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DOE OSTI2014

Nuclear Data Sheets for A=85

Evaluated experimental data are presented for 13 known nuclides of mass 85 (Zn, Ga, Ge, As, Se, Br, Kr, Rb, Sr, Y, Zr, Nb, Mo). Since the previous 1990 evaluation of A=85, {sup 85}Zn, {sup 85}Ga, {sup 85}Ge and {sup 85}nuclides are newly added here. Excited state data for {sup 85}Se, {sup 85}Zr have become available from radioactive decay and in–beam γ–ray studies. New and improved high–spin data are available for {sup 85}Br, {sup 85}Kr, {sup 85}Rb, {sup 85}Y, {sup 85}Nb and {sup 85}Mo. New direct and precise measurement of atomic masses of {sup 85}Ge, {sup 85}As, {sup 85}Se, {sup 85}Br, {sup 85}Rb, {sup 85}Zr, {sup 85}Nb and {sup 85}Mo have greatly improved the landscape of β decay–Q values and separation energies in this mass region. In spite of extensive experimental work on the isobaric nuclei of this mass chain several deficiencies remain. No excited states are known in {sup 85}Zn, {sup 85}Ga, {sup 85}As. Only a few excited state are assigned in {sup 85}Ge from {sup 85}Ga β– decay. From radioactivity studies, the decay schemes of {sup 85}Zn and {sup 85}Mo are not known, and those for {sup 85}Ga, {sup 85}Ge, {sup 85}As and 10.9–s isomer of {sup 85}Zr are incomplete. Level lifetimes are not known for excited states in {sup 85}Se, {sup 85}Br, {sup 85}Nb and {sup 85}Mo. The {sup 85}Tc nuclide has not been detected in fragmentation experiments at GANIL, alluding to its unbound nature for proton emission. The {sup 85}Kr, {sup 85}Rb, {sup 85}Sr, and {sup 85}Y nuclides remain the most extensively studied from many different reactions and decays. The evaluation of A=85 nuclides has been done after a span of 23 years, thus includes an extensive amount of new data for almost each nuclide. This work supersedes the data for A=85 nuclides presented in earlier full NDS publication by J. Tepel in 1980Te04 and a later one published in an update mode by H. Sievers in 1991Si01.

73 NUCLEAR PHYSICS AND RADIATION PHYSICS↗

DOE OSTI2015

Electrical and optical properties of molybdenum doped zinc oxide films prepared by reactive RF magnetron sputtering

Molybdenum doped zinc oxide (MZO) films were deposited on to glass substrates held at temperatures in the range from 303 to 673 K by reactive RF magnetron sputtering method. The chemical composition, crystallographic structure and surface morphology, electrical and optical properties of the films were determined. The films contained the molybdenum of 2.7 at. % in ZnO. The films deposited at 303 K were of X-ray amorphous. The films formed at 473 K were of nanocrystalline in nature with wurtzite structure. The crystallite size of the films was increased with the increase of substrate temperature. The optical transmittance of the films was in the visible range was 80–85%. The molybdenum (2.7 at %) doped zinc oxide films deposited at substrate temperature of 573 K were of nanocrystalline with electrical resistivity of 7.2×10{sup −3} Ωcm, optical transmittance of 85 %, optical band gap of 3.35 eV and figure of merit 30.6 Ω{sup −1}cm{sup −1}.

36 MATERIALS SCIENCE↗

DOE OSTI2019

Dual Protection Layer Strategy to Increase Photoelectrode–Catalyst Interfacial Stability: A Case Study on Black Silicon Photoelectrodes

