Engineering Papers⌕ Search

SEARCH · Engineering Papers

Results for “small sample size”

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.

At least 1,027 records · Page 57
All sourcesNASA NTRSDOE OSTI
DOE OSTI2014

Influence of substrate miscut angle on surface morphology and luminescence properties of AlGaN

The influence of substrate miscut on Al{sub 0.5}Ga{sub 0.5} N layers was investigated using cathodoluminescence (CL) hyperspectral imaging and secondary electron imaging in an environmental scanning electron microscope. The samples were also characterized using atomic force microscopy and high resolution X-ray diffraction. It was found that small changes in substrate miscut have a strong influence on the morphology and luminescence properties of the AlGaN layers. Two different types are resolved. For low miscut angle, a crack-free morphology consisting of randomly sized domains is observed, between which there are notable shifts in the AlGaN near band edge emission energy. For high miscut angle, a morphology with step bunches and compositional inhomogeneities along the step bunches, evidenced by an additional CL peak along the step bunches, are observed.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2026

Evaluation of an event-driven 3FI ASIC for spectroscopic X-ray detection with synchrotron radiation

The novel design and evaluation on the NSLS-II beamline of the 3FI application-specific integrated circuit (ASIC) bump-bonded to a simple, planar, 2D segmented silicon sensor are presented. The ASIC was developed for full-field fluorescence spectral X-ray imaging (3FI). It is a small-scale prototype that features a square array of 32 × 32 pixels, and the size of the pixels is 100 µm × 100 µm. The ASIC was implemented in a 65 nm CMOS integrated circuit fabrication process. Each pixel incorporates a charge-sensitive amplifier, a shaping filter, a discriminator, a peak detector and a sample-and-hold circuit, allowing detection of events and storage of signal amplitudes. The system operates in a frameless event-driven readout mode, outputting analog values for threshold-triggered events, allowing high-speed multi-element X-ray fluorescence data acquisition. The 3FI ASIC achieves per-channel spectrometric performance at a power consumption of only 200 µW per pixel, with nearly all dissipation confined to the analog front-end. An energy resolution is measured at the level of 308 eV full width at half-maximum (FWHM) at 8.04 keV (Cu Kα), and 138 eV FWHM at 3.69 keV (Ca Kα). This per-pixel capability makes the prototype suitable for in situ trace element microanalysis in biological and environmental studies. Moreover, the frameless architecture of the detector is designed to address limitations of conventional X-ray fluorescence microscopy, which typically requires mechanical scanning, by enabling continuous high-throughput data acquisition in future full-field implementations.

47 OTHER INSTRUMENTATION↗
DOE OSTI2013

Magnetic and electrical properties of weakly doped manganese-deficient La{sub 1-x}Ca{sub x}Mn{sub 1-z}O{sub 3} manganites

Samples of La{sub 1-x}Ca{sub x}Mn{sub 1-z}O{sub 3+{delta}} (x = 0.05-0.15) with deficient manganese and excess oxygen {delta} do not pass into a metallic state and have low spin ordering temperatures T{sub C} at acceptor Mn{sup 4+} concentrations near the percolation threshold. These results are explained by carrier localization in clusters near cation vacancies. A break in the carrier transport chain Mn-O-Mn in the form of absent manganese favors cluster formation and decreases the double exchange energy and T{sub C} of the samples. Closeness to the percolation threshold results in strong (more than four orders of magnitude) changes in the electrical resistivity in a magnetic field. The changes in the cluster sizes with the temperature and the magnetic field that are determined from the magnetotransport properties are satisfactorily described in the model of phase separation into small-radius metallic droplets in a dielectric paramagnetic and an antiferromagnetic matrices.

