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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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All sourcesNASA NTRSDOE OSTI
DOE OSTI2023

Elusive Double Perovskite Iodides: Structural, Optical, and Magnetic Properties

Halide double perovskites [A 2 M I M III X 6 ] are an important class of materials that have garnered substantial interest as non-toxic alternatives to conventional lead iodide perovskites for optoelectronic applications. While numerous studies have examined chloride and bromide double perovskites, reports of iodide double perovskites are rare, and their definitive structural characterization has not been reported. Predictive models have aided us here in the synthesis and characterization of five iodide double perovskites of general formula Cs 2 NaLnI 6 (Ln=Ce, Nd, Gd, Tb, Dy). Finally, the complete crystal structures, structural phase transitions, optical, photoluminescent, and magnetic properties of these compounds are reported.

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2018

Structural Analysis and Magnetic Properties of Lithium-Doped Ni-Zn Ferrite Nanoparticle

Lithium-doped nickel-zinc ferrite compound with formula Ni{sub 0.8}Zn{sub 0.2−2x}Li{sub x}Fe{sub 2+x}O{sub 4} (x = 0, 0.01, 0.03, 0.05) was prepared using the sol-gel technique. The results of XRD proved a cubic spinel system of crystal. The lattice parameters, average particle sizes, and crystal density were calculated. It was found that the distance between magnetic ions decreases with lithium concentration and crystal density values ranging from 5.3 to 5.2 g/cm{sup 3}. SEM and AFM show the lithium substitution effect on the morphology of the samples. The saturation magnetization (M{sub s}) and coercivity (H{sub c}) of Ni{sub 0.8}Zn{sub 0.2−2x}Li{sub x}Fe{sub 2+x}O{sub 4} increase with an increasing content of Li{sup 1+} ion, where x is equal to 0, 0.01, 0.03, and 0.05. The M{sub s} and H{sub c} increase from 52 to 65 emu/g and from 99 to 119 Oe, respectively. The squareness ratio (M{sub r}/M{sub s}) appeared at a maximum value of x = 0.01.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Electrochemical and Magnetic Properties of Electrospun SrTi{sub 1−x}Fe{sub x}O{sub 3} (x = 0, 0.05 and 0.10) Nanofibers for Anodes of Li-Ion Batteries

SrTi{sub 1−x}Fe{sub x}O{sub 3} (x = 0, 0.05 and 0.1) nanofibers (NFs) were fabricated by electrospinning technique. As prepared products were calcined at 800 {sup ∘} C in argon atmosphere for 3 h to obtain a perovskite phase. The crystal structure and morphology of samples were investigated using X-ray diffraction (XRD), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). Electrochemical and magnetic properties of calcined NFs were studied using a potentiostat/galvanostat electrochemical cell system and vibrating sample magnetometer (VSM), respectively. XRD results showed the cubic perovskite structure of calcined samples with the diameter estimated by TEM in the range of 137.4–141.3 nm SEM micrographs revealed the linkage of crystalline grains in NFs of porous and rough surfaces. Electrochemical properties performed on coin-cell-type Li-ion batteries (LIBs) with calcined SrTi{sub 1−x}Fe{sub x}O{sub 3} (x = 0.05 and 0.10) NF-based anodes showed a significant increase of the specific capacity from 305 to 431 mAh/g for the first cycle with the reversible values of 100 and 130 mAh/g, respectively. VSM measurements at room temperature (RT) indicated that calcined SrTiO{sub 3} NFs exhibited paramagnetic (PM) behavior, while calcined SrTi{sub 1−x}Fe{sub x}O{sub 3} NFs displayed ferromagnetic (FM) behavior at RT with the increase of unsaturated magnetization at 10 kOe from 0.46 to 0.82 emu/g for samples with x = 0.05 and 0.10, respectively. The observed FM behavior in calcined SrTi{sub 1−x}Fe{sub x}O{sub 3} (x = 0.05 and 0.1) NFs was suggested to originate from the face center exchange (FCE) mechanism owing to Fe{sup 3+} –Vo–Fe{sup 3+} couplings.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Magnetic Properties of Mn-Substituted Zn–Mg- and Zn–Co-Nanosized Compounds

