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1.
The n-type Co-doped β-FeSi 2 (Fe 0.98Co 0.02Si 2) with dispersion of several oxides, such as ZrO 2 or several rare-earth oxides (Y 2O 3, Nd 2O 3, Sm 2O 3 and Gd 2O 3), was synthesized by mechanical alloying and subsequent hot pressing. The effects of these oxide dispersions on the thermoelectric properties of Fe 0.98Co 0.02Si 2 were investigated. ZrO 2 was decomposed in the β phase, and the ZrSi and -FeSi phases, which are metallic phases, were formed in the samples with ZrO 2 addition. The Seebeck coefficient and the electrical resistivity were significantly decreased with increasing amount of ZrO 2, indicating that a part of the Zr atoms was substituted for Fe atoms in the β phase. In the case of the samples with rare-earth oxide addition, a decomposition of a large amount of these added oxides did not occur. However, the rare-earth oxide addition caused a slight increase in the amount of the phase. The Seebeck coefficient was significantly enhanced by the rare-earth oxide addition especially in the low temperature range. These facts indicated that a small amount of rare-earth oxides was decomposed in the β phase, and rare-earth elements were substituted for Fe atoms as a p-type dopant, resulting in the decrease in the carrier concentration. The rare-earth oxide addition was also effective in reducing the thermal conductivity. 相似文献
2.
A study of phase relationships and crystallography in the pseudobinary system Gd 5(Si xGe 1−x) 4 revealed: (1) that both terminal binary compounds Gd 5Si 4 and Gd 5Ge 4 crystallize in the Sm 5Ge 4-type orthorhombic structure, and (2) the appearance of an intermediate (ternary) phase with a monoclinic crystal structure which is similar to both Gd 5Si 4 and Gd 5Ge 4. The formation of the monoclinic phase at 0.24≤ x≤0.5 [between Gd 5(Si 0.96Ge 3.03)Gd 5(Si 1Ge 3) and Gd 5(Si 2Ge 2)] is probably due to the large difference in bonding characteristics of Si and Ge in the Gd 5Si 4-Gd 5Ge 4 pseudobinary system which limits the ability of the mutual substitution of Si for Ge and vice versa without a change of the crystal structure. For the composition Gd 5(Si 2Ge 2) the lattice parameters of the monoclinic structure (space group P112 1/a) are a=7.580865), b=14.802(1), c=7.7799(5)Å, γ=93.190(4)°. A distinct difference in the magnetic behaviors of the alloys from three different phase regions in this system follows the distinct difference in the crystal structures observed for the alloys from the three phase regions. 相似文献
3.
The kinetics of copper clustering and primary crystallization of FINEMET type alloys with the compositions Fe 74.5−xSi 13.5B 9Nb 3Cu x and Fe 77Si 11B 9Nb 3−xCu x have been studied by small-angle neutron scattering (SANS) and high-sensitivity differential scanning calorimetry (DSC) in order to explain the different optimized Cu contents, x, for obtaining the highest permeability in these two alloys. SANS results have shown that the alloys with the optimized Cu contents have the finest nanocrystalline microstructures. Kinetic analyses of Cu clustering prior to primary crystallization have shown that the number density of Cu clusters becomes highest at the crystallization stage of -Fe primary crystals in the alloy containing an optimized amount of Cu. 相似文献
4.
The a.c. susceptibility and high field magnetization on TbRh 2−xPd xPd xSi 2 and TbRu 2−xPd xSi 2 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
5.
Cubic (Pb 50Te 52) 100−x(PbI 2) x (0 ≤ x ≤ 0.065) bulk thermoelectric (TE) materials with enhanced power factor were prepared by high-pressure and high-temperature (HPHT) method. The mean grain size of the samples was about 10 μm. The dependence of electrical transport properties on composition was studied at room temperature. With an increase of x, the Seebeck coefficient in absolute value and the electrical resistivity firstly increase slightly and then decrease dramatically. The maximum power factor reaches 24.2 μW cm −1 K −2 at x = 0.015, which is much higher than that reported previously for the PbTe doped with PbI 2 prepared at normal pressure. The results indicate that HPHT combined with trace quantity doping is an effective method to enhance the thermoelectric properties for PbTe. 相似文献
7.