36 MATERIALS SCIENCE↗
NASA NTRS2001

Biotechnology Approaches to Life Detection

The direct detection of organic biomarkers for living or fossil microbes on Mars by an in situ instrument is a worthy goal for future lander missions. Several new and innovative biotechnology approaches are being explored. Firstly we have proposed an instrument based on immunological reactions to specific antibodies to cause activation of fluorescent stains. Antibodies are raised or acquired to a variety of general and specific substances that might be in Mars soil. These antibodies are then combined with various fluorescent stains and applied to micron sized numbered spots on a small (2-3 cm) test plate where they become firmly attached after freeze drying. Using technology that has been developed for gene mining in DNA technology up to 10,000 tests per square inch can now be applied to a test plate. On Mars or the planet/moon of interest, a sample of soil from a trench or drill core is extracted with water and/or an organic solvent and ultrasonication and then applied to the test plate. Any substance, which has an antibody on the test plate, will react with its antibody and activate its fluorescent stain. At the moment a small UV light source will illuminate the test plate, which is observed with a small CCD camera, although other detection systems will be applied. The numbered spots that fluoresce indicate the presence of the tested-for substance, and the intensity indicates relative amounts. Furthermore with up to a thousand test plates available false positives and several variations of antibody can also be screened for. The entire instrument can be quite small and light, on the order of 10 cm in each dimension. A possible choice for light source may be small UV lasers at several wavelengths. Some of the wells or spots can contain simply standard fluorescent stains used to detect live cells, dead cells, DNA, etc. The stains in these spots may be directly activated, with no antibodies being necessary. The proposed system will look for three classes of biomarkers: those from extant life, such as DNA, those from extinct life such as hopanes, and those from organic compounds not necessarily associated with life such as PAHs, rocket exhaust contamination and other a/pre-biotic chemicals. Both monoclonal and polyclonal antibodies can be used. Monoclonal antibodies react with a very specific compound, but polyclonal antibodies may react to any of a whole family of compounds. Furthermore the technique of phage display to raise antibodies against classically non-antigenic molecules is also being considered. Additional information is contained in the original extended abstract.

Steele, Andrew↗
NASA NTRS2015

Final Results of Shuttle MMOD Impact Database

The Shuttle Hypervelocity Impact Database documents damage features on each Orbiter thought to be from micrometeoroids (MM) or orbital debris (OD). Data is divided into tables for crew module windows, payload bay door radiators and thermal protection systems along with other miscellaneous regions. The combined number of records in the database is nearly 3000. Each database record provides impact feature dimensions, location on the vehicle and relevant mission information. Additional detail on the type and size of particle that produced the damage site is provided when sampling data and definitive spectroscopic analysis results are available. Guidelines are described which were used in determining whether impact damage is from micrometeoroid or orbital debris impact based on the findings from scanning electron microscopy chemical analysis. Relationships assumed when converting from observed feature sizes in different shuttle materials to particle sizes will be presented. A small number of significant impacts on the windows, radiators and wing leading edge will be highlighted and discussed in detail, including the hypervelocity impact testing performed to estimate particle sizes that produced the damage.

Hyde, J. L.↗
DOE OSTI2013

Synthesis, Characterization (Molecular-Morphological) and Theoretical Morphology Predictions of Poly(cyclohexadiene) Containing Linear Triblock Terpolymers

The synthesis via anionic polymerization of six linear triblock terpolymers with various sequences of blocks such as PS (polystyrene), PB (polybutadiene), PI (polyisoprene) and PCHD (poly(1,3-cyclohexadiene)) is reported. The synthesis of the terpolymers was accomplished by the use of anionic polymerization with high vacuum techniques and sequential monomer addition. Molecular characterization of the samples was performed via size exclusion chromatography and membrane osmometry to measure polydispersity indices and the number-average molecular weights, respectively. Proton nuclear magnetic resonance spectroscopy was adopted to verify the type of microstructure for the polydienes as well as to calculate the molar composition. Structural characterization was performed via transmission electron microscopy and small angle X-ray scattering and several morphologies were observed including one which has not been reported previously. Real-space self-consistent field theory (SCFT) without a priori knowledge about the symmetry of the periodic structures was used to elucidate the thermodynamics of the synthesized triblock copolymers.

