Thermal properties of Nb2SnC (original) (raw)
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Advances in Materials Science and Engineering
In this work, the total electronic energy, the electronic thermal conductivity, and the heat capacity of erbium nickel borocarbide, ErNi2B2C, in the normal and superconducting states are calculated using Boltzmann transport equations (BTEs) and energy dispersion relation function. Results from the electronic thermal conductivity versus temperature (T) are presented. From the result, electrical and thermal conductivity at low temperature obey the Wiedemann–Franz law. Moreover, at the normal state, the electronic thermal conductivity of ErNi2B2C is directly proportional to the temperature (T) and reaches its maximum (kink) at the transition temperature, Tc. After the superconducting transition temperature, the electronic thermal conductivity begin to decrease. The drop in electronic thermal conductivity beyond its peak (kink) value is due to the formation of energy gap and the absence of Cooper pairs.
Specific heat studies of pure Nb 3 Sn single crystals at low temperature
Journal of Physics: Condensed Matter, 2009
Specific heat measurements performed on high purity vapor-grown Nb 3 Sn crystals show clear features related to both the martensitic and superconducting transitions. Our measurements indicate that the martensitic anomaly does not display hysteresis, meaning that the martensitic transition could be a weak first or a second order thermodynamic transition. Careful measurements of the two transition temperatures display an inverse correlation between both temperatures. At low temperature specific heat measurements show the existence of a single superconducting energy gap feature.
Chemical vapor transport of Nb3Sn
Materials Research Bulletin, 1990
A chemical vapor transport method has been used to produce free standing thick films of Nb3Sn utilizing TeC14 as a transport agent.
Physical Properties of the NbC Carbide
Metals, 2016
Transition metal carbides are interesting materials with a singular combination of properties, such as high melting points, high hardness, good transport properties and relatively low costs, which makes them excellent candidates for several technological applications. The possible applications of NbC carbide remained unexplored as it was in the past expensive and available in limited volumes. In order to guide investigations of the applicability of NbC, a deeper understanding of the physical properties of this carbide is fundamental. In this review paper, key physical properties of NbC are compiled with emphasis on its chemical bonding, a careful description of the C-Nb phase diagram, the phases formed and the crystal structures. Thermal properties are discussed and correlated with the intrinsic and extrinsic features of NbC. Finally, elastic properties are discussed.
Superconductivity in the Nb2SnC compound
Solid State Communications, 2006
Nb 2 SnC is a member of the large family of lamellar materials that crystallize in the hexagonal structure with space group P6 3 /mmc which are isomorphs with Cr 2 AlC, also named H-phase. In spite of the great number of compounds which belong to this family, the superconductivity has been reported only for two cases: Mo 2 GaC and Nb 2 SC. In this work we show that superconductivity can be observed in Nb 2 SnC depending on the synthesis method used. The quality of the superconductor is strongly dependent of the synthesis method and the optimal results were reached for samples synthesized at 2.5 GPa and 523 ± 50ºC. This sample showed a critical temperature close to 7.8K, revealed from magnetization and transport measurement, the highest critical temperature reported up to now for an Hphase.
Thermal Conductivity of Uranium Nitride and Carbide
International Journal of Nuclear Energy, 2014
We investigate the electronic thermal conductivity of alternative fuels like uranium nitride and uranium carbide. We evaluate the electronic contribution to the thermal conductivity, by combining first-principles quantum-mechanical calculations with semiclassical correlations. The electronic structure of UN and UC was calculated using Quantum Espresso code. The spin polarized calculations were performed for a ferromagnetic and antiferromagnetic ordering of magnetic moments on uranium lattice and magnetic moment in UC was lower than in UN due to stronger hybridization between 2p electrons of carbon and 5f electrons of uranium. The nonmagnetic electronic structure calculations were used as an input to BolzTrap code that was used to evaluate the electronic thermal conductivity. It is predicted that the thermal conductivity should increase with the temperature increase, but to get a quantitative agreement with the experiment at higher temperatures the interaction of electrons with phono...
