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All sourcesNASA NTRSDOE OSTI
DOE OSTI2020

Crystal structure and physical properties of Yb 2 In and Eu 2–x Yb x In alloys

While binary R E 2 In , where R E = rare earth , have been reported a few decades ago, recent investigations revealed intriguing new physical insights. For instance, the discovery of a nearly ideal first-order ferromagnetic transition in Eu 2 In calls for further exploration of structures and properties of R E 2 In , in particular for the least-documented R E = Eu and Yb cases. In this work, we investigate Eu 2 – x Yb x In pseudobinaries with nominal values of x = 0.25 , 0.5, 0.75, 1, 1.5, 2 by powder x-ray diffraction (including as function of temperature from 100 to 375 K for Yb 2 In ), magnetization (5–300 K), as well as electrical resistivity (5–300 K) and calorimetric (2–150 K) measurements for Yb 2 In . Compared to other RE , Yb or Eu always raise challenging questions linked to their valence states. From average atomic volume, Yb is anticipated to be divalent in Yb 2 In , at least between 100 and 375 K, which is in line with the absence of 4 f magnetism. In agreement with x-ray diffraction and magnetization data, the resistivity of Yb 2 In is rather featureless and typical of a metal. Establishing Yb 2 In as a nonmagnetic isostructural reference for Eu 2 In allows one to use its heat capacity to revisit that of the latter, and get experimental insights into the exceptional magnetocaloric effect of the compound with Eu. In particular, we show that a third of the total magnetic entropy ( S m ≈ 35.6 J mo l – 1 K – 1 at T = 100 K ) is concentrated in a 3 K temperature window around the T C of Eu 2 In . Starting from the ferromagnetic compound Eu 2 In [ T C = 55.2 ( 5 ) K ] , we show that Yb substitutions in Eu 2 – x Yb x In lead to a decrease in both the Curie temperature [ T C = 41 ( 2 ) and 32(2) K for x = 0.25 and 0.5] and magnetic saturation, while weakening the first-order character of the transition as x increases. A significant isothermal entropy change of 5.1 ( 4 ) J mo l – 1 K – 1 for Δ B = 2 T is found at 44 K in Eu 1.75 Yb 0.25 In , demonstrating that the giant magnetocaloric effect of Eu 2 In can be tuned to lower temperatures by Yb substitutions.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(In2Au)2 by Materials Project

Eu(AuIn2)2 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Eu is bonded in a 11-coordinate geometry to four Au and ten In atoms. There are two shorter (3.46 Å) and two longer (3.53 Å) Eu–Au bond lengths. There are a spread of Eu–In bond distances ranging from 3.35–3.76 Å. There are two inequivalent Au sites. In the first Au site, Au is bonded in a 7-coordinate geometry to two equivalent Eu and seven In atoms. There are a spread of Au–In bond distances ranging from 2.85–2.89 Å. In the second Au site, Au is bonded in a 9-coordinate geometry to two equivalent Eu and seven In atoms. There are a spread of Au–In bond distances ranging from 2.83–3.05 Å. There are four inequivalent In sites. In the first In site, In is bonded to one Eu and four Au atoms to form a mixture of distorted corner and edge-sharing InEuAu4 tetrahedra. In the second In site, In is bonded in a 3-coordinate geometry to three equivalent Eu and three equivalent Au atoms. In the third In site, In is bonded in a 3-coordinate geometry to three equivalent Eu and three equivalent Au atoms. In the fourth In site, In is bonded in a 4-coordinate geometry to three equivalent Eu and four Au atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(In4Ir)2 by Materials Project

