High Temperature Thermoelectric Properies of LnPdX (Ln = lanthanide; X = Sb, Bi) Ternary Compounds

2005 ◽  
Vol 886 ◽  
Author(s):  
Takeyuki Sekimoto ◽  
Ken Kurosaki ◽  
Hiroaki Muta ◽  
Shinsuke Yamanaka
Keyword(s):  
Band Gap ◽  
Room Temperature ◽  
Band Gap Energy ◽  
Type Structure ◽  
Ternary Compounds ◽  
Plasma Sintering ◽  
Electrical Resistivities ◽  
Spark Plasma ◽  
Hall Effect Measurements ◽  
The Difference

ABSTRACTTernary compounds LnPdX (Ln = lanthanide elements of La, Gd, Er; X = Sb, Bi) were prepared by a spark plasma sintering (SPS) technique. The crystal structure of LaPdSb and GdPdSb was confirmed to be a hexagonal ZrBeSi-type structure and different from the other compounds with a MgAgAs-type structure. The electrical resistivities ρ of LaPdSb and GdPdSb indicate the metallic or semimetallic characteristics, while those of ErPdSb and LnPdBi indicate semiconductor characteristics. From the ln ρ − 1/T plot, the band gap energies Eg were estimated to be 0.28, 0.053, 0.081, and 0.049 eV for ErPdSb, LaPdBi, GdPdBi, and ErPdBi, respectively. All the samples have positive thermoelectric powers S above room temperature. The largest power factor S2/ρ was obtained as 49.5 μW/K2 cm at 327 K for LaPdSb. From the Hall effect measurements on ErPdX, the carrier concentration n of ErPdSb and ErPdBi were obtained as 5.9×1018 and 3.21×1019 cm−3 at room temperature, respectively. It is considered that the difference of n at room temperature is mainly due to the magnitude of the band gap energy.

Thermal Conductivities of Cs-M-O (M= Mo or U) Ternary Compounds

2009 ◽  
Vol 1215 ◽  
Author(s):  
Kazuyuki Tokushima ◽  
Kosuke Tanaka ◽  
Ken Kurosaki ◽  
Hiromichi Gima ◽  
Hiroaki Muta ◽  
...  
Keyword(s):  
Heat Capacity ◽  
Thermal Diffusivity ◽  
Room Temperature ◽  
Laser Flash ◽  
Flash Method ◽  
Ternary Compounds ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Thermal Diffusivities ◽  
Thermal Conductivities

AbstractThermal conductivities of Cs-M-O (M= Mo or U) ternary compounds, observed in the pellet-cladding gap region and in the pellet periphery in irradiated oxide fuels with high oxygen potentials, were investigated. Bulk samples of Cs2MoO4and Cs2UO4were prepared by hot pressing or spark plasma sintering, and their thermal diffusivities were measured by the laser flash method from room temperature to 823 K for Cs2MoO4and to 900 K for Cs2UO4. The thermal conductivities were evaluated from the thermal diffusivity and bulk density, and the specific heat capacity values available in the literature. The thermal conductivities of Cs2MoO4and Cs2UO4were quite low compared with UO2(e.g. 0.5 Wm−1K−1at 800 K for Cs2MoO4).

scholarly journals The Extrusion and SPS of Zirconium–Copper Powders and Studies of Selected Mechanical Properties

Materials ◽  
2021 ◽  
Vol 14 (13) ◽  
pp. 3560
Author(s):  
Tomasz Skrzekut ◽  
Grzegorz Boczkal ◽  
Adam Zwoliński ◽  
Piotr Noga ◽  
Lucyna Jaworska ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Intermetallic Compounds ◽  
Room Temperature ◽  
Intermetallic Phase ◽  
Extrusion Process ◽  
Strength Properties ◽  
Plasma Sintering ◽  
Copper Powders ◽  
Spark Plasma ◽  
Zirconium Copper

Zr-2.5Cu and Zr-10Cu powder mixtures were consolidated in the extrusion process and using the spark plasma sintering technique. In these studies, material tests were carried out in the fields of phase composition, microstructure, hardness and tensile strength for Zr-Cu materials at room temperature (RT) and 400 °C. Fractography analysis of materials at room temperature and 400 °C was carried out. The research took into account the anisotropy of the materials obtained in the extrusion process. For the nonequilibrium SPS process, ZrCu2 and Cu10Zr7 intermetallic compounds formed in the material at sintering temperature. Extruded materials were composed mainly of α-Zr and ZrCu2. The presence of intermetallic compounds affected the reduction in the strength properties of the tested materials. The highest strength value of 205 MPa was obtained for the extruded Zr-2.5Cu, for which the samples were cut in the direction of extrusion. For materials with 10 wt.% copper, more participation of the intermetallic phase was formed, which lowered the mechanical properties of the obtained materials. In addition to brittle intermetallic phases, the materials were characterized by residual porosity, which also reduced the strength properties.

