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All sourcesNASA NTRSDOE OSTI
DOE OSTI2022

Persistent Room-Temperature Photodarkening in Cu-Doped β - Ga 2 O 3

β–Ga 2 O 3 is an ultrawide band gap semiconductor with emerging applications in power electronics. Here, the introduction of acceptor dopants yields semi-insulating substrates necessary for thin-film devices. In the present work, exposure of Cu-doped β–Ga 2 O 3 to UV light > 4 eV is shown to cause large, persistent photo-induced darkening at room temperature. Electron paramagnetic resonance spectroscopy indicates that light exposure converts Cu 2+ to Cu 3+ , a rare oxidation state that is responsible for the optical absorption. The photodarkening is accompanied by the appearance of O–H vibrational modes in the infrared spectrum. Hybrid function calculations show that Cu acceptors can favorably complex with hydrogen donors incorporated as interstitial (Hi) or substitutional (HO) defects. When Cu Ga –HO complexes absorb light, hydrogen is released, contributing to the observed Cu 3+ species and O–H modes.

36 MATERIALS SCIENCE↗
NASA NTRS1972

Space shuttle system program definition. Volume 4: Cost and schedule report

The supporting cost and schedule data for the second half of the Space Shuttle System Phase B Extension Study is summarized. The major objective for this period was to address the cost/schedule differences affecting final selection of the HO orbiter space shuttle system. The contending options under study included the following booster launch configurations: (1) series burn ballistic recoverable booster (BRB), (2) parallel burn ballistic recoverable booster (BRB), (3) series burn solid rocket motors (SRM's), and (4) parallel burn solid rocket motors (SRM's). The implications of varying payload bay sizes for the orbiter, engine type for the ballistics recoverable booster, and SRM motors for the solid booster were examined.

Source record↗
DOE OSTI2022

Anisotropic magnon damping by zero-temperature quantum fluctuations in ferromagnetic CrGeTe 3

Spin and lattice are two fundamental degrees of freedom in a solid, and their fluctuations about the equilibrium values in a magnetic ordered crystalline lattice form quasiparticles termed magnons (spin waves) and phonons (lattice waves), respectively. In most materials with strong spin-lattice coupling (SLC), the interaction of spin and lattice induces energy gaps in the spin wave dispersion at the nominal intersections of magnon and phonon modes. Here we use neutron scattering to show that in the two-dimensional (2D) van der Waals honeycomb lattice ferromagnetic CrGeTe 3 , spin waves propagating within the 2D plane exhibit an anomalous dispersion, damping, and breakdown of quasiparticle conservation, while magnons along the c axis behave as expected for a local moment ferromagnet. These results indicate the presence of dynamical SLC arising from the zero-temperature quantum fluctuations in CrGeTe 3 , suggesting that the observed in-plane spin waves are mixed spin and lattice quasiparticles fundamentally different from pure magnons and phonons.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho2ReB6 by Materials Project

Ho2ReB6 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. there are two inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded in a 4-coordinate geometry to fourteen B2- atoms. There are a spread of Ho–B bond distances ranging from 2.74–2.83 Å. In the second Ho3+ site, Ho3+ is bonded to twelve B2- atoms to form a mixture of edge and face-sharing HoB12 cuboctahedra. There are a spread of Ho–B bond distances ranging from 2.59–2.62 Å. Re6+ is bonded in a 10-coordinate geometry to ten B2- atoms. There are a spread of Re–B bond distances ranging from 2.36–2.41 Å. There are six inequivalent B2- sites. In the first B2- site, B2- is bonded in a 9-coordinate geometry to six Ho3+ and three B2- atoms. There are a spread of B–B bond distances ranging from 1.84–1.95 Å. In the second B2- site, B2- is bonded in a 3-coordinate geometry to four equivalent Ho3+, two equivalent Re6+, and three B2- atoms. There are a spread of B–B bond distances ranging from 1.80–1.83 Å. In the third B2- site, B2- is bonded in a 9-coordinate geometry to four Ho3+, two equivalent Re6+, and three B2- atoms. The B–B bond length is 1.81 Å. In the fourth B2- site, B2- is bonded in a 9-coordinate geometry to four Ho3+, two equivalent Re6+, and three B2- atoms. There is one shorter (1.74 Å) and one longer (1.85 Å) B–B bond length. In the fifth B2- site, B2- is bonded in a 9-coordinate geometry to four Ho3+, two equivalent Re6+, and three B2- atoms. The B–B bond length is 1.80 Å. In the sixth B2- site, B2- is bonded in a 9-coordinate geometry to four Ho3+, two equivalent Re6+, and three B2- atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ho(Ni2B)6 by Materials Project

