O₃/15 mol % CaO stabilized ZrO₂/FeO, Fe, Pt. For the galvanic cell reaction 1/2 La₂O₃ + 3/2 FeO 1/2Fe + LaFeO₃, the standard Gibbs energy change, G _r ⁰ , was measured to be (G _r ⁰ ±0.34) (kJ)=–22.67–0.011 55T (K) for the passage of 3 F of electricity. From this, the stability of LaFeO₃ with respect to La₂O₃ and FeO as well as with La₂O₃ and Fe₂O₃ was computed and compared with other equilibrium measurements on LaFeO₃ reported in the literature. In addition, a comparison was made on the stabilities of LaMO₃ compounds (where M=Mn, Fe, Co or Ni) with respect to dissociation into La₂O₃ and MO making use of the published data on other compounds. Likewise a comparison of disproportionation of LaFeO₃ and LaMO₃ into their respective sesquioxides was also made.     

Quaternary chalcogenides of formula MII2MV2−2yM′2yS6 and Se6

Compositions of the title formula where M^II = Ba and Sr, M^V = Ta and Nb, M′ = Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Rh and Ir, and y = 0.5 and 0.33 were prepared by two methods: reaction of the elements in evacuated silica tubes and reaction of M^IICO₃, M^V₂O₅, and M′ oxides with H₂S. When M^II = Ba, all members have the BaNiO₃ structure. When M′ = Mn and Cu, structural distortions are present. Some compositions have Ta or S vacancies. When M^II = Sr, compositions were prepared only with Ta, for y = 0.5 and when M′ = Cr and Fe. Electrical measurements on selected compositions showed semiconductivity.     

Synthesis of new (Bi,La)<Subscript>3</Subscript>MSb<Subscript>2</Subscript>O<Subscript>11</Subscript> phases (M = Cr,Mn, Fe) with KSbO<Subscript>3</Subscript>-type structure and their magnetic and photocatalytic properties

Synthesis and structure of new (Bi, La)₃MSb₂O₁₁ phases (M = Cr, Mn, Fe) are reported in conjunction with their magnetic and photocatalytic properties. XRD refinements reflect that Bi₃CrSb₂O₁₁, Bi₂LaCrSb₂O₁₁, Bi₂LaMnSb₂O₁₁ and Bi₂LaFeSb₂O₁₁ adopt KSbO₃-type structure (space group, Pn[`3])Pn\overline{3}). The structure can be described through three interpenetrating networks where the first is the (M/Sb)O₆ octahedral network and other two are the identical networks having Bi₆O₄ composition. The magnetic measurements on Bi₂LaCrSb₂O₁₁ and Bi₂LaMnSb₂O₁₁ show paramagnetic behaviour with magnetic moments close to the expected spin only magnetic moments of Cr^+ 3 and Mn^+ 3. The UV-Visible diffuse reflectance spectra are broad and indicate that these materials possess a bandgap of ∼ 2 eV. The photocatalytic activity of these materials has been investigated by degrading Malachite Green (MG) under exposure to UV light.     

The preparation of Al2O3/M (Fe,Co, Ni) nanocomposites by mechanical alloying and the catalytic growth of carbon nanotubes

Mechanical alloying was employed to produce Al₂O₃/M (M=Fe, Co, Ni) nanocomposites. It was found that high-energy mechanical milling could realize not only drastic refinement but also the well dispersion of catalyst precursors in oxide matrixes. After mechanical milling, the solid-state alloying and the accelerated substitutional reactions were observed between the parent oxides. The as-obtained Al₂O₃/M nanocomposites possessed the fine-grained and porous structures and thus high reducibility. Large-scale formation of multiwalled and single-walled carbon nanotubes were achieved by using these mechanical alloying-derived Al₂O₃/M nanocomposites.     

Magnetic scattering of conduction carriers in 3d transition-metal intercalates of M x TiS2 (M=Mn,Fe, Co,and Ni)

Galvanomagnetic measurements on layer-structured 3d transition-metal intercalates of M_xTiS₂ (M = Mn, Fe, Co, and Ni;x0.33) have been made over the temperature range 0.34–20 K. Resistivity minima and negative magneto-resistances are observed for paramagnetic Mn, Fe, and Ni intercalates with low guest concentrations (x0.1), as found in well-known dilute alloys. However, in the case of the weak-ferromagnetic phase of Co_xTiS₂ (0.10x0.33) with the Curie temperatureT _c =120–140 K, such anomalous behaviors are also observed, which is not commonly found in the magnetically ordered phases of various magnetic materials. With these data we have given qualitative discussions on the magnetic scattering process of conduction carriers. Further, some of the experimental results are discussed in connection with the band calculations for M_1/3TiS₂.     

Structural determination of some MPS3 layered phases (M = Mn,Fe, Co,Ni and Cd)

The structures of most of the MPS₃ phases (M = Mn, Fe, Co, Ni, Cd) were determined from single crystal analysis. They show the expected CdCl₂ structural type, some weak disorder on the cationic sites being detected on NiPS₃ and CoPS₃. Fair stoichiometry is inferred for the phases since no interslab cation could be seen in the Van der Waals' gap of the structures. Polytypism may occur in the case of NiPS₃.     

