FeSn Phase Research Articles

Epitaxial growth and magnetic properties of kagome metal FeSn/elemental ferromagnet heterostructures

Binary kagome compounds TmXn (T = Mn, Fe, Co; X = Sn, Ge; m:n = 3:1, 3:2, 1:1) have garnered recent interest owing to the presence of both topological band crossings and flatbands arising from the geometry of the metal-site kagome lattice. To exploit these electronic features for potential applications in spintronics, the growth of high-quality heterostructures is required. Here, we report the synthesis of Fe/FeSn and Co/FeSn bilayers on Al2O3 substrates using molecular beam epitaxy to realize heterointerfaces between elemental ferromagnetic metals and antiferromagnetic kagome metals. Structural characterization using high-resolution x-ray diffraction, reflection high-energy electron diffraction, and electron microscopy reveals that the FeSn films are flat and epitaxial. Rutherford backscattering spectroscopy was used to confirm the stoichiometric window where the FeSn phase is stabilized, while transport and magnetometry measurements were conducted to verify metallicity and magnetic ordering in the films. Exchange bias was observed, confirming the presence of antiferromagnetic order in the FeSn layers, paving the way for future studies of magnetism in kagome heterostructures and potential integration of these materials into devices.

Thermodynamical and topological properties of metastable Fe3Sn

The Fe–Sn-based kagome compounds attract intensive attention due to its attractive topological transport and rich magnetic properties. Combining experimental data, first-principles calculations, and Calphad assessment, thermodynamic and topological transport properties of the Fe–Sn system were investigated. Density functional theory (DFT) calculations were performed to evaluate the intermetallics’ finite-temperature heat capacity (Cp). A consistent thermodynamic assessment of the Fe–Sn phase diagram was achieved by using the experimental and DFT results, together with all available data from previous publications. Here, we report that the metastable phase Fe3Sn was introduced into the current metastable phase diagram, and corrected phase locations of Fe5Sn3 and Fe3Sn2 under the newly measured corrected temperature ranges. Furthermore, the anomalous Hall conductivity and anomalous Nernst conductivity of Fe3Sn were calculated, with magnetization directions and doping considered as perturbations to tune such transport properties. It was observed that the enhanced anomalous Hall and Nernst conductivities originate from the combination of nodal lines and small gap areas that can be tuned by doping Mn at Fe sites and varying magnetization direction.

Effect of Cu and Co addition on non-isothermal crystallization kinetics of rapidly quenched Fe-Sn-B based alloys

Crystallization kinetics of rapidly quenched Fe-Sn-B alloys under non-isothermal conditions were studied using differential scanning calorimetry. Formation of crystalline phases was analyzed by X-ray diffraction. Nominal chemical compositions were Fe81Sn7B12, (Fe3Co1)81Sn7B12 and (Fe81Sn7B12)99Cu1. Alloys were prepared by planar flow casting in the form of ribbons approximately 20 µm thick and 6 mm wide. Mechanism of crystallization was studied under framework of the Johnson-Mehl-Avrami-Kolmogorov model. Alloys exhibit two stages of crystallization. Results show decrease in activation energy of the first stage of crystallization with addition of Cu and increase with addition of Co. Crystallization mechanism of the first stage of crystallization for Fe81Sn7B12 and (Fe81Sn7B12)99Cu1 alloy starts as growth with increasing nucleation rate and continues as growth with decreasing nucleation rate. Addition of Co changes mechanism of crystallization. Which in case of (Fe3Co1)81Sn7B12 alloy starts as a growth with increasing nucleation rate. Then changes to growth with decreasing nucleation rate. After which nucleation rate decreases to zero. Rest of crystallization stage is governed by growth of pre-existing nuclei. In the first stage of crystallization α-Fe phase with bcc structure crystallizes from amorphous matrix. In the second stage of crystallization the remaining amorphous matrix crystalizes into tetragonal Fe2B phase and hexagonal FeSn phase. After the first stage of crystallization, 50 % to 55 % volume of studied alloys were crystalized. Addition of Cu decreases crystalline size of α-Fe crystallites by 60 % and decreases concentration of Sn in α-Fe phase by 0.8 at. %. Addition of Co doesn't affect the size of α-Fe crystallites and decreases the concentration of Sn in α-Fe phase by 1.7 at. %.

