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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Materials Data on Rb(In3Au2)2 by Materials Project

Rb(Au2In3)2 crystallizes in the hexagonal P-6m2 space group. The structure is three-dimensional. Rb is bonded to six equivalent Au and six equivalent In atoms to form face-sharing RbIn6Au6 cuboctahedra. All Rb–Au bond lengths are 3.74 Å. All Rb–In bond lengths are 3.65 Å. There are two inequivalent Au sites. In the first Au site, Au is bonded in a 6-coordinate geometry to two equivalent Rb and six In atoms. There are two shorter (2.91 Å) and four longer (2.94 Å) Au–In bond lengths. In the second Au site, Au is bonded in a 9-coordinate geometry to nine In atoms. There are three shorter (2.90 Å) and six longer (3.00 Å) Au–In bond lengths. There are two inequivalent In sites. In the first In site, In is bonded in a 5-coordinate geometry to five Au atoms. In the second In site, In is bonded in a 4-coordinate geometry to two equivalent Rb and four Au atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Structures and Magnetic Properties of K 2 Pd 4 U 6 S 17 , K 2 Pt 4 U 6 S 17 , Rb 2 Pt 4 U 6 S 17 , and Cs 2 Pt 4 U 6 S 17 Synthesized Using the Boron–Chalcogen Mixture Method

A series of A 2 M 4 U 6 S 17 (A = Alkali metal, M = Pd or Pt) compounds, specifically K 2 Pd 4 U 6 S 17 , K 2 Pt 4 U 6 S 17 , Rb 2 Pt 4 U 6 S 17 , and Cs 2 Pt 4 U 6 S 17 , were synthesized using the combined Boron-Chalcogen Mixture (BCM) and molten flux crystal growth methods. The formation of the Rb- and Cs- containing analogues resulted from the in-situ alkali polysulfide flux formation formed from the alkali carbonates. The successful synthesis of single crystals of the title compounds allowed for their structural characterization by single crystal X-ray diffraction. The structure determination revealed disorder of the alkali cations in Rb 2 Pt 4 U 6 S 17 , and Cs 2 Pt 4 U 6 S 17 , while the potassium cations in K 2 Pd 4 U 6 S 17 and K 2 Pt 4 U 6 S 17 were fully ordered. Here, magnetic measurements were performed on samples of K 2 Pt 4 U 6 S 17 , Rb 2 Pt 4 U 6 S 17 , and Cs 2 Pt 4 U 6 S 17 that contained small amounts of paramagnetic β-US 2 and diamagnetic PtS. Antiferromagnetic order is observed at T N = 9.1 K for K 2 Pt 4 U 6 S 17 . No long-range magnetic order was observed for Rb 2 Pt 4 U 6 S 17 and Cs 2 Pt 4 U 6 S 17 . Uranium moments of 2.5, 2.6, and 2.6 μB were measured for K 2 Pt 4 U 6 S 17 , Rb 2 Pt 4 U 6 S 17 , and Cs 2 Pt 4 U 6 S 17 , respectively.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2025

In Situ Observation of Ion Migration in a Ferroelectric Ionic Conductor Rb-KTP during Thermal Annealing

Ion exchange in Rb-doped KTiOPO 4 has facilitated significant advancements in ferroelectric domain engineering, yet understanding the underlying mechanisms remains in its infancy. We perform time-of-flight secondary ion mass spectrometry analysis on multiple periodically ion-exchanged and periodically poled Rb-doped KTiOPO 4 samples under different temperatures and annealing durations. The results are compared between annealing in air, which involved ex situ annealing before periodic poling, and vacuum annealing conducted in situ after periodic poling. The Rb + diffusion profile after periodic ion exchange forms a tooth-shaped pattern. We show that in situ annealing causes a surface pinning effect on the nonpolar face, limiting Rb + migration along the polar axis at the surface. Once the pinned layer is removed through milling, the underlying Rb + diffusion is distinctively different from the surface. Additionally, the rate of Rb + diffusion during in situ annealing is linear, while the periodic domain structures remain stable after annealing. These results contribute to understanding the ionic diffusion process in a ferroelectric ionic conductor and using ion exchange to tailor the linear and nonlinear properties of KTiOPO 4 .

36 MATERIALS SCIENCE↗
NASA NTRS2012

Derivation of Apollo 14 High-Al Basalts at Discrete Times: Rb-Sr Isotopic Constraints

Pristine Apollo 14 (A-14) high-Al basalts represent the oldest volcanic deposits returned from the Moon [1,2] and are relatively enriched in Al2O3 (>11 wt%) compared to other mare basalts (7-11 wt%). Literature Rb-Sr isotopic data suggest there are at least three different eruption episodes for the A-14 high-Al basalts spanning the age range approx.4.3 Ga to approx.3.95 Ga [1,3]. Therefore, the high-Al basalts may record lunar mantle evolution between the formation of lunar crust (approx.4.4 Ga) and the main basin-filling mare volcanism (<3.85 Ga) [4]. The high-Al basalts were originally classified into five compositional groups [5,6], and then regrouped into three with a possible fourth comprising 14072 based on the whole-rock incompatible trace element (ITE) ratios and Rb-Sr radiometric ages [7]. However, Rb-Sr ages of these basalts from different laboratories may not be consistent with each other because of the use of different 87Rb decay constants [8] and different isochron derivation methods over the last four decades. This study involved a literature search for Rb-Sr isotopic data previously reported for the high-Al basalts. With the re-calculated Rb-Sr radiometric ages, eruption episodes of A-14 high-Al basalts were determined, and their petrogenesis was investigated in light of the "new" Rb-Sr isotopic data and published trace element abundances of these basalts.