Eu(IrIn4)2 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. Eu is bonded in a 10-coordinate geometry to thirteen In atoms. There are a spread of Eu–In bond distances ranging from 3.47–3.88 Å. There are two inequivalent Ir sites. In the first Ir site, Ir is bonded in a 9-coordinate geometry to nine In atoms. There are a spread of Ir–In bond distances ranging from 2.69–2.97 Å. In the second Ir site, Ir is bonded in a 9-coordinate geometry to nine In atoms. There are a spread of Ir–In bond distances ranging from 2.72–3.02 Å. There are nine inequivalent In sites. In the first In site, In is bonded in a 4-coordinate geometry to four equivalent Ir atoms. In the second In site, In is bonded in a linear geometry to two equivalent Eu, two equivalent Ir, and four equivalent In atoms. All In–In bond lengths are 3.17 Å. In the third In site, In is bonded in a 4-coordinate geometry to two equivalent Eu, two equivalent Ir, and eight In atoms. There are a spread of In–In bond distances ranging from 3.22–3.38 Å. In the fourth In site, In is bonded in a 2-coordinate geometry to two equivalent Eu, two equivalent Ir, and one In atom. The In–In bond length is 2.99 Å. In the fifth In site, In is bonded in a 2-coordinate geometry to two equivalent Eu, two equivalent Ir, and one In atom. In the sixth In site, In is bonded in a 2-coordinate geometry to two equivalent Eu, two equivalent Ir, and three In atoms. In the seventh In site, In is bonded in a 2-coordinate geometry to two equivalent Eu, two equivalent Ir, and one In atom. In the eighth In site, In is bonded in a distorted linear geometry to two equivalent Eu, two Ir, and two equivalent In atoms. In the ninth In site, In is bonded in a 1-coordinate geometry to three Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2025

Structural Investigation of Six Quinary Sulfides Synthesized via the Flux-Assisted Boron-Chalcogen Mixture (BCM) Method: Eu 2+ Containing Members of the RE 3 MTQ 7 (M and T = Transition or Main Group Metals, Q = Chalcogens) Family

For this work, a series of six quinary rare-earth sulfides Ce 4+ 1.85 Eu 2+ 1.15 Na 0.30 SiS 7 , Ce 4+ 1.91 Eu 2+ 1.09 K 0.18 SiS 7 , Ce 4+ 1.96 Eu 2+ 1.04 Rb 0.08 SiS 7 , Ce 4+ 1.98 Eu 2+ 1.02 Cs 0.05 SiS 7 , Ce 4+ 1.97 Eu 2+ 1.03 Ag 0.06 SiS 7 , and Ce 4+ 1.50 Eu 2+ 1.50 CuSiS 7 were obtained in an alkali iodide flux using the boron-chalcogen mixture (BCM) method. Single crystal X-ray diffraction was used to determine the structures of the high quality single crystals that were grown; their elemental compositions were confirmed by energy-dispersive spectroscopy (EDS). The compounds crystallize in the hexagonal crystal system in the noncentrosymmetric space group P63. The crystal structure consists of a three-dimensional network composed of mixed cerium and europium bicapped trigonal prisms, isolated SiS4 tetrahedra, and monovalent metals (Na, K, Rb, Cs, Ag, and Cu) located in cavities created by linked Ce/EuS 8 polyhedra. The structures are charge-balanced when Ce and Eu are in their +4 and +2 oxidation states, respectively. The effective magnetic moment of Ce 1.50 4+ Eu 1.50 2+ CuSiS 7 determined from the temperature dependence of the magnetic susceptibility data is consistent with the presence of Ce 4+ and Eu 2+ . Clear correlations between the alkali ion site occupancy, the ionic radius of the alkali cations, and the average bond length of Ce 4+ /Eu 2+ –S, were established. UV–vis diffuse reflectance data were collected for Ce 1.50 4+ Eu 1.50 2+ CuSiS 7 and a band gap of 1.9(1) eV was established.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
NASA NTRS2006

