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At least 91 records · Page 5
All sourcesNASA NTRSDOE OSTI
DOE OSTI2024

Superconducting (Ba,K)Fe 2 As 2 epitaxial films on single and bicrystal SrTiO 3 substrates

The realization of single crystal and bicrystal films of superconducting materials is of great interest because they allow the investigation of the intragrain performance as well as the understanding of potential limitations in the grain boundary transparency. For many years, the realization of a high-quality (Ba,K)Fe 2 As 2 film has been challenging. Here, the realization of (Ba,K)Fe 2 As 2 epitaxial thin films on single crystal SrTiO 3 (001) and [001]-tilt-type SrTiO 3 bicrystal substrates with high superconducting properties is demonstrated. The epitaxial growth of (Ba,K)Fe 2 As 2 was enabled by implementing an undoped BaFe 2 As 2 buffer layer between the SrTiO 3 substrate and (Ba,K)Fe 2 As 2 film. The film exhibits a high T c of 38.0 K and an extremely high J c of 14.3 MA/cm 2 at 4.2 K. Artificial grain boundaries of (Ba,K)Fe 2 As 2 were also successfully achieved on bicrystals with misorientation angles up to 36.8° by the same preparation methods. The artificial grain boundaries exhibited an identical T c of 38.0 K and an excellent transfer of the grain orientation from the bicrystal substrates with high crystallinity comparable to that of the high-quality Ba(Fe,Co) 2 As 2 films. Furthermore, this enables the investigation of the intrinsic (Ba,K)Fe 2 As 2 grain boundary nature, which will clarify its potential for superconducting applications, like Josephson junctions, wires, and magnets.

(Ba,K)Fe2As2↗
DOE OSTI2025

Synthesis, Structures, and Transport Properties of Quaternary Ba–Ag– Tr –As Materials ( Tr = Ga, In)

The synthesis, structures, and properties of two quaternary barium–arsenide materials are presented. The first, Ba 4 Ag 2.3 In 1.7 As 8 , is a novel material with the monoclinic unit cell ( P 2 1 / m space group). The layered crystal structure of Ba 4 Ag 2.3 In 1.7 As 8 may be considered a lower‐symmetry, distorted analog of the LaCuSb 2 structure. The structure features a rare As fragment, cis‐trans As chains along the [010] direction. Large crystals of Ba 4 Ag 2.3 In 1.7 As 8 can be grown from Bi flux and are used for subsequent transport property measurements. Electrical resistivity and heat capacity properties are reported, establishing Ba 4 Ag 2.3 In 1.7 As 8 as a metallic phase. The second material, Ba 4 AgGa 5 As 8 , is a 3D material that crystallizes in the orthorhombic unit cell (noncentrosymmetric and polar Iba 2 space group). Expanding upon its original discovery, the optimized synthetic profile for single‐phase polycrystalline samples as well as transport properties relevant to thermoelectric applications are presented. Ba 4 AgGa 5 As 8 exhibits a high Seebeck coefficient of 290 μV K −1 at room temperature, indicative of lower carrier concentrations typical for nonmetallic phases. Electrical resistivity measurements also affirm conventional semiconducting behavior for Ba 4 AgGa 5 As 8 .

Kyveryga, Victoria [Department of Chemistry Iowa S↗
DOE OSTI2025

Pressure-induced cation and vacancy disorder-order transition and near-zero τ f in deficient hexagonal perovskite Ba 8 ZnTa 6 O 24 dielectrics

Pressure applications can enable the tuning of atomic/defect ordering and provide access to new functional materials. Here, in this study, we report that pressure-induced structural transformation featuring disorder-order transition of both cations and vacancies in the 8-layer deficient hexagonal perovskite tantalate dielectrics Ba 8 ZnTa 6 O 24 , which transformed the structure from twin to shift and remarkably lowered the temperature coefficient of resonant frequency τ f down to near zero (∼0.56 ppm/°C) from 38 ppm/°C for the twinned precursor. The atomic scale STEM-HAADF and EDS results confirm the ordering of Zn in the Ta host at the nanometer scale in the shifted material featuring well-ordered Ba 8 ZnTa 6 O 24 slabs intergrown with Ba 3 ZnTa 2 O 9 and Ba 5 Ta 4 O 15 monolayers and anti-phase grain boundaries as planar defects. The pressure-induced twin-shift structural transformation of Ba 8 ZnTa 6 O 24 features the rare constant concentration of the hexagonal stacked layers, which is allowed by the vacancy ordering at the central layers of face-shared octahedral (FSO) trimers avoiding the FSO B-B repulsion, and remarkably the faster cationic ordering kinetics compared with the 2:1 ordered complex perovskites. Although the inclusion of numerous planar defects and the oxidizable atomic defects led to significant p-type conduction and inhomogeneous electrical microstructures, resulting in an extraordinarily high extrinsic dielectric loss for the high-pressure shifted Ba 8 ZnTa 6 O 24 pellet, the intrinsically near-zero τ f could make the shifted Ba 8 ZnTa 6 O 24 perovskite an ideal microwave dielectric resonator candidate if the defects could be eliminated.