Ho(Ni2B)6 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. Ho3+ is bonded in a distorted hexagonal planar geometry to six B3- atoms. There are a spread of Ho–B bond distances ranging from 2.96–3.29 Å. There are seven inequivalent Ni+1.25+ sites. In the first Ni+1.25+ site, Ni+1.25+ is bonded to four B3- atoms to form a mixture of edge and corner-sharing NiB4 tetrahedra. There are a spread of Ni–B bond distances ranging from 1.98–2.09 Å. In the second Ni+1.25+ site, Ni+1.25+ is bonded in a 3-coordinate geometry to four B3- atoms. There are a spread of Ni–B bond distances ranging from 2.10–2.57 Å. In the third Ni+1.25+ site, Ni+1.25+ is bonded to four B3- atoms to form a mixture of distorted edge and corner-sharing NiB4 tetrahedra. There are a spread of Ni–B bond distances ranging from 2.02–2.10 Å. In the fourth Ni+1.25+ site, Ni+1.25+ is bonded in a T-shaped geometry to three B3- atoms. There are two shorter (2.00 Å) and one longer (2.09 Å) Ni–B bond lengths. In the fifth Ni+1.25+ site, Ni+1.25+ is bonded in a distorted T-shaped geometry to three B3- atoms. There are one shorter (2.05 Å) and two longer (2.13 Å) Ni–B bond lengths. In the sixth Ni+1.25+ site, Ni+1.25+ is bonded in a T-shaped geometry to three B3- atoms. There are a spread of Ni–B bond distances ranging from 2.03–2.10 Å. In the seventh Ni+1.25+ site, Ni+1.25+ is bonded to four B3- atoms to form a mixture of edge and corner-sharing NiB4 tetrahedra. There are a spread of Ni–B bond distances ranging from 2.01–2.08 Å. There are four inequivalent B3- sites. In the first B3- site, B3- is bonded in a 7-coordinate geometry to one Ho3+ and seven Ni+1.25+ atoms. In the second B3- site, B3- is bonded in a 7-coordinate geometry to one Ho3+ and seven Ni+1.25+ atoms. In the third B3- site, B3- is bonded in a 7-coordinate geometry to one Ho3+ and seven Ni+1.25+ atoms. In the fourth B3- site, B3- is bonded in a 9-coordinate geometry to one Ho3+ and eight Ni+1.25+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Theoretical search for possible Li–Ni–B crystal structures using an adaptive genetic algorithm

The structural diversity of rare-earth and transition metal borides indicates that alkali-transition metal borides (A-T-B) show tremendous promise in exhibiting a variety of crystal structures with different dimensionalities of T-B frameworks. On the other hand, the A-T-B ternary systems are severely underexplored because of the synthetic challenges associated with their preparation. Accurate and efficient computational predictions of low-energy stable and metastable phases can identify the optimal compositions of the hypothetical compounds in the A-T-B systems to guide the synthesis. As such, in this work, we have computationally discovered several new phases in the Li–Ni–B ternary system. The newly discovered LiNiB, Li 2 Ni 3 B, and Li 2 NiB phases expand the existing theoretical database, and the convex-hull surface of Li–Ni–B has been re-constructed. The lowest energy structure of the LiNiB compound has been found by an adaptive genetic algorithm with layered motif, which matches with the experimentally determined structure. According to our electrochemical calculations, LiNiB and another predicted layered Li 2 NiB compounds have great potential as anode materials for lithium batteries. The Li 2 Ni 3 B compound with the space group P4 3 32 was predicted to crystallize in a cubic structure composed of distorted octahedral units of BNi 6 , which is isostructural to two noncentrosymmetric superconductors Li 2 Pd 3 B and Li 2 Pt 3 B. While we were unable to experimentally confirm the Li 2 Ni 3 B compound utilizing the hydride synthetic route, attempts to synthesize this compound by alternate methods remain highly desirable, considering its potential superconducting properties.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Increased Ion Temperature and Neutron Yield Observed in Magnetized Indirectly Driven $\mathrm{D_2}$-Filled Capsule Implosions on the National Ignition Facility

Here, the application of an external 26 Tesla axial magnetic field to a D 2 gas-filled capsule indirectly driven on the National Ignition Facility is observed to increase the ion temperature by 40% and the neutron yield by a factor of 3.2 in a hot spot with areal density and temperature approaching what is required for fusion ignition. The improvements are determined from energy spectral measurements of the 2.45 MeV neutrons from the D(d, n) 3 He reaction, and the compressed central core B field is estimated to be ~4.9 kT using the 14.1 MeV secondary neutrons from the D(T, n) 4 He reactions. The experiments use a 30 kV pulsed-power system to deliver a ~ 3 μs current pulse to a solenoidal coil wrapped around a novel high-electrical-resistivity AuTa 4 hohlraum. Radiation magnetohydrodynamic simulations are consistent with the experiment