Laser power influence on track’s geometry and microstructure aspects of Fe and Sn-based alloy processed by directed energy deposition

Additive manufacturing of metal matrix composite (MMC) is a challenging field to explore. Besides components’ geometric constitution, requirements related to final microstructures must be met. Depending on the application, such as tribology, machining, or magnetism related, there is a need to preserve a specific phase, which is generally responsible for the engineering function of the fabricated component. This work analyzes the laser power (P) parameter influence on track’s geometry and microstructure aspects of Fe and Sn-based alloy processed by directed energy deposition (DED). Objectives are observing the interaction between Fe-α and Sn-based alloy as a function of P and, then, define a processing window that allows the MMC microstructure. Experimental methodology relied on single-tracks bead-on-plate deposits with P variations. To assess track’s geometry and microstructure changes, postprocessing analyses were performed by scanning electron microscopy (SEM) and energy dispersive x-ray spectroscopy (EDS). Results show that P influences positively on tracks’ height, width, and cross section area. Greater laser power resulted in higher geometric aspects. Microstructure evolution was observed as P was enhanced from 150 to 700 W. In lower P ranges, Fe particles are not strongly affected by the heat source, resulting in an MMC microstructure mainly composed by Fe-α dispersed on a Sn-rich alloying matrix. When more thermal energy is provided due to higher laser power levels, Fe and Sn diffuse to a greater extent, resulting in an increased quantity of Fe-Sn phases and a more homogeneous microstructure. EDS mapping suggests that formed phases are Fe solid solutions containing Sn. Then, it is concluded that MMC microstructures are possible to be achieved around a P window of 150 W.

Experimental and computational analysis of binary Fe-Sn ferromagnetic compounds

Ferromagnetic Fe3Sn, Fe5Sn3 and Fe3Sn2 single crystals were synthesized using the reactive flux technique. Derived from single crystal x-ray diffraction and Transmission Electron Microscopy (TEM), a new structural model is proposed for the Fe5Sn3 crystals - the threefold twinning of an orthorhombic unit cell with (3 + 1) dimensional space group Pbcm(α00)0s0. The spontaneous magnetization (Ms) and the anisotropy constants K1 and K2 of Fe3Sn, Fe5Sn3 and Fe3Sn2 single crystals were determined in a wide temperature range using M(H) dependencies and a modified Sucksmith-Thompson technique. Ms and K1 were also evaluated in the framework of Density Functional Theory (DFT) and an overall good agreement was observed between the calculated and experimental results. Furthermore, a critical evaluation of different analytical models for the assessment of magnetocrystalline anisotropy was performed, which are restricted to the analysis of uniaxial magnetic domain patterns, and it is shown that such high-throughput techniques can lead to unrealistic results. Finally, a DFT high-throughput screening of the Fe-Sn phase diagram was used to identify Fe-Sn based phases with potential to be stabilized upon alloying, and their magnetization and magnetocrystalline anisotropy were evaluated. The results show that a similar strong anisotropy as observed in Fe3Sn may also be found in other Fe-Sn based phases, having higher potential to be used as hard magnetic material.

The Zinc-Rich Corner of the Fe-Si-Sn-Zn Quaternary System at 450 °C

The 450 °C isothermal sections of the Fe-Si-Sn-Zn quaternary system with Zn composition fixed at 70 and 93 at.% were determined experimentally using optical microscopy, scanning electronic microscopy coupled with energy dispersive X-ray spectroscopy (SEM-EDS), and X-ray diffractometry (XRD). Five four-phase regions were identified in the 70 at.% Zn section, whereas no four-phase region was found in the 93 at.% Zn section. The liquid phase was found to be in equilibrium with almost all phases in the two sections, including the FeSn, FeSi, FeSi2, Γ1, δ, ζ, and α-Fe phases. The solubility of Sn in the ζ, FeSi, and FeSi2 phases was rather limited; however, the maximum solubility of Si in the FeSn phase was 0.5 wt.%. No quaternary compound was found in the study.

