Thermoelectric Properties of CexCo4Sb12 Prepared by MA-SPS

Starting with elementary powders, thermoelectric materials CexCo4Sb12 were prepared by mechanical alloying and spark plasma sintering (MA-SPS). XRD analyses reveal that the expected major phase, named skutterudite was formed in MA process and was kept after SPS. The thermoelectric properties of MA-SPS samples including resistivity, Seebeck coefficient, power factor, thermal conductivity and the dimensionless figure of merit (ZT) were studied by varying Ce content and temperature. Depending on Ce levels, both P and N types of thermoelectric semiconductors were obtained. MA-SPS sintered Ce1.0Co4Sb12 exhibits the highest ZT in the range of 100-500℃ and the maximum ZT is found at x=1.0 and 400℃.     

Rapid Preparation and Thermoelectric Properties of NdxCo4Sb12 Compounds

ratory of Advanced Functional Materials, Ministry of Education, Beijing University of Technology,Beijing 100022, China )     

Thermoelectric Properties of （Ce, La）yFe1.0Co3.0Sb12 Compounds Syntiesized by Solid State Reaction

The filled Skutterudite compounds (Ce,La)yFexCo4-xSb12 with x= 1.0 and y=0-0.3 were synthesized by solid state reaction and Spark PlasmaSintefing (SPS) using powders of Co, Sb, Fe and rare earth Ce, La as starting materials. The thermoe-lectric properties of the compounds were also studied.It is shown that the almost single phase Skutterudite compounds (Ce, La)yFex Co4-xSb12 are synthesized at900-1000K and all samples show p-type.     

Thermoelectric properties of Yb x Co_4 Sb_（12） system

Yb x Co 4 Sb 12 polycrystals were fabricated by vacuum melting combined with hot-press sintering.The effect of Yb-filling on thermoelectric property of unfilled skutterudite CoSb 3 was investigated,which indicated the enhancement of the power factor of the material.Transport properties of materials changed from semi-conductor to semi-metal during the measurement of electrical conductivity,which indicated the change of electronic band structure.The maximum value of electrical conductivity was about 190000 S/m at 300 K for all samples.On the basis of Yb-filling,power factor of Yb 0.2 Co 4 Sb 12 reached 5-6 mW/(m·K) during the measurement temperature.Thermal conductivity decreased with increase of Yb content,and the thermal conductivity of Yb 0.2 Co 4 Sb 12 reached 3.2 W/(m·K) at 600 K.The ZT value of Yb 0.2 Co 4 Sb 12 reached 1.16 at 700 K due to positive contribution from high power factor and low thermal conductivity.     

聚苯胺/Co0.5Zn0.5La0.1Fe1.9O4复合材料的表征及电磁损耗

采用原位聚合法制备聚苯胺（Pani）/复合材料,使用X射线衍射仪（XRD）、扫描电子显微镜（TEM）和紫外可见吸收光谱（UV-vis）对复合材料进行了表征。XRD结果表明样品为纯Pani和Pani/Co0.5Zn0.5La0.1Fe1.9O4复合材料,SEM照片可知,纯Pani和Pani/Co0.5Zn0.5La0.1Fe1.9O4粒子的平均粒径分别约为150 nm和500 nm,UV-vis光谱表明Pani/Co0.5Zn0.5La0.1Fe1.9O4苯环上的π-π＊和n-π＊分别红移了13 nm和10 nm.在8.2-12.4GHz测试频率范围内,Pani/Co0.5Zn0.5La0.1Fe1.9O4复合材料的介电损耗角正切（tgε）在0.22-0.34之间,磁损耗正切（tgμ）在0.27-0.35之间.     

Synthesis and Thermoelectric Properties of Ca2.6Nd0.4 Co4O9 Compound

Atemperaturedifferenceappliedacrossasolidgeneratesanelectromotiveforce ,characterizedbythethermoelectricpowerofthesolid .ThisphenomenonisnamedSeebeckeffect .Metaloxidematerialswithhighthermoelectricpropertiesaregoodcandidatesforappli cationtothermoelectricpowergenerationbecausefig ureofmeritZ ,definedasZ =S2 σ/κwhereS ,σ ,κaretheSeebeckcoefficient ,electricalconductivityandthermalconductivity ,respectively ,canevaluatetheperformanceofthermoelectricmaterials .Severalsystemshavebeeninvesti…     

纳米颗粒Ag2Te掺杂p-(Ag2Te)x(Bi0.5Sb1.5Te3)1-x的快速热压制备和热电性能表征

通过溶剂热法制备出六方相Bi2 Te3纳米粉体,采用真空封管熔炼法得到Sb掺杂的Bi0.5Sb1.5Te3合金.采用溶剂热法合成粒度为40 nm的Ag2 Te纳米粉体,并通过高能球磨工艺将其掺入Bi0.5Sb1.5Te3合金,从而得到p-(Ag2 Te)x(Bi0.5 Sb1.5 Te3)1-x合金(x为Ag2 Te摩...     

