AxMn1-xFe2O4铁氧体(A=Zn,Ni)中阳离子的占位有序化行为研究

基于尖晶石晶体结构信息,本文采用热力学三亚晶格模型,将材料热力学计算和第一性原理计算相结合,研究了Zn_xMn_1-x Fe₂O₄和Ni_xMn_1-xFe₂O₄立方相中的Zn²⁺、Ni²⁺、Mn²⁺以及Fe³⁺在8a和16d亚晶格上的占位有序化行为。结果表明:在锰铁氧体中,室温下Mn²⁺完全占据在8a亚晶格上,Fe³⁺完全占据在16d亚晶格上,属于正尖晶石结构;随着热处理温度升高,在1 273 K达到热处理平衡时的占位构型为(Fe_0.09³⁺Mn_0.91²⁺)[Fe_1.91³⁺Mn_0.09²⁺]O₄,在热处理温度升至1 473 K时,达到热处理平衡时的占位构型为(Fe_0.11³⁺ Mn_0.89²⁺)[Fe_1.89³⁺Mn_0.11²⁺]O₄,均与实验结果符合较好。在锌铁氧体中,室温下Zn²⁺完全占据在8a亚晶格上,Fe³⁺完全占据在16d亚晶格上,属于正尖晶石结构;在热处理温度较高时,Zn²⁺和Fe³⁺发生部分置换,符合实验结果。在镍铁氧体中,半数的Fe³⁺在室温下占据在8a亚晶格上,Ni²⁺与剩下另一半的Fe³⁺共同占据在16d亚晶格上,仅在热处理温度较高的时候发生微弱变化,亦与已有的实验结果吻合。在此基础上,本文进一步通过热力学预测建立了立方相尖晶石结构的Zn_xMn_1-xFe₂O₄、Ni_xMn_1-xFe₂O₄复合体系中阳离子占位行为与热处理温度对占位的影响。     

AxMn1-xFe2O4铁氧体(A=Zn,Ni)中阳离子的占位有序化行为研究

基于尖晶石晶体结构信息,本文采用热力学三亚晶格模型,将材料热力学计算和第一性原理计算相结合,研究了Zn_xMn_(1-x) Fe_2O_4和Ni_xMn_(1-x)Fe_2O_4立方相中的Zn~(2+)、Ni~(2+)、Mn~(2+)以及Fe~(3+)在8a和16d亚晶格上的占位有序化行为。结果表明:在锰铁氧体中,室温下Mn~(2+)完全占据在8a亚晶格上,Fe~(3+)完全占据在16d亚晶格上,属于正尖晶石结构;随着热处理温度升高,在1 273 K达到热处理平衡时的占位构型为(Fe~(3+)0.09Mn~(2+)0.91)[Fe~(3+)1.91Mn~(2+)0.09]O_4,在热处理温度升至1 473 K时,达到热处理平衡时的占位构型为(Fe~(3+)0.11Mn~(2+)0.89)[Fe~(3+)1.89Mn~(2+)0.11]O_4,均与实验结果符合较好。在锌铁氧体中,室温下Zn~(2+)完全占据在8a亚晶格上,Fe~(3+)完全占据在16d亚晶格上,属于正尖晶石结构;在热处理温度较高时,Zn~(2+)和Fe~(3+)发生部分置换,符合实验结果。在镍铁氧体中,半数的Fe~(3+)在室温下占据在8a亚晶格上,Ni~(2+)与剩下另一半的Fe~(3+)共同占据在16d亚晶格上,仅在热处理温度较高的时候发生微弱变化,亦与已有的实验结果吻合。在此基础上,本文进一步通过热力学模型研究了立方相尖晶石结构的Zn_xMn_(1-x)Fe_2O_4、Ni_xMn_(1-x)Fe_2O_4复合体系中阳离子占位行为与热处理温度对占位的影响规律。     