Hui. Hejiu↗
DOE OSTI2020

Materials Data on Rb(CO)2 by Materials Project

Rb(CO)2 crystallizes in the monoclinic C2/m space group. The structure is two-dimensional and consists of two Rb(CO)2 sheets oriented in the (1, 0, 0) direction. Rb is bonded in a 6-coordinate geometry to six equivalent O atoms. There are a spread of Rb–O bond distances ranging from 2.90–3.06 Å. C is bonded in a distorted single-bond geometry to one O atom. The C–O bond length is 1.27 Å. O is bonded in a distorted single-bond geometry to three equivalent Rb and one C atom.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb(CuO5)2 by Materials Project

Rb(CuO5)2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Rb is bonded in a 6-coordinate geometry to six O atoms. There are two shorter (2.81 Å) and four longer (3.04 Å) Rb–O bond lengths. Cu is bonded in a distorted square co-planar geometry to six O atoms. There are a spread of Cu–O bond distances ranging from 1.81–2.61 Å. There are four inequivalent O sites. In the first O site, O is bonded in a distorted single-bond geometry to one Rb, one Cu, and one O atom. The O–O bond length is 1.39 Å. In the second O site, O is bonded in a bent 120 degrees geometry to two equivalent O atoms. In the third O site, O is bonded in a distorted trigonal non-coplanar geometry to two equivalent Cu and one O atom. The O–O bond length is 1.25 Å. In the fourth O site, O is bonded in a distorted bent 120 degrees geometry to one Rb and two equivalent Cu atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb by Materials Project

Rb is Copper structured and crystallizes in the cubic Fm-3m space group. The structure is three-dimensional. Rb is bonded to twelve equivalent Rb atoms to form a mixture of corner, edge, and face-sharing RbRb12 cuboctahedra. All Rb–Rb bond lengths are 5.05 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb by Materials Project

Rb is Hg_xSn-like structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Rb is bonded to eight equivalent Rb atoms to form a mixture of corner and edge-sharing RbRb8 hexagonal bipyramids. There are a spread of Rb–Rb bond distances ranging from 4.76–4.88 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb by Materials Project

Rb is Magnesium structured and crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Rb is bonded to twelve equivalent Rb atoms to form a mixture of face, edge, and corner-sharing RbRb12 cuboctahedra. There are six shorter (5.03 Å) and six longer (5.05 Å) Rb–Rb bond lengths.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb by Materials Project

Rb is Magnesium structured and crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. Rb is bonded to twelve equivalent Rb atoms to form a mixture of edge, face, and corner-sharing RbRb12 cuboctahedra. There are a spread of Rb–Rb bond distances ranging from 4.99–5.11 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb by Materials Project

Rb crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. Rb is bonded to seven equivalent Rb atoms to form a mixture of distorted edge and corner-sharing RbRb7 pentagonal bipyramids. There are a spread of Rb–Rb bond distances ranging from 4.61–4.98 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Rb by Materials Project

Rb is alpha-like structured and crystallizes in the orthorhombic Fddd space group. The structure is three-dimensional. Rb is bonded in a distorted hexagonal planar geometry to six equivalent Rb atoms. There are a spread of Rb–Rb bond distances ranging from 4.58–4.97 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Low Temperature Water-Gas Shift: Enhancing Stability through Optimizing Rb Loading on Pt/ZrO 2

Recent studies have shown that appropriate levels of alkali promotion can significantly improve the rate of low-temperature water gas shift (LT-WGS) on a range of catalysts. At sufficient loadings, the alkali metal can weaken the formate C–H bond and promote formate dehydrogenation, which is the proposed rate determining step in the formate associative mechanism. In a continuation of these studies, the effect of Rb promotion on Pt/ZrO 2 is examined herein. Pt/ZrO 2 catalysts were prepared with several different Rb loadings and characterized using temperature programmed reduction mass spectrometry (TPR-MS), temperature programmed desorption (TPD), diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS), an X-ray absorption near edge spectroscopy (XANES) difference procedure, extended X-ray absorption fine structure spectroscopy (EXAFS) fitting, TPR-EXAFS/XANES, and reactor testing. At loadings of 2.79% Rb or higher, a significant shift was seen in the formate ν(CH) band. The results showed that a Rb loading of 4.65%, significantly improves the rate of formate decomposition in the presence of steam via weakening the formate C–H bond. However, excessive rubidium loading led to the increase in stability of a second intermediate, carbonate and inhibited hydrogen transfer reactions on Pt through surface blocking and accelerated agglomeration during catalyst activation. Optimal catalytic performance was achieved with loadings in the range of 0.55–0.93% Rb, where the catalyst maintained high activity and exhibited higher stability in comparison with the unpromoted catalyst.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2021

