共查询到20条相似文献,搜索用时 15 毫秒
1.
The structure and magnetic properties of Nd1−xYxMn2Ge2 (0.0≤x≤0.6) were studied by X-ray powder diffraction and magnetization measurements. All compounds crystallize in the ThCr2Si2-type structure with space group I4/mmm. Substitution of Y for Mn led to a linear decrease in the lattice constants and the unit cell volume. Increasing substitution of Y for Nd in NdMn2Ge2 shows a depression of ferromagnetic ordering and the gradual development of antiferromagnetic ordering. 相似文献
2.
In order to improve the thermoelectric properties via efficient phonon scattering Didymium (DD), a mixture of Pr and Nd, was used as a new filler in ternary skutterudites (Fe1−xCox)4Sb12 and (Fe1−xNix)4Sb12. DD-filling levels have been determined from combined data of X-ray powder diffraction and electron microprobe analyses (EMPA). Thermoelectric properties have been characterized by measurements of electrical resistivity, thermopower and thermal conductivity in the temperature range from 4.3 to 800 K. The effect of nanostructuring in DD0.4Fe2Co2Sb12 was elucidated from a comparison of both micro-powder (ground in a WC-mortar, 10 μm) and nano-powder (ball-milled, 150 nm), both hot pressed under identical conditions. The figure of merit ZT depends on the Fe/Co and Ni/Co-contents, respectively, reaching ZT > 1. At low temperatures the nanostructured material exhibits a higher thermoelectric figure of merit. The Vickers hardness was measured for all samples being higher for the nanostructured material. 相似文献
3.
《Journal of Alloys and Compounds》2004,370(1-2):47-52
The structure and magnetic properties of the Pr1−xGdxMn2Ge2 (0.0≤x≤1.0) compounds have been investigated by means of X-ray diffraction (XRD), differential scanning calorimetry (DSC) techniques and AC magnetic susceptibility measurements. All compounds crystallize in the ThCr2Si2-type structure with the space group I4/mmm. The lattice constants and the unit cell volume obey Vegard’s law. Samples in this alloy system exhibit a crossover from ferromagnetic ordering for PrMn2Ge2 to antiferromagnetic ordering for GdMn2Ge2 as a function of Gd concentration x. At low temperatures, the rare earth sublattice also orders and reconfigures the ordering in the Mn sublattice. The results are summarized in the x–T magnetic phase diagram. 相似文献
4.
A high electromechanical activity is observed in the [(K0.5Na0.5)1−xLix](Nb0.8Ta0.2)O3 (x = 0, 0.02, and 0.03) lead-free ceramic system at and around the orthorhombic (O)–tetragonal (T) phase transition temperature (TO–T). This activity is found to originate from an O–T phase transition region at ambient temperature rather than a classical morphotropic phase boundary (MPB) region intrinsic in the Pb(Zr1−xTix)O3 (PZT) lead-based ceramic system. Li modification enables a large decrease in TO–T instead of constituting a classical MPB. In contrast to the nearly temperature-independent classical MPB behavior in the PZT system, the strong temperature-dependent phase transition behavior in the system may impose a challenge to temperature demanding applications. 相似文献
5.
The structure and magnetic properties of CeMn2−xCoxGe2 (0.0≤x≤1.0) were studied by X-ray powder diffraction and magnetization measurements. All compounds crystallize in the ThCr2Si2-type structure with space group I4/mmm. Substitution of Co for Mn leads to a linear decrease in the lattice constants and the unit cell volume. Increasing substitution of Co for Mn shows a depression of ferromagnetic ordering. 相似文献
6.
Guoyan Huo Guanghui Rao Zhiyu Qiao Jingkui Liang Weihua Tang Baogen Shen 《Journal of Alloys and Compounds》1998,270(1-2)
Single-phase compounds Gd3(Fe1−xTix)29 (x=0.0110.034) have been synthesized. Gd3(Fe1−xTix)29 crystallises in a monoclinic lattice with space group P21/c, and the crystal structure is refined by the Rietveld technique based on X-ray powder diffraction data. Thermomagnetic analysis indicates that the Curie temperature of the compounds ranges from 517 K to 538 K. The saturation magnetizations of the Gd3(Fe1−xTix)29 (x=0.011, 0.022, 0.034) at 1.5 K are 103.6, 102.0 and 94.3 Am2/kg, and the anisotropy fields at 1.5 K are 6.0, 6.2 and 6.4T, respectively. 相似文献
7.