La- and K-doped perovskite-type ceramics, (Sr 0.6Ba 0.4) 1−xLa xPbO 3 with x = 0.0−0.1 and (Sr 0.6Ba 0.4) 1−xK xPbO 3 with x = 0.00−0.15, were prepared to modify thermoelectric properties of semi-metallic Sr 0.6Ba 0.4PbO 3 via the doping of electrons and holes, respectively. The electrical conductivity σ and Seebeck coefficient S for the ceramics were measured at temperatures of 373–1073 K in air. With the La doping, electron carriers were successively doped and the material changed from a semi-metal for the undoped Sr 0.6Ba 0.4PbO 3 to a metal for the (Sr 0.6Ba 0.4) 0.9La 0.1PbO 3. With the K doping, the thermoelectric properties were essentially unchanged probably due to the carrier compensation effect by the generation of oxygen deficiencies. The thermoelectric power factor S2σ was maximized to a value of 3.1 × 10 −4 Wm −1 K −2 at 773 K for the undoped Sr 0.6Ba 0.4PbO 3 ceramic. 相似文献
8.
The temperature dependence of the iron concentrations in the individual sublattices of hyperstoichiometric binary Fe 72Al 28 and ternary Fe 68Al 28Cr 4 alloys were obtained from X-ray diffraction data measured in a high temperature vacuum chamber during linear heating around the phase transformation B2↔D0 3. A method for the processing of the diffraction pattern based on the splitting of the diffraction lines of the structure D0 3 into three groups is presented. Applying this method it was found that the structure B2 was not well developed in both samples. The maximum value of cC≈0.8 gives SB2 equal to 0.4 and 0.3 for binary and ternary alloy, respectively. The D0 3-order was not well developed too, because structure D0 3 arises from the structure B2. D0 3-ordering, i.e. redistribution of atoms within the sublattices A and B, is given only by the total number of iron atoms in these sublattices before the phase transformation B2↔D0 3. 相似文献
9.
The new phases KFe 2(SeO 2OH)(SeO 3) 3 and SrCo 2(SeO 2OH) 2(SeO 3) 2 have been synthesized under low-hydrothermal conditions and their structures were determined by single-crystal X-ray methods. Both compounds are monoclinic; KFe 2(SeO 2OH)(SeO 3) 3: space group P2, A = 9.983(4), B = 5.270(1), C = 10.614(4) Å, β = 97.42(2)°, V = 553.7 Å 3, Z = 2; SrCo 2(SeO 2OH) 2(SeO 3) 2: space group P2 ln, A = 14.984(2), B = 5.286(1), C = 13.790(2) Å, β = 94.72(1)°, V = 1088.5 Å 3 , Z = 4. The refinements converged to R-values of 2.9 and 3.6% respectively. The atomic arrangement in KFe2(SeO2OH)(SeO3)3 and SrCo2(SeO2OH)2(SeO3)2 is based on isolated MO6 octahedra (M = Fe3+, Co2+), which are corner-linked via trigonal pyramidal selenite groups to a framework structure. Interstitials are occupied by potassium or strontium atoms in ten- or eight-coordination respectively, and by the lone-pair electrons of the Se4+ atoms. Both compounds are not isotypic but are closely related and may be interpreted as different distortions of an idealized structure type in space group P2/m, which was modelled for a theoretical compound SrFe2(SeO3)4 by distance least squares refinement (program
). 相似文献
10.
Hydrogen-induced phases, relaxation and hysteretic phenomena in Fe 55Cr 25Ni 20 and Fe 50Ni 50 alloys were studied using neutron scattering and internal friction. Substitution of chromium by nickel prevents the hydrogen-induced γ→ transformation, which was used for interpretation of the IF peaks. A new relaxation peak is observed in the hydrogen-charged Fe 50Ni 50 alloy. 相似文献
11.
The crystal structure of the compound Sm 4Pd 4Si 3 was determined by the single-crystal method (KM-4 automatic diffractometer, Mo K radiation. Sm 4Pd 4Si 4 has the monoclinic Nd 4Rh 4Ge, type structure: space C2/c, mC44 (No. 15). a = 20.693(6), B = 5.584(1), C = 7.699(2) Å, β = 109.48(3)°, V = 838 Å, Z = 4, μ - 36.23 mm 1, R = F = 0.0537, R F = 0.0435 for 1652 unique reflections. The coordination numbers of samarium atoms are 17 and 18. For palladium and silicon atoms icosahedra and trigonal prisms with additional atoms are typical as coordination polyhedra. The structure of Sm 4Pd 4Si 4 is composed of fragments of the YPd 2Si and Y 1Rh 2Si 2 structure in a ratio 1:1. 相似文献
12.