Kumar, Rajeev↗
DOE OSTI2018

Predicting Effective Diffusion Coefficients in Mudrocks Using a Fractal Model and Small-Angle Neutron Scattering Measurements

The determination of effective diffusion coefficients of gases or solutes in the water–saturated pore space of mudrocks is time consuming and technically challenging. Yet, reliable values of effective diffusion coefficients are important to predict migration of hydrocarbon gases in unconventional reservoirs, dissipation of (explosive) gases through clay barriers in radioactive waste repositories, mineral alteration of seals to geological CO 2 storage reservoirs and contaminant migration through aquitards. In this study, small angle and very small angle neutron scattering techniques have been utilized to determine a range of transport properties in mudrocks, including porosity, pore size distributions and surface and volume fractal dimensions of pores and grains, from which diffusive transport parameters can be estimated. Using a fractal model derived from Archie's Law, we calculate effective diffusion coefficients from these parameters and compare them to laboratory–derived effective diffusion coefficients for CO 2 , H 2 , CH 4 and HTO on either the same or related mudrock samples. The samples include Opalinus Shale from the underground laboratory in Mont Terri, Switzerland; Boom Clay from a core drilled in Mol, Belgium and a marine claystone cored in Utah, USA. The predicted values were compared to laboratory diffusion measurements. The measured and modeled diffusion coefficients show good agreement, differing generally by less than factor 5. Furthermore, neutron or X–ray scattering analysis is therefore proposed as a novel method for fast, accurate estimation of effective diffusion coefficients in mudrocks, together with simultaneous measurement of multiple transport parameters including porosity, pore size distributions and surface areas, important for (reactive) transport modelling.

58 GEOSCIENCES↗
DOE OSTI2011

Changes in intracortical microporosities induced by pharmaceutical treatment of osteoporosis as detected by high resolution micro-CT

Bone's microporosities play important biologic and mechanical roles. Here, we quantified 3D changes in cortical osteocyte-lacunae and other small porosities induced by estrogen withdrawal and two different osteoporosistreatments. Unlike 2D measurements, these data collected via synchrotron radiation-based {mu}CT describe the size and 3D spatial distribution of a large number of porous structures. Six-month old female Sprague-Dawley rats were separated into four groups of age-matched controls, untreated OVX, OVX treated with PTH, and OVX treated with Alendronate (ALN). Intracortical microporosity of the medial quadrant of the femoral diaphysis was quantified at endosteal, intracortical, and periosteal regions of the samples, allowing the quantification of osteocyte lacunae that were formed primarily before versus after the start of treatment. Across the overall thickness of the medial cortex, lacunar volume fraction (Lc.V/TV) was significantly lower in ALN treated rats compared to PTH. In the endosteal region, average osteocyte lacunar volume (< Lc.V >) of untreated OVX rats was significantly lower than in age-matched controls, indicating a decrease in osteocyte lacunar size in bone formed on the endosteal surface after estrogen withdrawal. The effect of treatment (OVX, ALN, PTH) on the number of lacunae per tissue volume (Lc.N/TV) was dependent on the specific location within the cortex (endosteal, intracortical, periosteal). In both the endosteal and intracortical regions, Lc.N/TV was significantly lower in ALN than in untreated OVX, suggesting a site-specific effect in osteocyte lacuna density with ALN treatment. There also were a significantly greater number of small pores (5-100 {micro}m{sup 3} in volume) in the endosteal region for PTH compared to ALN. The mechanical impact of this altered microporosity structure is unknown, but might serve to enhance, rather than deteriorate bone strength with PTH treatment, as smaller osteocyte lacunae may be better able to absorb shear forces than larger lacunae. Together, these data demonstrate that current treatments of osteoporosis can alter the number, size, and distribution of microporosities in cortical rat lamellar bone.