Abstract Photoelectrode degradation under harsh solution conditions continues to be a major hurdle for long‐term operation and large‐scale implementation of solar fuel conversion. In this study, a dual‐layer TiO 2 protection strategy is presented to improve the interfacial durability between nanoporous black silicon and photocatalysts. Nanoporous silicon photocathodes decorated with catalysts are passivated twice, providing an intermediate TiO 2 layer between the substrate and catalyst and an additional TiO 2 layer on top of the catalysts. Atomic layer deposition of TiO 2 ensures uniform coverage of both the nanoporous silicon substrate and the catalysts. After 24 h of electrolysis at pH = 0.3, unprotected photocathodes layered with platinum and molybdenum sulfide retain only 30% and 20% of their photocurrent, respectively. At the same pH, photocathodes layered with TiO 2 experience an increase in photocurrent retention: 85% for platinum‐coated photocathodes and 91% for molybdenum sulfide–coated photocathodes. Under alkaline conditions, unprotected photocathodes experience a 95% loss in photocurrent within the first 4 h of electrolysis. In contrast, TiO 2 ‐protected photocathodes maintain 70% of their photocurrent during 12 h of electrolysis. This approach is quite general and may be employed as a protection strategy for a variety of photoabsorber–catalyst interfaces under both acidic and basic electrolyte conditions.

Yang, Fan↗

DOE OSTI2024

Simple separation of technetium from molybdenum for tracer isotope production

A procedure for the separation of technetium isotopes from bulk molybdenum was developed in nitric acid media. After irradiation of nat Mo foils, and dissolution in H 2 O 2 , the solution is acidified to 2 M HNO 3 , and anion exchange resin is used to separate technetium from molybdenum. The procedure is simple, requiring only basic laboratory equipment and, with a two-column separation, the technetium yield is high (~ 85%) with extremely high purity (< 0.1 ppm nat Mo). In conclusion, this is ideally suited for laboratory production of technetium tracer isotopes, particularly 95m Tc.

38 RADIATION CHEMISTRY, RADIOCHEMISTRY, AND NUCLEA↗

DOE OSTI2015

Facile synthesis of α-MoO{sub 3} nanorods with high sensitivity to CO and intrinsic sensing performance

Highlights: • α-MoO{sub 3} nanorods were synthesized by facile hydrothermal method at 85 °C for 1.5 h. • α-MoO{sub 3} nanorods exhibit the highest sensitivity of 239.6–40 ppm CO at 292 °C. • XPS and PL confirmed that the gas sensing arises from stoichiometric defect of α-MoO{sub 3}. • The sensing mechanism of α-MoO{sub 3} to CO was postulated from bulk defect of material. - Abstract: Orthorhombic molybdenum trioxide (α-MoO{sub 3}) nanorods with well-defined morphology and high crystalline have been synthesized by a facile and fast hydrothermal method under 85 °C for 1.5 h without employing surfactants or templates. The controlling of stirring time, thermostatic time and HNO{sub 3} amount is crucial for the growth of α-MoO{sub 3} nanorods. The morphology and structure of α-MoO{sub 3} were characterized by field emission scanning electron microscopy (FESEM) and X-ray diffraction (XRD). The obtained α-MoO{sub 3} nanorods as a novel sensing material exhibit high sensitivity, the highest response to 40 ppm CO is 239.6 at operating temperature of 292 °C. The intrinsic sensing performance arises from the non-stoichiometry of the α-MoO{sub 3} due to the presence of Mo{sup 5+} in MoO{sub 3} lattice, that is, the molecular formula of MoO{sub 3} should be expressed as MoO{sub 3−x} (x = 0.08), which has been confirmed by X-ray photoelectron spectroscopic (XPS) analysis and room temperature photoluminescence (PL). The sensing mechanism of α-MoO{sub 3} to CO was also discussed in terms of lattice oxygen in MoO{sub 3}.

77 NANOSCIENCE AND NANOTECHNOLOGY↗

DOE OSTI2023

Fuel cycle depletion validation and code-to-code verification studies for High Flux Isotope Reactor highly and low-enriched uranium fuel designs

Here, this paper documents fuel cycle depletion validation and code-to-code verification studies for the High Flux Isotope Reactor (HFIR) highly enriched uranium (HEU) and proposed low-enriched uranium (LEU) fuel designs. In support of HFIR’s world-leading performance, transport and depletion simulations are performed to ensure safe operations, design and qualify irradiation experiments, enhance core components and irradiation facilities, and design and characterize LEU fuel designs. Identifying well-validated, computationally efficient codes is required for the success of these efforts. The HFIR Controller, Shift, and VESTA codes were deployed to simulate HEU uranium–oxide dispersion fuel cycles at 85, 95, and 100 MW operations, as well as LEU fuel cycles operating at 95 MW with uranium–silicide dispersion and uranium–molybdenum monolithic alloy fuel forms. Excellent agreement between the codes and with experimentally obtained 235 U enrichment distributions provides increased confidence in the ability of these codes to model and simulate HFIR’s unique core design.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2016