Calibration of the EU Oxybarometer for Nakhlites

Martian meteorites have various characteristics, which are direct clues to understanding the petrogenesis of Mars rocks. The variation in oxidation state among the Martian meteorites must have important implications for redox conditions of the Martian crust/mantle and overall differentiation on Mars. Wadhwa [1] and Herd et al. [2] reported that Martian basalts were formed under a range of oxidation states, suggesting complex petrogenesis processes. The nakhlites, which have rather different characteristics from basaltic shergottites, may give us additional clues to Martian petrogenesis. The oxidation states of meteorites are usually described by the oxygen fugacity (fO2) under which the meteorites crystallized. One of the methods to estimate the oxygen fugacity is the depth of Eu anomaly. Eu(2+)/Eu(3+) is determined by the oxygen fugacity and partitioning is different for Eu(2+) and Eu(3+). Therefore, the depth of Eu anomaly in a mineral is a function of the oxygen fugacity and the Eu2+/Eu3+ in the melt from which the mineral crystallized. This method has some advantages over another major method, the two-oxide oxybarometer [3], which can more easily be affected by subsolidus processes. The Eu oxybarometer can analyze the cores of the earliest formed crystals in Martian meteorites, which means it can give us a better indication of the oxygen fugacity of the parent melt. The calibration of the Eu oxybarometer has been done with the basaltic shergottites before [4]. However, it has never been applied to nakhlites (Oe et al. [5] measured the depth of Eu anomaly in the synthetic pyroxene only at QFM). Partition coefficients are strongly affected by phase compositions, especially pyroxene Ca content and melt Al content [e.g., 5,6]. The composition of nakhlite pyroxene is rather different from basaltic shergottite pyroxene. Thus, there may be problems in applying the Eu oxybarometer calibration for the basaltic shergottites [7] to nakhlites. Thus, we report in this abstract preliminary results of our experimental calibration of the depth of Eu anomaly in pyroxene vs. oxygen fugacity for nakhlites.

Makishima, J.↗
DOE OSTI2020

Materials Data on Eu(In4Rh)2 by Materials Project

EuRh2In8 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. Eu is bonded in a 12-coordinate geometry to thirteen In atoms. There are a spread of Eu–In bond distances ranging from 3.41–3.81 Å. There are two inequivalent Rh sites. In the first Rh site, Rh is bonded in a 9-coordinate geometry to nine In atoms. There are a spread of Rh–In bond distances ranging from 2.68–2.98 Å. In the second Rh site, Rh is bonded in a 9-coordinate geometry to nine In atoms. There are a spread of Rh–In bond distances ranging from 2.65–2.93 Å. There are nine inequivalent In sites. In the first In site, In is bonded in a linear geometry to two equivalent Eu, two equivalent Rh, and four equivalent In atoms. All In–In bond lengths are 3.12 Å. In the second In site, In is bonded in a 4-coordinate geometry to two equivalent Eu, two equivalent Rh, and eight In atoms. There are a spread of In–In bond distances ranging from 3.15–3.32 Å. In the third In site, In is bonded in a 2-coordinate geometry to two equivalent Eu, two equivalent Rh, and one In atom. The In–In bond length is 2.93 Å. In the fourth In site, In is bonded in a 2-coordinate geometry to two equivalent Eu, two equivalent Rh, and one In atom. In the fifth In site, In is bonded in a 4-coordinate geometry to four equivalent Rh atoms. In the sixth In site, In is bonded in a 2-coordinate geometry to two equivalent Eu, two equivalent Rh, and one In atom. In the seventh In site, In is bonded in a 1-coordinate geometry to three Rh atoms. In the eighth In site, In is bonded in a 2-coordinate geometry to two equivalent Eu, two equivalent Rh, and three In atoms. In the ninth In site, In is bonded in a distorted linear geometry to two equivalent Eu, two Rh, and two equivalent In atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(Al4Fe)2 by Materials Project