high pressure↗
DOE OSTI2024

Organizing Chaos: Boosting Thermoelectric Properties by Ordering the Clathrate Framework of Ba 8 Cu 16 As 30

The type I clathrate, Ba 8 Cu 16 As 30 , is reinvestigated and found to have a low-temperature polymorph mP 108-Ba 8 Cu 16 As 30 with ordered Cu and As sites. In situ temperature-dependent powder X-ray diffraction experiments guided synthetic efforts toward the synthesis of the ordered monoclinic ( mP 108) and disordered cubic ( cP 54) polymorphs with high phase purity. While a transition from mP 108-Ba 8 Cu 16 As 30 to cP 54-Ba 8 Cu 16 As 30 is not directly observed, cP 54-Ba 8 Cu 16 As 30 is stabilized through quenching from high temperatures and is confirmed through high-resolution synchrotron powder X-ray diffraction. Further, combined theoretical predictions and experimental observations of the thermoelectric properties of both polymorphs reveal that the ordering of Cu and As atoms in the clathrate framework simultaneously enhances the Seebeck coefficient and electronic conductivity by increasing the hole effective mass and reducing the electronic scattering events. Consequently, the zT of mP 108-Ba 8 Cu 16 As 30 reaches a maximum of 0.2 at 575 K, an order of magnitude higher than that of cP 54-Ba 8 Cu 16 As 30 .

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

Materials Data on Ba(GeRh)2 by Materials Project

Ba(RhGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba is bonded in a 8-coordinate geometry to eight equivalent Rh and eight equivalent Ge atoms. All Ba–Rh bond lengths are 3.72 Å. All Ba–Ge bond lengths are 3.49 Å. Rh is bonded to four equivalent Ba and four equivalent Ge atoms to form a mixture of distorted corner, edge, and face-sharing RhBa4Ge4 tetrahedra. All Rh–Ge bond lengths are 2.46 Å. Ge is bonded in a 8-coordinate geometry to four equivalent Ba and four equivalent Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(BIr)2 by Materials Project

Ba(IrB)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba is bonded in a 8-coordinate geometry to eight equivalent Ir and eight equivalent B atoms. All Ba–Ir bond lengths are 3.50 Å. All Ba–B bond lengths are 3.50 Å. Ir is bonded in a 4-coordinate geometry to four equivalent Ba and four equivalent B atoms. All Ir–B bond lengths are 2.13 Å. B is bonded in a 4-coordinate geometry to four equivalent Ba and four equivalent Ir atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(AgGe)2 by Materials Project

Ba(AgGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba is bonded in a 8-coordinate geometry to eight equivalent Ag and eight equivalent Ge atoms. All Ba–Ag bond lengths are 3.59 Å. All Ba–Ge bond lengths are 3.54 Å. Ag is bonded in a 12-coordinate geometry to four equivalent Ba and four equivalent Ge atoms. All Ag–Ge bond lengths are 2.75 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ba, four equivalent Ag, and one Ge atom. The Ge–Ge bond length is 2.56 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(MnSn)2 by Materials Project

Ba(MnSn)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba is bonded in a 8-coordinate geometry to eight equivalent Mn and eight equivalent Sn atoms. All Ba–Mn bond lengths are 3.82 Å. All Ba–Sn bond lengths are 3.70 Å. Mn is bonded to four equivalent Ba and four equivalent Sn atoms to form a mixture of distorted edge, corner, and face-sharing MnBa4Sn4 tetrahedra. All Mn–Sn bond lengths are 2.75 Å. Sn is bonded in a 9-coordinate geometry to four equivalent Ba, four equivalent Mn, and one Sn atom. The Sn–Sn bond length is 3.18 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(ClO3)2 by Materials Project

Ba(ClO3)2 crystallizes in the orthorhombic Fdd2 space group. The structure is three-dimensional. Ba is bonded in a 10-coordinate geometry to ten O atoms. There are a spread of Ba–O bond distances ranging from 2.82–3.15 Å. There are three inequivalent O sites. In the first O site, O is bonded in a bent 150 degrees geometry to one Ba and one Cl atom. The O–Cl bond length is 1.49 Å. In the second O site, O is bonded in a 1-coordinate geometry to two equivalent Ba and one Cl atom. The O–Cl bond length is 1.51 Å. In the third O site, O is bonded in a distorted trigonal planar geometry to two equivalent Ba and one Cl atom. The O–Cl bond length is 1.52 Å. Cl is bonded in a trigonal non-coplanar geometry to three O atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(BRh)2 by Materials Project

Ba(RhB)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba is bonded in a 8-coordinate geometry to eight equivalent Rh and eight equivalent B atoms. All Ba–Rh bond lengths are 3.49 Å. All Ba–B bond lengths are 3.50 Å. Rh is bonded in a 4-coordinate geometry to four equivalent Ba and four equivalent B atoms. All Rh–B bond lengths are 2.12 Å. B is bonded in a 4-coordinate geometry to four equivalent Ba and four equivalent Rh atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(MgGe)2 by Materials Project

