共查询到20条相似文献,搜索用时 62 毫秒
1.
Cheng-Liang Huang Yu-Hua ChienChen-Yi Tai Chi-Yuen Huang 《Journal of Alloys and Compounds》2011,509(9):L150
The microwave dielectric properties and the microstructures of (Mg1−xZnx)Al2O4 (x = 0-0.1) ceramic system prepared by the conventional solid-state route were investigated. The forming of spinel-structured (Mg1−xZnx)Al2O4 (x = 0-0.1) solid solutions was confirmed by the XRD patterns and the measured lattice parameters, which linearly varied from a = b = c = 8.0815 Å for MgAl2O4 to a = b = c= 8.0828 Å for (Mg0.9Zn0.1)Al2O4. By increasing x, the Q × f of (Mg1−xZnx)Al2O4 can be tremendously boosted from 82,000 GHz at x = 0 to a maximum of 156,000 GHz at x = 0.05. The Zn substitution was effective in reducing the dielectric loss without detrimental effects on the ?r and τf values of the ceramics. 相似文献
2.
Shan Tao Zubair AhmadHong Jian Tianyu MaMi Yan 《Journal of Alloys and Compounds》2011,509(9):3843-3846
A series of [(Fe1−xCox)72Mo4B24]94Dy6 (x = 0.1, 0.2, 0.3, 0.4 and 0.5 at.%) bulk metallic glasses (BMGs) in rod geometries with critical diameter up to 3 mm were fabricated by copper mold casting method. This alloy system exhibited good thermal stability with high glass transition temperature (Tg) 860 K and crystallization temperature (Tx) 945 K. The addition of Co was found to be effective in adjusting the alloy composition deeper to eutectic, leading to lower liquidus temperature (Tl). The [(Fe0.8Co0.2)72Mo4B24]94Dy6 alloy showed the largest supercooled liquid region (ΔTx = Tx − Tg = 92 K), reduced glass transition temperature (Trg = Tg/Tl = 0.622) and gamma parameter (γ = Tx/(Tg + Tl) = 0.424) among the present system. Maximum compressive fracture strength of 3540 MPa and micro-Vickers hardness of 1185 kg/mm2 was achieved, resulting from the strong bonding structure among the alloy constituents. The alloy system possessed soft magnetic properties with high saturation magnetization of 56.61-61.78 A m2/kg and coercivity in the range of 222-264.2 A/m, which might be suitable for application in power electronics devices. 相似文献
3.
Dong TuYujun Liang Rong LiuZheng Cheng Fan YangWenlong Yang 《Journal of Alloys and Compounds》2011,509(18):5596-5599
Rare-earth ions (Sm3+ or Eu3+) doped LiSrxBa1−xPO4 (x = 0, 0.2, 0.4, 0.6, 0.8, 1.0) f-f transition phosphor powders were prepared by a high temperature solid-state reaction. The resulted phosphors were characterized by X-ray diffraction (XRD) and photoluminescence (PL) spectroscopy. The results of XRD indicate that the phase structure of the sample changes from LiBaPO4 to LiSrPO4 when x changes from 0 to 1.0. The excitation spectra indicate that only direct excitation of rare earth ions (Sm3+ or Eu3+) can be observed. The doped rare earth ions show their characteristic emission in LiSrxBa1−xPO4, i.e., Eu3+5D0-7FJ (J = 0, 1, 2, 3, 4), Sm3+4G5/2 → 6HJ (J = 5/2, 7/2, 9/2, 11/2), respectively. The dependence of the emission intensities of the LiSrxBa1−xPO4:Sm3+ and LiSrxBa1−xPO4:Eu3+ phosphors on the x value and Ln3+ (Ln3+ = Sm3+, Eu3+) concentration is also investigated. 相似文献
4.