Effect of Mn Substitution on Microstructure Evolution and Magnetic Phase Transition in La(Fe1−x Mn x )10.8Co0.7Si1.5 Compounds

The influences of Mn substitution for Fe on microstructures of La(Fe_1?x Mn _x )_10.8Co_0.7Si_1.5 (x = 0, 0.01, 0.02, 0.03) alloys in both the as-cast state and the annealed state have been studied. The results show that Mn substitution promotes the fining of the as-cast microstructure and increases the formation of 1:13 phase significantly when annealed. An almost single 1:13 phase is obtained for x = 0.01 when annealed at 1373 K (1100 °C) for 3 days, while a large amount of impurity phases is still present for x = 0. By increasing the amount of Mn to x = 0.02, a more purified annealed microstructure can be obtained. However, further substitution of Mn up to x = 0.03 is harmful for the formation of 1:13 phase. The Curie temperature T _C of the annealed La(Fe_1?x Mn _x )_10.8Co_0.7Si_1.5 (x = 0, 0.01, 0.02, 0.03) varies monotonously with Mn content x, decreasing from ~279 K (6 °C) for x = 0 to ~236 K (?37 °C) for x = 0.03. When x = 0.01, a higher maximum entropy change (?ΔS)_max of 5.3 J/(kgK) and relative cooling power (RCP) of 166 J/kg can be obtained under a magnetic field of 2T. Further substitution of Mn (x = 0.02) results in a slight decrease of (?ΔS)_max, whereas a larger RCP can still be kept.     

Characterization of an Al-Y-Zn Intermetallic Particle Phase in Extruded Mg96−x Al x Zn2Y1.9La0.1 Alloys

This study focuses on extruded Mg_96?x Al _x Zn₂Y_1.9La_0.1 alloys, which contain the long period stacking ordered Mg₁₂ZnY phase. The presence of Al results in the precipitation of Al-Y-Zn precipitates, the crystal structure of which is not adequately described by ternary Al-Y-Zn phases reported in the literature. Therefore, the purpose of this investigation is to characterize the precipitates morphologically, chemically, and crystallographically. After casting, the precipitates exist as complexly shaped micron-scale clusters within the microstructure. After extrusion, the phase appears as slightly faceted particles with a plate-like morphology. The crystal structure is hexagonal and its space group is $ P6_{3} /mmc $ . For the specific composition of Mg_95.50Al_0.50Zn₂Y_1.9La_0.1, the lattice parameters of this ternary phase are a ≈ 8.98 Å and c ≈ 7.1 Å and the stoichiometry is near equiatomic. However, with decreasing Al content of the alloy, the c parameter, degree of atomic ordering, and Zn content of the phase are all observed to increase. Specifically, for Mg_95.75Al_0.25Zn₂Y_1.9La_0.1, c ≈ 7.3 Å, and the stoichiometry is approximately AlYZn₂.     

Magnetic Properties of Melt-Spun Nanocomposite PrloFe74-x Co10＋x C4B4（x=0,2,4,6,8） Ribbons

Phase evolution and magnetic properties of melt-spun Pr10Fe74-xCo10 xC4B4(x=0,2,4,6,8 ) alloy ribbons were investigated. Increasing the Co content is found to promote the generation of the 2: 14:1 phase, which results in a significant increase of coercivity and remanence.     

Influence of annealing on spin state of cobalt ions in La1-xSrxCoO3（0≤x≤0.5） system

Perovskite oxide La1-xSrxCoO3 (0≤x≤0.5) series were prepared and effect of oxygen annealing on crystal structure and magnetic susceptibility were studied. High-temperature susceptibility could be well fitted by Curie-Weiss law for all Sr-doped samples. Weiss constant and effective magnetic moment were determined, and their variations with Sr doping and oxygen annealing condition were obtained. The result suggested that by assuming that the Co3+ ions were in the intermediate-spin (IS) state, most of the Co4+ ions in the as-prepared samples might be in the high-spin (HS) state, but both the Co3+ and Co4+ ions might be in the IS state after oxygen annealing, which indicated that annealing in flowing oxygen could cause transition of the spin state of Co4+ ions from the HS state to IS state.     