Al8Fe2Eu crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. Eu is bonded in a 11-coordinate geometry to thirteen Al atoms. There are a spread of Eu–Al bond distances ranging from 3.15–3.35 Å. There are two inequivalent Fe sites. In the first Fe site, Fe is bonded in a 9-coordinate geometry to nine Al atoms. There are a spread of Fe–Al bond distances ranging from 2.37–2.59 Å. In the second Fe site, Fe is bonded in a 9-coordinate geometry to nine Al atoms. There are a spread of Fe–Al bond distances ranging from 2.35–2.57 Å. There are nine inequivalent Al sites. In the first Al site, Al is bonded in a 12-coordinate geometry to two equivalent Eu, two equivalent Fe, and eight Al atoms. There are a spread of Al–Al bond distances ranging from 2.67–3.02 Å. In the second Al site, Al is bonded in a distorted linear geometry to two equivalent Eu, two equivalent Fe, and eight Al atoms. All Al–Al bond lengths are 2.89 Å. In the third Al site, Al is bonded in a 12-coordinate geometry to four equivalent Fe and four Al atoms. There are two shorter (2.64 Å) and two longer (2.65 Å) Al–Al bond lengths. In the fourth Al site, Al is bonded in a 2-coordinate geometry to two equivalent Eu, two equivalent Fe, and three Al atoms. There are one shorter (2.72 Å) and one longer (2.73 Å) Al–Al bond lengths. In the fifth Al site, Al is bonded in a 2-coordinate geometry to two equivalent Eu, two equivalent Fe, and six Al atoms. There are one shorter (2.71 Å) and two longer (2.84 Å) Al–Al bond lengths. In the sixth Al site, Al is bonded in a 2-coordinate geometry to two equivalent Eu, two equivalent Fe, and five Al atoms. There are one shorter (2.73 Å) and two longer (2.83 Å) Al–Al bond lengths. In the seventh Al site, Al is bonded in a 1-coordinate geometry to three Fe and two equivalent Al atoms. Both Al–Al bond lengths are 3.02 Å. In the eighth Al site, Al is bonded in a distorted linear geometry to two equivalent Eu, two Fe, and six Al atoms. In the ninth Al site, Al is bonded in a 2-coordinate geometry to two equivalent Eu, two equivalent Fe, and eight Al atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Observation of an Unexpected n -Type Semiconducting Behavior in the New Ternary Zintl Phase Eu 3 InAs 3

The ternary arsenides Eu 3 InAs 3 and Sr 3 InAs 3 have been obtained by reactions of the elements in In flux at 1373 K. Structure elucidation by single-crystal X-ray diffraction reveals that Eu 3 InAs 3 and Sr 3 InAs 3 adopt the same orthorhombic structure (space group Pnma, Z = 4, Ca 3 AlAs 3 structure type) with unit cell parameters a = 12.9179(9) Å, b = 4.3990(3) Å, c = 13.9337(10) Å and a = 13.0218(11) Å, b = 4.4364(4) Å, c = 14.1339(12) Å, respectively. The structure consists of linear chains of corner-sharing InAs4 tetrahedra, [InAs 2 As 2/2 ] 6– , and Eu 2+ /Sr 2+ cations. Therefore, both Eu 3 InAs 3 and Sr 3 InAs 3 are valence-precise Zintl phases. As expected from the closed-shell electronic configurations, semiconducting behavior is confirmed by resistivity measurements on single crystals for both and by electronic band structure calculations for Sr 3 InAs 3 . The temperature dependence of resistivity and the computational work are in agreement that Eu 3 InAs 3 and Sr 3 InAs 3 are intrinsic semiconductors with narrow band gaps. Thermopower measurement on single-crystalline samples of Eu 3 InAs 3 shows that in the whole measured temperature range, from 300 to 700 K, the values for the Seebeck coefficient are negative. The observation of a negative Seebeck coefficient with very large absolute value (>400–500 μV K –1 at 700 K) is unexpected among the Zintl phases and suggestive that electrons are the majority charge carriers. Such a rare, n-type charge transport in an undoped compound such as Eu 3 InAs 3 , a material that has not been purposely optimized, could indicate native “defect” chemistry, and not extrinsic doping, as a reason for the unusual behavior. Here, a possible explanation involves a mixed-valent Eu 2+ /Eu 3+ state, which might be inferred from the measured effective paramagnetic moment of 7.2 μB per Eu atom, which is lower than the theoretically predicted value for free-ion moment of 7.9 μ B /Eu.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2020