Mn-substituted Zn–Mg and Zn–Co with chemical formula Mn{sub 0.3}Mg{sub 0.2}TM{sub 0.5}Fe{sub 2}O{sub 4} (TM = Zn or Co) fine powders have been synthesized by glycol-thermal process. XRD results reveal the formation of a cubic phase without any impurity phases. TEM images show nearly spherical particles with fairly distributed particles with an average crystallite size of about 14 nm. {sup 57}Fe Mössbauer spectral studies show well-resolved magnetic splitting in the Mn–Mg–Co oxide due to stronger superexchange interactions. FC and ZFC magnetization data revealed the superparamagnetic nature of the compounds investigated. Mn–Mg–Zn nanoparticles are blocked at about 206 K while the maximum blocking temperature of Mn–Mg–Co-nanosized oxide is above 300 K. These differences were discussed on the basis of Stoner-Wohlfath relation T{sub B} = KV /25k{sub B}.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2019

Structural, Electrical, and Magnetic Properties of Ferrite-Reinforced PANI Composites

A Y-type hexagonal ferrite with chemical composition CaBaCo{sub 2}In{sub 0.5}Fe{sub 11.5}O{sub 22} was prepared by a sol-gel auto combustion technique. Y-ferrite/PANI nanocomposites were prepared by in situ polymerization of PANI with general formula CaBaCo{sub 2}In{sub 0.5}Fe{sub 11.5}O{sub 22} (1-x) + PANI (x) (x = 0.30, 0.50, 0.8, and 1) with nomenclature CF1, CF2, CF3, and P respectively. The samples were characterized by X-ray diffraction (XRD) and electrical and magnetic measurements. X-ray diffraction revealed that Y-type ferrite was successfully prepared in a single phase form. DC resistivity increases with increasing ferrite filler in nanocomposites due to large resistive behavior of ferrite in conducting polymer matrix. The dielectric constant, dielectric loss, and AC conductivity decreases with the increase of ferrite content. The dielectric is high due to interfacial polarization at low frequency, and it is low at high frequency following Maxwell-Wagner model. The coercivity increases with the decrease of ferrite filler content whereas saturation magnetization and remanence decreases which is due to random distribution of ferrite filler particles in PANI matrix. Due to large coercivity and low values of ε′ and ε″, the present samples may be useful in recording media and electromagnetic shielding.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Magnetic Properties and Photocatalytic Behavior of Co Co-doped BiFeO{sub 3}:Er

The multiferroic materials Bi{sub 0.95}Er{sub 0.05}Fe{sub 1−x}Co{sub x} O{sub 3} (x = 0, 0.01, 0.03, and 0.05) are synthesized by solvothermal method. X-ray diffraction pattern is used to confirm the formation of rhombohedral crystal structure. TEM images show agglomerated nanosize particles. With the concentration of Co, a red shift is observed in the charge transfer transition of O{sub 2p}-Fe{sub 3d} band and band gap decreases. At higher concentration of Co, the saturation magnetization enhances and coercivity also varies with the concentration of Co. The photocatalytic degradation of methylene blue is evaluated under the visible light with the assistance of H{sub 2}O{sub 2}. With the increase in Co concentration, the photocatalytic activity decreases. The main species responsible for the degradation is found out using scavengers like ammonium oxalate, silver nitrate, p-benzoquinone, and tert-butyl-alcohol. The possible mechanism for the degradation of dye is explained.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Effect of Ti and Zn Doping on the Structural, Electric, and Magnetic Properties of GaFeO{sub 3}

Multidoped (Zn,Ti) gallium orthoferrite [GaFeO{sub 3} and Ga{sub 0.98}Zn{sub 0.02}Fe{sub 0.98}Ti{sub 0.02}O{sub 3}] ceramic was synthesized through a solid-state reaction. X-ray analysis of the prepared material provides its basic crystal data of a single-phase orthorhombic system. The scattered crystallite size and lattice strain of the material were estimated. Analysis of the micrograph of field emission scanning electron microscope shows uniform grain distribution in the sample, suggesting the formation of good quality of sample. Founded on the magnetic measurements, it is concluded that (Zn,Ti)-modified gallium ferrite has provided a reduction in the Curie temperature (T{sub C}); however, no significant changes in the magnetization values with Zn and Ti integration in GaFeO{sub 3} lattice. A noteworthy effect of substitution of multiple elements at the Ga and Fe sites on dielectric constant and tangent loss of GaFeO{sub 3} has been observed. Complete studies of temperature (180–400 K) and frequency (10–10{sup 7} Hz) dependence of dielectric constant and impedance have provided the effect of grains and grain boundaries on the conduction mechanism and dielectric relaxation of the material.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2018