70 PLASMA PHYSICS AND FUSION TECHNOLOGY↗
DOE OSTI2020

Materials Data on HoMg(BO2)5 by Materials Project

MgHo(BO2)5 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Mg2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Mg–O bond distances ranging from 2.08–2.37 Å. Ho3+ is bonded in a 9-coordinate geometry to ten O2- atoms. There are a spread of Ho–O bond distances ranging from 2.28–2.98 Å. There are five inequivalent B3+ sites. In the first B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.47–1.49 Å. In the second B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.47–1.50 Å. In the third B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.37 Å) and one longer (1.38 Å) B–O bond length. In the fourth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.46–1.51 Å. In the fifth B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.35–1.40 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 120 degrees geometry to one Ho3+ and two B3+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+, one Ho3+, and two B3+ atoms. In the third O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ho3+ and two B3+ atoms. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Mg2+, one Ho3+, and two B3+ atoms. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Mg2+, one Ho3+, and one B3+ atom. In the sixth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Ho3+ and one B3+ atom. In the seventh O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ho3+ and two B3+ atoms. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+ and two B3+ atoms. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+ and two B3+ atoms. In the tenth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ho3+ and two B3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Crystal structures and comparisons of potassium rare-earth molybdates KRE(MoO 4 ) 2 (RE = Tb, Dy, Ho, Er, Yb, and Lu)

Six potassium rare-earth molybdates KRE(MoO 4 ) 2 (RE = Tb, Dy, Ho, Er, Yb, and Lu) were synthesized by flux-assisted growth in K 2 Mo 3 O 10 . The crystal structures were determined using single-crystal X-ray diffraction data. The synthesized molybdates crystallize with the orthorhombic Pbcn space group (No. 60). Trendlines for unit-cell parameters were calculated using data from the current study. The unit-cell parameters a and c increase linearly whereas b decreases with larger RE cations, based on crystal radii. The unit-cell volumes increase linearly and the densities decrease linearly with larger RE cations. The average distances between the RE cations and the nearest O atoms increase with larger cations whereas the average distances of Mo—O and K—O do not show specific trends.

36 MATERIALS SCIENCE↗
DOE OSTI2021

Design and Realization of Ohmic and Schottky Interfaces for Oxide Electronics

Understanding band alignment and charge transfer at complex oxide interfaces is critical to tailoring and utilizing their diverse functionality. Toward this goal, both Ohmic- and Schottky-like charge transfers at oxide/oxide semiconductor/metal interfaces are designed and experimentally validated. A method for predicting band alignment and charge transfer in ABO 3 perovskites is utilized, where previously established rules for simple semiconductors fail. The prototypical systems chosen are the rare class of oxide metals, SrBO 3 with B = V–Ta, when interfaced with the multifaceted semiconducting oxide, SrTiO 3 . For B = Nb and Ta, it is confirmed that a large accumulation of charge occurs in SrTiO 3 due to the higher energy Nb and Ta states relative to Ti. Furthermore, this gives rise to a high mobility metallic interface, which is an ideal epitaxial oxide/oxide Ohmic contact. On the contrary, for B = V, there is no charge transfer into the SrTiO 3 interface, which serves as a highly conductive epitaxial gate metal. Going beyond these specific cases, this work opens the door to integrating the vast phenomena of ABO 3 perovskites into a wide range of practical devices.

36 MATERIALS SCIENCE↗
NASA NTRS1996

Pasma Wave Characteristics of the Jovian Magnetopause Boundary Layer: Can Wave-Particle Interactions Cause the Jovian Aurora?

The full Jovian magnetopause boundary layer (BL) plasma wave spectra from 10(sup -3) to 10(sup 3) Hz, have been measured for the first time...The B'/E' ration does not have a f(sup -1) dependency, so it was suggested that the waves are a mixture of whistler mode electromagnetic emissions and electrostatic waves.

jovian magnetosphere Jupiter Jovian magnetopause E↗
DOE OSTI2020

Mechanoadaptive strain and functional osseointegration of dental implants in rats