Preparation of binary single-phase line compounds via diffusion couples: The subnitride phases η-Hf3N2−x and ζ-Hf4N3−x

It is shown that diffusion couples allow the preparation of pure line compounds, i.e. compounds with a very narrow homogeneity region, which are otherwise difficult or even impossible to prepare in single-phase form. With appropriate reaction conditions even a line compound forms a relatively large core in a symmetric diffusion couple of “finite” plane-sheet diffusion geometry due to the formation of a flat diffusion profile in the centered phase. The core of such a diffusion couple can then be isolated to obtain single-phase (and compact) material. This was shown for the phases η-Hf₃N_2−x and ζ-Hf₄N_3−x, which have a homogeneity region of only 2.5 at.% and <1 at.% N, respectively, in the temperature range of 1200–1700°C. The diffusion process was characterized by computational simulation, metallography, EPMA and XRD. By means of powder XRD and chemical nitrogen analysis it was possible to obtain more precise data on the two subnitride phases. η-Hf₃N_2−x has hexagonal lattice parameters of a = 0.32124(1) and c = 2.32790(10)nm for [N]/([Hf] + [Zr]) = 0.58(1) and 2.5 wt%Zr, and ζ-Hf₄N_3−x has hexagonal lattice parameters of a = 0.32084(1) and c = 3.10800(9)nm for [N]/([Hf] + [Zr]) = 0.62(1) and 3.1 wt%Zr. By this technique a single-phase sample of a ζ-phase, ζ-Hf₄N_3−x, could be prepared for the first time.     

Synthesis, Structure and Ionic Conductivity of La2／3-x Li3x MoO4

AlargenumberofM0 .5A0 .5M′O4 (M :rareearthion ,Bi3+,Fe3+,Cr3+,etc .A :alkaliion ,Cu+,Ag+,etc .M′ :Mo ,W )withtetragonalscheelite typestructurehavegoodcatalyticproperties .Aslumines centsubstrates ,theyhaveexcellentsensitizationtolu minescenceofrareearthion .Manyresearchesontheirstructure ,catalytic ,magneticandluminescentproper tieshavebeenmadesince 196 0s[1～ 10 ] .Thegeneralformulaforcompoundswiththetetragonalscheelite typestructureisAM′O4 wherethecationM′istetrahe drallycoordinat…     

Magnetic Transition of La0.8Sr0.2Mn1-xCoxO3（x =0, 0.3, 0.5, 1.0）

A series of rare earth compound oxides with the formula of La0.8Sr0.2Mn1-xCoxO3（ were prepared by the method of citric acid. Structures, figures and magnetic properties of the x=0.0, 0.3, 0.5, 1.0） samples were analyzed by means of XRD, SEM and SQUID. Experiment results prove that all the samples are hexagonal, but their figures and magnetic properties are different. La0.8Sr0.2MnO3 is ferromagnetic. La0.8Sr0.2Mn0.7CO0.3O3 and La0.8Sr0.2Mn0.5Co0.5O3 are ferrimagnetic. La0.8Sr0.2CoO3 is antiferromagnetic. SEM results indicate that the structure of the first three are three-dimensional reticulations which are made up of some small ellipsoids which link up at the head and the end. The fourth sample looks like some dispersed small balls.     

Dependence of the lattice parameter of {\gamma '} iron nitride,Fe4N1−x,on nitrogen content; Accuracy of the nitrogen absorption datairon nitride,Fe4N1−x,on nitrogen content; Accuracy of the nitrogen absorption data

Pure iron foils were converted into { \(\gamma ' - Fe_4 N_{1 - x} \) } foils of various compositions by means of nitriding in selected NH₃/H₂ gas mixtures at 803 and 843 K. The lattice parameter and the linear thermal expansion coefficient of { \(\gamma ' - Fe_4 N_{1 - x} \) } nitride and the surrounding gas atmosphere.     

Electrochemical Behavior of Lao. 7Mgo. 3 （ Ni1-x Cox ） 3.5 （ 0≤x≤0.5 ）Hydrogen Storage Alloys

The low-temperature phase transformation of LaCrO3 and doped-LaCrO3 was studied by DSC andXRD, and thermal expansion during phase trans formation was measured. It is found that the phase transformation of LaCrO3 begins near 240℃ and ends up to 265℃. The phase transformation temperature range obviously raises as the Ca content increases. The low temperature transformation changes the crystal structure of LaCrO3 and Ca-doped LaCrO3 from orthorhombic to rhombohedral and is a heat-absorbing reaction.There is no weight change but shrink of the sample happened during transformation.     