Chemischer Transport ternärer Cadmiummolybdate

Chemical Vapor Transport of Ternary Cadmium Molybdates The ternary phase diagram Cd/Mo/O at 923 K have been investigated. Single crystals of CdMoO₄ and Cd₂Mo₃O₈ have been obtained via chemical vapor transport using X₂ and NH₄X (X = Cl, Br, I) as transport agent. Deposition rates are very different: up to 10 mg/h for CdMoO₄, maximum 10^–3 mg/h for Cd₂Mo₃O₈. The observed transport behaviour is compared with results of thermodynamical model calculations. The influence of source composition, transport agent and temperature gradient is described in detail.     

Beiträge zum Chemischen Transport oxidischer Metallverbindungen. II. Bemerkungen zum Transport von α-Fe2O3 über monomeres Eisen(III)-chlorid

Transport of α? Fe₂O₃ with HCl via monomeric iron(III) chloride according to Fe₂O_3(s) + 6 HCl_(g) = 2FeCl_3(g) + 3 H₂O_(g); T₂ → T₁ between T₂ = 1000°C and T₁ = 800°C in the region of diffusion produced crystals which contained, in dependence of total pressure, different amounts of divalent iron. By addition of oxygen to the transport gas stoichiometric crystals of hematite by otherwise unchanged conditions were obtained. The necessary amount of oxygen was calculated from the phase diagram Fe? O, and an explanation of the gas phase reactions is given. Dependence of the transport rate of hematite on total pressure in the region of diffusion (0.009 to 6 atm) is reported.     

Preparation of MnxNi0.5-xZn0.5Fe2O4 Nanorods by the Co-precipitation Method

Mn_xNi_0:5-xZn_0:5Fe₂O₄ nanorods were successfully synthesized by the thermal treatment of rod-like precursors that were fabricated by the co-precipitation of Mn²⁺, Ni²⁺, and Fe²⁺ in the lye. The phase, morphology, and particle diameter were examined by the X-ray diffrac-tion and transmission electron microscopy. The magnetic properties of the samples were stud-ied using a vibrating sample magnetometer. The results indicated that pure Ni_0:5Zn_0:5Fe₂O₄ nanorods with a diameter of 35 nm and an aspect ratio of 15 were prepared. It was found that the diameter of the Mn_xNi_0:5-xZn_0:5Fe₂O₄ (0≤x≤0.5) samples increased, the length and the aspect ratio decreased, with an increase in x value. When x=0.5, the diameter and the aspect ratio of the sample reached up to 50 nm and 7～8, respectively. The coercivity of the samples first increased and then decreased with the increase in the x value. The coer-civity of the samples again increased when the x value was higher than 0.4. When x=0.5,the coercivity of the Mn_xNi_0:5-xZn_0:5Fe₂O₄ sample reached the maximal value (134.3 Oe)at the calcination temperature of 600 oC. The saturation magnetization of the samples first increased and then decreased with the increase in the x value. When x=0.2, the satura-tion magnetization of the sample reached the maximal value (68.5 emu/g) at the calcination temperature of 800 oC.     

Chemischer Transport fester Lösungen. 8 [1] Zum Chemischen Transport von ternären und quaternären Cobalt(II)‐ und Nickel(II)‐germanaten

Chemical Vapor Transport of Solid Solutions. 8 The Chemical Vapor Transport of Ternary and Quarternary Cobalt and Nickel Germanates By means of chemical vapor transport methods using HCl as transport agent CoGeO₃, Co₂GeO₄, and Ni₂GeO₄ have been prepared (1000 → 900 °C and 900 → 700 °C). In this system the formation of a continuous crystalline solid solution of Co₂GeO₄ and Ni₂GeO₄ was found as well as the deposition of the compound NiGeO₃ which — although unknown as a pure solid — can be stabilized as a mixed crystal Ni_xCo_1—xGeO₃ (0 < x < 0, 6).     

