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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.

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At least 469 records · Page 26
All sourcesNASA NTRSDOE OSTI
NASA NTRS2016

Filled Nd(sub z) Fe(sub x) Co(sub 4-x) Sb(sub 12-y) Ge(sub y) Skutterudites: Processing and Thermoelectric Properties

Skutterudites have proven to be a useful thermoelectric system as a result of their enhanced figure of merit (ZT1), cheap material cost, favorable mechanical properties, and good thermal stability. The majority of skutterudite interest in recent years has been focused on binary skutterudites like CoSb3. Binary skutterudites are often double and triple filled, with a range of elements from the lanthanide series, in order to reduce the lattice component of thermal conductivity. Ternary and quaternary skutterudites, such as Co4Ge6Se6 or Ni4Sb8Sn4, provide additional paths to tune the electronic structure. The thermal conductivity can further be improved in these complex skutterudites by the introduction of fillers. The Nd (sub z) Fe (sub x) Co (sub 4-x) Sb (sub 12-y)Ge (sub y) system has been investigated as a p-type thermoelectric material, and is stable up to 600 degrees Centigrade. The influence of Fe and Ge content, along with filler Nd, was investigated on thermoelectric transport properties. In addition to the chemical influence on properties, some processing details of the system will also be addressed.

Electical Conductivity↗
NASA NTRS2016

Filled Nd(z)Fe(x)Co(4-x)Sb(12-y)Ge(y) Skutterudites: Processing and Thermoelectric Properties

Skutterudites have proven to be a useful thermoelectric system as a result of their enhanced figure of merit (ZT1), cheap material cost, favorable mechanical properties, and good thermal stability. The majority of skutterudite interest in recent years has been focused on binary skutterudites like CoSb3. Binary skutterudites are often double and triple filled, with a range of elements from the lanthanide series, in order to reduce the lattice component of thermal conductivity. Ternary and quaternary skutterudites, such as Co4Ge6Se6 or Ni4Sb8Sn4, provide additional paths to tune the electronic structure. The thermal conductivity can further be improved in these complex skutterudites by the introduction of fillers. The Nd(z)Fe(x)Co(4-x)Sb(12-y)Ge(y) system has been investigated as a p-type thermoelectric material, and is stable up to 600 C. The influence of Fe and Ge content, along with filler Nd, was investigated on thermoelectric transport properties. In addition to the chemical influence on properties, some processing details of the system will also be addressed.

Thermoelectric↗
NASA NTRS2017

Recent Radiation Test Results for Trench Power MOSFETs

Single-event effect (SEE) radiation test results are presented for various trench-gate power MOSFETs. The heavy-ion response of the first (and only) radiation-hardened trench-gate power MOSFET is evaluated: the manufacturer SEE response curve is verified and importantly, no localized dosing effects are measured, distinguishing it from other, non-hardened trench-gate power MOSFETs. Evaluations are made of n-type commercial and both n- and p-type automotive grade trench-gate device using ions comparable to of those on the low linear energy transfer (LET) side of the iron knee of the galactic cosmic ray spectrum, to explore suitability of these parts for missions with higher risk tolerance and shorter duration, such as CubeSats. Part-to-part variability of SEE threshold suggests testing with larger sample sizes and applying more aggressive derating to avoid on-orbit failures. The n-type devices yielded expected localized dosing effects including when irradiated in an unbiased (0-V) configuration, adding to the challenge of inserting these parts into space flight missions.

Schottky Diodes↗
NASA NTRS2017

Unipolar Barrier Dual-Band Infrared Detectors

Dual-band barrier infrared detectors having structures configured to reduce spectral crosstalk between spectral bands and/or enhance quantum efficiency, and methods of their manufacture are provided. In particular, dual-band device structures are provided for constructing high-performance barrier infrared detectors having reduced crosstalk and/or enhance quantum efficiency using novel multi-segmented absorber regions. The novel absorber regions may comprise both p-type and n-type absorber sections. Utilizing such multi-segmented absorbers it is possible to construct any suitable barrier infrared detector having reduced crosstalk, including npBPN, nBPN, pBPN, npBN, npBP, pBN and nBP structures. The pBPN and pBN detector structures have high quantum efficiency and suppresses dark current, but has a smaller etch depth than conventional detectors and does not require a thick bottom contact layer.