Stoichiometric Nd 2(Fe 1−xCo x) 14B alloys ( x=0, 0.25, 0.5, 0.75 and 1) have been disproportionated into NdH 2+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 Nd 2Co 14B alloy. This reaction is not possible via the conventional hydrogenation disproportionation desorption and recombination (HDDR) process. Grain sizes of disproportionated and recombined Nd 2(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 Nd 2Co 14B alloy shows on average slightly smaller grain sizes than the Nd 2Fe 14B compound. A more effective exchange coupling leading to enhanced remanences, possibly due to the slightly smaller grain size, has been observed for Nd 2Co 14B powders recombined at 600–700°C. 相似文献
13.
The phase content of the Sm(Fe 1−xSi x) y alloys (0.05≤ x≤0.15; 8.5≤ y≤12) has been studied by X-ray diffraction using micromonocrystals. The compounds Sm 2(Fe,Si) 17, Sm(Fe,Si) 12 and a novel Sm 3(Fe,Si) 29 compound with a monoclinic unit cell are found. The lattice parameters of Sm 3(Fe,Si) 29 are: a=1.056 nm, b=0.850 nm, c=0.966 nm, β=96.8°. This compound forms as a result of a solid state transformation from the high-temperature Sm 2(Fe,Si) 17 phase. Diffuse effects observed in rocking photographs suggest transition structures arising from this transformation. The Curie temperatures of Sm 3(Fe,Si) 29 vary in the interval 496–521 K. 相似文献
14.
The phase relations and hydrogenation behavior of Sr(Al 1−xMg x) 2 alloys were studied. The pseudobinary C36-type Laves phase Sr(Al,Mg) 2 was found as a structural intermediate between the Zintl phase and the C14 Laves phase. The single-phase regions for the Zintl phase, C36 phase and C14 phase, were determined to be x=0–0.10, 0.45–0.68 and 0.80–1, respectively. The Mg-substituted Zintl phase Sr(Al 0.95Mg 0.05) 2 can be hydrogenated to Sr(Al,Mg) 2H 2 at about 473 K. However, the Sr(Al,Mg) 2H 2 directly decomposes into SrH 2 and Sr(Al,Mg) 4 starting at 513 K. When the temperature is 573 K, the C36 Laves phase Sr(Al 0.5Mg 0.5) 2 can be hydrogenated into SrMgH 4 and Al, while the C14 Laves phase Sr(Al 0.1Mg 0.9) 2 is hydrogenated into SrMgH 4, Mg 17Al 12 and Mg. 相似文献
15.
Lithium ion conductors, Li 3−2x(Sc 1−xZr x) 2(PO 4) 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 Zr 4+ for Sc 3. 相似文献
16.
The crystal structure and magnetization of Hf 0.8Ta 0.2(Fe 1−xCo x) 2 are investigated by X-ray powder diffraction and magnetization measurements. The compounds exhibit the Laves C14 structure for x=0.0–0.2 and the C15 structure for x≥0.3. The structural transition from C14 to C15 leads to an anomaly of the unit cell volume between x=0.2 and 0.3. When x=0.0, the compound undergoes a magnetic phase transition from ferromagnetic to paramagnetic state via the antiferromagnetic state, in which a field-induced metamagnetic transition is observed. When x=0.1 and 0.2, the compounds exhibit unusually small saturation moments, which are considered as antiferromagnetism (with weak ferromagnetic impurities) and weak ferromagnetism or ferrimagnetism, respectively. The formation of the AFM state is associated with a small bond length of Fe atom in the 6 h site. When x≥0.3, the compounds exhibit a ferromagnetic to paramagnetic transition, which can be explained by itinerant electron metamagnetism. 相似文献
17.
The microalloying effect of Cu and Nb on the microstructure and magnetic properties of an Fe 3B/Nd 2Fe 14B nanocomposite permanent magnet has been studied by transmission electron microscopy (TEM) and atom probe field ion microscopy (APFIM). Additions of Cu are effective in refining the nanocomposite microstructure and the temperature range of the heat treatment to optimize the hard magnetic properties is significantly extended compared with that of the ternary alloy. Combined addition of Cu and Nb is further effective in reducing the grain size. Optimum magnetic properties obtained by annealing a melt-spun Nd 4.5Fe 75.8B 18.5Cu 0.2Nb 1 amorphous ribbon at 660°C for 6 min are Br=1.25 T, HcJ=273 kA/m and ( BH) max=125 kJ/m 3. The soft magnetic Fe 23B 6 phase coexists with the Fe 3B and Nd 2Fe 14B phases in the optimum microstructure of the Cu and Nb containing quinternary alloy. Three-dimensional atom probe (3DAP) results show that the finer microstructure is due to the formation of a high number density of Cu clusters prior to the crystallization reaction, which promote the nucleation of the Fe 3B phase. The Nb atoms appear to induce the formation of the Fe 23B 6 phase when the remaining amorphous phase is crystallized. 相似文献
18.