N. Sheloudko C. Safaridis M. Gjoka M. Mikhov O. Kalogirou 《Journal of Alloys and Compounds》2008,458(1-2):37-40
The effect of Co substitution for Fe in Nd3(Fe1−xCox)27.7Ti1.3Ny (0 ≤ x ≤ 0.4) compounds on the magnetocrystalline anisotropy has been investigated. The anisotropy constants K's and the anisotropy field HA have been deduced from the magnetization curves measured on magnetically aligned powder (4–7 μm) samples. The obtained results show that at RT the anisotropy is uniaxial and HA (about 10 T) does not change substantially upon the substitution. At 5 K the results for K's give evidence for the presence of easy-cone-type anisotropy. The cone angle as well as the anisotropy field decrease upon the substitution from 21.6° to 11.8° and from 22.8 to 18.6 T, respectively. 相似文献
8.
Stoichiometric Nd2(Fe1−xCox)14B alloys (x=0, 0.25, 0.5, 0.75 and 1) have been disproportionated into NdH2+δ and bcc–(Fe,Co) (0≤x≤0.75) or fcc–Co (x=1), respectively, by milling in hydrogen at enhanced temperatures. Reactive milling leads to the disproportionation of the thermodynamically very stable Nd2Co14B alloy. This reaction is not possible via the conventional hydrogenation disproportionation desorption and recombination (HDDR) process. Grain sizes of disproportionated and recombined Nd2(Fe,Co)14B materials were found to be <10 nm and 40–50 nm, respectively — approximately an order of magnitude smaller than those of conventional-HDDR processed alloys. The recombined Nd2Co14B alloy shows on average slightly smaller grain sizes than the Nd2Fe14B compound. A more effective exchange coupling leading to enhanced remanences, possibly due to the slightly smaller grain size, has been observed for Nd2Co14B powders recombined at 600–700°C. 相似文献
9.
G.B Song J.K Liang L.T Yang Q.L Liu G.Y Liu H.F Yang G.H Rao 《Journal of Alloys and Compounds》2004,370(1-2):302-306
The PrBa2−xSrxCu3O7±δ solid solution was investigated by means of X-ray powder diffraction in combination with Rietveld analysis. The Sr-doped Pr123 single phase could be synthesized at 950 °C in air. The solubility of PrBa2−xSrxCu3O7±δ solid solution is 0.2≤x≤0.6. The structure of PrBa2−xSrxCu3O7±δ is orthorhombic for x=0.2. The structure transforms into tetragonal for 0.3≤x≤0.6. In the PrBa2−xSrxCu3O7±δ structure, Sr ions can replace Ba ions, the highest value is x=0.6 under our experimental condition. But Sr ions could not replace Pr ions. Furthermore Pr ions could not occupy the sites of Ba ions in the PrBa2−xSrxCu3O7±δ system. Both ionic radii and chemical properties play an important role in the mutual substitution of Pr, Ba and Sr ions in the Pr123 structure of the PrBa2−xSrxCu3O7±δ system. 相似文献
10.
Mineo Sato Takahito Suzuki Kenji Yoshida Kazuyoshi Uematsu Kenji Toda Zuo-Guang Ye 《Journal of Alloys and Compounds》1997,250(1-2):510-514
Lithium ion conductors, Li3−2x(Sc1−xZrx)2(PO4)3 (0
x
0.3), were prepared by a solid-state reaction. TG–DTA analysis indicated no phase transition in the samples with x superior to 0.05. X-ray powder diffraction analysis of these samples clearly showed the stabilization of a superionic conduction phase at room temperature with an orthorhombic system Pbcn. The highest conductivity was observed for the sample with x=0.05, and ascribed to the stabilization of the superionic conduction phase and the introduction of vacancies on the Li+ sites by substituting Zr4+ for Sc3. 相似文献
11.
The a.c. susceptibility and high field magnetization on TbRh2−xPdxPdxSi2 and TbRu2−xPdxSi2 compounds were investigated up to 140 kOe. The (T,x) magnetic phase diagrams were determined. For both systems, an increase in the Pd content causes a decrease in the Néel temperature and changes the magnetization curves. 相似文献
12.