Formation region of monophase with cubic spinel-type oxides in Mn–Co–Ni ternary system

This study was performed to find the composition area of cubic spinel-type monophase oxides composed of the Mn–Co–Ni ternary system. Starting materials were prepared by mixing Mn, Co, and Ni nitrates then evaporating to dryness. Each starting oxide was fired at 700, 800, 900, 1000, and 1100 °C in air. The regions of cubic spinel monophase (CSM) were confirmed to spread with decreasing firing temperatures. The region of CSM at 1000 °C was seen near the line connecting the points of Mn : Co : Ni = 2 : 4 : 0 and 4.5 : 0 : 1.5. The area at 800 °C spread toward Co and Ni, as compared to the results at 1000 °C. In the region containing more Mn above the area of CSM at 800 °C, the phase had tetragonal spinel or -Mn₂O₃ besides cubic spinel structure. Below this area, the phase contained rock-salt-type crystal besides cubic spinel structure. This tendency at 1000 °C was the same as that at 800 °C.     

Role of alloying elements in microstructures of beta titanium alloys with carbon additions

Abstract

The effect of 0.2 wt-%C on the microstructure of beta titanium alloys Ti-15X(Fe, Cr, Mn, Mo, Ni, Co, Cu, and V) has been studied using scanning and transmission electron microscopy. It has been found that coarse eutectic TiC_x tends to be formed in beta titanium alloys containing Fe, Cr, Mo, and Mn, and relatively finer homogeneous TiC_x is formed in alloys containing V, Ta, Co, Ni, or Cu. The volume fraction of TiC_x in alloys containing Cu, Co, and Ni is much less than that in other beta titanium alloys. The oxygen content of the matrix is lower than that of Ti₂C in Cr or alloys containing Mn and higher than that of Ti₂C in alloys containing Mo or Ni. These observations are discussed in terms of the role of phase diagrams and the effect of atomic radius of alloying elements on the dimension of interstitial sites in the host alloy and the sublattice of TiC_x.     

Lattice dynamic study on 3d transition metal intercalates M x TiS2 (M=Mn,Fe, Co,and Ni) using point-contact spectroscopy

The derivatives of the current-voltage characteristics of a homojunction point contact of 1T-CdI₂-type layered crystal TiS₂ and its intercalation compounds M_1/4TiS₂ (M=Mn, Fe, Co, and Ni) have been measured at 1.4 K. With reference to the available data on lattice dynamics, we have identified various inter- and intralayer acoustic and optical phonon modes. The acoustic phonon modes are strongly anisotropic compared with the optical ones in these materials. The variations of the acoustic phonon energies upon intercalation of 3d metals are strongly correlated with those of the interlayer spacingc, for which qualitative discussions are given.     

Crystallization of (Fe,Mn)-based nanoparticles in sodium-silicate glasses

In this investigation, glasses from the system Na₂O/MnO/SiO₂/Fe₂O₃ are prepared using a conventional glass-melting technique. During annealing the glass, a nanocrystalline (Fe, Mn)-based spinel phase is precipitated. The phase composition and microstructure of the formed glass–ceramics are studied using X-ray diffraction and electron microscopy. Anomalous small-angle X-ray scattering experiment is used to gather information on the size, composition and element distribution for the precipitated (Fe, Mn)-based nanocrystals. The sizes of the formed spinel crystals, as determined by scanning electron microscopy and anomalous X-ray scattering, are in the range from 12 to 50 nm for annealing temperatures in the range from 550 to 700 °C. Annealing for a longer period of time at temperatures ≥600 °C results in the formation of a second crystalline phase, NaFe(SiO₃)₂ (aegirine). The ASAXS data show the formation of core–shell structure for the (Fe, Mn)-based crystals with core consisting mostly of iron oxide and a shell, depleted of Fe and Mn. The growth of the spinel crystals is assumed to be kinetically self-constrained.     

Dependence of non-linearity coefficients on transition metal oxide concentration in simplified compositions of ZnO+Bi2O3+MO varistor ceramics (M=Co or Mn)

Ceramics with simplified compositions of ZnO + Bi₂O₃ + CoO or MnO show non-linearity coefficients () of 40–65 provided the concentration of transition metal ions is > 1.5mol.... Samples doped with Co have higher non-linearity coefficients than those with Mn. This is attributed to the stability of multiple oxidation states of Co(III) + Co(II) in contrast to Mn(II) as the stable species in sintered ZnO ceramics. Electron paramagnetic resonance and diffuse reflectance spectral studies establish this fact. Low-signal capacitance-voltage measurements show that donor density (N _d) in these ceramics ranges from 0.3 to 1.8 × 10¹⁹ cm^–3, which is comparatively larger than those of commercial varistors. The barrier height (_b) reaches up to 0.66 eV and the breakdown voltage is around 3.4–3.7 eV. Admittance spectroscopy and isothermal capacitance transient spectroscopy (ICTS) are used for characterizing the bulk traps originating from the transition metal dopants. Capacitance-voltage analyses above the breakdown voltages show negative capacitance, indicative of oscillatory charge redistribution involving multivalent states of Co and the shallower interface states. Multiple trapping relaxations are evident from the complex-plane capacitance studies.