59 BASIC BIOLOGICAL SCIENCES↗
DOE OSTI2025

Role of Intersections in Fracture Connectivity

Networks of intersecting fractures often provide the flow paths through subsurface reservoirs. Assessing network connectivity is challenging because fracture intersections compose a vanishingly small fraction of the network void volume. In this paper, motivated by 3D X-ray imaging of the simplest element of fracture network, that is, two orthogonal fractures, we perform a percolation and finite-size scaling analysis to study the connectivity provided by fracture intersections. The conditions when an intersection enhances connectivity across a sample depend on spatial correlations in the fracture aperture distributions, on the stress state, and on the direction of flow. Here we consider three flow directions: (a) across intersections, (b) parallel to intersections and (c) around corners. For (a), intersections provide minimal enhancement of connectivity because they contribute little additional void area. For (b), intersections increase the probability of a connected path near threshold by enabling 3D connected pathways that are not possible in parallel fractures. Flow around corners, (c), is fundamentally the result of the intersection connecting two fractures in series and spatial correlations are broken around corners, suppressing the connectivity relative to (a). When the connected fractures are stressed equally, a joint percolation threshold emerges that continues to have scale invariance. However, when the fractures are stressed unequally, the system has mixed percolation without clearly defined percolation thresholds. In all cases, percolation probabilities are found to be scale dependent which has important consequences for the connectivity of larger fracture networks composed of the fundamental element studied here.

02 PETROLEUM↗
DOE OSTI2016

Measurement of Size-dependent Dynamic Shape Factors of Quartz Particles in Two Flow Regimes

Understanding and modeling the behavior of quartz dust particles, commonly found in the atmosphere, requires knowledge of many relevant particles properties, including particle shape. This study uses a single particle mass spectrometer, a differential mobility analyzer, and an aerosol particle mass analyzer to measure quartz aerosol particles mobility, aerodynamic, and volume equivalent diameters, mass, composition, effective density, and dynamic shape factor as a function of particle size, in both the free molecular and transition flow regimes. The results clearly demonstrate that dynamic shape factors can vary significantly as a function of particle size. For the quartz samples studied here, the dynamic shape factors increase with size, indicating that larger particles are significantly more aspherical than smaller particles. In addition, dynamic shape factors measured in the free-molecular (χv) and transition (χt) flow regimes can be significantly different, and these differences vary with the size of the quartz particles. For quartz, χv of small (d < 200 nm) particles is 1.25, while χv of larger particles (d ~ 440 nm) is 1.6, with a continuously increasing trend with particle size. In contrast χt, of small particles starts at 1.1 increasing slowly to 1.34 for 550 nm diameter particles. The multidimensional particle characterization approach used here goes beyond determination of average properties for each size, to provide additional information about how the particle dynamic shape factor may vary even for particles with the same mass and volume equivalent diameter.

Environmental Molecular Sciences Laboratory↗
DOE OSTI2015

Density functional theory calculations of magnetocrystalline anisotropy energies for (Fe 1-x Co x ) 2 B

We present and discuss density functional theory calculations of magnetic properties of the family of ferromagnetic compounds, (Fe 1-x Co x ) 2 B, focusing specifically on the magnetocrystalline anisotropy energy (MAE). Using periodic supercells of various sizes (up to 96 atoms), it is shown that the general qualitative features of the composition dependence of the MAE is in agreement with experimental findings, while our predicted magnitudes are larger than those of experiment. We find that the use of small supercells (6 and 12-atom) favors larger MAE values relative to a statistical sample of configurations constructed with 96-atom supercells. As a result, the effect of lattice relaxations is shown to be small. Calculations of the Curie temperature for this alloy are also presented.