Chemischer Transport fester Lösungen. 10 [1] Zum Chemischen Transport von quaternären Cobalt(II)‐Zink‐ und Mangan(II)‐Zinkgermanaten

Chemical Vapor Transport of Solid Solutions 10 [1] The Chemical Vapor Transport of quarternary Cobalt(II)‐Zinc and Manganese(II)‐Zinc Germanates By means of chemical vapor transport methods using HCl or Cl₂ as transport agent the crystalline solid solutions (Zn_xCo_1—x)₂GeO₄ and (Mn_xZn_1—x)₂GeO₄ have been prepared (1050 → 900 °C, 850 → 700 °C, respectively). ZnGeO₃ — although unknown as a pure solid — can be stabilized as a mixed crystal (Mn_xZn_1—x)GeO₃ (x > 0, 5).     

Beiträge zum chemischen Transport oxidischer Metallverbindungen. IV. Der Transport der Spinelle Me3O4(Me = Fe,Co, Mn) und der Ferrite MeFe2O4 (Me = Ni,Co, Mn,Mg) über ihre Metallchloride

The transport effect by means of HCl in the case of spinels Me₃O₄ and ferrites MeFe₂O₄ (equations see “Inhaltsübersicht”) between T₂ = 1000°C and T₁ = 800°C was experimentally investigated under so-called “standard conditions”. Transported crystals and residues were characterized by chemical analysis and the magnetic moment. For nickel ferrite, the effect of transport was calculated by the model of diffusion in dependence on total pressure and compared with experimental values. In the case of nickel and magnesium ferrite, transport starting from the basic oxides was also achieved. By measurements of the line width of ferromagnetic resonance the quality of the transported crystals of the last two ferrites has been checked.     

单分散NixZn1-xFe2O4纳米颗粒的制备及其磁热效应

以乙酰丙酮金属盐为前驱体,三乙二醇为溶剂,采用多元醇法制备了镍锌不同配比的Ni_xZn_(1-x)Fe_2O_4(x=0,0.3,0.5,0.7和1.0)铁氧体,并通过X射线衍射仪(XRD),透射电子显微镜(TEM)和振动样品磁强计(VSM)等对样品的结构、形貌、磁性能和磁热性能进行了表征。结果表明:Ni_xZn_(1-x)Fe_2O_4铁氧体分散性较好,尺寸均一,形状近似球形,平均粒径为4~5 nm。Ni_xZn_(1-x)Fe_2O_4纳米颗粒在室温下表现出亚铁磁性,饱和磁化强度随着镍含量的增加先增大后减小,当x=0.5时达到最大值29.38 emu·g~(-1)。在382k Hz交变磁场作用下,Ni_(0.5)Zn_(0.5)Fe_2O_4铁氧体温度可升温至313 K,表现出较好的磁热性能。     

Chemischer Transport ternärer Indiummolybdate

Chemical Vapor Transport of Ternary Indium Molybdates An isothermal section of the phase diagram of the system In/Mo/O at 1273 K was established by isothermal equilibration and XRD analyses of quenched samples. The chemical vapor transport of In₂Mo₃O₁₂ was investigated in dependence on mean transport temperature (823 K to 1123 K) and amount of transport agent (Cl₂ or Br₂). The observed transport behaviour is compared with results of thermodynamical calculations and the influence of mean temperature, transport agent and moisture contents is described in detail. Single crystals of the metal rich compound InMo₄O₆ were grown by chemical vapor transport in a temperature gradient 1273 K to 1173 K using H₂O as transport agent. The gaseous compound In₂MoO₄(g) accounts for the chemical vapor transport of molybdenium compounds in the metal rich part of the ternary phase diagram In/Mo/O.     