Ba(MgGe)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba is bonded in a 8-coordinate geometry to eight equivalent Mg and eight equivalent Ge atoms. All Ba–Mg bond lengths are 3.71 Å. All Ba–Ge bond lengths are 3.58 Å. Mg is bonded to four equivalent Ba and four equivalent Ge atoms to form a mixture of corner, edge, and face-sharing MgBa4Ge4 tetrahedra. All Mg–Ge bond lengths are 2.81 Å. Ge is bonded in a 9-coordinate geometry to four equivalent Ba, four equivalent Mg, and one Ge atom. The Ge–Ge bond length is 2.67 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(AgSn)2 by Materials Project

Ba(AgSn)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba is bonded in a 8-coordinate geometry to eight equivalent Ag and eight equivalent Sn atoms. All Ba–Ag bond lengths are 3.79 Å. All Ba–Sn bond lengths are 3.77 Å. Ag is bonded in a 12-coordinate geometry to four equivalent Ba and four equivalent Sn atoms. All Ag–Sn bond lengths are 2.84 Å. Sn is bonded in a 9-coordinate geometry to four equivalent Ba, four equivalent Ag, and one Sn atom. The Sn–Sn bond length is 2.92 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(FeO2)4 by Materials Project

Ba(FeO2)4 crystallizes in the trigonal P-31m space group. The structure is two-dimensional and consists of one Ba(FeO2)4 sheet oriented in the (0, 0, 1) direction. Ba is bonded to twelve O atoms to form BaO12 cuboctahedra that share edges with six equivalent BaO12 cuboctahedra and edges with twelve equivalent FeO4 tetrahedra. There are six shorter (2.98 Å) and six longer (3.25 Å) Ba–O bond lengths. Fe is bonded to four O atoms to form FeO4 tetrahedra that share corners with four equivalent FeO4 tetrahedra and edges with three equivalent BaO12 cuboctahedra. There is three shorter (1.86 Å) and one longer (1.87 Å) Fe–O bond length. There are two inequivalent O sites. In the first O site, O is bonded in a linear geometry to three equivalent Ba and two equivalent Fe atoms. In the second O site, O is bonded in a distorted bent 120 degrees geometry to one Ba and two equivalent Fe atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(GeAu)2 by Materials Project

Ba(AuGe)2 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. Ba is bonded in a 8-coordinate geometry to eight equivalent Au and eight equivalent Ge atoms. There are four shorter (3.53 Å) and four longer (3.59 Å) Ba–Au bond lengths. All Ba–Ge bond lengths are 3.60 Å. Au is bonded in a 4-coordinate geometry to four equivalent Ba and four equivalent Ge atoms. There are two shorter (2.70 Å) and two longer (2.74 Å) Au–Ge bond lengths. Ge is bonded in a 9-coordinate geometry to four equivalent Ba and four equivalent Au atoms.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(MgIn)2 by Materials Project

Ba(MgIn)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba is bonded in a 8-coordinate geometry to eight equivalent Mg and eight equivalent In atoms. All Ba–Mg bond lengths are 4.00 Å. All Ba–In bond lengths are 3.75 Å. Mg is bonded to four equivalent Ba and four equivalent In atoms to form a mixture of corner, edge, and face-sharing MgBa4In4 tetrahedra. All Mg–In bond lengths are 2.99 Å. In is bonded in a 9-coordinate geometry to four equivalent Ba, four equivalent Mg, and one In atom. The In–In bond length is 2.90 Å.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(ClO)2 by Materials Project

(BaO2Cl)2Cl2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional and consists of four hydrochloric acid molecules and one BaO2Cl framework. In the BaO2Cl framework, Ba is bonded in a 4-coordinate geometry to four O and three equivalent Cl atoms. There are a spread of Ba–O bond distances ranging from 2.72–2.81 Å. There are a spread of Ba–Cl bond distances ranging from 3.24–3.33 Å. There are two inequivalent O sites. In the first O site, O is bonded in a distorted bent 120 degrees geometry to two equivalent Ba and one Cl atom. The O–Cl bond length is 2.41 Å. In the second O site, O is bonded in a distorted bent 120 degrees geometry to two equivalent Ba atoms. Cl is bonded to three equivalent Ba and one O atom to form a mixture of distorted corner and edge-sharing ClBa3O trigonal pyramids.

36 MATERIALS SCIENCE↗
DOE OSTI2020

Materials Data on Ba(AlGa)2 by Materials Project

Ba(GaAl)2 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. Ba is bonded in a 8-coordinate geometry to eight equivalent Ga and eight equivalent Al atoms. All Ba–Ga bond lengths are 3.49 Å. All Ba–Al bond lengths are 3.62 Å. Ga is bonded in a 9-coordinate geometry to four equivalent Ba, one Ga, and four equivalent Al atoms. The Ga–Ga bond length is 2.75 Å. All Ga–Al bond lengths are 2.69 Å. Al is bonded to four equivalent Ba and four equivalent Ga atoms to form a mixture of distorted corner, edge, and face-sharing AlBa4Ga4 tetrahedra.

36 MATERIALS SCIENCE↗