Spatiotemporal implant-bone biomechanics and mechanoadaptive strains in peri-implant tissue are poorly understood. Physical and chemical characteristics of an implant-bone complex (IBC) were correlated in three-dimensional space (along the length and around a dental implant) to gather insights into time related integration of the implant with the cortical portion of a jaw bone in a rat. Rats (N = 9) were divided into three experimental groups with three rats per time point; 3-, 11-, and 24-day. All rats were fed crumbled hard pellets mixed with water (soft-food diet) for the first 3 days followed by a hard-food diet with intact hard-food pellets (groups of 11- and 24-day only). Biomechanics of the IBCs harvested from rats at each time point was evaluated by performing mechanical testing in situ in tandem with X-ray imaging. The effect of physical association (contact area) of a loaded implant with adapting peri-implant tissue, and resulting strain within was mapped by using digital volume correlation (DVC) technique. The IBC stiffness at respective time points was correlated with mechanical strain in peri-implant tissue. Results illustrated that IBC stiffness at 11-day was lower than that observed at 3-day. However, at 24-day, IBC stiffness recovered to that which was observed at 3-day. Furthermore, correlative microscopy and spectroscopy illustrated that the lower IBC stiffness was constituted by softer and less mineralized peri-implant tissue that contained varying expressions of osteoconductive elements. Lower IBC stiffness observed at 11-day was constituted by less mineralized peri-implant tissue with osteoconductive elements that included phosphorus (P) which was co-localized with higher expression of zinc (Zn), and lower expression of calcium (Ca). Higher IBC stiffness at 24-day was constituted by mineralized peri-implant tissue with higher expressions of osteoconductive elements including Ca and P, and lower expressions of Zn. These spatiotemporal correlative maps of peri-implant tissue architecture, heterogeneous distribution of mineral density, and elemental colocalization underscore mechanoadaptive physicochemical properties of peri-implant tissue that facilitate functional osseointegration of an implant. These results provided insights into 1) plausible "prescription" of mechanical loads as an osteoinductive "therapeutic dose" to encourage osteoconductive elements in the peri-implant tissue that would facilitate functional osseointegration of the implant; 2) a "critical temporal window" between 3 and 11 days, and perhaps it is this acute phase during which key candidate regenerative molecules can be harnessed to accelerate osseointegration of an implant under load.

60 APPLIED LIFE SCIENCES↗
DOE OSTI2021

Initial Characterization of Active Transitioning Centaur, P/2019 LD{sub 2} (ATLAS), Using Hubble, Spitzer, ZTF, Keck, Apache Point Observatory, and GROWTH Visible and Infrared Imaging and Spectroscopy

We present visible and mid-infrared imagery and photometry of temporary Jovian co-orbital comet P/2019 LD{sub 2} taken with Hubble Space Telescope/Wide Field Camera 3 (HST/WFC3), Spitzer Space Telescope/Infrared Array Camera (Spitzer/IRAC), and the GROWTH telescope network, visible spectroscopy from Keck/Low-Resolution Imaging Spectrometer (LRIS), and archival Zwicky Transient Facility observations taken between 2019 April and 2020 August. Our observations indicate that the nucleus of LD{sub 2} has a radius between 0.2 and 1.8 km assuming a 0.08 albedo and a coma dominated by ∼100 μm-scale dust ejected at ∼1 m s{sup −1} speeds with a ∼1′ jet pointing in the southwest direction. LD{sub 2} experienced a total dust mass loss of ∼10{sup 8} kg at a loss rate of ∼6 kg s{sup −1} with Afρ/cross section varying between ∼85 cm/125 km{sup 2} and ∼200 cm/310 km{sup 2} from 2019 April 9 to 2019 November 8. If the increase in Afρ/cross section remained constant, it implies LD{sub 2}'s activity began ∼2018 November when within 4.8 au of the Sun, implying the onset of H{sub 2}O sublimation. We measure CO/CO{sub 2} gas production of ≲10{sup 27} mol s{sup −1}/≲10{sup 26} mol s{sup −1} from our 4.5 μm Spitzer observations; g–r = 0.59 ± 0.03, r–i = 0.18 ± 0.05, and i–z = 0.01 ± 0.07 from GROWTH observations; and H{sub 2}O gas production of ≲80 kg s{sup −1} scaling from our estimated C {sub 2} production of Q{sub C{sub 2}}≲7.5×10{sup 24} mol s{sup −1} from Keck/LRIS spectroscopy. We determine that the long-term orbit of LD{sub 2} is similar to Jupiter-family comets having close encounters with Jupiter within ∼0.5 Hill radius in the last ∼3 y and within 0.8 Hill radius in ∼9 y. Additionally, 78.8% of our orbital clones are ejected from the solar system within 1 × 10{sup 6} yr, having a dynamical half-life of 3.4 × 10{sup 5} yr.

