High Sn Content Research Articles

Fluid inclusion LA-ICP-MS constraint on hydrothermal evolution of proximal cassiterite-bearing quartz veins in the giant Gejiu orefield: Implications for controls on metallogenic potential of granite-related skarn system

Sn and Cu are proposed to have their mineralization potential predetermined by their contents in initial fluids of granite-related magmatic-hydrothermal systems. However, it remains ambiguous whether the giant Sn-mineralized skarn system is applicable, and whether the Sn-Cu association in some deposits is predominantly determined by their initial metal contents. The Gejiu orefield is one of the most essential Sn-polymetallic districts worldwide, with proven resources of 3.27 million tons of tin, 3.25 million tons of copper, 4.29 million tons of lead and zinc, and >20 other metals with economic significance. Sn-polymetallic mineralization at Gejiu constitutes a composite skarn ore system that includes proximal skarn and related cassiterite-sulfide, greisen, and tourmaline-vein types. The Laochang Sn-polymetallic deposit hosts several largest skarn and cassiterite-sulfide orebodies in the eastern part of Gejiu. Recent exploitation at Laochang discovered Sn-mineralized quartz veins hosted in the concealed granite, providing a valuable opportunity to characterize the proximal magmatic-hydrothermal process of the mineralizing granitic system. Here, fluid inclusion analysis is carried out on these veins to discuss the fluid evolution, cassiterite precipitation mechanism and whether metal content in early proximal magmatic fluids determines the metal association and endowment in the deposit.Based on the paragenesis of ore and gangue minerals, three hydrothermal stages are distinguished, including quartz-tourmaline stage (Stage I), cassiterite-arsenopyrite-quartz stage (Stage II) and late sulfide stage (Stage III). Fluid evolution controlling vein formation is constrained by microthermometry and LA-ICP-MS analysis of four fluid inclusions generations successively entrapped in quartz and cassiterite. The fluids involved during vein formation show an interplay between single-sourced magmatic fluids and meteoric water. The intermediate-density single phase fluid recorded at stage I quartz is derived from initial fluids directly exsolving from granitic magma. At stage II, fluid immiscibility occurred and the separated brines were entrapped in quartz and early-formed cassiterite. Along with cassiterite precipitation, brines were mixed with low-salinity and cooler meteoric water, leading to entrapment of low-salinity aqueous fluid in outer growth zones of cassiterite at stage II. The constructed fluid evolution history suggests that fluid immiscibility may have facilitated the nucleation of cassiterite crystals at the onset of deposition while mixing of magmatic fluid with meteoric water likely dominate later cassiterite mineralization.Compared with the fluid dataset of barren and mineralized granitic systems worldwide, pre-ore fluids of the studied quartz veins are enriched in Sn, confirming that high Sn content in the initial magmatic fluid can serve as indicator to distinguish mineralized system. In contrast, although Cu mineralization is economically important in the Laochang deposit, predicted Cu contents in pre-ore proximal magmatic fluids are as low as those obtained from Cu-barren system. This implies introduction of Cu into the hydrothermal system from other sources.

Multiple generations of garnet and their genetic significance in the Niukutou cobalt-rich Pb-Zn-(Fe) skarn deposit, East Kunlun orogenic belt, western China