36 MATERIALS SCIENCE↗
DOE OSTI2016

Strong Lyα emission in the proximate damped LYα absorption trough toward the quasar SDSS J095253.83+011422.0

SDSS J095253.83+011422.0 (J0952+0114) was reported by Hall et al. as an exotic quasar at z{sub em} = 3.020. In contrast to prominent broad metal-line emission with FWHM ∼ 9000 km s{sup −1}, only a narrow Lyα emission line is present with FWHM ∼ 1000 km s{sup −1}. The absence of a broad Lyα emission line has been a mystery for more than a decade. In this paper, we demonstrate that this absence is due to dark proximate damped Lyα absorption (PDLA) at z{sub abs} = 3.010 by identifying associated Lyman absorption line series from the damped Lyβ up to Ly9, as well as the Lyman limit absorption edge. The PDLA cloud has a column density of logN{sub HI}(cm{sup −2})=21.8±0.2, a metallicity of [Zn/H] > −1.0, and a spatial extent exceeding the narrow emission line region (NELR) of the quasar. With a luminosity of L{sub Lyα}∼10{sup 45} erg s{sup −1}, the residual Lyα emission superposed on the PDLA trough is two orders of magnitude stronger than found by previous reports. This is best explained as re-radiated photons arising from the quasar outflowing gas on a larger scale than in the NELR. The PDLA here, acting like a natural coronagraph, provides us with valuable insight into the illuminated gases in the vicinity of the quasar, which are usually hard to resolve due to their small size and the “seeing fuzz” of bright quasars. Notably, J0952+0114 analogs might be easily omitted in the spectroscopic surveys of DLAs and PDLAs because their damped Lyα troughs can be fully filled by additional strong Lyα emissions. Our preliminary survey shows that such systems are not very rare. They could potentially be a unique sample for probing strong quasar feedback phenomena in the early universe.

79 ASTRONOMY AND ASTROPHYSICS↗
NASA NTRS2009

Sm-Nd, Rb-Sr, and Mn-Cr Ages of Yamato 74013

Yamato 74013 is one of 29 paired diogenites having granoblastic textures. The Ar-39 - Ar-40 age of Y-74097 is approximately 1100 Ma. Rb-Sr and Sm-Nd analyses of Y-74013, -74037, -74097, and -74136 suggested that multiple young metamorphic events disturbed their isotopic systems. Masuda et al. reported that REE abundances were heterogeneous even within the same sample (Y-74010) for sample sizes less than approximately 2 g. Both they and Nyquist et al. reported data for some samples showing significant LREE enrichment. In addition to its granoblastic texture, Y-74013 is characterized by large, isolated clots of chromite up to 5 mm in diameter. Takeda et al. suggested that these diogenites originally represented a single or very small number of coarse orthopyroxene crystals that were recrystallized by shock processes. They further suggested that initial crystallization may have occurred very early within the deep crust of the HED parent body. Here we report the chronology of Y-74013 as recorded in chronometers based on long-lived Rb-87 and Sm-147, intermediate- lived Sm-146, and short-lived Mn-53.

Nyquist, L. E.↗
NASA NTRS2013

The Mission Accessible Near-Earth Objects Survey (MANOS)

Near‐Earth objects (NEOs) are essential to understanding the origin of the Solar System. Their relatively small sizes and complex dynamical histories make them excellent laboratories for studying ongoing Solar System processes. The proximity of NEOs to Earth makes them favorable targets for space missions. In addition, knowledge of their physical properties is crucial for impact hazard assessment. However, in spite of their importance to science, exploration, and planetary defense, a representative sample of physical characteristics for sub‐km NEOs does not exist. Here we present the Mission Accessible Near‐Earth Objects Survey (MANOS), a multi‐year survey of subkm NEOs that will provide a large, uniform catalog of physical properties (light curves + colors + spectra + astrometry), representing a 100‐fold increase over the current level of NEO knowledge within this size range. This survey will ultimately characterize more than 300 mission‐accessible NEOs across the visible and near‐infrared ranges using telescopes in both the northern and southern hemispheres. MANOS has been awarded 24 nights per semester for the next three years on NOAO facilities including Gemini North and South, the Kitt Peak Mayall 4m, and the SOAR 4m. Additional telescopic assets available to our team include facilities at Lowell Observatory, the University of Hawaii 2.2m, NASA's IRTF, and the Magellan 6.5m telescopes. Our focus on sub‐km sizes and mission accessibility (dv < 7 km/s) is a novel approach to physical characterization studies and is possible through a regular cadence of observations designed to access newly discovered NEOs within days or weeks of first detection before they fade beyond observational limits. The resulting comprehensive catalog will inform global properties of the NEO population, advance scientific understanding of NEOs, produce essential data for robotic and spacecraft exploration, and develop a critical knowledge base to address the risk of NEO impacts. We intend to conduct this survey with complete transparency, publicly sharing our target lists and survey progress. We invite collaborative uses for these data as a way to broaden the scientific impact of this survey.

