Solubility Of Sn Research Articles

Room- and elevated-temperature strength of as-cast Mg-Sn-Y alloys mediated by Sn and Y solubility via intrinsic stability and deformation resistance

Microstructure evolution and first-principles calculations were adopted to explore alloying elements Sn and Y proportion influence on room- and elevated-temperature mechanical properties of as-cast Mg-Sn-Y alloy in the present study. The results show that the room- and elevated-temperature compression yield strength and ultimate compression strength of Mg-1Sn-yY alloy simultaneously improves with Y addition from 0.5 wt.% to 2 wt.%. Decreasing Sn to 0.5 wt.% in Mg-1Sn-2Y alloy, Mg-0.5Sn-2Y alloy yields comparable room-temperature strength to Mg-1Sn-1.5Y alloy with similar alloying element addition. Notably, the elevated-temperature strength of Mg-0.5Sn-2Y alloy is even greater than that of counterpart Mg-1Sn-1.5Y alloy and achieves increment by ∼42 MPa at 200 °C, 48 MPa at 250 °C, and 29 MPa at 300 °C, respectively. Combined with microstructure analysis and first-principles calculations, the mechanism behind this is mainly attributed to increased Y solubility in the matrix. Sn content reduction leads to the MgSnY ternary phase (4.97%) in Mg-1Sn-1.5Y alloy being replaced by the low-content Sn3Y5 phase (2.30%) so as to high Y solid solution in the Mg-0.5Sn-2Y alloy. Raised Y solubility is more favorable to decrease cohesive energy and increase bulk modulus, shear modulus and Young’s modulus, which avails enhancing intrinsic cohesive strength and deformation resistance of alloy other than Sn solubility. Thus, improvement of cohesive strength and deformation resistance by Y solubility promotes Mg-0.5Sn-2Y alloy to endure high loading at elevated temperatures.

Structural changes in Ge1−xSnx and Si1−x−yGeySnx thin films on SOI substrates treated by pulse laser annealing

Ge1−xSnx and Si1−x−yGeySnx alloys are promising materials for future opto- and nanoelectronics applications. These alloys enable effective bandgap engineering, broad adjustability of their lattice parameter, exhibit much higher carrier mobility than pure Si, and are compatible with the complementary metal-oxide-semiconductor technology. Unfortunately, the equilibrium solid solubility of Sn in Si1−xGex is less than 1% and the pseudomorphic growth of Si1−x−yGeySnx on Ge or Si can cause in-plane compressive strain in the grown layer, degrading the superior properties of these alloys. Therefore, post-growth strain engineering by ultrafast non-equilibrium thermal treatments like pulse laser annealing (PLA) is needed to improve the layer quality. In this article, Ge0.94Sn0.06 and Si0.14Ge0.8Sn0.06 thin films grown on silicon-on-insulator substrates by molecular beam epitaxy were post-growth thermally treated by PLA. The material is analyzed before and after the thermal treatments by transmission electron microscopy, x-ray diffraction (XRD), Rutherford backscattering spectrometry, secondary ion mass spectrometry, and Hall-effect measurements. It is shown that after annealing, the material is single-crystalline with improved crystallinity than the as-grown layer. This is reflected in a significantly increased XRD reflection intensity, well-ordered atomic pillars, and increased active carrier concentrations up to 4 × 1019 cm−3.

Comparison of GeSn alloy films prepared by ion implantation and remote plasma-enhanced chemical vapor deposition methods