Effects of Sn-foil addition on the microstructure and mechanical properties of laser welding joint for dual phase steel and magnesium alloy

The aim of present research was investigating the effects of Sn-foil addition on the microstructure and mechanical properties of laser welding joint for DP600 dual phase steel and AZ31 magnesium alloy in an overlap steel-on-magnesium configuration. Results showed that when Sn-foil was added as interlayer, some defects, such as surface pit, spatter and softening in heat affected zone, can be avoided,oxide and porosity are also no obvious in the weld. A good weld surface with continuous and uniform fish scale welding line is obtained. Fe–Sn phases, such as FeSn, Fe1.3Sn, and Fe3Sn, are formed in steel side, while Mg2Sn is found in magnesium side. These new phases are favorable for realizing the steel/magnesium metallurgical connection, and adding Sn-foil laser welding is an effective way in joining steel to magnesium alloy. However, mechanical property for steel/magnesium joint is closely connected with the brittleness of Mg2Sn phase, how to regulate its brittleness is the key in order to improve the joint properties.

Bulk combinatorial analysis for searching new rare-earth free permanent magnets: Reactive crucible melting applied to the Fe-Sn binary system

The reactive crucible melting method is known to be an efficient and low-cost bulk combinatorial synthesis technique to search for new phases. In this work, we tested this technique by investigating the Fe-Sn binary system. For high-throughput characterization, this synthesis technique was combined with energy dispersive x-ray spectroscopy as well as magneto-optical Kerr microscopy. The latter was used for identification of desired phases with uniaxial magnetic anisotropy. Reliability of the reactive crucible method was evaluated by comparison of the phase composition forming in the reactive crucible with phases appearing in conventionally melted samples and with the phases represented in the reported Fe-Sn phase diagram. It was found that the Fe5Sn3 phase, existing in the equilibrium phase diagram at 800 °C and forming in conventionally melted alloys, does not exist in the diffusion zone of the reactive crucible. The problem of ‘missing phases’ is discussed. In addition, we have shown that the anisotropy energy obtained by quantitative analysis of the uniaxial domain structure of Fe3Sn2 phase, gives the value of 1 MJ/m3, whereas K1 evaluated by conventional magnetometry is ∼ 0.07 MJ/m3 only, by this demonstrating how erroneous the assessment of K1 from domain structure can be. Finally, a new unit cell is proposed for Fe5Sn3 phase, which is commensurately modulated by the orthorhombic unit cell with lattice parameters of a = 4.221 Å, b = 7.322 Å, c = 5.252 Å and the space group Pbcm(α00)0s0 with a modulation vector of q = (½,0,0).

Microstructure, mechanical properties, and electronic simulations of steel/aluminum alloy joint during deep penetration laser welding

This paper presents microstructure and mechanical properties of deep penetration laser welding joints with/without Mn, Zr, or Sn powder in an overlap steel-on-aluminum configuration. Heats of formation, elastic modulus, and thermodynamic properties of intermetallic phases (IMCs) formed in joining steel to aluminum are determined by the use of first-principle calculation. A good agreement between the experimental results and theoretical predictions can be seen. In the case of adding Sn powder, no obvious porosity, cracks, and other defects are seen, and the layer thickness of IMCs is smallest among all the powders. In addition, the FeSn phase is formed at the steel/aluminum interface, the structure of FeSn is more stable than that of FeAl, and the ductility of FeSn is also better than that of FeAl; hence, mechanical properties of the welding joint are significantly improved.

Influences of electric current on the wettability and interfacial microstructure in Sn/Fe system

The wettability of oxidized and clean Fe substrates by liquid Sn was investigated using a dispensed sessile drop method with and without the application of a direct current (DC) and their interfacial microstructures were compared. The initial contact angles were 107±3° at 623K when the Fe substrate was covered by an oxide film, and they did not show an appreciable decrease during isothermal dwells in the absence of DC application but progressively decreased to 42±3° when a 7.5 ampere current was applied. However, in the case of the oxide film being removed by a high-vacuum pre-annealing treatment at 1073K, the current and its polarity had a negligible effect on the wetting behavior. Nevertheless, they had a noticeable influence on the interfacial microstructure. In the absence of DC, the interface was covered by a product layer consisting of a single FeSn2 phase for the samples tested at 623K and the FeSn2/FeSn2 grain boundaries were incompletely wetted by the Sn melt; whereas, under DC, the reaction layer was much thicker and the Sn melt wet well the FeSn2/FeSn2 grain boundaries. Moreover, a FeSn phase also formed as a result of enhanced mass transfer. The amount of the FeSn phase was larger and the grain boundary wetting of FeSn2 by liquid Sn was better for the current flowing from the molten Sn drop to the Fe substrate due to an electromigration effect.