Materials Data on Eu(GePt)2 by Materials Project

Eu(PtGe)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Eu is bonded in a 12-coordinate geometry to nine Pt and nine Ge atoms. There are a spread of Eu–Pt bond distances ranging from 3.33–3.81 Å. There are a spread of Eu–Ge bond distances ranging from 3.35–3.86 Å. There are two inequivalent Pt sites. In the first Pt site, Pt is bonded in a 4-coordinate geometry to four equivalent Eu and four equivalent Ge atoms. There are a spread of Pt–Ge bond distances ranging from 2.62–2.73 Å. In the second Pt site, Pt is bonded in a 5-coordinate geometry to five equivalent Eu and five Ge atoms. There are a spread of Pt–Ge bond distances ranging from 2.66–2.69 Å. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 8-coordinate geometry to four equivalent Eu and four equivalent Pt atoms. In the second Ge site, Ge is bonded in a 5-coordinate geometry to five equivalent Eu and five Pt atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(GePt)2 by Materials Project

Eu(PtGe)2 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. Eu is bonded in a 12-coordinate geometry to eight Pt and eight Ge atoms. There are a spread of Eu–Pt bond distances ranging from 3.32–3.43 Å. There are a spread of Eu–Ge bond distances ranging from 3.30–3.41 Å. There are two inequivalent Pt sites. In the first Pt site, Pt is bonded in a 9-coordinate geometry to four equivalent Eu and five Ge atoms. There are a spread of Pt–Ge bond distances ranging from 2.49–2.56 Å. In the second Pt site, Pt is bonded in a 4-coordinate geometry to four equivalent Eu and four equivalent Ge atoms. There are a spread of Pt–Ge bond distances ranging from 2.54–2.57 Å. There are two inequivalent Ge sites. In the first Ge site, Ge is bonded in a 9-coordinate geometry to four equivalent Eu and five Pt atoms. In the second Ge site, Ge is bonded in a 4-coordinate geometry to four equivalent Eu and four equivalent Pt atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(SnPd)2 by Materials Project

Eu(PdSn)2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Eu is bonded in a 12-coordinate geometry to eight Pd and eight Sn atoms. There are four shorter (3.53 Å) and four longer (3.58 Å) Eu–Pd bond lengths. There are four shorter (3.59 Å) and four longer (3.60 Å) Eu–Sn bond lengths. There are two inequivalent Pd sites. In the first Pd site, Pd is bonded in a 9-coordinate geometry to four equivalent Eu and five Sn atoms. There are one shorter (2.65 Å) and four longer (2.74 Å) Pd–Sn bond lengths. In the second Pd site, Pd is bonded in a 4-coordinate geometry to four equivalent Eu and four equivalent Sn atoms. All Pd–Sn bond lengths are 2.68 Å. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded in a 4-coordinate geometry to four equivalent Eu and four equivalent Pd atoms. In the second Sn site, Sn is bonded in a 5-coordinate geometry to four equivalent Eu and five Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(BiPd)2 by Materials Project

Eu(PdBi)2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Eu is bonded in a 4-coordinate geometry to eight Pd and eight Bi atoms. There are four shorter (3.56 Å) and four longer (3.76 Å) Eu–Pd bond lengths. There are four shorter (3.69 Å) and four longer (3.73 Å) Eu–Bi bond lengths. There are two inequivalent Pd sites. In the first Pd site, Pd is bonded in a 8-coordinate geometry to four equivalent Eu and four equivalent Bi atoms. All Pd–Bi bond lengths are 2.79 Å. In the second Pd site, Pd is bonded in a 9-coordinate geometry to four equivalent Eu and five Bi atoms. There are one shorter (2.71 Å) and four longer (2.81 Å) Pd–Bi bond lengths. There are two inequivalent Bi sites. In the first Bi site, Bi is bonded in a 4-coordinate geometry to four equivalent Eu and four equivalent Pd atoms. In the second Bi site, Bi is bonded in a 5-coordinate geometry to four equivalent Eu and five Pd atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2022