Thin films of germanium-tin (GeSn) alloy with Sn content well above its equilibrium solubility limit in Ge are produced using both remote plasma-enhanced chemical vapor deposition (RPECVD) directly on silicon substrates and ion implantation of Sn into Ge. For RPECVD, the growth temperature of 302 °C resulted in fully relaxed GeSn alloys with high defect density, principally threading dislocations related to the large lattice mismatch between Si and GeSn. For the implantation case, pulsed laser melting was used to melt and crystallize the GeSn layer on a time scale of a few tens of nanoseconds. The resulting GeSn layers were also relaxed and defective, presumably again as a result of lattice mismatch with the underlying Ge lattice. However, the nature of the defects was quite different to the RPECVD method, whereby the line defects were not threading dislocations but stackinglike defects, which developed into arrays of these defects in the high Sn content region close to the surface. For the purpose of comparing RPECVD and ion-implantation methods, alloy films of similar thickness (400–450 nm) and Sn content (4.5–6.5 at. %) were examined. Film parameters (thickness, Sn content, Sn solubility, and segregation), as well as film quality and defect structures, were examined for both fabrication methods using several analytical techniques. This comparison provided us with a better physical understanding of our GeSn films and will help inform future growth/fabrication strategies targeted at minimizing defects formed in the GeSn films for the realization of optoelectronic devices.

Improving Hybrid Tin Halide Films by Tin Trifluoromethanesulfonate for Lead-Free Perovskite Solar Cells.

Tin-based perovskite solar cells (Sn-PSCs) without toxic lead ions outperform other types of lead-free PSCs in terms of photovoltaic performance. To avoid the oxidation of Sn2+ cations and the formation of vacancy defects, most reports involve the addition of SnF2 to the perovskite precursor solution, but hybrid tin halide (Sn-PVK) films still suffer from poor crystallinity and stability. In this work, we used an alternative additive of tin trifluoromethanesulfonate (Sn(OTF)2). Compared to SnF2, the solubility of Sn(OTF)2 in the precursor solution is greatly improved, and the crystal nucleation process is delayed, resulting in the enhancement of crystal growth. The coordination ability of the OTF- anions suppresses the oxidation of Sn2+ cations, which promotes the stability of Sn-PVK films. By replacing the conventional additive of SnF2 with Sn(OTF)2, the device achieves an increase in power conversion efficiency from 7.96% to 10.3%, while the stability of the devices is improved simultaneously.

Interfacial Segregation of Sn during the Continuous Annealing and Selective Oxidation of Fe-Mn-Sn Alloys.

The effect of Mn on interfacial Sn segregation during the selective oxidation of Fe-(0-10)Mn-0.03Sn (at.%) alloys was determined for annealing conditions compatible with continuous galvanizing. Significant Sn enrichment was observed at the substrate free surface and metal/oxide interface for all annealing conditions and Mn levels. Sn enrichment at the free surface was insensitive to the Mn alloy concentration, which was partially attributed to the opposing effects of Mn on segregation thermodynamics and kinetics: Mn increases the driving force for Sn segregation via reducing Sn solubility in Fe but also reduces the effective Sn diffusivity by increasing the austenite volume fraction. This insensitivity was exacerbated by the depletion of solute Mn near the surface due to the selective oxidation of Mn. Thus, Sn segregation occurred in regions with a local Mn concentration lower than the nominal bulk composition of the alloys suggested. Sn enrichment at the metal/external oxide interface was reduced compared to the free surface and decreased with increasing bulk Mn content, which was attributed to changes in the external oxide morphology and metal/internal oxide interfaces acting as Sn sinks.

Contribution to the Ti–Co–Sn system

The ternary phase diagram Ti–Co–Sn was studied using X-ray diffraction (XRD), scanning electron microscopy (SEM) and electron probe microanalysis (EPMA). Isothermal sections at 1000 and 1200 °C have been determined experimentally for the first time in the entire range of compositions. Thirteen and ten three-phase regions were found at 1000 °C and 1200 °C, respectively. Vertical sections at 10, 20 and 30 at.% Sn were plotted. The most striking feature of the ternary Ti–Co–Sn phase diagram is formation of a ternary compound TiCo2Sn (Heusler phase, τ), which was found at both investigated temperatures. The TiCoSn compound (half-Heusler phase) was not found. Among binary compounds, Ti5Sn3 and TiCo have the widest homogeneity regions. The Ti5Sn3 phase dissolves 10.0 and 9.8 at.% Co at 1200 and 1000 °C, respectively, forming an interstitial solid solution. The solubility of Sn in TiCo is more than 10 at.% at both 1200 and 1000 °C. The remaining binary intermetallic phases hardly dissolved the third component. The liquid phase at 1000 °C mainly exists in the Sn-rich corner, while at 1200 °C it stretches along Co–Sn side spreading from the Sn corner and is also present on the Ti-rich side. In addition, two four-phase invariant transition type reactions TiCo2 (h) + (αCo) ⇄ τ + TiCo3 and TiCo + TiCo2 (h) ⇄ τ + TiCo2 (c) were deduced.