Nanospheres of a New Intermetallic FeSn5 Phase: Synthesis, Magnetic Properties and Anode Performance in Li-ion Batteries

We synthesized monodisperse nanospheres of an intermetallic FeSn(5) phase via a nanocrystal-conversion protocol using preformed Sn nanospheres as templates. This tetragonal phase in P4/mcc space group, along with the defect structure Fe(0.74)Sn(5) of our nanospheres, has been resolved by synchrotron X-ray diffraction and Rietveld refinement. Importantly, FeSn(5), which is not yet established in the Fe-Sn phase diagram, exhibits a quasi-one dimensional crystal structure along the c-axis, thus leading to interesting anisotropic thermal expansion and magnetic properties. Magnetization measurements indicate that nanospheres are superparamagnetic above the blocking temperature T(B) = 300 K, which is associated with the higher magnetocrystalline anisotropy constant K = 3.33 kJ m(-3). The combination of the magnetization measurements and first-principles density functional theory calculations reveals the canted antiferromagnetic nature with significant spin fluctuation in lattice a-b plane. The low Fe concentration also leads Fe(0.74)Sn(5) to enhanced capacity as an anode in Li ion batteries.

Investigation on the 773 K isothermal section of La-Fe-Sn ternary systems by X-ray powder diffraction

The 773 K isothermal section of the La-Fe-Sn ternary system was investigated and constructed by X-ray powder diffraction (XRD). The existence of two reported ternary intermetallic compounds, La6Fe13Sn and La3FeSn6, is confirmed in this work. Compared with other R-Fe-Sn phase diagrams (R = Pr and Sm), the binary alloys Fe3Sn and Fe5Sn3 are not present. The compound Fe3Sn2 was observed from the XRD pattern of Fe3Sn2 samples, but it is not an equilibrium phase at 773 K and decomposes into Fe and FeSn phases completely for a longer heat treated time. Up to now, the crystal structure data of La2Sn3 has not been reported, so the X-ray pattern of La2Sn3 was only estimated. The phase relationship for this compound was drawn by a dotted line.

Dissolution and interfacial reactions of Fe in molten Sn-Cu and Sn-Pb solders

Solder pots used in wave soldering are usually made using different kinds of steel. Dissolution and interfacial reactions of the Fe substrate in molten Sn-Pb and Sn-Cu solders are investigated in this study. FeSn2 phase is formed in the Sn-0.7wt%Cu/Fe couples reacted at 250, 400, and 500 °C, as well as in the Sn-37wt%Pb/Fe couples reacted at 250 and 400 °C. The activation energies of formation are 123 and 121 kJ/mol in the Sn-Cu/Fe and Sn-Pb/Fe couples, respectively. FeSn phase is the reaction product in the Sn-37wt%Pb/Fe couples reacted 500 °C. The dissolution rates of Fe in the Sn-0.7wt%Cu melt are much higher than those in-the Sn-37wt%Pb melt. The FeSn2 phase layer in the Sn-Cu/Fe couple is not as dense as that in the Sn-Pb/Fe couple and accounts for the very different dissolution rates. Detachment of the reaction FeSn2 phase into the solder matrix is observed in the Sn-Cu/Fe couples, and is a potential contaminant source in wave soldering.

Study of the structure and morphology of plasma-sprayed tin coating

The structure and the morphology of a tin (Sn) coating deposited on carbon steel St-37 with plasma spray are characterized with Scanning Electron Microscopy (SEM), X-Ray Diffraction (XRD), Conventional Transmission Electron Microscopy (CTEM) and microhardness measurements. The microhardness of the as-cast coating is of the same order of magnitude with the hardness of the Sn-based “white” alloys. Its porosity is very low, as the SEM observation of the cross-section showed, and as a result it is rather unlikely to affect its tribological properties. Furthermore the coating is mainly composed of pure Sn, while a tin oxide film is likely to cover its surface. Nevertheless the XRD revealed that the coating is stress-free and composed of tetragonal tin, while CTEM showed that interdiffusion of Fe and Sn takes place at the interface between the coating and the substrate and Fe–Sn phases are formed. This phenomenon ensures good adhesion of the coating to the underlying steel.