Hui-qun Guo Hong-ying Yang Bao-gen Shen Lin-yuan Yang Ru-qi Li 《Journal of Alloys and Compounds》1993,190(2):255-258
Measurements of magnetic properties, X-ray diffraction and magnetostriction were made on Tb0.27Dy0.73(Fe1 − xAlx)2 (x = 0.1, 0.2, …, 0.7) compounds. It was found that the system has the cubic MgCu2 structure over almost the whole (Fe,Al) concentration range investigated, except for a narrow intermediate range (x = 0.4–0.6) where the hexagonal MgZn2 structure appears. With increasing Al content x, the lattice constant a increases linearly with x. The first replacement of Fe results in a marked decrease in the Curie temperature, which is followed by a slight decrease in TC with x. A linear decrease in magnetostriction of |λ| − λ| at room temperature with x was also observed from 1530 × 10−6 for x=0 to 36×10−6 for x=0.3. The saturation magnetization σs exhibits a complex concentration dependence in the Tb0.27Dy0.73(Fe)1 − xAlx)2 system: in the range x < 0.5, σs increases linearly with x and, for x = 0.5–0.6, σs decreases and then increases again. An enhancement of the magnetic ‘hardness’ in this system was also observed at low temperature. 相似文献
13.
14.
Nanocrystalline (Nd,Dy)16(Fe,Co)76−xTixB8 magnets were prepared by mechanical alloying and respective heat treatment at 973–1073 K/30–60 min. An addition of 0.5 at.% of Ti results in increase of coercivity from 796 to 1115 kA/m. Partial substitution of Nd by Dy results in an additional increase of coercivity up to 1234 kA/m. The highest corrosion resistance have magnets with 0.5–0.75 at.% of Ti. Beside the Ti, the Co and Dy content significantly improve the corrosion resistance, too. It was found, that for Ti content smaller than x ≤ 1, the (Nd,Dy)16(Fe,Co)76−xTixB8 powders are single phase. For higher Ti contents (x > 1) the mechanically alloyed powders heat treated at 973 K are no more single phase, and the coercivity as well as corrosion resistance decreases due to the presence of an amorphous phase and -Fe. A heat treatment at a higher temperature (1073 K/30 min) or at 973 K for longer time (1 h) results in the full recrystallisation of the powders. The obtained homogenized structure results in higher corrosion resistance. 相似文献
15.
M. Tseggai P. Nordblad R. Tellgren H. Rundlf A.K. Azad S.G. Eriksson J. Eriksen 《Journal of Alloys and Compounds》2008,458(1-2):372-377
Perovskite oxides with the composition La1−xNdxFe0.5Cr0.5O3 (x = 0.10, 0.15 and 0.20) have been studied. The samples have been prepared using the standard solid-state reaction method in air. The X-ray and neutron diffractograms indicates that the samples crystallize in the orthorhombic perovskite structure with space group Pnma (No. 62). The Nd-substitution causes minor changes in the cell parameters and bond lengths but the nuclear structure remains orthorhombic in the whole range of substitutions and in the temperature range of 10–700 K. The magnetic structure of the samples at room temperature and below is G-type antiferromagnetic with an average magnetic moment of the Fe/Cr ions of 3.29(3) μB/atom at 10 K independent of the Nd content. At room temperature the average magnetic moment of the Fe/Cr ions reduces to 1.23 μB/atom. At temperatures below 250 K a weak but increasing uncompensated spontaneous magnetic moment develops that reaches a magnitude of about 0.5 emu/g (or 0.02 μB per Fe/Cr site) at 10 K. This moment saturates rather rapidly in the magnetization versus magnetic field curve and is at higher field superposed on the response of the antiferromagnetic spin system. 相似文献
16.
Composites with ferromagnetic nanoparticles, Fe and Fe50Ni50, dispersed in Al2O3 have been synthesized by a solution phase technique. The structure and magnetic properties of these composites with varying fractions of Al2O3 have been investigated. Both Fe and Fe50Ni50 nanoparticles are amorphous in the as-prepared state and become crystalline on heat treating with near equilibrium lattice parameters of 0.287 nm and 0.358 nm respectively. The interparticle distance increases with increasing Al2O3 from 0 wt.% to 20 wt.%. The size of Fe nanoparticles is 40 nm while the Fe50Ni50 nanoparticles are 20 nm in size. The Fe and Fe50Ni50 nanoparticles dispersed composites are found to be ferromagnetic at room temperature both in the as-prepared and heat treated conditions with clear coercive fields of 5.5–35 × 103 A m−1. The saturation magnetization increases by orders of magnitude on heat treatment, for e.g. from <1.0 emu g−1 to 143.4 emu g−1 for Fe–15 wt.% Al2O3 and 95.6 emu g−1 for Fe50Ni50–15 wt.% Al2O3. The Fe-composites exhibit a Curie transition at 1000 K while the Fe50Ni50 composites exhibit a transition at 880 K, both temperatures close to bulk values. 相似文献
17.