(Invited) Epitaxial Growth Technique for Si1−X Sn x Binary Alloy Thin Films

Silicon tin (Si1−x Sn x ) binary alloys are attractive materials for next-generation Si-based photonics and thermoelectronics. The energy band calculations predicted that the conduction band at the Γ point is more rapidly decreased than the others by the Sn substitution, and direct band gap semiconductors can be realized at more than sufficient Sn content [1], although they varied from 25 to 90% by the calculation methods. The corresponding wavelength range will be matched to the optical communication band, suggesting Si1−x Sn x can be applied to near-infrared light source and detector. Another interest is the dramatic reduction of the thermal conductivity by the Sn substitution owing to the mass-difference phonon scattering. Theoretically [2], the thermal conductivity of bulk Si (145 Wm−1K−1 [3]) can be decreased to ~5 Wm−1K−1 by the 10% Sn substitution; the lowest thermal conductivity (3 Wm−1K−1) is obtained at 50% Sn, which is the lowest value among bulk group-IV alloys. The low thermal conductivity achieves high thermoelectric performance and can help to ensure temperature differences within small thermoelectric generators (TEGs) integrated on Si chips, as is the case of Si nanowire TEGs [4].In contrast to the theoretical studies mentioned above, experimental studies are very limited compared with other group-IV alloys such as silicon germanium and germanium tin. Difficulties of the Si1−x Sn x synthesizing are the extremely low solid solubility of Sn in Si (0.1%), a tenth of that in Ge, and the large (∼20%) mismatch between the Si and α-Sn lattices. Nevertheless, some research groups, including us, showed some possibilities to achieve a high Sn content Si1−x Sn x thin films (x>10%) experimentally; reported the optical properties such as photoluminescence and photo-absorption. However, the technology for freely controlling Sn content is still in its infancy; the Si1−x Sn x ’s thermoelectric properties have not been clarified yet. We will discuss the recent progress on the growth techniques of Si1−x Sn x thin films using solid phase epitaxy/crystallization [5-7], molecular beam epitaxy [8,9], sputtering [10], and the potential in thin-film TEGs application. Acknowledgments This work was partly supported by JSPS KAKENHI (Nos. 19K21971, 20H05188, and 21H01366), PRESTO (No. JPMJPR15R2), and CREST (No. JPMJCR19Q5) from JST, the TEPCO Memorial Foundation, and the Naito Research Grant.

Tracing tungsten-tin mineralization processes with tourmaline geochemistry in the Wangxianling-Hehuaping district, Nanling Range (South China)