Magnetic Properties of a Layered Cobaltite Sr{sub 1–x}Y{sub x}CoO{sub 3–δ} (x = 0.1)

The structure, the magnetic and magnetotransport properties of perovskite Sr{sub 0.9}Y{sub 0.1}CoO{sub 2.63} have been studied. The sample is shown to have a two-phase structure. The main phase has a tetragonally distorted unit cell and is described by space group I4/mmm. The broadening of the reflections with indices corresponding to doubling unit cell parameter c indicates the absence of the rigorous translation symmetry along axis c. The existence of the broadened superstructure reflection observed in the diffraction pattern at small angles at temperature lower than 400 K is explained by the existence of the monoclinic phase whose content is significantly lower than that of the tetragonal phase, but is dominant in the Sr{sub 0.8}Y{sub 0.2}CoO{sub 3–δ} composition. The spontaneous magnetization appears as the monoclinic phase forms. The magnetic structure is mainly G-type antiferromagnetic with magnetic moments 1.5μ{sub B} in the layers of CoO{sub 6} octahedra and 2μ{sub B} in the anion-deficit CoO{sub 4+γ} layers. The conduction of the Sr{sub 0.9}Y{sub 0.1}CoO{sub 2.63} composition has a semiconducting character. The magnetoresistance is 57% in a field of 14 T at a temperature of 5 K and strongly decreases with the temperature increase.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Relevance of the Preparation of the Target for PLD on the Magnetic Properties of Films of Iron-Doped Indium Oxide

This paper concerns the importance of the preparation of the targets that may be used for pulsed laser deposition of iron-doped indium oxide films. Targets with a fixed concentration of iron are fabricated from indium oxide and iron metal or one of the oxides of iron, FeO, Fe3O4 and Fe2O3. Films from each target were ablated onto sapphire substrates at the same temperature under different oxygen pressures such that the thickness of the films was kept approximately constant. The films were studied using X-ray diffraction, X-ray absorption (both XANES and EXAFS), optical absorption and magnetic circular dichroism. The magnetic properties were measured with a SQUID magnetometer. At the lowest oxygen pressure, there was evidence that some of the iron ions in the films were in the state Fe2+, rather than Fe3+, and there was also a little metallic iron; these properties were accompanied by a substantial magnetisation. As the amount of the oxygen was increased, the number of defect phases and the saturation magnetisation was reduced and the band gap increased. In each case, we found that the amount of the oxygen that had been included in the target from the precursor added to the effect of adding oxygen in the deposition chamber. It was concluded that the amount of oxygen in the target due to the precursor was an important consideration but not a defining factor in the quality of the films.

(InFe)2O3↗
DOE OSTI2019

Spin Crossover and Magnetic Properties of Ba-Substituted Cobaltites

The dependence of the properties of the La{sub 0.45}Ba{sub 0.55}CoO{sub 3 – δ} and La{sub 0.4}Ba{sub 0.6}CoO{sub 3 – δ} cobaltites on the oxygen content has been studied. A decrease in the oxygen content leads to the stabilization of cobalt ions in the 3+ oxidation state and to a transition from a conducting state with positive exchange interaction to an antiferromagnetic insulating state with a long range magnetic order with decreasing temperature. Application of a magnetic field gradually transforms the antiferromagnetic state to the ferromagnetic one. The cubic lattice parameter is independent of temperature and an anomalous dependence of the magnetization, electrical conductivity, and magnetoresistance is treated within a spin crossover scenario. It is assumed that the high-temperature conducting phase and ferromagnetic clusters correspond to a collective intermediate spin state of cobalt ions, whereas the low-temperature antiferromagnetic phase corresponds to a mixed high-spin/low-spin state.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2024

Transfer of Millimeter‐Scale Strained Multiferroic Epitaxial Thin Films on Rigid Substrates via an Epoxy Method Producing Magnetic Property Enhancement

The demonstration of epitaxial thin film transfer has enormous potential for thin film devices free from the traditional substrate epitaxy limitations. However, large-area continuous film transfer remains a challenge for the commonly reported polymer-based transfer methods due to bending and cracking during transfer, especially for highly strained epitaxial thin films. In this work, a new epoxy-based, rigid transfer method is used to transfer films from an SrTiO 3 (STO) growth substrate onto various new substrates, including those that will typically pose significant problems for epitaxy. An epitaxial multiferroic Bi 3 Fe 2 Mn 2 O x (BFMO) layered supercell (LSC) material is selected as the thin film for this demonstration. The results of surface and structure studies show an order of magnitude increase in the continuous area of transferred films when compared to previous transfer methods. The magnetic properties of the BFMO LSC films are shown to be enhanced by the release of strain in this method, and ferromagnetic resonance is found with an exceptionally low Gilbert damping coefficient. The large-area transfer of this highly strained complex oxide BFMO thin film presents enormous potential for the integration of many other multifunctional oxides onto new substrates for future magnetic sensors and memory devices.