Formation of a unique glass by spark plasma sintering of a zeolite

2009 ◽  
Vol 24 (10) ◽  
pp. 3241-3245 ◽  
Author(s):  
Lianjun Wang ◽  
Wan Jiang ◽  
Lidong Chen ◽  
Zhijian Shen
Keyword(s):  
Spark Plasma Sintering ◽  
Glass Sample ◽  
Room Temperature ◽  
Vickers Microhardness ◽  
Simple Approach ◽  
Electron Microscopic ◽  
Plasma Sintering ◽  
Transmission Electron ◽  
Transmission Electron Microscopic ◽  
Spark Plasma

A simple approach, order–disorder transition (ODT), has been developed to synthesize a novel glass using ZSM-5 as starting materials. In this process, the ZSM-5 powders were pressed uniaxially in a graphite die and rapidly sintered using spark plasma sintering (SPS). High-resolution transmission electron microscopic images revealed that a few crystalline zeolite fragments were still preserved locally inside the SPS consolidated sample. Vickers microhardness and fracture toughness of this as-prepared transparent glass sample at room temperature reaches 7.3 ± 0.2 GPa and 2.0 ± 0.3MPa·m1/2, respectively. It is very interesting that these novel bulk transparent glasses exhibit ultraviolet photoluminescence (PL) properties at about ∼360 nm.

Spark Plasma Sintering of Ti-4.5Al-3V-2Fe-2Mo (SP-700)

2010 ◽  
Vol 654-656 ◽  
pp. 819-822
Author(s):  
Genki Kikuchi ◽  
Hiroshi Izui ◽  
Yuya Takahashi ◽  
Shota Fujino
Keyword(s):  
Spark Plasma Sintering ◽  
Room Temperature ◽  
Volume Fraction ◽  
Titanium Boride ◽  
Tensile Tests ◽  
X Ray Diffraction ◽  
X Ray ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Tib2 Particles

In this study, we focused on the sintering performance of Ti-4.5Al-3V-2Mo-2Fe (SP-700) and mechanical properties of SP-700 reinforced with titanium boride (TiB/SP-700) fabricated by spark plasma sintering (SPS). TiB whiskers formed in titanium by a solid-state reaction of titanium and TiB2 particles were analyzed with scanning electron microscopy and X-ray diffraction. The TiB/SP-700 was sintered at temperatures of 1073, 1173, and 1273 K and a pressure of 70 MPa for 10, 30, and 50 min. The volume fraction of TiB ranged from 1.7 vol.% to 19.9 vol.%. Tensile tests of TiB/SP-700 were conducted at room temperature, and the effect of TiB volume fraction on the tensile properties was investigated.

Optical Detection of Band Gap Variations Due to Ordering in Ga0.47In0.53As on InP

1992 ◽  
Vol 281 ◽  
Author(s):  
D. J. Arent ◽  
K. A. Bertness ◽  
Sarah R. Kurtz ◽  
M. Bode ◽  
J. M. Olson
Keyword(s):  
Band Gap ◽  
Atmospheric Pressure ◽  
Room Temperature ◽  
Energy Gap ◽  
Growth Conditions ◽  
Band Gap Energy ◽  
Optical Energy Gap ◽  
Lower Growth ◽  
Transmission Electron ◽  
High Resolution Images

ABSTRACTA reduction in the optical energy gap of more than 65 meV has been observed in In0.53Ga0.47 As grown on (100) InP by atmospheric pressure metalorganic vapor phase epitaxy. The band gap energies were deduced from room temperature photocurrent spectroscopic measurements, accounting for differences in composition and strain. Spontaneous CuPt type ordering of In and Ga atoms on the (111) subplanes of the InGaAs2 was confirmed by transmission electron microscopy. Superlattice signatures in the transmission micrographs were observed only for samples with associated reduced band gap energies, and were confirmed by visible double periodicity in high resolution images. In0.53Ga0.47 As was grown under a variety of conditions, some which promoted ordering. In general, lower growth temperatures and moderate (∼4 μ/hr) growth rates promoted a greater degree of ordering and reduction of the band gap energy. The influence of growth conditions on the ordered structure is considered within the context of current theories.