Factors affecting eluation characteristics of sorption generators of technetium-99m

The influence of the adsorbed mass of molybdenum on the width of eluation profiles of generators and the patterns of molybdenum distribution in the amount of chromatographic columns by scanning them on the germanium-gallium detector using collimating device are studied. The boundary conditions under which the maximum value of {sup 99m}Tc yield from generators Y{sub e} = 1 are defined. After scanning the columns, it was found out that the degree of filling the columns with molybdenum Q and the value of its maximum adsorption depend naturally on the total weight of the adsorbed mass. In order to achieve the condition Y{sub e} = 1 the value of Q should be at least 85%.

07 ISOTOPE AND RADIATION SOURCES↗

DOE OSTI2019

Eutectoid Transformation in U10Mo Alloy: Effect of Deformation History and Homogenization Heat Treatment

In the United States, uranium 10 wt.% molybdenum (U10Mo) alloy has been selected as the nuclear fuel that will be used when transitioning research reactors and radioisotope production facilities from highly enriched uranium (>85% 235 U) fuel to low-enriched uranium (<20% 235 U) fuel. The fabrication steps for producing U10Mo fuel foil involve multiple hot-rolling/cold-rolling/intermediate annealing steps. The U10Mo alloy, which can retain the desirable high-temperature body-centered cubic γ-U (A2) structure at room temperature as a metastable phase for optimum in-reactor performance, goes through a eutectoid reaction below ~560°C and forms a-U as a reaction product, which is highly undesirable. Because the fabrication steps are carried out in the temperature range of 500 to 700°C, it is critical to understand the eutectoid reaction kinetics as a function of rolling/annealing steps. In this study, we determined the eutectoid transformation behavior of various rolled/annealed U10Mo coupons at 450, 500, and 525°C. The results show that the highest degree of phase transformation occurs when the U10Mo billet is rolled down from the as-cast condition without any prior homogenization treatment. Further, we observed that mechanical deformation (in the form of hot-rolling/cold-rolling) leads to increased eutectoid transformation compared to the billets that were not deformed.

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2014

Measurement of the anisotropic thermal conductivity of molybdenum disulfide by the time-resolved magneto-optic Kerr effect

We use pump-probe metrology based on the magneto-optic Kerr effect to measure the anisotropic thermal conductivity of (001)-oriented MoS{sub 2} crystals. A ≈20 nm thick CoPt multilayer with perpendicular magnetization serves as the heater and thermometer in the experiment. The low thermal conductivity and small thickness of the CoPt transducer improve the sensitivity of the measurement to lateral heat flow in the MoS{sub 2} crystal. The thermal conductivity of MoS{sub 2} is highly anisotropic with basal-plane thermal conductivity varying between 85–110 W m{sup -1} K{sup -1} as a function of laser spot size. The basal-plane thermal conductivity is a factor of ≈50 larger than the c-axis thermal conductivity, 2.0±0.3 W m{sup -1} K{sup -1}.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗

DOE OSTI2015

Molybdenum Availability Is Key to Nitrate Removal in Contaminated Groundwater Environments

ABSTRACT The concentrations of molybdenum (Mo) and 25 other metals were measured in groundwater samples from 80 wells on the Oak Ridge Reservation (ORR) (Oak Ridge, TN), many of which are contaminated with nitrate, as well as uranium and various other metals. The concentrations of nitrate and uranium were in the ranges of 0.1 μM to 230 mM and <0.2 nM to 580 μM, respectively. Almost all metals examined had significantly greater median concentrations in a subset of wells that were highly contaminated with uranium (≥126 nM). They included cadmium, manganese, and cobalt, which were 1,300- to 2,700-fold higher. A notable exception, however, was Mo, which had a lower median concentration in the uranium-contaminated wells. This is significant, because Mo is essential in the dissimilatory nitrate reduction branch of the global nitrogen cycle. It is required at the catalytic site of nitrate reductase, the enzyme that reduces nitrate to nitrite. Moreover, more than 85% of the groundwater samples contained less than 10 nM Mo, whereas concentrations of 10 to 100 nM Mo were required for efficient growth by nitrate reduction for two Pseudomonas strains isolated from ORR wells and by a model denitrifier, Pseudomonas stutzeri RCH2. Higher concentrations of Mo tended to inhibit the growth of these strains due to the accumulation of toxic concentrations of nitrite, and this effect was exacerbated at high nitrate concentrations. The relevance of these results to a Mo-based nitrate removal strategy and the potential community-driving role that Mo plays in contaminated environments are discussed.