bismuth oxides↗
DOE OSTI2022

SrNi(VO 4 )(OH): The High-Temperature Hydrothermal Synthesis and Magnetic Properties of an Adelite-Descloizite-Type Structure

Single crystals of a new transition metal adelite-descloizite-type structure were synthesized using a high temperature (580 °C) high-pressure hydrothermal technique. Single crystal X-ray diffraction and energy dispersive X-ray analysis (EDX) were used to investigate the structure and elemental composition, respectively. SrNi(VO 4 )(OH) crystallizes in an acentric orthorhombic crystal system in the space group P2 1 2 1 2 1 (no. 19); Z = 4, a = 5.9952(4) Å, b = 7.5844(4) Å, c = 9.2240(5) Å. The structure is comprised of a Ni–O–V framework where Sr 2+ ions reside inside the channels. Single-crystal magnetic measurements display a significant anisotropy in both temperature- and field-dependent data. The temperature dependent magnetic measurement shows antiferromagnetic behavior at T N ~8 K. Overall, the magnetic properties indicate the presence of competing antiferromagnetic and ferromagnetic interactions of SrNi(VO 4 )(OH).

37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CH↗
DOE OSTI2019

Template Synthesis, Structure, and Magnetic Properties of Layered Nanowires

Nanowires (NWs) consisting of Ni/Cu and Co/Cu alternating layers with a diameter of 100 nm and layer thicknesses varying between 10 and 500 nm are prepared by template synthesis in pores of polymer track-etched membranes. Bath compositions and different regimes for pulsed electrodeposition of NWs are explored. A procedure for electrodeposition of NWs using pulses of equal charge is developed. By diminishing the amount of charge per pulse, initially we manage to lower the layer thickness to 10–15 nm, but further diminishing of charge in pulses leads to the blending of elemental composition of adjacent layers and/or formation of rod–shell nanostructures within the NWs. The coercive force (15–30 mT) and residual magnetization of our layered NWs are determined from magnetization measurements. For NWs with a layer thickness of 50–100 nm, the magnetization curves recorded in the out-of-plane and in-plane geometries are similar in shape and have similar parameters. For NWs with thicker layers (250 and 500 nm), magnetization curves are markedly different due to magnetic anisotropy (an easy magnetization axis emerges longitudinally to NWs) and interference between neighboring NWs. Magnetic force microscopy of isolated NWs identifies that the NWs comprise magnetic regions extending over ~100–150 nm. The NW can be partially remagnetized by applying an external magnetic field (+16 mT) longitudinally.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Effects of Nd, Er Doping on the Structure and Magnetic Properties of YFeO{sub 3}

Nd, Er co-doped YFeO{sub 3} compounds were synthesized by sol-gel method. The prepared compounds were characterized by powder x-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), energy-dispersive x-ray (EDX), and vibrating sample magnetometer (VSM) integrated in a physical property measurement system (PPMS-9), respectively. The results show that the compounds possess orthorhombic perovskite structure. The Y{sub 0.5}Er{sub 0.1}Nd{sub 0.4}FeO{sub 3} compound mainly consists of five elements (Er, Nd, Y, Fe, and O) and atom ratio matched well with the formula. With the increase of Nd{sup 3+} doping content in Y{sub 0.5}Er{sub 0.5−x}Nd{sub x}FeO{sub 3} (x = 0, 0.1, 0.2, 0.3, and 0.4), the coercivity increases gradually while the saturation magnetization and remanent magnetization decrease at the same time. Introducing Nd{sup 3+} and Er{sup 3+} ions into YFeO{sub 3} will make a change on a structure distortion, resulting in the decrease of the Fe–O–Fe angle and the consequent reduction of superexchange effect. From our research results, the relationship between the r (R{sup 3+}) and the superexchange bond angle is different from pure-phase orthoferrites R FeO{sub 3}.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Magnetic Properties of MFeCrO{sub 4} (M = Co/Ni) Prepared by Solution Combustion Method