The Niukutou deposit, situated within the Qimantagh ore-concentrated area of the East Kunlun Orogenic Belt (EKOB), represents a typical skarn-type Pb-Zn-(Fe) deposit that is also associated with cobalt (Co) mineralization. The main ore minerals include galena, sphalerite, magnetite, hematite, Co-bearing arsenopyrite, cobaltite and glaucodot. This study conducted geochronological and chemical composition analyses of multi-generational garnets from the deposit, aiming to elucidate their genetic significance in the mineralization process. Field and mineralogical observations indicate the presence of three generations of garnets: Grt-I, Grt-II, and Grt-III. The earliest garnet generation (Grt-I) formed during the prograde stage, typically in garnet skarns, and is often replaced by epidote. The second generation (Grt-II), which coexists with pyroxene, also formed during the prograde stage, whereas the third generation (Grt-III) is associated with pyrrhotite stockworks, suggesting its formation during the sulfide stage. Using in-situ LA-ICP-MS U-Pb dating, garnets yield ages of approximately 230–234 Ma, which aligns with the age of 231.8 ± 7.5 Ma obtained from hydrothermal titanite in the deposit. These ages, combined with those of the previous studies, indicate major magmatic and metallogenic activity of 220–240 Ma in the Qimantagh area. Each generation of garnets displays oscillatory zoning characterized by alternating andradite and grossular compositions. The variations in Sn and high field-strength element (HFSE) contents across different garnet generations indicate an increasing trend in oxygen fugacity as mineralization progresses. The high Sn contents in the Niukutou garnets provide geochemical clues for the potential of Sn-W mineralization in this deposit, which should pay attention to in future exploration. Additionally, the high As concentrations in the Niukutou garnets suggest an As-rich hydrothermal fluid, which, owing to the stronger affinity of cobalt for sulfarsenides over sulfides, provides a geochemical indicator for the formation of abundant Co-bearing sulfarsenides rather than cobaltiferous sulfides in the deposit.

Comprehensive study on epitaxial growth of GeSn(111) layers with high Sn content on Si(111) featuring Ge buffer layer

The study comprehensively discussed the crystalline properties of GeSn(111) epitaxial layers on Si(111) using Ge double buffer layers toward the formation of the direct transition GeSn(111) with a Sn content around 10%. We found that the introduction of Ge double buffer layers is rather effective to improve the crystallinity of GeSn(111) than the single buffer case. However, thicker Ge buffer layer degrades the crystallinity of GeSn(111) because the strain relaxation of GeSn layer is likely to occur. In this study, through optimizing the thicknesses of Ge buffer layers formed at low and high temperatures (LT-Ge and HT-Ge, respectively), it was clarified that 100 and 500 nm for LT- and HT-Ge thicknesses, respectively, are suited to realize a high quality GeSn(111). The grown GeSn(111) epitaxial layer includes a Sn content of ~8–11% with a compressive strain of ~1–2%, which is contained within the region of direct transition GeSn(111).

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.

Perhitungan Volume Stockpile dan Pengoptimalan Waktu Pengolahan Stockpile 3, 5 dan 6 Terhadap Produksi Alat Gali muat dan Alat Angkut pada TB Primer Batubesi PT Timah Tbk

PT Timah Tbk's Batubesi Primary Large Mine has experienced a significant decline in production in recent years, causing a change in the mining process to stockpile management that is still economical with a grade of 0.2%. This study aims to determine the volume and production of stockpiles 3, 5 and 6, the type of sediment and Sn content of stockpile material and the time required to spend stockpile material 3, 5 and 6 in order to get the optimal time. The method used is a quantitative method by taking cycle time data as much as 30 data and analyzing sample levels using XRF on each stockpile. The results of this study obtained the volume of stockpile 3 material is 132,648.42 m3,, stockpile 5 is 162,570.25 m3, and stockpile 6 is 33,090.19 m3. The calculated machine productivity at stockpile 3 is 42.17 tons/hour, stockpile 5 is 48.11 tons/hour and stockpile 6 is 39.53 tons/hour. The highest Sn content is found in stockpile 6 which is 0.33% with the type of skarn sediment. While the lowest Sn content is found in stockpile 3 which is 0.2% with oxide clay sediment type. In stockpile 5, the Sn content is 0.31% with the type of oxide clay sediment. The remaining volume of stockpile material in stockpiles 3, 5 and 6 can be spent with a time of 2.78 years using 1 unit of excavation equipment and 1 unit of transportation equipment. Optimization is carried out so that the remaining stockpile reserves can be spent within 1.74 years using 1 unit of excavation equipment and 2 units of transport equipment.