Thorgersen, Michael P.↗

DOE OSTI2016

Cathode based on molybdenum disulfide nanoflakes for lithium-oxygen batteries.

Lithium-oxygen (Li-O-2) batteries have been recognized as an emerging technology for energy storage systems owing to their high theoretical specific energy. One challenge is to find an electrolyte/cathode system that is efficient, stable, and cost-effective. We present such a system based on molybdenum disulfide (MoS2) nanoflakes combined with an ionic liquid (IL) that work together as an effective cocatalyst for discharge and charge in a Li-O-2 battery. Cyclic voltammetry results show superior catalytic performance for this cocatalyst for both oxygen reduction and evolution reactions compared to Au and Pt catalysts. It also performs remarkably well in the Li-O-2 battery system with 85% round-trip efficiency and reversibility up to 50 cycles. Density functional calculations provide a mechanistic understanding of the MoS2 nanoflakes/IL system. cocatalyst reported in this work could open the way for exploiting the unique properties of ionic liquids in Li-air batteries in combination with nanostructured MoS2 as a cathode material.

Asadi, Mohammad↗

DOE OSTI2020

A CRISPRi-dCas9 System for Archaea and Its Use To Examine Gene Function during Nitrogen Fixation by Methanosarcina acetivorans

CRISPR-based systems are emerging as the premier method to manipulate many cellular processes. In this study, a simple and efficient CRISPR interference (CRISPRi) system for targeted gene repression in archaea was developed. The Methanosarcina acetivorans CRISPR-Cas9 system was repurposed by replacing Cas9 with the catalytically dead Cas9 (dCas9) to generate a CRISPRi-dCas9 system for targeted gene repression. To test the utility of the system, genes involved in nitrogen (N2) fixation were targeted for dCas9-mediated repression. First, the nif operon (nifHI 1 I 2 DKEN) that encodes molybdenum nitrogenase was targeted by separate guide RNAs (gRNAs), one targeting the promoter and the other targeting nifD. Remarkably, growth of M. acetivorans with N 2 was abolished by dCas9-mediated repression of the nif operon with each gRNA. The abundance of nif transcripts was >90% reduced in both strains expressing the gRNAs, and NifD was not detected in cell lysate. Next, we targeted NifB, which is required for nitrogenase cofactor biogenesis. Expression of a gRNA targeting the coding sequence of NifB decreased nifB transcript abundance >85% and impaired but did not abolish growth of M. acetivorans with N2. Finally, to ascertain the ability to study gene regulation using CRISPRi-dCas9, nrpR1, encoding a subunit of the repressor of the nif operon, was targeted. The nrpR1 repression strain grew normally with N2 but had increased nif operon transcript abundance, consistent with NrpR1 acting as a repressor. Furthermore, these results highlight the utility of the system, whereby a single gRNA when expressed with dCas9 can block transcription of targeted genes and operons in M. acetivorans.

59 BASIC BIOLOGICAL SCIENCES↗

DOE OSTI2016

Improving a high-efficiency, gated spectrometer for x-ray Thomson scattering experiments at the National Ignition Facility

We are developing x-ray Thomson scattering for applications in implosion experiments at the National Ignition Facility. In particular we have designed and fielded MACS, a high-efficiency, gated x-ray spectrometer at 7.5–10 keV [T. Döppner et al., Rev. Sci. Instrum. 85, 11D617 (2014)]. Here we report on two new Bragg crystals based on Highly Oriented Pyrolytic Graphite (HOPG), a flat crystal and a dual-section cylindrically curved crystal. We have performed in situ calibration measurements using a brass foil target, and we used the flat HOPG crystal to measure Mo K-shell emission at 18 keV in 2nd order diffraction. Such high photon energy line emission will be required to penetrate and probe ultra-high-density plasmas or plasmas of mid-Z elements.