Eu 5 Al 3 Sb 6 : Al 4 Tetrahedra Embedded in a Rock-Salt-Like Structure

The new Eu 5 Al 3 Sb 6 phase has been successfully synthesized as a pure phase through Sn flux methods yielding large, high-quality crystals. This structure type features disordered Al clusters that appear in the form of dual tetrahedra. It crystallizes in the monoclinic C2/m space group exhibiting a rock-salt-like Eu–Sb framework with [Al 4 ] tetrahedra replacing some of the cationic Eu atoms (space group: C2/m, a = 8.151(1) Å, b = 14.181(2) Å, c = 8.145(1) Å, β = 109.577(2)°). The structure models the [Al 4 ] as dual tetrahedra with the Al atom sites 37.5% occupied along with Eu present on the central site at 8% occupancy and the remainder of the site being vacant. The presence of the [Al 4 ] cluster is further supported by HRTEM. Electronic structure calculations show that this material is a semimetal with observed band crossings close to the Fermi level. Strong Al–Sb antibonding interactions were found from COHP calculations close to the Fermi level and provide the rationale for the deficiency of the Al cluster. Mössbauer spectroscopy on Eu-151 and Sb-121 provides oxidation states of 2+ and 3– along with the local environment. Magnetic susceptibility measurements can be described well with a Curie–Weiss law where an effective moment of 7.80 μB/mol Eu is obtained, consistent with Eu 2+ , and show canted antiferromagnetic behavior below 10 K. Temperature dependent resistivity shows a Kondo-like low-temperature upturn caused by enhanced scattering of the itinerant electrons with the 4f orbitals of Eu.

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

Magnetic Properties and Large Second-Harmonic Generation Response of a Chiral Ternary Chalcogenide: Eu 2 SiSe 4

Eu(II)-containing chalcogenides are an emerging class of materials that are of great interest due to their high optical activity and intriguing magnetism. Here, we synthesized Eu 2 SiSe 4 as red-colored single crystals and characterized its structure with single-crystal X-ray diffraction, confirming the reported chiral monoclinic P2 1 symmetry at room temperature. The crystal structure of Eu 2 SiSe 4 comprises distorted SiSe 4 tetrahedral units and charge-balancing Eu(II) cations. Here, we develop a two-step solid-state synthesis method for Eu 2 SiSe 4 and compare it to the known boron chalcogenide method. We find the second-harmonic generation (SHG) activity of polycrystalline Eu 2 SiSe 4 to be ∼7 × AgGaS 2 , placing it among the highest-known SHG-active chalcogenides. No symmetry lowering is observed down to 100 K in single-crystal X-ray diffraction, although an anomalous expansion in the b-axis lattice parameter occurs and may be correlated to lattice modes of the SiSe 4 tetrahedra. We investigate the physical properties of Eu 2 SiSe 4 using magnetometry and heat capacity measurements and find a transition to an antiferromagnetic ground state at T N ≈ 5.5 K. The low-temperature transition releases less entropy than expected, which may be due to the complex crystal electric field effects of Eu(II).

36 MATERIALS SCIENCE↗
DOE OSTI2021

Magnetic and dielectric property control in the multivalent nanoscale perovskite Eu 0.5 Ba 0.5 TiO 3

