SEARCH · Engineering Papers
Results for “Te”
Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.
Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.
Electronic Topological Transition as a Route to Improve Thermoelectric Performance in Bi 0.5 Sb 1.5 Te 3
The electronic structure near the Fermi surface determines the electrical properties of the materials, which can be effectively tuned by external pressure. Bi0.5Sb1.5Te3 is a p-type thermoelectric material which holds the record high figure of merit at room temperature. Here it is examined whether the figure of merit of this model system can be further enhanced through some external parameter. With the application of pressure, it is surprisingly found that the power factor of this material exhibits λ behavior with a high value of 4.8 mW m –1 K –2 at pressure of 1.8 GPa. Such an enhancement is found to be driven by pressure-induced electronic topological transition, which is revealed by multiple techniques. Together with a low thermal conductivity of about 0.89 W m –1 K –1 at the same pressure, a figure of merit of 1.6 is achieved at room temperature. The results and findings highlight the electronic topological transition as a new route for improving the thermoelectric properties.
Binary and Ternary Colloidal Cu–Sn–Te Nanocrystals for Thermoelectric Thin Films
Recent advances in copper chalcogenide-based nanocrystals (NCs), copper sulfide, and copper selenide derived nanostructures, have drawn considerable attention. However, reports of crystal phase and shape engineering of binary or ternary copper telluride NCs remain rare. Here, a colloidal hot-injection approach for producing binary copper/tin telluride, and ternary copper tin telluride NCs with controllable compositions, crystal structures, and morphologies is reported. Here, the crystal phase and growth behavior of these tellurides are systematically studied from both experimental and theoretical perspectives.
TEM Studies of Segregation in a Ge-Sb-Te Alloy during Heating.
Abstract not provided.
In-situ high-energy X-ray diffraction and crystal plasticity modeling to predict the evolution of te
Explore the source record for details and available documents.
Thermoelectric transport enhancement of Te-rich bismuth antimony telluride (Bi0.5Sb1.5Te3+x) through controlled porosity
Not Available
Direct observations of Pd–Te compound formation within noble metal inclusions in spent nuclear fuel
Not Available
Structural and electronic phase transition in Bi[subscript 2]Se[subscript 2.1]Te[subscript 0.9] unde
Explore the source record for details and available documents.
Bandgap engineering of Cd 1 - x Zn x Te 1 - y Se y ( 0 < x < 0 . 27 , 0 < y < 0 . 026 )
CdZnTe (CZT) detectors with more than 10% zinc content did not show a remarkable improvement in the detector performance due to the additional defects introduced by the higher zinc content. However, recent research showed that the formation of defects was suppressed effectively by adding a small amount of selenium (2%) in CZT. On this basis, we attempted to enhance the detector performance through bandgap engineering by increasing the zinc content up to 25 %, while adding 2 % of selenium. Multiple CdZnTeSe (CZTS) ingots with Zn = 10, 12.5, 15, 20 and 25%, while fixing the Se composition at 2%, were grown by the Bridgman method. The bandgap of CZTS for the different Zn and Se contents was analyzed and then equations for predicting the bandgap for other alloy compositions were introduced. Furthermore, the crystallinity of CZTS was evaluated by photoluminescence measurements. The pulse height spectra for Am-241 and Co-57 sources were used to evaluate the detector performance for the CZTS samples.
High-pressure X-ray diffraction and Mössbauer spectroscopy study of Fe1.087Te
Not Available
Bond valence sum analysis of pyrochlore oxides including the novel dielectric Te 6+ pyrochlores: A Bi M TeO 7-y ( A = Cd, Ca; M = Cr, Ga, Sc, In, Fe)
Bond valence sum analysis is a powerful tool used in evaluating and validating crystal structures; especially when those structures are complex in nature. The pyrochlore structure type is versatile in not only the unique bonding that it exhibits, but also in the properties that results from the structure. Here this paper aims to center the discussion of evaluating the pyrochlore structure using the bond valence sum method. In this study, novel quaternary pyrochlores with a general stoichiometry of ABiMTeO 7 (A = Cd, Ca; M = Cr, Ga, Sc, In, Fe) were synthesized and characterized for their structural, magnetic, and dielectric properties. Two representative compounds within this series of pyrochlores, BiCaFeTeO7 and BiCdFeTeO 7 , were structurally characterized utilizing a combination of high-resolution synchrotron X-ray diffraction and neutron diffraction revealing oxygen deficient pyrochlore systems which were off from the expected stoichiometry with respect to the M site. The A site of both pyrochlores were found to be moved off-center from the expected 16d site to the 96h displaced position at a magnitude of 0.25 Å and 0.22 Å for the Bi/Ca and Bi/Cd systems, respectively. These structures were evaluated using the bond valence sum method and compared with trends in the literature. The properties are also reported for the Bi/Ca system for the first time, showing relatively high dielectric constants with a low dielectric loss which are primarily independent of frequency and temperature. The magnetic measurements for the Bi/Ca system for the magnetic substitutions reveal a paramagnet and antiferromagnetic properties for the Fe and Cr analogs, respectively. The novel BiCaMTeO 7 quaternary pyrochlore system shows great promise as an emerging dielectric material.
Into the Void: Single Nanopore in Colloidally Synthesized Bi 2 Te 3 Nanoplates with Ultralow Lattice Thermal Conductivity
Not Available
Electron–Hole Asymmetry of Surface States in Topological Insulator Sb 2 Te 3 Thin Films Revealed by Magneto-Infrared Spectroscopy
When surface states (SSs) form in topological insulators (TIs), they inherit the properties of bulk bands, including the electron–hole (e–h) asymmetry but with much more profound impacts. Here via combining magneto-infrared spectroscopy with theoretical analysis, we show that e–h asymmetry significantly modifies the SS electronic structures when interplaying with the quantum confinement effect. Compared with the case without e–h asymmetry, the SSs now bear not only a band asymmetry, such as that in the bulk, but also a shift of the Dirac point relative to the bulk bands and a reduction of the hybridization gap of up to 70%. Here, our results signify the importance of e–h asymmetry in the band engineering of TIs in the thin-film limit.