Ching-Hwa Ho 《Journal of Alloys and Compounds》2011,509(26):7198-7204
Single crystals of S- and Se-incorporated As2Te3 have been grown by vertical Bridgman method. The electronic structure and optical property of As2(Te1−xSx)3 [ATS] and As2(Te1−xSex)3 [ATSe] series compounds have been characterized experimentally by thermoreflectance (TR) measurements in a wide energy range of 0.7-6 eV. X-ray diffraction measurements showed that the diffraction peaks of sulfur- and selenium-incorporated As2(Te1−xSx)3 0 ≤ x ≤ 0.3 and As2(Te1−xSex)3 0 ≤ x ≤ 0.6 crystals shift to higher diffraction angles with the increase of the sulfur or selenium incorporations. The analysis of X-ray measurement revealed similar crystalline phase for the As2Te3 and those of the S- or Se-incorporated As2Te3. The experimental TR spectra of As2(Te1−xSx)3 (0 ≤ x ≤ 1) and As2(Te1−xSex)3 (0 ≤ x ≤ 1) exhibit a lot of derivative-like spectral features in the vicinity of band edge as well as in the higher-lying bands. Transition energies and broadening parameters of the TR features at 40 and 300 K were analyzed. Compositional dependences of band gap and interband transition energies of the ATS and ATSe series were evaluated. The origins for the interband transitions in the ATS and ATSe are assigned. Based on the experimental analyses, the electronic structure of the diarsenic trichalcogenides, As2(Te1−xSex)3 and As2(Te1−xSx)3, is hence being realized. 相似文献
5.
Guifang JuYihua Hu Li ChenXiaojuan Wang Zhongfei MuHaoyi Wu Fengwen Kang 《Journal of Alloys and Compounds》2011,509(18):5655-5659
A series of Eu3+ activated Na3Gd1−xEux(PO4)2 (0 ≤ x ≤ 1) phosphors were synthesized by solid-state reaction method. The structures and photo-luminescent properties of these phosphors were investigated at room temperature. The results of XRD patterns indicate that these phosphors are isotypic to the orthorhombic Na3Gd(PO4)2. The excitation spectra indicate that these phosphors can be effectively excited by near UV (370-410 nm) light. The intensities of magnetic dipole transition 5D0 → 7F1 and forced electric dipole transition 5D0 → 7F2 are comparable, and the energy ratio (5D0 → 7F1/5D0 → 7F2) is 1.1. The emission spectra exhibit strong reddish orange performance (CIE chromaticity coordinates: x = 0.62, y = 0.38), which is due to the 5D0 → 7FJ transitions of Eu3+ ions. The correlation between the structure and the photo-luminescent properties of the phosphors was studied. The energy transfer and concentration quenching of the phosphors were discussed. Na3Gd1−xEux(PO4)2 has a potential application for white light-emitting diodes. 相似文献
6.
The phase relation, microstructure, Curie temperatures (TC), magnetic transition, and magnetocaloric effect of (Gd1−xErx)5Si1.7Ge2.3 (x = 0, 0.05, 0.1, 0.15, and 0.2) compounds prepared by arc-melting and then annealing at 1523 K (3 h) using purity Gd (99.9 wt.%) are investigated. The results of XRD patterns and SEM show that the main phases in those samples are mono-clinic Gd5Si2Ge2 type structure. With increase of Er content from x = 0 to 0.2, the values of magnetic transition temperatures (TC) decrease linearly from 228.7 K to 135.3 K. But the (Gd1−xErx)5Si1.7Ge2.3 compounds display large magnetic entropy near their transition temperatures in a magnetic field of 0-2 T. The maximum magnetic entropy change in (Gd1−xErx)5Si1.7Ge2.3 compounds are 24.56, 14.56, 16.84, 14.20, and 13.22 J/kg K−1 with x = 0, 0.05, 0.1, 0.15, and 0.2, respectively. 相似文献
7.
Yuanhua XiaHonglin Du Jianhui XuYan Zhang Changsheng WangJinbo Yang Xiangzhen HanKai Sun 《Journal of Alloys and Compounds》2012,512(1):212-215
DyCuxGa2−x (x = 0-2.0) compounds have been synthesized; meanwhile, their crystal structure and magnetic properties have been investigated by X-ray diffraction and magnetic measurements. The result shows that the continuous solid-solution series crystallize in three phases, with the structure types of AlB2 (x = 0-0.2), DyCuGe (x = 0.3-0.6) and CeCu2 (x = 0.7-2.0), respectively. The main reason to form the three structure types is considered to be the average atomic radius ratio of R to Cu/Ga. Magnetic-ordering transition of the compounds with x = 0.2-0.6 takes place at about 20 K and 113 K, while those of other compounds only takes place at about 20 K, which is attributed to the change of the near Dy-Dy distances and the ordered substitution of Ga by Cu. 相似文献
8.
The Ce2Fe17−xMnx (x = 0-2) compounds demonstrate a complex temperature dependence of the magnetocaloric effect MCE, which is inverse in a narrow temperature interval just below Néel temperature TN and normal at higher or lower temperatures. The normal MCE exhibits two peaks in the vicinity of temperatures of ferromagnetic ordering ΘT and TN for compositions x = 0-0.35, 1.3-2 or one peak near TN for antiferromagnets with x = 0.5-1. The maximal change of the peak entropy −SM is about 3 J/kg K in a field of 5 T for the compounds with x = 0-0.5 at T ∼230 K close to TN. The drastic decrease of the MCE, by half, in the Ce2Fe17−xMnx system is traceable to a decrease of the spontaneous magnetization and the helical type of magnetic states in the compounds. 相似文献
9.