Neue Beobachtungen zum chemischen Transport von GeO2. VI. Temperaturabhängigkeit mit dem Transportmittel Chlor

New Observations on the Chemical Transport of GeO₂. VI. Temperature Dependence with the Transport Agent Chlorine In a temperature gradient T₂ ? T₁ = 100 K the chemical transport of tetragonal GeO₂ is kinetically controlled at an average transport temperature T ≤ 1080 K. The same is true for the metastable hexagonal modification at T ≤ 1150 K. An Arrhenius equation describes the rate of deposition in a satisfactory way. The activation energy amounts to 21 kcal/Mol. At higher temperatures diffusion determines the rate of transport whereby GeCl₄, Cl₂, and O₂ are looked upon as prominent gaseous molecules and the formation of a solid solution of hexagonal GeO₂ with SiO₂ is taken into account. For a transport temperature T < 1100 K GeO₂ is deposited at T₁ only if seeds of the specific modification are present. The deposition of GeO₂(hex.) ceases at temperatures lower than T ≈ 1000 K. The formation of GeO₂(tetr.) requires not only seeds but also NaCl as mineralizer and the temperature should not be lower than T ≈ 900 K.     

The structural characteristics of Zn-Mn ferrite synthesized by spray pyrolysis

The applicability of IR spectroscopy in studies of the structural characteristics of the ferrite spinel phase was shown for Zn_0.5Mn_0.5Fe₂O₄ samples prepared by the pyrolysis of aerosols of aqueous solutions of metal nitrates. The IR spectra of synthesized (ZnMn)Fe₂O₄ ferrites, Fe₂O₃, ZnO, MnO, and Mn₂O₃ pure oxides, and mixtures of these oxides in the region of characteristic M-O stretching vibration and M-O-H bending vibration frequencies were compared to determine the degree of concentration and structural uniformity of the ferrite spinel phase.     

Löslichkeit von Nickel-Zink-Ferriten in Säuren

Dissolution of zinc and nickel ferrites were previously found^2,3 to conform to the equations: $$\frac{{dx}}{{dt}} = ks_0 \left( {1 - x} \right)^3 K = \frac{1}{t}\left[ {\frac{1}{{\left( {1 - x} \right)^2 }} - 1} \right]$$ x-solubility (%),t=time (min),s ₀=initial specific surface (m ²·g^?1),k-rate constant independent of specific surface,K=apparent rate constant dependent on specific surface (min^?1). The aim of this work was to check the applicability of these equations to the dissolution of nickel—zinc ferrites. The experimental results obtained for 3 mixed ferrites (Ni_0.3Zn_0.7Fe₂O₄, Ni_0.5Zn_0.5Fe₂O₄, Ni_0.7Zn_0.3Fe₂O₄) revealed that kinetics of their dissolution in HCl, HNO₃ and their mixtures also conform to the equations stated above.     

Chemischer Transport fester Lösungen. 11 [1] Mischphasen und Chemischer Transport in den Systemen CrIII/InIII/GeIV/O,GaIII/InIII/GeIV/O,MnIII/InIII/GeIV/O und FeIII/InIII/GeIV/O

Chemical Vapor Transport of Solid Solutions. 11 Mixed Phases and Chemical Vapor Transport in the Systems Cr^III/In^III/Ge^IV/O, Ga^III/In^III/Ge^IV/O, Mn^III/In^III/Ge^IV/O und Fe^III/In^III/Ge^IV/O By means of chemical vapor transport methods the following mixed phases have been prepared: Cr_{0, 18}In_{1, 82}Ge₂O₇ (Cl₂, 950 → 850 °C), (Ga_{0, 6}In_{1, 4})₂Ge₂O₇ (Thortveitit‐type, Cl₂, 1050 → 950 °C), (Ga_{1, 9}In_{0, 1})₂Ge₂O₇ (Ga₂Ge₂O₇‐type, 1050 → 950 °C), (In_{1, 9}Mn_{0, 1})₂Ge₂O₇ (Thortveiti‐type, Cl₂, 1000 → 800 °C), mixed phase crystallizing in the Mn₂Ge₂O₇‐structure showing a composition near MnInGe₂O₇ (Cl₂, 1000 → 800 °C), Mn_{6, 5}In_{0, 5}GeO₁₂ (Braunit‐type, Cl₂, 1000 → 800 °C), (Fe_xIn_1‐x)Ge₂O₇ (Thortveitit‐type with x = 0…0, 94; Cl₂, 840 → 780 °C). Changing the compositions of the starting materials showed no effect on the composition of the deposit except for the system Fe₂O₃‐In₂O₃‐GeO₂.     