Magmatic–Hydrothermal Evolution at the Barren Wushan Pluton, Southeast China: Insight into Controls on Mineralization Potential

Abstract A-type granites typically exhibit enrichment and mineralization of critical metals such as molybdenum and tin, essential for emerging technologies. However, the key factors influencing their mineralization potential remain elusive. The scarcity of studies on barren systems impedes the understanding of this question. Here, a detailed melt and fluid inclusion study was conducted on the barren Wushan pluton to reconstruct its magmatic evolution and magmatic–hydrothermal transition and explore the factors controlling the metallogenic potential of Mo and Sn in A-type granites. The Wushan pluton displays apparent lithological zoning consisting of two major phases, i.e., medium-grained seriate to porphyritic alkali feldspar granite and fine-grained porphyritic granite. Miarolitic cavities are widely developed in each lithofacies. The silicate melt inclusions from two granitic phases are rhyolitic, with moderate F contents (0.06–0.53 wt %) and depleted H2O contents (2.0–3.5 wt %). Melt inclusions show a wide range of incompatible element contents, such as Cs (9–1977 μg/g) and Rb (268–2601 μg/g), suggesting that Wushan has undergone a high degree of magma evolution. Mo behaves incompatibly in the magmatic evolution, and its content is enriched with the increasing degree of fractional crystallization, but remains constant after the Cs content exceeds 50 μg/g. Rayleigh fractionation model suggests that a large amount of Mo is extracted from fluid exsolution, which restrains Mo from further enrichment. In contrast, Sn behaves as a mildly incompatible element during the entire magmatic evolution history. The contents of Sn increase slowly compared to the trend of Mo, and the maximum contents reach ~30 μg/g in the highly evolved melts. The separation and crystallization of Sn-bearing minerals such as biotite, magnetite, and titanite inhibit the enrichment of Sn. Intermediate-density (ID-type) fluid inclusions hosted in the miarolitic quartz, representing the initial fluid exsolving from magma, display high Mo but low Sn concentrations. Constrained from two assemblages of coexisting ID-type fluid and melt inclusions, the fluid/melt partition coefficients of metals are obtained, with DMo, fluid/melt at 16–19, while DSn, fluid/melt is only about 1. The comparison between Mo-mineralized and barren intrusions worldwide shows that the metal contents in melts and fluids are not fundamentally different. The mineralized intrusions are characterized by the lower melt viscosity and the development of apophyses, both of which facilitate the extraction of metals and fluids from large magma chambers, followed by their concentration into a small rock volume. Consequently, it appears that physical and structural conditions rather than chemical compositions play a crucial role in the Mo mineralization process. Enrichment of Sn in melts is necessary but not decisive for Sn mineralization, whereas Sn enrichment in the initial exsolving fluid determines the Sn mineralization potential of a given granitic system. Compared to Sn enrichment in source melting and fractional crystallization which commonly enhance final Sn fertility in the highly evolved melts, the efficiency of Sn partitioning between melt and fluid plays a fundamental role in converting melt fertility into Sn-enriched fluids and thereby high mineralization potential of the magmatic–hydrothermal system. Our findings suggest a prospect for Mo exploration in the coastal A-type granite belt in South China, while the potential for Sn mineralization is expected to be limited.

Mineralogy and 40Ar-39Ar dating of the recently discovered tainiolite occurrences in the Kaerqiaer fluorite Belt, western Altyn Tagh Terrane