47 OTHER INSTRUMENTATION↗
DOE OSTI2020

Materials Data on Ho2Cu(BO2)8 by Materials Project

Ho2Cu(BO2)8 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. Ho3+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ho–O bond distances ranging from 2.28–2.47 Å. Cu2+ is bonded in an octahedral geometry to six O2- atoms. There are four shorter (1.99 Å) and two longer (2.44 Å) Cu–O bond lengths. There are three inequivalent B3+ sites. In the first B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.35–1.40 Å. In the second B3+ site, B3+ is bonded in a tetrahedral geometry to four O2- atoms. There is two shorter (1.47 Å) and two longer (1.48 Å) B–O bond length. In the third B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.35 Å) and two longer (1.40 Å) B–O bond length. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Ho3+ and one B3+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Ho3+, one Cu2+, and one B3+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Ho3+ and two B3+ atoms. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ho3+ and two B3+ atoms. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Cu2+ and two equivalent B3+ atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2023

In Situ High-Temperature Structural Analysis of High-Entropy Rare-Earth Sesquioxides

High-entropy rare-earth (RE) sesquioxides (RE 2 O 3 ) containing five cations in equimolar amounts have been investigated for a variety of applications, but little is known about their polymorphic behavior and coefficient of thermal expansion. Here, in this work, we evaluate the effect of the average ionic radius (AIR) on the polymorphism of high-entropy RE 2 O 3 . Powder samples of compositions 1 (Lu,Y,Ho,Nd,La) 2 O 3 (AIR = 0.938 Å) and 2 (Gd,Eu,Sm,Nd,La) 2 O 3 (AIR = 0.982 Å) were synthesized via a wet chemical method, and bead samples were prepared for aerodynamic levitation by melting the powders in a copper hearth. Structural transitions were monitored upon cooling from the melt to 1000 °C via in situ X-ray diffraction on aerodynamically levitated samples. The phase evolution was liquid, hexagonal H-type, and monoclinic B-type for composition 1 and liquid, cubic X-type, H-type, and B-type for composition 2. Based on their AIR, the general polymorphic transformations of the high-entropy RE 2 O 3 follow the trend of single-RE RE 2 O 3 , but the transition temperatures differ from those of single-RE RE 2 O 3 . The coefficient of thermal expansion values of the B-type phase of compositions 1 and 2 are similar to those of Gd 2 O 3 and previously published high-entropy RE 2 O 3 .

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2013

Einstein@Home All-Sky Search for Periodic Gravitational Waves in LIGO S5 Data

This paper presents results of an all-sky search for periodic gravitational waves in the frequency range [50, 1 190] Hzand and with frequency derivative range of approx. [-20,1.1] x 10(exp-10) H(sub 0)z s(exp-1) for the fifth LIGO science run (S5). The search uses a noncoherent Hough-transform method to combine the information from coherent searches on time scales of about one day. Because these searches are very computationally intensive, they have been carried out with the Einstein@Home volunteer distributed computing project. Postprocessing identifies eight candidate signals; deeper follow-up studies rule them out. Hence, since no gravitational wave signals have been found, we report upper limits on the intrinsic gravitational wave strain amplitude ho. For example, in the 0.5 Hz-wide band at 152.5 Hz, we can exclude the presence of signals with h(exp 0) greater than 7.6 x 10(exp-25) at a 90% confidence level. This search is about a factor 3 more sensitive than the previous Einstein@Home search of early S5 LIGO data.

J Aasi↗
DOE OSTI2020

Materials Data on HoCo(BO2)5 by Materials Project

HoCo(BO2)5 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Ho3+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ho–O bond distances ranging from 2.25–2.92 Å. Co2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Co–O bond distances ranging from 2.06–2.43 Å. There are five inequivalent B3+ sites. In the first B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.37 Å) and two longer (1.38 Å) B–O bond length. In the second B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.35–1.40 Å. In the third B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.47–1.51 Å. In the fourth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.47–1.50 Å. In the fifth B3+ site, B3+ is bonded to four O2- atoms to form corner-sharing BO4 tetrahedra. There are a spread of B–O bond distances ranging from 1.47–1.50 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to one Ho3+, two equivalent Co2+, and one B3+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ho3+, one Co2+, and two B3+ atoms. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to one Ho3+ and two B3+ atoms. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ho3+ and two B3+ atoms. In the fifth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ho3+ and two B3+ atoms. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Co2+ and two B3+ atoms. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one Ho3+, one Co2+, and two B3+ atoms. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Co2+ and two B3+ atoms. In the ninth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ho3+ and two B3+ atoms. In the tenth O2- site, O2- is bonded in a distorted single-bond geometry to two equivalent Ho3+ and one B3+ atom.

36 MATERIALS SCIENCE↗