Ting, David Z.↗
NASA NTRS2019

Simultaneous Ohmic Contact to Silicon Carbide

A simultaneous ohmic contact to silicon carbide includes a mixture of platinum, titanium, and silicon compounds deposited on a silicon carbide substrate. The silicon carbide substrate includes an n-type surface and a p-type surface.

Okojie, Robert S.↗
NASA NTRS2019

Sublimation Protection Coatings for Thermoelectric Materials for Space Power Applications

The compounds such as Yb14MnSb11 are relatively new p-type thermoelectric materials, respectively. NASA's interest in these material are to replace the state-of-the-art Si-Ge legs of the current radioisotope thermoelectric generators (RTGs). Ideally, the hot end of this leg would operate at 1000 degrees C in the vacuum of space. These materials, however, suffer from a high sublimation rate at elevated temperatures and would require a coating in order to survive the required RTG lifetime of 14 years. The purpose of present work is to develop sublimation protection coatings for Yb14MnSb11 at temperatures up to 1000 degrees C. Coatings for Yb14MnSb11 present many challenges. The coating must not significantly react or interdiffuse with the substrate thereby degrading the substrate or consuming the coating, must remain intact and not crack or spall during thermal cycling prior to launch, and must be a good insulator both electrically and thermally so as not to provide a short circuit for either electron flow or heat through the coating rather than through the leg. Based on these requirements, several oxides have been selected as possible coating candidates. This paper discusses the development of slurry processes to deposit these oxides coatings on thermoelectric materials.

Sublimation↗
NASA NTRS2019

The Random Transiter – EPIC 249706694/HD 139139

We have identified a star, EPIC 249706694 (HD 139139), that was observed during K2 Campaign 15 with the Kepler extended mission that appears to exhibit 28 transit-like events over the course of the 87-day observation. The unusual aspect of these dips, all but two of which have depths of 200 ± 80 ppm, is that they exhibit no periodicity, and their arrival times could just as well have been produced by a random number generator. We show that no more than four of the events can be part of a periodic sequence. We have done a number of data quality tests to ascertain that these dips are of astrophysical origin, and while we cannot be absolutely certain that this is so, they have all the hallmarks of astrophysical variability on one of two possible host stars (a likely bound pair) in the photometric aperture. We explore a number of ideas for the origin of these dips, including actual planet transits due to multiple or dust emitting planets, anomalously large TTVs, S- and P-type transits in binary systems, a collection of dust-emitting asteroids, ‘dipper-star’ activity, and short-lived starspots. All transit scenarios that we have been able to conjure up appear to fail, while the intrinsic stellar variability hypothesis would be novel and untested.

S. Rappaport↗
NASA NTRS2020

Microwave Power Detection With Voltage-Gated Graphene

Commercially available, chemical vapor deposition grown, graphene has been used to realizevoltage-gate tunable, microwave power detectors. Corbino disc structures with chrome/gold contacts havebeen fabricated on top of graphene deposited on P-type silicon substrates with silicon dioxide gate oxides.Devices of varying sizes were used to detect a 433.92 MHz signal. These test structures exhibited a peak power detection sensitivity of 3.25 mV/mW at 292 K and 5.43 mV/mW at 80 K. The improved graphene detectors exceed the sensitivity of previously reported graphene detectors, 0.86 mV/mW, as well as previously explored carbon nanotube bolometers, 0.36 mV/mW

Michael R. Gasper↗
NASA NTRS2022

InAs/InAsSb Type-II Stained Layer Superlattice Infrared Detectors and Focal Plane Arrays

We explore long wavelength InAs/InAsSb superlattice complementary barrier infrared detectors that contain p-type absorber layers for quantum efficiency enhancement. We also discuss type-II superlattice infrared detector technology for NASA Earth Science applications, including LWIR FPAs for land imaging, and MWIR FPAs for CubeSat hyperspectral imaging.