B. Pato-DoldánM. Sánchez-Andújar S. Castro-García M.A. Señarís-Rodríguez 《Journal of Alloys and Compounds》2011,509(5):1529-1533
We have prepared polycrystalline single-phase ACo2+xRu4−xO11 (A = Sr, Ba; 0 ≤ x ≤ 0.5) using the ceramic method and we have studied their structure, electrical resistivity and Seebeck coefficient, in order to estimate their power factor (P.F.). These layered compounds show values of electrical resistivity of the order of 10−5 Ωm and their Seebeck coefficients are positive and range from 1 μV K−1 (T = 100 K) to 20 μV K−1 (T = 450 K). The maximum power factor at room temperature is displayed by BaCo2Ru4O11 (P.F.: 0.20 μW K−2 cm−1), value that is comparable to that shown by compounds such as SrRuO3 and Sr6Co5O15. 相似文献
10.
Mingzhe Hu Chunya LuoHuyong Tian Haoshuang Gu 《Journal of Alloys and Compounds》2011,509(6):2993-2999
The phase evolution, crystal structure and dielectric properties of (1 − x)Nd(Zn0.5Ti0.5)O3 + xBi(Zn0.5Ti0.5)O3 compound ceramics (0 ≤ x ≤ 1.0, abbreviated as (1 − x)NZT-xBZT hereafter) were investigated. A pure perovskite phase was formed in the composition range of 0 ≤ x ≤ 0.05. The B-site Zn2+/Ti4+ 1:1 long range ordering (LRO) structure was detected by both XRD and Raman spectra in x ≤ 0.05 samples. However, this LRO structure became gradually degraded with an increase in x. The dielectric behaviors of the compound ceramic at various frequencies were investigated and correlated to its chemical composition and crystal structure. A gradually compensated τf value was obtained in (1 − x)NZT-xBZT microwave dielectrics at x = 0.03, which was mainly due to the dilution of dielectric constant in terms of Claussius-Mossotti differential equation. 相似文献
11.
I. MatosS. Sério M.E. LopesM.R. Nunes M.E. Melo Jorge 《Journal of Alloys and Compounds》2011,509(40):9617-9626
Nanocrystalline Ca1−xSmxMnO3 (0 ≤ x ≤ 0.4) manganites were prepared by a soft chemical method (Pechini method) followed by auto-combustion and sintering in air at 1073 or 1473 K. Single-phase powders with general composition Ca1−xSmxMnO3 were obtained after 18 h annealing. The particle and grain sizes of the substituted Sm-manganites did not exhibit variation with samarium content, but increase with increasing the sintering temperature. All manganites show two active IR vibrational modes near 400 and 600 cm−1 characteristic of the BO6 octahedron vibrations.For the samples sintered at Ts = 1473 K, the partial substitution of calcium by samarium in the CaMnO3 phase induces a marked decrease in the electrical resistivity, in the temperature range of 300-900 K, and at the same time a metal-to-insulator transition occurs; for Ts = 1073 K all the samples present semiconductor behaviour. With the increase of the annealing temperature the grain size increases and a metal-semiconductor transition appears. The results can be ascribed to the Mn4+/Mn3+ ratio and particle grain size. The effects of particle size on the electrical properties can be attributed to the domain status, changes in the Mn-O-Mn bond angle and Mn-O bond length. 相似文献
12.
Chongfeng Guo Xu DingHyo Jin Seo Zhaoyu RenJintao Bai 《Journal of Alloys and Compounds》2011,509(14):4871-4874
A series of Ce3+ doped novel borate phosphors MSr4(BO3)3 (M = Li or Na) were successfully synthesized by traditional solid-state reaction. The crystal structures and the phase purities of samples were characterized by powder X-ray diffraction. The optimal concentrations of dopant Ce3+ ions in compound MSr4(BO3)3 (M = Li or Na) were determined through the measurements of photoluminescence spectra of phosphors. Ce3+ doped phosphors MSr4(BO3)3 (M = Li or Na) show strong broad band absorption in UV spectral region and bright blue emission under the excitation of 345 nm light. In addition, the temperature dependences of emission spectra of M1+xSr4−2xCex(BO3)3 (M = Li or Na) phosphors with optimal composition x = 0.05 for Li and x = 0.09 for Na excited under 355 nm pulse laser were also investigated. The experimental results indicate that the M1+xSr4−2xCex(BO3)3 (M = Li or Na) phosphors are promising blue emitting phosphors pumped by UV light. 相似文献
13.