The mechanisms controlling the enrichment and separate precipitation of tungsten and tin ores are obscure. To unravel the physicochemical changes in the mineralization system during the magmatic-hydrothermal transition, we investigate the petrography, geochemistry, and boron isotopes of tourmaline in the Wangxianling-Hehuaping district (Nanling Range, South China). Four types of tourmalines were identified: Magmatic (Tur-WG) and hydrothermal (Tur-WV) tourmaline in the Triassic W-mineralized tourmaline-two-mica granite (ca. 220 Ma); Magmatic (Tur-SnG) and hydrothermal (Tur-SnV) tourmaline in the Jurassic Sn-mineralized biotite granite (ca. 155 Ma). Tur-WV and Tur-SnV have lower Fe3+/(Fe2+ + Fe3+) ratios than those of Tur-WG and Tur-SnG, suggesting that W-Sn mineralization occurred in a relatively reducing environment. In addition, the δ11B values of all four types of tourmalines are similar, suggesting that the ore-forming fluids were primarily exsolved from the granitic magma. Significant chemical variations (e.g., Mg, Fe, Sc, V, Ni, and REEs) between Tur-SnG and Tur-SnV may have been resulted from fractionation and intense ore fluid-wall rock reactions. In contrast, Tur-WG has similar chemical compositions to Tur-WV, suggesting that the Triassic W mineralization may have undergone a magmatic-hydrothermal process with little ore fluid-wall reaction. Tur-SnV has exceptionally high F content, which could enhance the Sn solubility and enrichment. This explains the low Sn content of granitic magmas with large-scale Jurassic tin mineralization. Considering that W has a large melt-fluid partition coefficient, we conclude that in the Triassic, W is enriched in the exsolved fluid from the granitic magma and precipitated with temperature drop. This may have caused the decrease in W content in the protolith and limited the Jurassic W mineralization. Subsequently, the mantle-derived F addition along the Chenzhou-Linwu fault in the Jurassic had led to Sn enrichment in the fluids, and mineralization is triggered by temperature drop and fluid-rock reactions. Eventually, the extensive Triassic W mineralization and Jurassic Sn mineralization exhibit the separation of tungsten-tin mineralization. The separated tungsten-tin mineralization model based on different volatile components could also be applicable to other tungsten-tin metallogenic belts.

Experimental phase equilibria of the Mg–Sn–Ce ternary system at 800 K

The phase equilibria of the Mg–Sn–Ce ternary system at 800 K were investigated by means of X-ray powder diffraction (XRD) and scanning electron microscope equipped with an energy dispersive spectrometer (SEM-EDS). Six stable ternary phases (τ1-τ6) and one suspected ternary compound (A2) were observed in the section. Three known ternary compounds τ1 (MgSnCe, Pnma, oP12), τ2 (MgSn2Ce, I-42m, tI32) and τ3 (Mg23SnCe6, Fm-3m, cF120) were confirmed at 800 K. The new ternary phase τ4 (Mg40+4Sn26–4Ce34) has the iso-structure of Mg3·9Sn2·1La3 (Cu4Si2Zr3 prototype, P-62m, hP9). The crystal structures of the two additional new ternary compounds τ5 (Mg44Sn34Ce22) and τ6 (Mg40Sn36Ce24) have not been determined. It has not been identified that A2 (Mg10Sn39Ce51) is a ternary compound or a Ce–Sn binary compound with a solubility of Mg. CeSn3, Ce3Sn5, αCe5Sn3 and Ce3Sn were detected to contain solubility of Mg as 13.6, 1.0, 2.0 and 2.7 at.%, respectively. The Mg3Ce and MgCe contain small solubility of Sn as 1.0 and 4.5 at.% Sn. The tie-triangles of the ternary system have been identified.

Ultrasound-assisted extraction of Sn from tinplate scraps by alkaline leaching: Novel acoustoelectric synergy effect underlying intensifying mechanism

Clean and fast extraction of tin from the surface of tinplate scraps is of great significance for the efficient utilization of waste resources. However, the dense tin layer causes the low efficiency of conventional leaching process. To improve Sn leaching efficiency, the ultrasound technique was adopted to extract Sn from tinplate scraps by alkaline leaching in this study. In the NaOH-H2O2 leaching system, metallic tin and alloyed tin in Fe-Sn alloy located on the surface of tinplate scraps can be oxidized and transferred to soluble Na2SnO3, while the iron in Fe-Sn alloy was oxidized to oxides which were chemically inert in alkaline solution. The differences in chemical solubility of Sn and Fe, and solubleness of stannate and iron oxides gave rise to the selective separation of Sn from the tinplate scraps. The effects of the leaching parameters on the Sn leaching behaviors in conventional and ultrasound-assisted leaching processes were compared. The conventional leaching temperature and time were significantly reduced during the ultrasound-assisted leaching process. Almost all of Sn can be extracted after conventional leaching at 1 mol/L NaOH, temperature of 80 ℃ and time of 60 min, however the same Sn leaching effect can be achieved by ultrasound-assisted leaching at 60 ℃ for 30 min with ultrasound power of 60% (360 W). Sn leaching kinetics based on the plate model demonstrated the reaction rate constant of the ultrasound-assisted leaching was 70% higher than that of the conventional leaching. A novel acoustoelectric synergy effect underlying intensifying mechanism by ultrasound irradiation was proposed in this study. Eventually, this work provided a rapid and clean tin extraction method from tinplate scraps via the ultrasound-assisted alkaline leaching treatment.