Beiträge zum chemischen Transport oxidischer Metallverbindungen. IX. Über den Chemischen Transport von SE3Fe5O12 (SE = Y,Gd) im System Festkörper/SECl3. Experimente

Contributions to the Chemical Transport of Metal Oxides. IX. Chemical Transport of SE₃Fe₅O₁₂ (SE = Y, Gd) in the System Solid/SECl₃. Experiments The chemical transport of Yttrium-Iron-Garnet with YCl₃ as transporting agens was systematically investigated. The relations between the ratio of the transported phases Fe₂O₃, Y₃Fe₅O₁₂, YFeO₃, and YOCl and the amount of YCl₃, the composition of starting solid material, and the temperature are in good agreement with calculations of a model, described in [1]. Similar results were obtained in some experiments with Gadolinium-Iron-Garnet and GdCl₃.     

Magnetic properties of binary and ternary mixed metal oxides NiFe<Subscript>2</Subscript>O<Subscript>4</Subscript> and Zn<Subscript>0.5</Subscript>Ni<Subscript>0.5</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> doped with rare earths by sol—gel synthesis

The spinel-type ferrites NiFe₂O₄ and Zn_0.5Ni_0.5Fe₂O₄ modified by lanthanide ions Eu³⁺ and Tb³⁺ were prepared by a sol—gel process with propylene oxide as a gelating agent. The phase homogeneity of the samples was tested by XRD and Mössbauer spectroscopy. Transmission electronic microscopy used for characterisation of the morphology of the samples revealed nanosized powdered samples with a narrow distribution of particle sizes. It was noted that the presence of Ln³⁺ ions influenced the magnetic properties of nanosized NiFe₂O₄ and Ni_0.5Zn_0.5Fe₂O₄ ferrites. The dependence of the magnetic properties of the samples on the rare-earth doping may be explained by the different grain sizes. The saturation magnetisation tends to decrease with increasing rare-earth doping and decreasing crystallite size. A similar trend was observed for the coercive field, with the exception of the Tb³⁺-doped Zn_0.5Ni_0.5Fe₂O₄ where it remained the same as in the pure ferrite.     

Synthesis and characterization of Ni<Subscript>0.6</Subscript>Zn<Subscript>0.4</Subscript>Fe<Subscript>2</Subscript>O<Subscript>4</Subscript> nano-particles obtained by auto catalytic thermal decomposition of carboxylato-hydrazinate complex

Ni_0.6Zn_0.4Fe₂O₄ nano-particles have been synthesized by self-propagating auto-combustion of nickel zinc ferrous fumarato-hydrazinate complex. The precursor complex has been characterized by chemical analysis, IR, AAS, thermal analysis and isothermal mass loss studies. The precursor on ignition undergoes self-propagating auto combustion to give Ni_0.6Zn_0.4Fe₂O₄. The X-ray diffraction studies confirmed the single phase formation of nano-size ‘as synthesized’ Ni_0.6Zn_0.4Fe₂O₄. TEM observation showed the average particle size to be 20 nm. Infrared and magnetization studies were also carried out on the ‘as synthesized’ Ni_0.6Zn_0.4Fe₂O₄. The lower value of saturation magnetization and higher Curie temperature of ‘as synthesized’ ferrite also hint at the nano size nature.     