We report nanoscale Eu 0.5 Ba 0.5 TiO 3 , a multiferroic in the bulk and candidate in the search to quantify the electric dipole moment of the electron. Eu 0.5 Ba 0.5 TiO 3 , in the form of nanoparticles and other nanostructures is interesting for nanocomposite integration, biomedical imaging and fundamental research, based upon the prospect of polarizability, f-orbital magnetism and tunable optical/radio luminescence. We developed a [non-hydrolytic]sol–[H 2 O-activated]gel route, derived from in-house metallic Ba (s) /Eu (s) alkoxide precursors and Ti{(OCH(CH 3 ) 2 } 4 . Two distinct nanoscale compounds of Ba:Ti:Eu with the parent perovskite crystal structure were produced, with variable dielectric, magnetic and optical properties, based on altering the oxidizing/reducing conditions. Eu 0.5 Ba 0.5 TiO 3 prepared under air/O 2 atmospheres produced a spherical core–shell nanostructure (30–35 nm), with perovskite Eu 0.5 Ba 0.5 TiO 3 nanocrystal core-insulating oxide shell layer (~3 nm), presumed a pre-pyrochlore layer abundant with Eu 3+ . Fluorescence spectroscopy shows a high intensity 5 D 0 → 7 F 2 transition at 622 nm and strong red fluorescence. The core/shell structure demonstrated excellent capacitive properties: assembly into dielectric thin films gave low conductivity (2133 GΩ mm -1 ) and an extremely stable, low loss permittivity of ε eff ~25 over a wide frequency range (tan δ < 0.01, 100 kHz–2 MHz). Eu 0.5 Ba 0.5 TiO 3 prepared under H 2 /argon produced more irregular shaped nanocrystals (20–25) nm, with a thin film permittivity around 4 times greater ( ε eff 101, tan δ < 0.05, 10 kHz–2 MHz, σ ~59.54 kΩ mm -1 ). Field-cooled magnetization values of 0.025 emu g -1 for EBTO-Air and 0.84 emu g -1 for EBTO-Argon were observed. X-ray photoelectron spectroscopy analysis reveals a complex interplay of Eu II/III /Ti III/IV configurations which contribute to the observed ferroic and fluorescence behavior.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2023

Eu speciation in apatite at 1 bar: An experimental study of valence-state partitioning by XANES, lattice strain, and Eu/Eu* in basaltic systems

Abstract Partition coefficients for rare earth elements (REEs) between apatite and basaltic melt were determined as a function of oxygen fugacity (fO2; iron-wüstite to hematite-magnetite buffers) at 1 bar and between 1110 and 1175 °C. Apatite-melt partitioning data for REE3+ (La, Sm, Gd, Lu) show near constant values at all experimental conditions, while bulk Eu becomes more incompatible (with an increasing negative anomaly) with decreasing fO2. Experiments define three apatite calibrations that can theoretically be used as redox sensors. The first, a XANES calibration that directly measures Eu valence in apatite, requires saturation at similar temperature-composition conditions to experiments and is defined by: ( E u 3 + ∑ E u ) Apatite = 1 1 + 10 - 0.10 ± 0.01 × l o g ⁡ ( f o 2 ) - 1.63 ± 0.16 . The second technique involves analysis of Sm, Eu, and Gd in both apatite and coexisting basaltic melt (glass), and is defined by: ( Eu E u * ) D Sm × Gd = 1 1 + 10 - 0.15 ± 0.03 × l o g ⁡ ( f o 2 ) - 2.46 ± 0.41 . The third technique is based on the lattice strain model and also requires analysis of REE in both apatite and basalt. This calibration is defined by ( Eu E u * ) D lattice strain = 1 1 + 10 - 0.20 ± 0.03 × l o g ⁡ ( f o 2 ) - 3.03 ± 0.42 . The Eu valence-state partitioning techniques based on (Sm×Gd) and lattice strain are virtually indistinguishable, such that either methodology is valid. Application of any of these calibrations is best carried out in systems where both apatite and coexisting glass are present and in direct contact with one another. In holocrystalline rocks, whole rock analyses can be used as a guide to melt composition, but considerations and corrections must be made to either the lattice strain or Sm×Gd techniques to ensure that the effect of plagioclase crystallization either prior to or during apatite growth can be removed. Similarly, if the melt source has an inherited either a positive or negative Eu anomaly, appropriate corrections must also be made to lattice strain or Sm×Gd techniques that are based on whole rock analyses. This being the case, if apatite is primary and saturates from the parent melt early during the crystallization sequence, these corrections may be minimal. The partition coefficients for the REE between apatite and melt range from a maximum DEu3+ = 1.67 ± 0.25 (as determined by lattice strain) to DLu3+ = 0.69 ± 0.10. The REE partition coefficient pattern, as observed in the Onuma diagram, is in a fortuitous situation where the most compatible REE (Eu3+) is also the polyvalent element used to monitor fO2. These experiments provide a quantitative means of assessing Eu anomalies in apatite and how they be used to constrain the oxygen fugacity of silicate melts.