Pagano, Thomas S.↗
NASA NTRS2022

Progress in InAs/InAsSb Superlattice Barrier Infrared Detectors

The InAs/InAsSb (Gallium-free) type-II strained-layer superlattice (T2SLS) has emerged in recent years as a viable infrared detector material. In particular, mid-wavelength InAs/InAsSb T2SLS focal plane array (FPA) based on the nBn detector architecture exhibits good operating characteristics at 160 K, demonstrating a considerably operating temperature advantage over InSb FPAs. In the long and very long cutoff wavelengths, InAs/InAsSb T2SLS detectors with n-type absorbers are limited in their attainable quantum efficiency (QE) due to shorter hole diffusion lengths and relatively modest absorption coefficients. We have explored long and very long wavelength InAs/InAsSb T2SLS complementary barrier infrared detectors (CBIRDs) that contain p-type absorber layers in order to take advantage of the longer electron diffusion length for QE enhancement. We also discuss recent development of the InAs/InAsSb T2SLS infrared detectors at the Jet Propulsion Laboratory for NASA Earth Science applications, including long-wavelength infrared FPAs for land imaging, and mid-wavelength infrared FPAs for CubeSat hyperspectral imaging.

Pagano, Thomas S.↗
DOE OSTI2024

Optical Modeling of Polysilicon: TOPCon PV

Determine how film thickness changes with different deposition methods. Analyze relationship between film thickness and optical constants. The deposition rate of intrinsic polysilicon is higher during initial deposition then begins to slow down as deposition time increases. Longer depositions of polysilicon are more crystalline in structure than shorter depositions. N-type doping of polysilicon is more crystalline in structure than p-type doping, despite similar film thicknesses.

Bruggeman effective media approximation↗
DOE OSTI2024

From Design to Device: Challenges and Opportunities in Computational Discovery of p -Type Transparent Conductors

A high-performance p -type transparent conductor (TC) does not yet exist but could lead to advances in a wide range of optoelectronic applications and enable new architectures for, e.g., next-generation photovoltaic (PV) devices. High-throughput computational material screenings have been a promising approach to filter databases and identify new p -type TC candidates and some of these predictions have been experimentally validated. However, most of these predicted candidates do not have experimentally achieved properties on par with n -type TCs used in solar cells and therefore have not yet been used in commercial devices. Thus, there is still a significant divide between transforming predictions into results that are actually achievable in the laboratory and an even greater lag in scaling predicted materials into functional devices. In this perspective, we outline some of the major disconnects in this materials discovery process—from scaling computational predictions into synthesizable crystals and thin films in the laboratory to scaling laboratory-grown films into real-world solar devices—and share insights to inform future strategies for TC discovery and design. Published by the American Physical Society 2024

14 SOLAR ENERGY↗
DOE OSTI2025

Hierarchical Hybrid Multifunctional Materials through Interface Engineering

This project focuses on the development of stimuli-responsive hybrid multifunctional materials. We place emphasis on the design, synthesis, structural characterization, evaluation of functional properties (electronic, thermal and optical) of several (1-x)Cu 2 Se/(x)WBGS hierarchical bulk composites between Cu 2 Se, a narrow band gap semiconductor (NBGS), with a range of wider band gap semiconductors (WBGS) such as CuMSe 2 (M = Al, Ga, In, Fe, Cr) and Cu 4 TiSe 4 . Cu2Se is a well-studied NBGS with excellent thermoelectric properties (high electrical conductivity, large thermopower, etc.) while CuMSe 2 and Cu 4 TiSe 4 are high performance solar absorber materials (large band gap, large absorption coefficient, etc.). Our primary objectives are (i) to demonstrate the ability to integrate dissimilar functional properties such as large optical absorption coefficient and high electronic conductivity, within (1-x)Cu 2 Se/(x)WBGS composite; and (ii) to establish the correlation between the hierarchical structural entanglement of Cu 2 Se with WBGS (CuMSe 2 or Cu 4 TiSe 4 ) phase, the interactions between native electronic defects within the coexisting phases in the resulting (1-x)Cu 2 Se/(x)WBGS bulk composites , and the impacts on their electronic conductivity, thermal transport and optical properties.

36 MATERIALS SCIENCE↗
NASA NTRS1997

Skutterudites: An Update

Explore the source record for details and available documents.

skutterudite crystal structure ZT values p-type co↗