Abell, Paul↗
NASA NTRS2011

Simulation and Characterization of a Miniaturized Scanning Electron Microscope

A miniaturized Scanning Electron Microscope (mSEM) for in-situ lunar investigations is being developed at NASA Marshall Space Flight Center with colleagues from the University of Alabama in Huntsville (UAH), Advanced Research Systems (ARS), the University of Tennessee in Knoxville (UTK) and Case Western Reserve University (CWRU). This effort focuses on the characterization of individual components of the mSEM and simulation of the complete system. SEMs can provide information on the size, shape, morphology and chemical composition of lunar regolith. Understanding these basic properties will allow us to better estimate the challenges associated with In-Situ Resource Utilization and to improve our basic science knowledge of the lunar surface (either precluding the need for sample return or allowing differentiation of unique samples to be returned to Earth.) The main components of the mSEM prototype includes: a cold field emission electron gun (CFEG), focusing lens, deflection/scanning system and backscatter electron detector. Of these, the electron gun development is of particular importance as it dictates much of the design of the remaining components. A CFEG was chosen for use with the lunar mSEM as its emission does not depend on heating of the tungsten emitter (lower power), it offers a long operation lifetime, is orders of magnitude brighter than tungsten hairpin guns, has a small source size and exhibits low beam energy spread.

Gaskin, Jessica A.↗
DOE OSTI2017

Report on the completion of the procurement of the first heat of Alloy 709

This report provides details on the completion of the procurement of the first commercial-sized heat of Alloy 709. The report is a Level 3 deliverable in FY17 (M3AT- 17OR1602053), under the Work Package AT-17OR160205, “Advanced Alloy Development” performed by Oak Ridge National Laboratory, as part of Advanced Structural Materials Program for the Advanced Reactor Technologies (ART). This work project supports the fabrication scale up effort for Alloy 709 that was started in FY16. The effort culminated in the placement of a Purchase Order in August 2016 with a commercial vendor to melt an Alloy 709 heat using industrial melt practice. Four ingots, totaling about 45,000 lb, had been bottom-poured from the melt in September 2016. Two of the ingots were hot rolled into 1.2”x60”x155” and 1.1”x60”x100” plates using standard hot rolling process in FY17. Some small test pieces were cut from the asrolled plates and sent to Argonne National Laboratory (ANL) for archival. The plates were then heat treated and surface pickled by the vendor. The plates were subsequently delivered to ANL and Oak Ridge National Laboratory (ORNL). Properties and microstructure screening were performed on these plates upon delivery in February 2017 at ANL. Several samples were cut from the as-rolled and heattreated plates and were analyzed for their microstructures, hardness values, grain sizes, and room temperature tensile properties. The results indicate that the scaled-up heat of Alloy 709 fabricated using commercial practice exhibit tensile properties that exceed the minimum values specified in the ASME Code Case for commercial heat of NF709. These plates will be used to support base metal testing for the 650°C, 100,000-h Alloy 709 Code Case development, for fabrication of weldments, and for the NEUP projects.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Tensile properties, strain rate sensitivity, and activation volume of additively manufactured 316L stainless steels [Tensile properties of 316L stainless steels made by laser powder-bed-fusion additive manufacturing]