Geochemistry & Geophysics↗
DOE OSTI2020

Materials Data on Eu(ZnSn)2 by Materials Project

EuZn2Sn2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Eu is bonded in a 8-coordinate geometry to eight Zn and eight Sn atoms. There are four shorter (3.54 Å) and four longer (3.61 Å) Eu–Zn bond lengths. There are four shorter (3.51 Å) and four longer (3.72 Å) Eu–Sn bond lengths. There are two inequivalent Zn sites. In the first Zn site, Zn is bonded to four equivalent Eu and four equivalent Sn atoms to form distorted ZnEu4Sn4 tetrahedra that share corners with twelve equivalent SnEu4Zn4 tetrahedra, edges with two equivalent SnEu4Zn4 tetrahedra, edges with four equivalent ZnEu4Sn4 tetrahedra, and faces with four equivalent ZnEu4Sn4 tetrahedra. All Zn–Sn bond lengths are 2.76 Å. In the second Zn site, Zn is bonded in a 9-coordinate geometry to four equivalent Eu and five Sn atoms. There are one shorter (2.60 Å) and four longer (2.80 Å) Zn–Sn bond lengths. There are two inequivalent Sn sites. In the first Sn site, Sn is bonded to four equivalent Eu and four equivalent Zn atoms to form distorted SnEu4Zn4 tetrahedra that share corners with twelve equivalent ZnEu4Sn4 tetrahedra, edges with two equivalent ZnEu4Sn4 tetrahedra, edges with four equivalent SnEu4Zn4 tetrahedra, and faces with four equivalent SnEu4Zn4 tetrahedra. In the second Sn site, Sn is bonded in a 9-coordinate geometry to four equivalent Eu and five Zn atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Eu(AlAu)2 by Materials Project

EuAu2Al2 crystallizes in the tetragonal P4/nmm space group. The structure is three-dimensional. Eu is bonded in a 12-coordinate geometry to eight Au and eight Al atoms. There are four shorter (3.40 Å) and four longer (3.46 Å) Eu–Au bond lengths. There are four shorter (3.41 Å) and four longer (3.47 Å) Eu–Al bond lengths. There are two inequivalent Au sites. In the first Au site, Au is bonded in a 5-coordinate geometry to four equivalent Eu and five Al atoms. There are one shorter (2.55 Å) and four longer (2.63 Å) Au–Al bond lengths. In the second Au site, Au is bonded to four equivalent Eu and four equivalent Al atoms to form distorted AuEu4Al4 tetrahedra that share corners with twelve equivalent AlEu4Au4 tetrahedra, edges with two equivalent AlEu4Au4 tetrahedra, edges with four equivalent AuEu4Al4 tetrahedra, and faces with four equivalent AuEu4Al4 tetrahedra. All Au–Al bond lengths are 2.61 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded in a 5-coordinate geometry to four equivalent Eu and five Au atoms. In the second Al site, Al is bonded to four equivalent Eu and four equivalent Au atoms to form AlEu4Au4 tetrahedra that share corners with twelve equivalent AuEu4Al4 tetrahedra, edges with two equivalent AuEu4Al4 tetrahedra, edges with four equivalent AlEu4Au4 tetrahedra, and faces with four equivalent AlEu4Au4 tetrahedra.

36 MATERIALS SCIENCE↗