Single phase MFeCrO{sub 4} (M = Co/Ni) nanosized samples are prepared by solution combustion method using glycine as fuel. Lattice parameter obtained after Rietveld refinement of the powder x-ray diffraction pattern of CoCrFeO{sub 4} and NiCrFeO{sub 4} samples are 8.374 and 8.325 Å and corresponding crystallite sizes are 40 and 27 nm, respectively. FTIR spectra of both samples show tetrahedral and octahedral metal oxygen bond stretching peaks at 596 and 488 cm{sup −1}, indicating spinel phase formation. DC magnetisation study indicates that both samples are ferrimagnetic at room temperature, with CoCrFeO{sub 4} having a higher value of saturation magnetisation. Mössbauer spectra indicate the presence of magnetic relaxation in the samples. Also, the strength of interaction with nearest neighbour Fe{sup 3+} cations is higher in NiCrFeO{sub 4}.

36 MATERIALS SCIENCE↗
DOE OSTI2019

Structural, Optical and Magnetic Properties of PANI/Se{sub 0.95}Fe{sub 0.05} Nanocomposites

Polyaniline (PANI) coupled with Se{sub 0.95}Fe{sub 0.05} in various weight percentage (5 and 10 wt%) were formed by in situ polymerization method of PANI in the presence of Se{sub 0.95}Fe{sub 0.05}. The functionality of the investigated nanocomposites was investigated by X-ray diffraction (XRD), Fourier transform infrared (FTIR), vibrating sample magnetometer (VSM), and photoluminescence (PL) analyses. The structural characteristics of PANI and the existence of Se{sub 0.95}Fe{sub 0.05} together with PANI were confirmed using XRD. The different functional groups of nanocomposite were studied using FTIR. PANI/Se{sub 0.95}Fe{sub 0.05} nanocomposites exhibited a weak ferromagnetic behavior. Law of Approach to saturation was used to determine the saturation magnetization of nanocomposites samples. The PL of PANI and nanocomposites emitted five emissions in violet and blue ranges. The PL intensity of the emission peaks is significantly reduced when Se{sub 0.95}Fe{sub 0.05} is introduced to PANI matrix.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2018

Influence of europium doping on magnetic properties of 3D topological semimetal Cd{sub 3}As{sub 2} from ESR data

Influence of weak doping by rare-earth elements on magnetic and transport properties of a 3D topological semimetal Cd{sub 3}As{sub 2} was studied experimentally. In particular, the doping by europium causes to change of the magnetoresistance sign from positive to negative. First measurements of electron spin resonance and magnetic susceptibility have shown that there are two types of Eu{sup 2+} magnetic ions that occupy the positions of cadmium ions and tetrahedral vacancies and form the ferromagnetic and antiferromagnetic phases, respectively. These facts give an evidence of small-scaled phase separation and a transformation of the Dirac semimetal to a Weyl semimetal induced by magnetic impurities.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2019

Solvothermal Synthesis of Mesoporous Fe{sub 3}O{sub 4} Nanoparticles in Mixed Solvent of Ethylene Glycol and Water: Structure and Magnetic Properties

Mesoporous Fe{sub 3}O{sub 4} nanoparticles were synthesized by a solvothermal method, via a mixed solvent of ethylene glycol (EG) and deionized water, using iron chloride and urea as the precursors. The phase, morphology, and pore structure are investigated by the characterization of X-ray diffraction (XRD), transmission electron microscopy (TEM), and N{sub 2} isotherm adsorption–desorption. The results show that the amount of water in the mixed solvent plays vital role in controlling the size of Fe{sub 3}O{sub 4} nanoparticles, specific surface area, and pore size. Additionally, solid Fe{sub 3}O{sub 4} nanospheres were prepared using only EG as solvent, while α-Fe{sub 2}O{sub 3} nanosized polyhedrals were obtained with only water as solvent. The mesoporous Fe{sub 3}O{sub 4} nanoparticles show a ferromagnetic behavior, with saturation magnetizations (Ms) of 78–82 emu g{sup − 1} and coercivities (Hc) ranging from 13–58 Oe. The α-Fe{sub 2}O{sub 3} nanoparticles also exhibit a weak-ferrimagnetic character, with a remanent magnetization (Mr) of 0.24 emu g{sup − 1}, and Hc of 558 Oe.

77 NANOSCIENCE AND NANOTECHNOLOGY↗