scholarly journals Processing and Study of Optical and Electrical Properties of (Mg, Al) Co-Doped ZnO Thin Films Prepared by RF Magnetron Sputtering for Photovoltaic Application

Materials ◽  
2020 ◽  
Vol 13 (9) ◽  
pp. 2146 ◽  
Author(s):  
Chayma Abed ◽  
Susana Fernández ◽  
Selma Aouida ◽  
Habib Elhouichet ◽  
Fernando Priego ◽  
...  
Keyword(s):  
Thin Films ◽  
Electrical Properties ◽  
Magnetron Sputtering ◽  
Band Gap ◽  
Rf Magnetron Sputtering ◽  
Band Gap Energy ◽  
Thin Layers ◽  
Working Pressure ◽  
Hall Effect Measurements ◽  
Diffraction Patterns

In this study, high transparent thin films were prepared by radio frequency (RF) magnetron sputtering from a conventional solid state target based on ZnO:MgO:Al2O3 (10:2 wt %) material. The films were deposited on glass and silicon substrates at the different working pressures of 0.21, 0.61, 0.83 and 1 Pa, 300 °C and 250 W of power. X-ray diffraction patterns (XRD), atomic force microscopy (AFM), UV-vis absorption and Hall effect measurements were used to evaluate the structural, optical, morphological and electrical properties of thin films as a function of the working pressure. The optical properties of the films, such as the refractive index, the extinction coefficient and the band gap energy were systematically studied. The optical band gap of thin films was estimated from the calculated absorption coefficient. That parameter, ranged from 3.921 to 3.655 eV, was hardly influenced by the working pressure. On the other hand, the lowest resistivity of 8.8 × 10−2 Ω cm−1 was achieved by the sample deposited at the lowest working pressure of 0.21 Pa. This film exhibited the best optoelectronic properties. All these data revealed that the prepared thin layers would offer a good capability to be used in photovoltaic applications.

scholarly journals Optical and Transport Properties of p-Type GaAs

2012 ◽  
Vol 36 (1) ◽  
pp. 97-107 ◽  
Author(s):  
Mehnaz Sharmin ◽  
Shamima Choudhury ◽  
Nasrin Akhtar ◽  
Tahmina Begum
Keyword(s):  
Light Intensity ◽  
Carrier Concentration ◽  
Hall Coefficient ◽  
Hall Mobility ◽  
Room Temperature ◽  
Diffraction Method ◽  
Lattice Parameter ◽  
Band Gap Energy ◽  
Hall Effect Measurements ◽  
P Type

Electrical properties such as electrical resistivity, Hall coefficient, Hall mobility, carrier concentration of p-type GaAs samples were studied at room temperature (300 K). Resistivity was  found to be of the order of 5.6 × 10-3?-cm. The Hall coefficient (RH) was calculated to be 7.69 × 10-1cm3/C and Hall mobility (?H) was found to be 131cm2/V-s at room temperature from Hall effect   measurements. Carrier concentration was estimated to be 8.12 × 1018/cm3 and the Fermi level was calculated directly from carrier density data which was 0.33 eV. Photoconductivity measurements  were carried on by varying sample current, light intensity and temperature at constant chopping     frequency 45.60 Hz in all the cases mentioned above. It was observed that within the range of sample current 0.1 - 0.25mA photoconductivity remains almost constant at room temperature 300K and it was found to be varying non-linearly with light intensity within the range 37 - 12780 lux. Photoconductivity was observed to be increasing linearly with temperature between 308 and 428 K. Absorption coefficient (?) of the samples has been studied with variation of wavelength (300 -  2500 nm). The value of optical band gap energy was calculated between 1.34 and 1.41eV for the material from the graph of (?h?)2 plotted against photon energy. The value of lattice parameter (a) was found to be 5.651 by implying X-ray diffraction method (XRD).DOI: http://dx.doi.org/10.3329/jbas.v36i1.10926Journal of Bangladesh Academy of Sciences, Vol. 36, No. 1, 97-107, 2012 

scholarly journals Tribological Characterization of Micron-/Nano-Sized WC-9%Co Cemented Carbides Prepared by Spark Plasma Sintering at Elevated Temperatures