We have carried out measurements of complex ac susceptibility χ=χ′+χ″ as a function of temperature and ac field amplitude on rectangular bar-shaped high-temperature superconductors (HTS) with nominal composition of Bi1.6Pb0.4Sr2(Ca1−xNdx)2Cu3Oδ superconducting samples prepared by the solid-state reaction method. The effect of Nd-substitution on the Bi–(Pb)–Sr–Ca–Cu–O system has been investigated in terms of ac susceptibility study. We estimated the effective volume fraction of the grains and the field dependence of the inter-granular critical current density comparing the maximum of the extracted matrix susceptibility and the corresponding calculated data which was obtained employing the power law critical state model. 相似文献
18.
Shi-Qiang Yang Ping-hua Lin Yin-sheng Dong Zhen-hua Chen 《Journal of Alloys and Compounds》2008,450(1-2):111-113
The effects of Mn partial substitution for Fe in TbFe10.5Mo1.5 on the structure and magnetic properties were investigated. TbFe10.5−xMnxMo1.5 samples (x = 1.5, 2.0, 3.0, 4.0, 5.0) were prepared by means of arc-melting and subsequent vacuum annealing. The structure and magnetic properties of TbFe10.5−xMnxMo1.5 compounds were investigated by X-ray powder diffraction and magnetic properties measurements. The following conclusions were obtained: all the TbFe10.5−xMnxMo1.5 compounds studied crystallize in the ThMn12-type structure; the unit-cell volume increases monotonically with increasing Mn concentration; a compensation temperature was observed in the magnetization-temperature curve of TbFe7.5Mn3Mo1.5 compounds. With increasing Mn concentration, the saturation magnetization at 4.4 K decreases to zero, and then increases again, the magnetic moments of the transition-metal sublattice of TbFe10.5−xMnxMo1.5 compounds decrease monotonically. 相似文献
19.
E. I. Zhilyaeva S. A. Torunova R. N. Lyubovskaya G. A. Mousdis G. C. Papavassiliou J. A. A. J. Perenboom S. I. Pesotskii R. B. Lyubovskii 《Synthetic Metals》2004,140(2-3):151-154
The new ambient pressure organic superconductor based on unsymmetrical donor, ethylenedithiotetrathiafulvalene, and the iodomercurate anion, (EDT-TTF)4Hg3−δI8, δ0.1–0.2, with Tc=8.1 K has been synthesized. Transport and magnetic properties have been investigated. Upper critical fields have been studied under parallel and perpendicular magnetic fields up to 17 T in the temperature region down to 1.3 K. The data show that upper critical fields are within the paramagnetic limit in all directions. The coherence lengths indicate that (EDT-TTF)4Hg3−δI8, δ0.1–0.2, is a quasi-two-dimensional organic superconductor. 相似文献
20.
P. Amornpitoksuk D. Ravot A. Mauger J.C. Tedenac 《Journal of Alloys and Compounds》2007,440(1-2):295-303
We report magnetic properties of iron in Co1−x Fex Sb3 for x in the range 0<x<0.2, since x=0.2 is found to be the limit of solubility of iron in the skutterudite lattice. The magnetic ions diluted in the matrix carry a small magnetic moment reduced to that of the spin-only S=1/2 value of the Fe3+ in the low spin d5 configuration in presence of a strong crystal field that screens the orbital momentum. The magnetic properties give evidence that a small fraction of iron is spin-frozen in magnetite ferrimagnetic clusters, and antiferromagnetic FeO clusters. Because both types of clusters represent only very minor phases, their detection by the usual analytical means such as X-rays is not possible. The remaining part is diluted in the matrix to form a semimagnetic semiconductor characterized by a Fe–Fe nearest-neighbor exchange interaction J that is antiferromagnetic, with |J|/kB19.6 K. 相似文献