To clarify the existence of metastable phases in the ZrO 2–CeO 2–CeO 1.5 system, evolved-oxygen gas analyses, (EGA), by heating a single phase of t′ and t″ (Ce (1−x)Zr xO 2) with various compositions, x, in a reducing gas and successive oxidation were carried out repeatedly. The oxygen release behaviour of the t′ and t″ phases was very complicated. The single κ phases, (Ce (1−x)Zr xO 2) with the composition, x=0.5 and 0.6, which were obtained by oxidizing the resulting pyrochlore as a precursor in O 2 gas at 873 K, exhibited a sharp oxygen release at the lowest temperature; the composition range of κ phase may be x=0.450.65. A new tetragonal phase t*, (Ce (1−x)Zr xO 2), which was attained by cyclic redox process together with annealing in O 2 gas at 1323 or 1423 K, exhibited a sharp oxygen release at the highest temperature; the composition range of t* phase may be as wide as x=0.200.65. A metastable solid solution expressed by a chemical formula of Ce (8−4y)Zr 4yO (14−δ) ( y=01) possessing a CaF 2-related structure appeared on deoxidation of the t* phase. A ternary phase diagram containing the t* and Ce (8−4y)Zr 4yO (14−δ) solid solution was proposed. 相似文献
19.
In the present work, the spectroscopic and magnetic properties of heteronuclear Cu:Pr squarate are reported. Single crystals of [Pr 2Cu(C 4O 4) 4(H 2O) 16]·2H 2O were obtained by reaction of squaric acid, praseodymium chloride and copper chloride in water solution according to the procedure described earlier. The crystals of title compound are isomorphic with [La 2Cu(C 4O 4) 4(H 2O) 16]·2H 2O crystal, where squarate anions participate as bridging ligands between metal ions. The UV region of absorption spectra of the title compound is dominated by C–T band of Cu(II), f–d transition of Pr(III) and internal π–π*(A1g→Eu) and π–π*(A1g→Eg) ligand transitions. In visible and IR regions, t2g–eg of copper Cu(II) as well as 3H4→3PJ, 1D2, 1G4, 3FJ, 3H6 Pr(III) transitions at 293 and 4 K were recorded. At low temperature splitting given by Jahn–Teller effect can be observed. Significant anisotropy of d–d transitions intensities confirms well the Jahn–Teller effect, too. Unexpectedly high intensity of 3H4→1G4 transition is probably due to the intensity borrowing from the Cu (II) d–d transition. The 3P0 and 1D2 emission of Pr(III) in the [Pr2Cu(C4O4)4(H2O)16]·2H2O crystals is quenched even at 77 K. Whereas emission of appropriate polynuclear europium squarate was detected. The pathways of excited state quenching by eg levels of Cu(II), multhiphonon relaxation and concentration quenching can be considered in the system under studies. Magnetic susceptibility measurements were carried out in 300–1.7 K temperature range and are discussed in relation to the structure. Effect of the polymeric structure on spectroscopic behaviour is presented. Selectivity of polymeric europium squarate in vitro test for different tumor cells is shown. 相似文献
20.
Measurements of magnetic properties, X-ray diffraction and magnetostriction were made on Tb 0.27Dy 0.73(Fe 1 − xAl x) 2 ( x = 0.1, 0.2, …, 0.7) compounds. It was found that the system has the cubic MgCu 2 structure over almost the whole (Fe,Al) concentration range investigated, except for a narrow intermediate range ( x = 0.4–0.6) where the hexagonal MgZn 2 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 σ s exhibits a complex concentration dependence in the Tb 0.27Dy 0.73(Fe) 1 − xAl x) 2 system: in the range x < 0.5, σ s increases linearly with x and, for x = 0.5–0.6, σ s decreases and then increases again. An enhancement of the magnetic ‘hardness’ in this system was also observed at low temperature. 相似文献
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