A direct fluorescence-on chemo-sensor for selective recognition of Zn(II) by a lower rim 1,3-di-derivative of calix[4]arene possessing bis-{N-(2-hydroxynaphthyl-1-methylimine)} pendants

The bis-{N-(2-hydroxynaphthyl-1-methylimine)} anchored 1,3-di-derivative of lower rim p-tert-butyl-calix[4]arene possessing a N₂O₂, N₂O₄ or N₂O₆ binding core was found to be selective for Zn(II) ions even at ?60 ppb by eliciting fluorescence-on behaviour while the other ions, viz., Ti⁴⁺, VO²⁺, Cr³⁺, Mn²⁺, Fe²⁺, Co²⁺, Ni²⁺, Cu²⁺, Mg²⁺, Cd²⁺ and Hg²⁺ caused no change in the fluorescence. The reaction between 1 and Zn²⁺ was found to be stoichiometric with the formation of a 1:1 complex; while H⁺ quenched the fluorescence of the complex, OH⁻ restored it. The studies of the 1:1 isolated complexes of Zn²⁺, Ni²⁺ and Cu²⁺ augmented the results.     

Untersuchungen an elektronenleitenden Oxidsystemen. XXI. Stabile spinelle ZnzNiMn2−zO4 und Vergleich mit Spinellen MgzNiMn2−zO4

Investigations on Electronically Conducting Oxide Systems. XXI [1] Stable Spinels Zn_zNiMn_2?zO₄ and Comparison with Spinels Mg_zNiMn_2?zO₄ Stable spinels are obtained in the result of substitution of Zn^II for manganese in the series Zn Ni^IIMnMnO₄ (O ? z ≤1). Different from spinels Mg Ni^IIMnMnO₄ (O ? z ?1)they don't be submitted to decomposition in air during slow cooling at medium temperatures. ZnNiMnO₄ (z=1) could not be prepared in a mono-phase state which is indicated by the composition of ZnNiMnO_3.96 deduced from analysis by oxidimetric titration. The comparably small variation of the specific electrical conductivity and of the activation energy observed in the range O ? z ? 2/3 for Zn_zNiMn_2?z is discussed in relation to larger alterations in the series Mg_zNiMn_2?zO₄. Structural interpretation is proposed based on the comparison of the molar volume of spinels M Mn₂O₄ (M: Mn, Fe, Co, Ni, Cu, Zn, Mg).     

A highly coercive carbon nanotube coated with Ni0.5Zn0.5Fe2O4 nanocrystals synthesized by chemical precipitation-hydrothermal process

Novel magnetic composites (Ni_0.5Zn_0.5Fe₂O₄-MWCNTs) of multi-walled carbon nanotubes (MWCNTs) coated with Ni_0.5Zn_0.5Fe₂O₄ nanocrystals were synthesized by chemical precipitation-hydrothermal process. The composites were characterized by X-ray powder diffractometer (XRD), X-ray photoelectron spectrometer (XPS), Fourier transform infrared spectroscopy (FTIR), Mössbauer spectroscopy (MS), transmission electron microscopy (TEM), and selected area electron diffraction (SAED), etc. A temperature of about 200 °C was identified to be an appropriate hydrothermal condition to obtain Ni_0.5Zn_0.5Fe₂O₄-MWCNTs, being lower than the synthesis temperature of a single-phase Ni_0.5Zn_0.5Fe₂O₄ nanocrystals. The sizes of Ni_0.5Zn_0.5Fe₂O₄ in the composites were smaller than those of Ni_0.5Zn_0.5Fe₂O₄ nanocrystals in single phase. The composites exhibited more superparamagnetic than Ni_0.5Zn_0.5Fe₂O₄ nanocrystals in their relaxation behaviors. The magnetic properties measured by a vibrating sample magnetometer showed that the composites had a high coercive field of 386.0 Oe at room temperature, higher than those of MWCNT and Ni_0.5Zn_0.5Fe₂O₄ nanocrystals.