The Temperature-Dependent Phase Transformation and Microstructural Characterisation in In-Sn Solder Alloys

Indium-based solder alloys are considered candidates for the next generation of low-temperature solder materials, especially for superconducting joints because of the properties of the β-In3Sn phase. The temperature-dependent phase transformation and thermal expansion behaviour of two different solder compositions including In-35Sn (in wt.%) and In-25.6Sn have been characterised using an in situ synchrotron powder X-ray diffraction method. The c-axis of the β-In3Sn unit cell in the In-35Sn alloy exhibited a complex relationship with increasing temperature compared to the positive increasing trend in In-25.6Sn due to the temperature-dependent solubility of Sn in β-In3Sn and change in the volume fraction of phases commencing at 80°C. In situ heating scanning electron microscopy recorded a real-time melting-solidification microstructure variation and phase transition during annealing at 90°C that was further analysed using energy dispersive X-ray spectroscopy. The observations are discussed with respect to the lattice parameters of the γ-InSn4 and β-In3Sn phases and the proportions and composition of both phases present within the alloys.

Corrosion behavior and discharge properties of Al-doped Mg–Sn alloys for high performance Mg-air batteries

In this study, we report a novel, non-rare earth Mg alloy-based anode for Mg air battery applications. The Mg-xAl-1Sn (x = 0, 3, 6, 9) alloy series were synthesized and subjected to extruding. The microstructural analyses indicated that the as-extruded Mg–0Al–1Sn(AT01) alloy showed coarse dynamically recrystallized (DRXed) grains. The Al-doped alloys showed uniform DRXed grain distribution, and their grain size decreased with increasing Al content. Meanwhile, the solid solubility of Sn changed with the addition of Al; as a result, the amount of Sn dissolved in the matrix was reduced. This promoted the precipitation of the Mg2Sn phase, and the precipitate content increased significantly in the Al-doped alloys. Furthermore, different corrosion behaviors were observed in the Al-doped alloys. Numerous discontinuous Mg17Al12 phases and strong cathode Mg2Sn phases induced rapid galvanic corrosion with the Mg matrix, which caused the latter one to be rapidly dissolved. However, the refined grains and discontinuous precipitates that existed in as-extruded Al-doped alloys were beneficial to the initiation of cracks within the alloy surface, making the self-peeling of discharge products easier. The AT91 alloy-based anode exhibited good discharge stability during long-term cycling at all applied current densities.

Reversible Thermal Conductivity Modulation of Non-equilibrium (Sn1–xPbx)S by 2D–3D Structural Phase Transition above Room Temperature