The tensile properties of additively manufactured (AM) metals and alloys are among the most important variables that impact the potential applications of these materials. Here we examine and report on the tensile properties of AM 316L stainless steels fabricated by the laser powder-bed-fusion (L-PBF) technique, via twelve sets of optimized laser processing parameters that produce materials with density >98.8 ± 0.10%. A heterogeneous microstructure is observed in all L-PBF samples, including microscopic features such as dislocations, cellular walls, elemental segregations, local misorientations, impurities, precipitates, and a large fraction of low-angle grain boundaries (2-10°, ~40–60%). The derived average grain size defined by high-angle grain boundaries (>10°) is ~30–50 μm. Tensile testing reveals a yield strength ranging from 552 to 635 MPa and a tensile-elongation-to-failure (TEF) of 0.09–0.42 for directly-printed samples, whereas these values are 592–690 MPa and 0.29–0.50 for samples machined from the as-built rectangular thin plates. In all samples, we observe a variation of tensile yield strength within ~15% but not the TEF, suggesting marginal microstructural changes despite a wide range of laser processing parameters. The large scatter of TEF in directly-printed samples originates from the sensitivity of thin gauge geometry (~2 mm 2 cross-section area) to the built-in flaws. We measured a substantially higher strain rate sensitivity (m~0.02–0.03) of L-PBF 316L compared to the coarse-grained counterparts (~0.006), together with a small activation volume of ~20–30b3 (where b is the Burgers vector of 316L). In conclusion, these deformation kinetics parameters suggest that the tensile plasticity of L-PBF 316L is controlled by a much finer microstructural length scale than the measured grain size, consistent with the high strength and juxtaposed nano- to macro-structures seen in these materials. Strategies to optimize the tensile properties of AM materials are discussed.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Synthesis, Crystal and Electronic Structures, Nonlinear Optical Properties, and Magnetic Properties of Two Thiophosphates: KInP 2 S 7 and KCrP 2 S 7

Two thiophosphates, KInP 2 S 7 and KCrP 2 S 7 , were structurally characterized without investigating any optical properties. Herein in this work, KInP 2 S 7 and KCrP 2 S 7 were revisited to investigate their optical and magnetic properties, respectively. Pure polycrystalline samples and crystals of KInP 2 S 7 and KCrP 2 S 7 were grown by high temperature solid state reactions, where mm-sized crystals of KCrP 2 S 7 were collected. KCrP 2 S 7 is isostructural to KInP 2 S 7 , which features a layered structure. KInP 2 S 7 and KCrP 2 S 7 possess close relationship to the layered thiophosphate M 2 P 2 S 6 (M = Fe, Co, Zn, etc.). The bonding pictures of KInP 2 S 7 were studied using the electron localization function (ELF) coupled with crystal orbital Hamilton population (COHP) calculations. The intrinsically distorted [PS 4 ] tetrahedra and [InS 6 ] octahedra are made by strong covalent P-S interactions and ionic In-S interactions, respectively. Electronic structure analysis confirmed that the optical properties of KInP 2 S 7 are mainly contributed to by [PS 4 ] tetrahedra together with small amounts of the contributions coming from [InS 6 ] octahedra. Magnetic measurement on mm-sized crystals of KCrP 2 S 7 verified that there is an antiferromagnetic transition around 21 K, and the Cr atoms are trivalent. KInP 2 S 7 is predicated to be an indirect bandgap semiconductor of 2.38 eV, which is confirmed by the UV-Vis measurement of 2.4(1) eV. KInP 2 S 7 is not a type-I phase-matching material and exhibits moderate second harmonic generation (SHG) response (0.51 × AgGaS 2 , sample of particle size of 100 µm). The laser damage threshold (LDT) of KInP 2 S 7 is very high of 5.2 × AgGaS 2 . Bandgap engineering were undergone to enhance the SHG response of KInP 2 S 7 .

36 MATERIALS SCIENCE↗