Structural study near the film/substrate interface of a plasma sprayed tin coating on low carbon steel

The structure near the film/substrate interface of tin coatings deposited with the plasma spray technique on a low carbon steel substrate is examined with scanning electron microscopy (SEM), X-ray diffraction (XRD), conventional transmission electron microscopy (CTEM) and high resolution electron microscopy (HREM), focusing on the structural properties affecting the corrosion performance. This examination revealed the presence of several Fe–Sn phases, which ensure good adhesion of the coatings to the underlying steel. Furthermore, amorphous Sn or SnO x were also detected in the coating, which, being in low concentration, have no effect on the coating properties.

Isothermal Section of the Dy—Fe—Sn Phase Diagram at 800 °C.

AbstractFor Abstract see ChemInform Abstract in Full Text.

Isothermal section of the Dy–Fe–Sn phase diagram at 800 °C

The isothermal section at 800 °C of the Dy–Fe–Sn ternary system has been systematically investigated by means of powder X-ray diffraction. At this temperature, the phase diagram is characterized by the formation of only two solid solution-based compounds, Dy x Fe 6Sn 6 (0.32 < x ≤ 1) and DyFe x Sn 2 (0 < x ≤ 0.2). The end member of the former solid solution, DyFe 6Sn 6 crystallizes with the YFe 6Sn 6-type structure. Dy x Fe 6Sn 6 with x approximately 0.32 and 0.5 were found to be defect isotypes of the partially-ordered SmMn 6Sn 6 type of structure as the defect Yb 0.6Fe 6Sn 6 and U x Fe 6Sn 6 intermetallics. DyFe x Sn 2 ( x = 0.05, 0.1 and 0.2) crystallize in the CeNiSi 2-type structure.

STUDY OF THE PHASES FORMED DURING THE GROWTH OF THICK COATINGS WITH COARSE GRAINED TIN

The microstructural and morphological properties of the as-prepared tin (Sn) coating on ferrous substrates affects the lifetime as well as the applicability of the coating itself. In order to improve our knowledge of this system, strips of steel St-37 were coated with Sn in the form of gas-atomized powder, with an average diameter of 110±10 μm, using plasma spraying. The plasma gas was an Ar-He mixture and the current intensity was 650 A. The as-casted coating was characterized with scanning electron microscopy (SEM), X-ray diffraction (XRD) and conventional transmission electron microscopy (CTEM). It was deduced that the coating is characterized by high integrity, although certain pores were detected far from the Fe-Sn interface. However they refer to less than 1% of the total volume. Nevertheless the examination with SEM and XRD proved that the coating is mainly composed of pure Sn. However, interdiffusion takes place between the two phases (Fe-Sn) at their interface as deduced by CTEM. As a result, certain Fe-Sn phases are formed, which seem to be scattered in the coating close to the interface in the form of small inclusions.

Effect of Aluminum Content on Tribological Behavior of a Cu-Fe-C Based Friction Material Sliding against FC30 Cast Iron

An experimental study was made on the effect of aluminum content on the tribological behavior of a Cu–Fe–C based friction material sliding against FC30 cast iron. As a result, the densities of all Cu–Fe–C materials decreased after sintering. In general, when Al content increased, the density decreased. Sintered 65.5mass%Cu–11.4mass%Fe–6.6mass%C based friction material (A0) had much lower hardness than 57.7mass%Cu–12.6mass%Fe–7.3mass%C and 48.1mass%Cu–14.0mass%Fe–8.0mass%C based friction materials (A10 and A20). During sintering in air, large amounts of oxides formed. The presence of Al caused Cu–Sn to decompose, Al–Cu and Fe–Sn phases to form, Cu to be oxidized, and Fe2O3 to be reduced. A10 demonstrated the highest and most stable friction coefficient, as well as the smallest weight loss among three materials. Both film type and particulate type debris morphologies were observed on worn surfaces of Cu–Fe–C specimens. Local delamination of debris film was frequently observed on A0 and A20 surfaces, but seldom observed on A10 surface. Significant amounts of iron transfers from FC30 to A10 and A20 during sliding, but less such transfer occurred in A0.

Hyperfine Interaction of 111 Cd in Fe 3 Sn Compound

The hyperfine interaction of 111 Cd in ferromagnetic Fe3Sn compound was investigated by TDPAC in the paramagnetic region and below the Curie temperature. The results are compared with hyperfine magnetic fields and EFGs on 111 Cd and 119 Sn in other stoichiometric Fe-Sn phases.