We demonstrated a reversible two-dimensional (2D) to three-dimensional (3D) crystal-structure transition and associated thermal conductivity switching (κ) well above room temperature (RT) in (Sn1–xPbx)S bulk polycrystals, solid solutions of 2D-layered SnS and 3D-cubic PbS. The direct phase boundary between the 2D and 3D structures does not exist in (Sn1–xPbx)S under the thermal equilibrium condition due to the solubility limit x = 0.5 in the 2D phase and x = 0.9 in the 3D phase. While, by applying a non-equilibrium synthesis process that combined a high-temperature solid-state reaction at 973 K and subsequent rapid thermal quenching to RT, the Sn solubility limit in the 3D (Sn1–xPbx)S was not changed but the Pb solubility limit was considerably expanded up to x = 0.9 in 2D (Sn1–xPbx)S. As a result, the direct 2D–3D phase boundary was formed in the Pb-rich (Sn0.2Pb0.8)S, which showed the reversible 2D–3D (3D–2D) structural phase transition at ∼573 K (473 K). This transition temperature is much higher than that previously reported for (Sn0.5Pb0.5)Se, which requires temperatures lower than RT for the reversible structure transition. The electronic band structure change from a 2D semiconducting state to a 3D metallic state caused a 20-times increase in electron κ (κele) during the structural phase transition in the (Sn0.2Pb0.8)S. Still, κele negligibly contributes to the total κ. In contrast, the lattice κ (κlat) was largely decreased by the 3D–2D structure transition due to the formation of a 2D-layered structure with strong phonon scattering, resulting in a 1.8-times modulation of the total κ (κ3D phase/κ2D phase) at 463 K. The realization of 2D–3D structural phase transition above RT in (Sn1–xPbx)S would accelerate the development of thermal management materials through a crystal-structure dimensionality switch using non-equilibrium phase boundaries.

Experimental investigation of Ag–Pd–Sn ternary system

Isothermal sections of the Ag–Pd–Sn system at 500 and 800 °C were plotted based on the XRD and EDX results. The solubility of Sn in palladium and silver-based fcc solid solution has nearly zero minimum around the Ag corner. The Pd3Sn and γ-Pd2–xSn phases show significant dissolution of Ag and extend towards the Ag corner. The other Pd–Sn and Ag–Sn binary phases dissolve under 5 at.% of the third component. A new τ1 ternary phase was discovered in the Pd-rich region. Its XRD pattern corresponds formally to In structure type, but the actual arrangement of the atoms in the τ1 phase most probably corresponds to tetragonal Al3Ti type structure.

Thermodynamic modeling of the Fe-Sn system including an experimental re-assessment of the liquid miscibility gap

The usage of low-grade ferrous scrap has increased over decades to decrease CO2 emissions and to produce steel products at a low cost. A serious problem in melting post-consumer scrap material is the accumulation of tramp elements, e.g., Cu and Sn, in the liquid steel. These tramp elements are difficult to remove during conventional steelmaking processes. Sn is considered as one of the most harmful tramp elements because, together with Cu, it sometimes induces the liquid metal embrittlement in high-temperature ferrous processing, e.g., continuous casting and hot rolling. Furthermore, the chemical interaction between Fe and Sn plays an important role in the Sn smelting process. The raw material used in the Sn smelting process is SnO2 (cassiterite), in which Fe3O4 is a gangue in the Sn ore. In the process, the reduction of Fe3O4 is unavoidable, which results in forming a Fe-Sn alloy (hardhead). The recirculation of the hardhead decreases the furnace capacity and increases the energy consumption in the smelting. The need to efficiently recover Sn from secondary resources is therefore inevitable. The CALculation of PHAse Diagrams (CALPHAD) approach helps to predict the equilibrium state of the multicomponent system. Previously reported studies of the Fe-Sn system show inconsistencies in the calculations and the experimental results. Mainly the miscibility gap in the liquid phase was under debate, as experimental data of the phase boundary are scattered. Experimental study and re-optimization of model parameters were carried out with emphasis on the correct shape of the miscibility gap. Three different experimental techniques were employed: differential scanning calorimetry, electromagnetic levitation, and contact angle measurement. The present thermodynamic model has higher accuracy in predicting the solubility of Sn in the body-centered cubic (bcc), compared to previous assessments. This is achieved by re-evaluating the Gibbs energies of the FeSn and FeSn2 compounds and the peritectic reaction related to Fe5Sn3. Also, the inconsistencies related to the miscibility gap around XSn = 0.31-0.81 were resolved. The database developed in the present study can contribute to the development of a large CALPHAD database containing tramp elements.