Luminescence properties of phosphate phosphors Ba3Gd1−x(PO4)3:xSm3+

A series of reddish orange phosphors Ba_3Gd_(1-x)(PO_4)_3:xSm~(3+)(x = 0.02.0.04,...,0.12) were prepared by the high-temperature solid-state reaction. X-ray powder diffraction(XRD) and diffuse reflectance and photoluminescence spectra were utilized to characterize the structure and spectral properties of the phosphors. The phosphors have strong absorption in the near-UV region. CIE chromaticity coordinates of the phosphors are located in the reddish orange region since the strongest emission band is around 598 nm and related to the ~4 G_(5/2)→~6 H_(7/2) transition of Sm~(3+). Optimal concentration of Sm~(3+) in the phosphors is about 6.0 at%. The quantum yield of the Ba_3Gd_(0.94)(PO_4)_3:0,06 Sm~(3+) under excitation at 403 nm is about 52.07%. Temperature dependent photoluminescence spectra of the Ba_3Gd_(0.94)(PO_4)_3:0.06 Sm~(3+) were measured and the phosphor exhibits high thermal stability of emission. All the results show that the Ba_3Gd(PO_4)_3:Sm~(3+) phosphor may be a potential red phosphor for near-UV based white LEDs.     

(1-x)La0.6Dy0.1Sr0.3MnO3/0.5x(Sb2O3)复合体系的电输运性质及低场磁电阻效应

用固相反应法制备了(1 -x)La0.6Dy0.1Sr0.3MnO3/0.5x( Sb2 O3)系列样品,通过电阻率-温度(ρ-T)曲线以及ρ-T拟合曲线,研究了样品的电输运性质,电输运机制及低场磁电阻效应.结果表明:所有样品在高温区表现为绝缘体导电,在低温区表现为金属导电,产生绝缘体-金属相变;在金属导电区主要是单磁子散射起作用,可以用公式ρ=ρ0+AT拟合;所有样品在整个温区随温度降低MR持续增大,表现出低场磁电阻特征,复合样品的磁电阻(MR)与纯的La0.6Dy0.1Sr0.3 MnO3的MR相比,在低温区减小,在高温区增大,对x=0.15的样品在高温区的MR大幅度提高,当B=0.2 T,T=300 K时,MR达7.79％,比纯La0.6Dy0.1 Sr0.3 MnO3的MR增大2.6倍,有利于MR的实际应用.     

Influence of reaction parameters on the luminescence properties of monodisperse NaGd(1−x−y)(WO4)2:xEu3+,yTb3+ phosphor by molten salt synthesis

Eu~(3+) activated and Eu~(3+), Tb~(3+) co-activated monodisperse sodium double tungstates NaGd(WO4)2 phosphors were prepared by molten salt method at 750 ℃ for 10 h using NaCl as a flux. The crystal structure and morphology of the as-synthesized phosphors were measured by XRD and SEM, respectively. The photoluminescence properties were characterized by PL spectra, decay lifetime and CIE. The presence of NaCl plays an important role in the morphology and luminescence properties. In this work,NaCl and one of the raw material Na_2 CO_3 in a certain proportion will form a low eutectic salt to decrease the reaction temperature and benefit the formation of monodisperse NaGd(WO_4)_2 crystals. The color of Eu~(3+) and Tb~(3+) co-doped NaGd(WO_4)_2 phosphors can be tuned from creamy white to orange, red and green by adjusting the doping concentration of rare earth ions, since the emission contain the broad blue-green emission origin from NaGd(WO_4)_2 host and characteristic red and green emission origin from Eu~(3+) and Tb~(3+) ions. The electroluminescent spectra and CIE measurement shows that the LED device with NaGd_((1-x))(WO_4)_2:xEu~(3+)(x = 0.24) phosphor can be excited by 365 nm and 380 nm LED chip, and their CIE coordinate is(x = 0.45, y = 0.45) and(x = 0.36, y = 0.37), Ra is 80.3 and 86.3, T_c is 3196 and4556 K, respectively. As a single-component phosphor, NaGd(WO_4)_2:Eu~(3+),Tb~(3+) have potential application in UV-pumped WLEDs.     

Electrical and dielectric properties of Ni0.5Co0.5GaxFe1.8-xO4(x≤1.0)spinel ferrite microspheres

Microspheres of Ni_0.5 Co_0.5Ga_xFe_2-xO₄(x≤1.0) microsphere spinel ferrites(NiCoGaFe-MSFs) and carbon spheres were prepared via a hydrothermal technique.The micro structure of microspheres was investigated through scanning and transmission electron microscopy(SEM and TEM),respectively,and X-ray diffraction(XRD).The electrical and dielectric properties of NiCoGaFe-MSF at temperatures ranging from20 to 120℃(between 293,1× 10³ and 393.1...