Structural, Chemical, Electrical, and Thermal Properties of n-Type NbFeSb
Inorganic Chemistry, 2019
We report on the structural, chemical, electrical, and thermal properties of n-type polycrystalline NbFeSb synthesized by induction melting of the elements. Although several studies on p-type conduction of this half-Heusler composition have recently been reported, including reports of relatively high thermoelectric properties, very little has been reported on the transport properties of n-type compositions. We combine transport property investigations together with short-and longrange structural data obtained by Mössbauer spectroscopy of iron-57 and antimony-121 and by neutron total scattering, as well as first-principles calculations. In our investigation, we show that n-type conduction can occur from antiphase boundaries in this material. This work is intended to provide a greater understanding of the fundamental properties of NbFeSb as this material continues to be of interest for potential thermoelectric applications.
Journal of Physics and Chemistry of Solids, 1967
The system Nb~Al Sn, exhibits complete solid solubility, a positive Seebeck voltage that increases monatomically from 1.8 to over 12 |dV/°K, and a superconducting transition temperature T that has a broad minimum of T « 15.3 °K at about y = 0.5. The c c pseudobinary Nb-Sn, Sb , on the other hand, contains two phases, ■3 x-"X X each with the A15 structure, in the interval 0.3 < x < 0.8. Whereas the Seebeck voltage of the low-Sb phase is positive and has a T > 14°K, the high Sb phase has a negative Seebeck voltage and is not superconducting above 4.2°K. These properties have been interpreted with the aid of a qualitative band-structure scheme. Thus, the rapid drop in T to below 4.2°K in the system Nb^Sn, Sb is believed to be associated with the filling of 3 1-x x the bonding, interchain d bands of the Nb subarray.
Thermal properties of NBT-BT systems
Phase Transitions, 2016
A conventional solid-phase sintering process was used to fabricate the (1 ¡ x)Na 0.5 Bi 0.5 TiO 3-xBaTiO 3 ceramics (x D 0, 0.04, 0.06, 0.08 and 0.1). X-ray measurements showed that all samples have a perovskite structure. The bulk density of the obtained samples exceeds 95% of the theoretical density. The thermal (DSC, dilatometry) and dielectric properties of these ceramics were investigated in a wide temperature range. Anomalies of the thermal expansion strain were observed at the temperatures which are not related to any phase transitions. The transition temperatures observed by means of thermal measurements are in good agreement with those obtained from dielectric studies.
Electronic Structure of the Superconducting Rare Earth-Metal Nickel Boron Carbide Compounds
Inorganic Chemistry, 1994
An analysis of the electronic structure and bonding in the superconducting LnNizBzC and nonsuperconducting LnNiBC phases is made, using extended Hiickel tight-binding calculations. The results show that these compounds are highly covalent and can be considered as intermetallic materials. Oxidation formalisms of (Ln2+)(NiO)z(BzC)2for LnNi2BzC and (Ln3+)(Ni0)(BC)I-for LnNiBC constitute good starting points to describe their electronic structure. The Fermi level cuts a narrow and sharp peak in the DOS for LuNizBzC, mainly composed of u-type NiB bonding states. This allows us to conclude that electrons transferred from the (BZC)~-entities into u-type metal-non-metal bonding states are responsible for the superconducting properties encountered for certain LnNi2B2C compounds. Flat bands are calculated in the planes perpendicular to the stacking c axis. These materials should be 2-D-like superconductors. The absence of superconductivity for LuNiBC seems to be associated with the rather weak DOS at the Fermi level, compared to that of LuNizB2C. Relatively high-transition temperatures (Tc's) up to 23 K have been reported for some rare-earth-metal transition-metal boron carbide compounds.14 Although their Tc values are far below those measured for the copper oxide superconductors,~ these new quaternary intermetallic materials could constitute milestones in terms of the discovery of a new family of high-Tc superconductors. We report here the band electronic structure of the wellcharacterized LnNizBzC compounds,6 some of which exhibit superconductivity above 15 K,4 using tight-binding calculations.7