Toward White Light Random Lasing Emission Based on Strained Nano Polygermanium Doped with Tin via Metal-Induced Crystallization (MIC)

Solubility of Sn in Ge network gives it a preference for photonic applications, because of the direct transition in GeSn alloy. Here, we employed the metal-induced crystallization (MIC) process of amorphous Ge and Si via Sn as a novel mechanism to incorporate Sn inside Ge and Si networks. (Al/Si/Sn/Ge/Sn) and (Al/Ge/Sn/Ge/Sn) multilayers are deposited by thermal vacuum evaporation on different substrates. The devices are annealed under low vacuum at 500 °C to incorporate the oxygen for band-gap tuning. The structure of Ge-doped nanocrystals is investigated. The direct transition and band-gap values have been estimated using diffuse reflectance spectroscopy and photoluminescence (PL) measurements. PL indicated that the junctions have emissions from visible to NIR regions that make them promising as optically pumped white-light sources as well as waveguide applications, and the impact of the base substrate on enhancing the emission has been investigated via PL measurements. Electroluminescence measurements show that the prepared heterostructures on fluorine-doped tin oxide (FTO) substrate have sharp random lasing spikes over the range of PL samples spectra as the sample can lase randomly by light scattering through the Ge-doped nanocrystalline materials. The charge carrier lifetime measurements show high lifetime for the prepared sample. These give them the chance to be a candidate for white-light random laser diode applications.

(Si)GeSn Isothermal Multilayer Growth for Specific Applications Using GeH4 and Ge2H6

The experimental demonstration of Ge1-xSnx alloys lasers opened group-IV materials towards high-performance electronic and photonic devices that can be easily integrated with the current Si semiconductor technology. In recent years, GeSn-based optoelectronic devices including light-emitting and detectors, modulators, and CMOS have been proven.The major challenges for the Ge1-xSnx epitaxy arise from the low solid solubility of Sn in Ge, the large lattice mismatch, and the reduced thermal stability between Ge and Sn. All these are becoming extremely critical at higher Sn contents. Non-equilibrium conditions offered by molecular beam epitaxy (MBE), chemical vapor deposition (CVD), flash lamp, or laser annealing have been lately investigated. Between them, CVD is to date the preferred growth technique for its current development compatible with the industry offering micron-thick layers with the highest crystal quality.While Tin-tetrachloride (SnCl4) becomes the standard Sn precursor, for Ge different gasses, like germane (GeH4) and digermane (Ge2H6) are used attempting to archive high Sn incorporation and high material quality. While Ge1-xSnx films with the same high Sn content can be obtained regardless of the used precursor, the advantages and disadvantages of each precursor are discussed in this work. The use of Ge2H6 is accompanied by high growth rates, being favorable in applications where relatively thick films are needed, such as laser structures. On the other hand, with a relatively low growth rate, GeH4 provides a greater thickness control, achieving clear and sharp interfaces in heterostructures. For this reason, GeH4 is the appropriate precursor for quantum transport or spintronic.The biggest challenge in heterostructure designs is going up and down in Sn content. The growth of a Ge1-ySny on a Ge1-xSnx, y<x, or SiGeSn layer cannot be performed by increasing the growth temperature. Post-annealing processes lead to strong crystallinity degradation of the already grown layer by strong Sn diffusion or Sn segregation due to the limited thermal stability of Ge1-xSnx alloys.In this work, we address simple methodologies to enhance the gradient or step Sn content without changing the process temperature. Controlling only the carrier gas flow while keeping the standard growth parameters constant, high-quality Ge1-xSnx alloys with uniform Sn content up to 15 at.% are obtained. The proposed method acts as guidance to produce Ge1-xSnx heterostructures that can be extended to any CVD reactor, independently of the used precursor, GeH4 or Ge2H6. Different devices structures are presented proving the applicability of the isothermal multilayer growth. Figure 1

Trace elements in apatite from Gejiu Sn polymetallic district: Implications for petrogenesis, metallogenesis and exploration