46 INSTRUMENTATION RELATED TO NUCLEAR SCIENCE AND ↗

DOE OSTI2022

High Flux Isotope Reactor Low Enriched Uranium U-10Mo Fuel Design Parameters

Activities to convert the HFIR from HEU to LEU are ongoing as part of the US Department of Energy (DOE) National Nuclear Security Administration (NNSA) nuclear nonproliferation mission. Design activities to study the conversion of HFIR from HEU to LEU fuel explored different fuel design features and shapes with a uranium-molybdenum (U-10Mo) monolithic alloy fuel. This high-density alloy contains 90 wt % uranium and 10 wt % molybdenum and has a uranium density of 15.318gU/cm 3 . The goal of these studies is to generate several candidate HFIR LEU fuel designs of varying fuel fabrication complexity that meet the current HEU performance metrics and safety requirements. Recent advancements in modeling and simulation tools and design methods enabled a thorough analysis of the available design space with U-10Mo fuel. A surrogate model used this analysis as training data to quickly determine the performance of a design given specific design parameters. An optimization module used this surrogate model to quickly search this multidimensional search space given specific desired performance characteristics. This approach was made possible by the large available design space with U-10Mo fuel. Shift, a Monte Carlo tool optimized for high-performance computing (HPC) architectures, was used for faster calculation and better data management for reactor physics simulations. Once most of these design studies were complete, a new suite called the Python HFIR Analysis and Measurement Engine (PHAME) was developed to connect all fuel design analysis steps, making design studies more efficient and reproducible. The post-processing capabilities of these new tools are leveraged for the information provided herein. Leveraging these tools, several candidate fuel designs were selected with varying levels of feature complexity and reactor performance. This report provides design feature details for four selected HFIR LEU U-10Mo fuel designs and their corresponding performance and safety metrics. Nominal best-estimate design parameters and irradiation conditions, including fission rate densities, power densities, heat fluxes, and cumulative fission densities, are provided. Simulations show that the high uranium density of U-10Mo fuel provides a large potential design space that enables various LEU designs to meet HEU core performance metrics and safety requirements with a power increase from 85 MW (HEU) to 95 MW or 100 MW (LEU).

11 NUCLEAR FUEL CYCLE AND FUEL MATERIALS↗

DOE OSTI2025

Tailoring mechanical properties of a multi-principal element alloy through a multi-length-scale approach

In this study, a multi-length-scale strengthening approach was used to tailor the microstructure and the mechanical properties of a NiCoCr-based multi-principal element alloy (MPEA). Grain size refinement, severe lattice distortion, and stacking fault energy (SFE) reduction with Mo addition (up to 10 at.%) enhance yield strength by 85% with only 10% reduction in ductility in as-annealed MPEAs. A pronounced increase in the strain hardening rate was observed with the addition of Mo, which is ascribed to the promotion of complex stacking fault (SF) interaction and intersection, accompanied by Lomer-Cottrell (L-C) and Hirth locks inhibiting dislocation motion and substantial increase in the accumulation of back stress. To push the limit of the yield strength further, the Suzuki segregation phenomenon was manipulated by a careful control of SF density by pre-straining and a subsequent 500 °C heat treatment. The stress-strain responses of the pre-strained and heat treated MPEAs showed an obvious SF density and Mo concentration dependence. Furthermore, the yield strength of the pre-strained Mo-added MPEAs with subsequent heat treatment was increased up to true stress of 2.3 GPa with a corresponding fracture elongation of 12% true strain. SFs formed during pre-straining served as Cr segregation sites during subsequent heat treatment, which substantially varies the local SFE within the SF, presenting a roughened landscape and frustrating the dislocation dynamics.