Keita TaniguchiNoriyuki Okinaka Tomohiro Akiyama 《Journal of Alloys and Compounds》2011,509(10):4084-4088
This paper proposes La1−xKxFeO3 prepared by self-propagating high-temperature synthesis (SHS) as an alternative to platinum catalysts for promoting diesel soot combustion. The catalytic property of eleven products SHSed with different substitution ratios of potassium (x = 0-1) was experimentally evaluated using a thermobalance. In the mass loss curves of the product, T50 was defined as the temperature at which the weight of the reference soot decreases to half its initial weight. The BET specific surface area of SHSed La1−xKxFeO3 depended on x strongly. All the products showed good oxidation catalytic activity. Despite having the smallest surface area (0.11 m2/g) among the obtained products, La0.9K0.1FeO3 (x = 0.1) was found to be the best catalyst with the lowest T50 (442 °C). T50 of La1−xKxFeO3 decreased with increasing x for x > 0.2. The products with x = 0.6 and 0.8 were the second-best catalysts in terms of their T50. Moreover, average apparent activation energy of La0.9K0.1FeO3 (x = 0.1) calculated by Friedman method using TG was as much as 61 kJ/mol lower than that of Pt/Al2O3 catalyst. In conclusion, potassium-substituted SHSed La1−xKxFeO3 can be used as an alternative to Pt/Al2O3 for soot combustion. 相似文献
14.
N. Keawprak S. Lao-ubolC. Eamchotchawalit Z.M. Sun 《Journal of Alloys and Compounds》2011,509(38):9296-9301
Bi2SexTe3−x crystals with various x values were grown by Bridgman method. The electrical conductivity, σ, was found to decrease with increasing Se content. The highest σ of 1.6 × 105 S m−1 at room temperature was reached at x = 0.12 with a growth rate of 0.8 mm h−1. The Seebeck coefficient, S, was less dependent on Se content, all with positive values showing p-type characteristics, and the highest S was measured to be 240 μV K−1 at x = 0.24. The lowest thermal conductivity, κ, was 0.7 W m−1 K−1 at x = 0.36. The electronic part of κ, κel, showed a decrease with increasing Se content, which implies that the hole concentration as the main carriers was reduced by the addition of Se. The highest dimensionless figure of merit, ZT, at room temperature was 1.2 at x = 0.36, which is attributed to the combination of a rather high electrical conductivity and Seebeck coefficient and low thermal conductivity. 相似文献
15.
Tanjore V. Jayaraman Laura BooneJeffrey E. Shield 《Journal of Alloys and Compounds》2011,509(5):1411-1417
A series of Gd100−xMnx (x = 0, 5, 10, 15, and 20 at.%) alloys were prepared by arc-melting. The Curie temperature (TC) associated with the ferromagnetic-paramagnetic transitions, derived from M-T curves, show decrease in TC for as-cast alloys (∼279 K) as compared to as-cast Gd (∼292 K). No appreciable decrease in the |ΔSM|max values ∼4.6 J/kg K (0-2 T) and ∼8.6 J/kg K (0-5 T) were observed upon alloying Gd with Mn up to x ≤ 15 at.%. Refrigerant capacity (q) showed negligible variation ∼195 J/kg (0-2 T) and ∼450 J/kg (0-5 T) with increasing Mn (up to x ≤ 15 at.%) content. Similar values of |ΔSM|max and q coupled with ∼13 K decrease in TC for as-cast Gd100−xMnx (0 ≤ x ≤ 15) alloys as compared to Gd, suggests expansion of working temperature region of Gd upon alloying with Mn up to 15 at.%. Low cost, adjustable TC, favorable magnetocaloric properties make Gd100−xMnx alloys potential candidates as second-order transition based magnetic refrigerants for near room temperature air-conditioning and magnetic refrigeration. 相似文献
16.