The world-class Gejiu tin polymetallic district is located in southeastern Yunnan Province. Yet, the largest deposits are concentrated in the Masong and Laoka granites in the eastern area of Gejiu. To investigate the factors controlling Sn mineralization among intrusions in the Gejiu area, we collected apatite from eight different intrusions (including gabbro, monzonite, and granite) and determined the fertility indices of Sn deposits through the chemical composition of apatite. Analysis of the redox-sensitive elements in apatite showed that the ore-bearing granites have high Mn and low S content, high Y/∑REE and low La/Sm ratios, extreme negative Eu anomalies, and weak Ce positive anomalies compared to the barren intrusions, indicating that the formation environment of the ore-bearing granites was more reducing. The apatites in ore-bearing intrusions have lower Sr and higher Y contents, which suggests that these intrusions have a higher degree of fractionation than barren intrusions. The apatites in the Masong and Laoka granites have a high F content, which reflects the high F content of magma that contributed to the enrichment of Sn. The decreasing (Sm/Yb)N ratios with stable Sr content imply exsolution of Cl-rich fluids or crystallization of monazite and allanite. The exsolution of Cl-rich fluids can increase Sn solubility in the melt and promote the extraction of Cu from basalt. The apatites in the ore-bearing intrusions have high Li, Mn, Fe, and F contents and extremely low (Eu/Eu*)N ratios (<0.05). These results show that apatite can be used to distinguish Sn deposits from other deposit types and guide the Sn exploration.

Interfacial reactions in Ni/Se-90 at.%Te and Ni/Pb1-xSnxSe couples

Se-90 at.%Te and Pb1-xSnxSe (x = 0, 0.1, 0.2, 0.3) alloys are important thermoelectric elements. Ni is commonly used as a diffusion barrier layer in contact with thermoelectric elements. The interfacial reactions in the Ni/Se-90 at.%Te and Ni/Pb1-xSnxSe (x = 0, 0.1, 0.2, 0.3) couples reacted at 500 °C are examined to study the reaction phase formation and microstructural evolution at the reaction zones. In the solid Ni/liquid Se-90 at.%Te couples reacted at 500 °C, two reaction phase layers, Ni3Te2 and NiTe2-x, are formed at the contact interface. Dendritic (SeTe) and needle-shaped NiTe2-x precipitates are found on the thermoelectric side, showing the reaction path is Ni/Ni3Te2/NiTe2-x/liquid (SeTe) + NiTe2-x/liquid Se-90 at.%Te. In the solid Ni/solid Pb1-xSnxSe couples reacted at 500 °C, the Ni3Pb2Se2 ternary phase is the primary reaction product, regardless of the Sn solubility. Doping of Sn in the Pb1-xSnxSe alloys (x ≥ 0.1) causes additional phase formation of Ni5.62SnSe2, Ni–Sn, and PbSe, giving rise to an interlarded multilayer structure at the reaction zones. The phase formation in the two reaction couples is rationalized by the dominant diffusion species of Ni. The related phase diagrams are assessed and used for illustrating the above-mentioned interfacial reactions.

The Effects of Temperature and Solute Diffusion on Volume Change in Sn-Bi Solder Alloys

The different rates of thermal expansion of the many materials that make up an electronic assembly combined with temperature fluctuations are the driver of the thermal fatigue failure of solder joints. A characteristic of the Sn-Bi system, which provided the basis for many of the low process temperature solder alloys that the electronics industry is now adopting, is the very temperature-sensitive solubility of Bi and Sn in the other phase. In this study, in situ synchrotron powder x-ray diffraction was used to characterize the temperature dependence of the lattice parameters of the βSn and Bi phases in Sn-57wt%Bi and Sn-37wt%Bi. The effects of temperature and solute were separated by comparing with the data from pure βSn and pure Bi and verified using density functional theory calculations. Furthermore, the coefficients of thermal expansion of βSn and Bi during heating were also derived to reveal the thermal expansion behavior.