mechanical properties↗

DOE OSTI2020

Materials Data on YMg30BO32 by Materials Project

Mg30YBO32 is Molybdenum Carbide MAX Phase-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. there are eight inequivalent Mg sites. In the first Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with two equivalent YO6 octahedra, corners with four MgO6 octahedra, and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Mg–O bond distances ranging from 2.06–2.16 Å. In the second Mg site, Mg is bonded to six O atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.00 Å) and four longer (2.17 Å) Mg–O bond lengths. In the third Mg site, Mg is bonded to six O atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.13 Å) and two longer (2.15 Å) Mg–O bond lengths. In the fourth Mg site, Mg is bonded to six O atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (2.12 Å) and two longer (2.16 Å) Mg–O bond lengths. In the fifth Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one YO6 octahedra, and edges with ten MgO6 octahedra. The corner-sharing octahedra tilt angles range from 3–6°. There are a spread of Mg–O bond distances ranging from 2.07–2.24 Å. In the sixth Mg site, Mg is bonded to six O atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedra tilt angles range from 1–3°. There are a spread of Mg–O bond distances ranging from 2.14–2.17 Å. In the seventh Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, an edgeedge with one YO6 octahedra, and edges with eleven MgO6 octahedra. The corner-sharing octahedral tilt angles are 2°. There are a spread of Mg–O bond distances ranging from 2.10–2.20 Å. In the eighth Mg site, Mg is bonded to six O atoms to form a mixture of corner and edge-sharing MgO6 octahedra. The corner-sharing octahedra tilt angles range from 2–9°. There are two shorter (2.14 Å) and four longer (2.16 Å) Mg–O bond lengths. Y is bonded to six O atoms to form YO6 octahedra that share corners with four equivalent MgO6 octahedra and edges with twelve MgO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.16 Å) and four longer (2.23 Å) Y–O bond lengths. B is bonded in a distorted linear geometry to two equivalent O atoms. Both B–O bond lengths are 2.15 Å. There are nine inequivalent O sites. In the first O site, O is bonded to five Mg and one Y atom to form OYMg5 octahedra that share corners with four OYMg5 octahedra, corners with two equivalent OMg5 square pyramids, and edges with twelve OYMg5 octahedra. The corner-sharing octahedral tilt angles are 0°. In the second O site, O is bonded to five Mg atoms to form OMg5 square pyramids that share corners with six OYMg4B octahedra, corners with three equivalent OMg5 square pyramids, and edges with eight OMg6 octahedra. The corner-sharing octahedra tilt angles range from 4–85°. In the third O site, O is bonded to six Mg atoms to form a mixture of corner and edge-sharing OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the fourth O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with four OMg6 octahedra, corners with two equivalent OMg5 square pyramids, edges with ten OMg6 octahedra, and edges with two equivalent OMg5 square pyramids. The corner-sharing octahedra tilt angles range from 0–1°. In the fifth O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with four OMg6 octahedra, corners with two equivalent OMg5 square pyramids, edges with ten OMg6 octahedra, and edges with two equivalent OMg5 square pyramids. The corner-sharing octahedra tilt angles range from 0–1°. There are two shorter (2.14 Å) and two longer (2.16 Å) O–Mg bond lengths. In the sixth O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with six equivalent OMg6 octahedra, edges with ten OYMg5 octahedra, and edges with two equivalent OMg5 square pyramids. The corner-sharing octahedra tilt angles range from 0–5°. In the seventh O site, O is bonded to four equivalent Mg, one Y, and one B atom to form OYMg4B octahedra that share corners with six OYMg4B octahedra, corners with four equivalent OMg5 square pyramids, and edges with eight OYMg5 octahedra. The corner-sharing octahedra tilt angles range from 0–5°. In the eighth O site, O is bonded to six Mg atoms to form OMg6 octahedra that share corners with six OYMg4B octahedra, edges with ten OYMg5 octahedra, and edges with two equivalent OMg5 square pyramids. The corner-sharing octahedra tilt angles range from 0–5°. In the ninth O site, O is bonded to six Mg atoms to form a mixture of corner and edge-sharing OMg6 octahedra. The corner-sharing octahedra tilt angles range from 0–2°.

36 MATERIALS SCIENCE↗