J. Olejní?ek L.E. FlanneryS.A. Darveau C.L. ExstromŠ. Kment N.J. IannoR.J. Soukup 《Journal of Alloys and Compounds》2011,509(41):10020-10024
CuIn1−xAlxS2 thin films (x = 0, 0.09, 0.27, 0.46, 0.64, 0.82 and 1) with thicknesses of approximately 1 μm were formed by the sulfurization of DC sputtered Cu-In-Al precursors. All samples were sulfurized in a graphite container for 90 min at 650 °C in a 150 kPa Ar + S atmosphere. Final films were studied via X-ray diffraction (XRD), scanning electron microscopy (SEM) and micro-Raman spectroscopy. It was found that all samples were polycrystalline in nature and their lattice parameters varied slightly nonlinearly from {a = 5.49 Å, c = 11.02 Å} for CuInS2 to {a = 5.30 Å, c = 10.36 Å} for CuAlS2. No unwanted phases such as Cu2−xS or others were observed. Raman were recorded at a room temperature and the most intensive and dominant A1 phonon frequency varied nonlinearly from 294 cm−1 (CuInS2) to 314 cm−1 (CuAlS2). 相似文献
17.
The effect of Ni/Cu substitution on the magnetic properties, crystal and electronic structure of the polycrystalline GdNi5−xCux series has been studied. All compounds crystallize in the hexagonal CaCu5 type of crystal structure (space group P6/mmm). The temperature dependence of magnetic phase transition (Tmag) estimated from χAC(T) susceptibility as well as magnetization M(T) below room temperature indicates the maximum for x = 1.0 copper concentration. In the paramagnetic range (above 300 K) the magnetic susceptibilities follow a Curie-Weiss-type dependence. The effective magnetic moments are higher than theoretical value for free Gd3+.From X-ray photoelectron spectroscopy (XPS) data the valence band as well as the core level spectra have been analyzed. The filling of Ni3d band in the GdNi5−xCux system by charge transfer of Gd conduction electrons is revealed by a reduction of the satellite intensities in the Ni2p core level spectrum. The obtained results exhibit that the valence bands at the Fermi level are dominated by hybridized Ni3d and Gd5d states, when Cu3d states are rather localized about 3 eV below the Fermi level. Quite good relation between the magnetic properties and electronic structure has been found. 相似文献
18.
Chesta Ruttanapun Aree WichainchaiWutthisak Prachamon Anucha YangthaisongAnek Charoenphakdee Tosawat Seetawan 《Journal of Alloys and Compounds》2011,509(13):4588-4594
The samples of Cu1−xPtxFeO2 (0 ≤ x ≤ 0.05) delafossite were synthesized by solid state reaction method for studying thermoelectric properties. The properties of Seebeck coefficient, electrical conductivity and thermal conductivity were measured in the high temperature ranging from 300 to 960 K. The results of Seebeck coefficient, electrical conductivity and power factor were increased with increasing Pt substitution and temperature. The thermal conductivity was decreased from 5.8 to 3.5 W/mK with increasing the temperature from 300 to 960 K. An important results, the highest value of power factor and ZT is 2.0 × 10−4 W/mK2 and 0.05, respectively, for x = 0.05 at 960 K. 相似文献
19.
Y.M. Sun 《Journal of Alloys and Compounds》2011,509(2):499-502
Multicomponent Fe68−xNixZr15Nb5B12 (x = 5, 10, 15, 20) alloy powders milled for 60 h were prepared by mechanical alloying (MA). The structure and crystallization behavior were investigated by X-ray diffraction (XRD), scanning electron microscopy (SEM) and differential thermal analysis (DTA). Ni enhances the amorphisation of alloy powders. Particle size increases with increasing Ni content. Both onset crystallization temperature Tx and the first crystallization peak temperature Tp of the four alloys shift to a higher temperature with increasing heating rate while melting temperature (Tm) is just the opposite. Fe68−xNixZr15Nb5B12 (x = 5, 10, 15, 20) alloys all have a large supercooled liquid region ΔTx. The supercooled liquid region ΔTx increases and the crystallization activation energy E decreases with increasing Ni content. 相似文献
20.
Ganghua ZhangGuobao Li Fuqiang HuangFuhui Liao Kuo LiYinxia Wang Jianhua Lin 《Journal of Alloys and Compounds》2011,509(41):9804-9808
Superconductors Ba1−xKxBiO3 and body-centered double perovskites Ba1−xKxBi1−yNayO3 have been selectively synthesized by a facile hydrothermal route. The appropriate ratio and adding sequence of initial reagents, alkalinity, reaction temperature and time are the critical factors that influence the crystal growth of the compounds. The purity and homogeneity of the crystals were detected by the ICP, SEM, EDX and TEM studies. Magnetic measurements show that the superconducting transition temperatures TC of Ba1−xKxBiO3 decrease from 22 K (for x = 0.35) to 8 K (for x = 0.55) with increasing the K doping level. 相似文献