Physical Properties of Candidate X-ray Detector Material Rb 4 Ag 2 BiBr 9

Recently, metal halide perovskites have emerged as promising semiconductor candidates for sensitive X-ray photon detection due to their suitable band gap energies, excellent charge transport properties, and low material cost afforded by their low-temperature solution-processing preparation. Furthermore, we report an improved methodology for single crystal growth and thermal and electrical properties of a two-dimensional (2D) layered halide material Rb 4 Ag 2 BiBr 9 , which has been identified as a potential candidate for X-ray radiation detection applications. The measured heat capacity for Rb 4 Ag 2 BiBr 9 implies that there are no structural phase transitions upon cooling. Temperature dependence of thermal transport measurements further suggests remarkably low thermal conductivities of Rb 4 Ag 2 BiBr 9 that are comparable to the lowest reported in literature. The bulk crystal resistivity is determined to be 2.59 × 10 9 Ω·cm from the current–voltage (I–V) curve. Density of trap states is estimated to be ~10 10 cm –3 using the space-charge-limited-current measurements. The fabricated Rb 4 Ag 2 BiBr 9 -based X-ray detector shows good operational stability with no apparent current drift, which may be ascribed to the 2D crystal structure of Rb 4 Ag 2 BiBr 9 . Finally, by varying the X-ray tube current to change the corresponding dose rate, the Rb4Ag2BiBr9 X-ray detector sensitivity is determined to be 222.03 μC Gy –1 cm –2 (at an electric field of E = 24 V/mm).

36 MATERIALS SCIENCE↗
DOE OSTI2021

Promoting the Selectivity of Pt/m-ZrO 2 Ethanol Steam Reforming Catalysts with K and Rb Dopants

The ethanol steam reforming reaction (ESR) was investigated on unpromoted and potassium- and rubidium-promoted monoclinic zirconia-supported platinum (Pt/m-ZrO 2 ) catalysts. Evidence from in situ diffuse reflectance infrared Fourier transform spectroscopy (DRIFTS) characterization indicates that ethanol dissociates to ethoxy species, which undergo oxidative dehydrogenation to acetate followed by acetate decomposition. The acetate decomposition pathway depends on catalyst composition. The decarboxylation pathway tends to produce higher overall hydrogen selectivity and is the most favored route at high alkali loading (2.55 wt.% K and higher or 4.25 wt.% Rb and higher). On the other hand, decarbonylation is a significant route for the undoped catalyst or when a low alkali loading (e.g., 0.85% K or 0.93% Rb) is used, thus lowering the overall H 2 selectivity of the process. Results of in situ DRIFTS and the temperature-programmed reaction of ESR show that alkali doping promotes forward acetate decomposition while exposed metallic sites tend to facilitate decarbonylation. In previous work, 1.8 wt.% Na was found to hinder decarbonylation completely. Due to the fact that 1.8 wt.% Na is atomically equivalent to 3.1 wt.% K and 6.7 wt.% Rb, the results show that less K (2.55% K) or Rb (4.25% Rb) is needed to suppress decarbonylation; that is, more basic cations are more efficient promoters for improving the overall hydrogen selectivity of the ESR process.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS1982

Microchrons - The Rb-87/Sr-87 dating of microscopic samples

The present investigation is concerned with the extension of the Rb-Sr dating technique to microscopic samples of individual mineral grains as small as approximately 30 micrometers in size. The measurement of the isotopic composition and the relative number of atoms of Rb and Sr has presented difficulties because of the need to separate Rb from Sr due to the isobaric interference at mass 87. This separation is critical since the changes in Sr-87/Sr-86 are directly related to the age of the sample. The approach used in the considered investigation is a modified version of the direct loading technique reported by Wasserburg et al. (1977). It is shown that measurements can be conducted of the Rb and Sr isotopic compositions and Rb/Sr atom ratios in microsamples containing 10 to the 11th to 10 to the 12th atoms of Sr. Rb-Sr model ages may prove to be of considerable importance in identifying and studying interplanetary dust particles.

Papanastassiou, D. A.↗
DOE OSTI2020

Materials Data on Rb(BH)6 by Materials Project

Rb(BH)6 crystallizes in the cubic Fm-3 space group. The structure is three-dimensional. Rb is bonded in a distorted q6 geometry to twelve equivalent H atoms. All Rb–H bond lengths are 3.00 Å. B is bonded in a single-bond geometry to one H atom. The B–H bond length is 1.20 Å. H is bonded in a single-bond geometry to two equivalent Rb and one B atom.

36 MATERIALS SCIENCE↗