Materials ◽  
2019 ◽  
Vol 12 (6) ◽  
pp. 920 ◽  
Author(s):  
Saleh Wohaibi ◽  
Abdul Mohammed ◽  
Tahar Laoui ◽  
Abbas Hakeem ◽  
Akeem Adesina ◽  
...  
Keyword(s):  
Wear Resistance ◽  
Spark Plasma Sintering ◽  
Room Temperature ◽  
Elevated Temperatures ◽  
Normal Load ◽  
Cemented Carbide ◽  
Plasma Sintering ◽  
Dry Conditions ◽  
Spark Plasma ◽  
Track Area

The present study investigates the high temperature tribological performance of spark plasma sintered, nano- and micron-sized tungsten carbide (WC) bonded by 9 wt.% cobalt (Co). The composites were fabricated using a two-step procedure of mixing followed by spark plasma sintering (SPS). Ball-on-disc wear tests were conducted at a normal load of 30 N, linear speed of 0.1 m/s under dry conditions and at three different temperatures (room temperature, 300 °C and 600 °C). Field emission scanning electron microscopy (FESEM), optical profilometry and energy dispersive X-ray (EDS) spectroscopy were used to analyze the surface morphology and the wear track area. At room temperature, it was observed that the nano-sized WC composites exhibited better wear resistance than the micron-sized WC composites. The wear resistance of the nano-sized samples declined significantly relative to that of the micron-sized samples with an increase in temperature. This decline in performance was attributed to the higher surface area of nano-sized WC particles, which underwent rapid oxidation at elevated temperatures, resulting in poor wear resistance. The wear rate observed at 600 °C for the micron-sized WC composites was 75% lower than that of the nano-sized cemented carbide. Oxidative wear was observed to be the predominant wear mechanism for both cemented carbide samples at elevated temperatures.

Electronic Bandgap and Refractive Index Dispersion of Single Crystalline Epitaxial ZnGeN2

1999 ◽  
Vol 607 ◽  
Author(s):  
L.D. Zhu ◽  
P.E. Norris ◽  
L.O. Bouthillette
Keyword(s):  
Refractive Index ◽  
Band Gap ◽  
Room Temperature ◽  
Band Gap Energy ◽  
Organic Chemical ◽  
Refractive Index Dispersion ◽  
Electronic Band ◽  
Single Crystalline ◽  
Gap Energy ◽  
Prism Coupling

AbstractThe electronic band gap of single crystalline ZnGeN2 epitaxial layer grown on sapphire substrate by metal organic chemical vapor deposition has been measured by optical transmission and room temperature photoluminescence. The band gap energy is 2.99eV at room temperature, and the band gap is a direct transition type. The interference oscillations of the transmission spectra together with rutile prism coupling measurements have been used to determine the r fractive index and the dispersion characteristics of the single crystal ZnGeN2 below the band gap energy. The rutile prism coupling measurement displays the wave guide modes of the film at 6 2.8nm wavelength of the He-Ne laser, enabling determination of the film thickness and refractive index precisely at the wavelength. The refractive index of ZnGeN2 crystal is 2.35 at 6328Å wavelength. The measured refractive index dispersion curve can be fitted with the first-order Sellmeier equation n2(λ) = A + λ2/(λ2-B), using fitting parameters A=4.3 1, B=0.076.

Enhanced thermoelectric properties in PbTe Nanocomposites

2009 ◽  
Vol 1166 ◽  
Author(s):  
Hillary Kirby ◽  
Joshua Martin ◽  
Anuja Datta ◽  
Lidong Chen ◽  
George S. Nolas
Keyword(s):  
Thermoelectric Properties ◽  
Room Temperature ◽  
Room Temperature Resistivity ◽  
Phase Reaction ◽  
Conductivity Measurements ◽  
Temperature Dependent ◽  
Plasma Sintering ◽  
Spark Plasma ◽  
Temperature Dependent Thermal Conductivity ◽  
Temperature Resistivity

AbstractDimensional nanocomposites of PbTe with varying carrier concentrations were prepared from undoped and Ag doped PbTe nanocrystals synthesized utilizing an alkaline aqueous solution-phase reaction. The nanocrystals were densified by Spark Plasma Sintering (SPS) for room temperature resistivity, Hall, Seebeck coefficient, and temperature dependent thermal conductivity measurements. The nanocomposites show an enhancement in the thermoelectric properties compared to bulk PbTe with similar carrier concentrations, thus demonstrating a promising approach for enhanced thermoelectric performance.

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