The Kaerqiaer Fluorite Belt (KFB) contains the Kaerqiaer, Xiaobaihegou, Kumutashi, Northern Layidan, and Gaijike fluorite deposits in the western Altyn Tagh Terrane of NW China. An occurrence of Li-bearing mica tainiolite (KLiMg2(Si4O10) F2) has been recently discovered, associated with fluorite-bearing alkali feldspar granite. The tainiolite is hosted by fluorite-calcite veins that contain assemblages of tainiolite-fluorite-calcite and apatite-bastnaesite-tainiolite-fluorite-calcite along the contact zone with alkali feldspar granite. The tainiolite occurs as euhedral crystals and has high concentrations in the veins. 40Ar-39Ar dating of the tainiolite from Xiaobaihegou yields an age of 421 ± 2 Ma, and single-crystal X-ray diffraction confirms the tainiolite has a monoclinic 1 M−type with a C2/m (#12) space group. Minor structural variations in the mica are attributed to the substitution of Li for Mg. EPMA and LA-ICP-MS analyses show that the tainiolite has high Li, Rb, Cs, Sn and Nb concentrations, and low Ta, total REE concentrations. The average Li2O content of the fluorite-tainiolite veins reaches 0.36 %, surpassing the economic cut-off grade. We suggest that the fluorite deposits formed from highly fractionated Li-F-P-rich residual melt evolved from the parental magmas of alkali feldspar granite. The tainiolite mineralisation may result from subsequent hydrothermal activities caused by the reactivation of regional faults under the extensional regime between the Middle Altyn and Eastern Kunlun terranes. The discovery of tainiolite occurrences made KFB a potential area for not only F but also Li resources.

Growth of single-crystalline GeSn films with high-Sn content on InP substrates by sputtering and rapid thermal annealing

In this work, the polycrystalline GeSn film with Sn content of 25.3 % on InP is obtained by sputtering at room temperature and then rapid thermal annealing (RTA) at 300 ℃. The single-crystalline GeSn film with Sn content of 24.7 % on InP is obtained by sputtering at 200 ℃ and then RTA at 300 ℃. This indicates that the growth temperature is one of the key factors affecting the formation of single-crystalline films. The effects of the sputtering power and film thickness on the crystallization of the GeSn films are investigated. The competition between the spontaneous and substrate-induced crystallization of the films limits the preparation of single-crystalline GeSn films. The strain relaxation of the film (R = 69.3 %) is achieved by annealing. The device fabricated by the GeSn film exhibits a high response of 18.1 A/W @-1 V at room temperature with the 1550-nm-line excitation. These suggest that sputtering epitaxy can be an effective method for growing single-crystalline GeSn films with high-Sn content on InP substrates, which is of great significance for developing high-performance mid-infrared devices.

Investigation of sensing properties of Sn-doped NiO thin films for the detection of ammonia gas

In this study, we detail the fabrication of Sn-doped nickel oxide thin films using the spin-coating technique, elucidating the impact of Sn doping on structural, optical, and gas sensing properties. Systematic analysis via XRD, SEM, AFM, and UV–Visible spectroscopy delves into the structural and optical characteristics of the films. Notably, gas sensing capabilities, specifically towards NH3, are investigated. XRD analysis reveals the polycrystalline nature of NiO thin films, with crystallinity diminishing as Sn concentration increases. SEM and AFM analyses highlight a uniform film surface with spherical-shaped particles, and increased surface roughness with higher Sn content, a crucial factor for gas sensing applications. Raman analysis showcases first-order phonon modes of vibrations of Ni-O, while optical studies affirm the films' transparency in the visible wavelength. Notably, in ammonia gas sensing tests at room temperature, the 8 mol% Sn-doped NiO thin film exhibits an exceptional response of 3200 %, with a rapid 40-second response time and a 25-second recovery time at a 150 ppm concentration of ammonia gas. These findings suggest that Sn-doped NiO thin films hold promise as effective gas sensors for NH3 detection.

Simultaneously enhanced strength and elongation capacity in Cu–15Sn-0.3Ti alloy via regulation of IMCs

Due to the technical requirements of preparing Nb3Sn superconducting wires using the bronze method, the Cu–Sn–Ti alloy with high Sn content and matching mechanical properties with pure Nb as the substrate is the key to the smooth preparation of superconducting wires. However, the high content of Sn leads to the generation of a large number of intermetallic compounds (IMCs) in Cu–Sn–Ti alloy are the main reasons for the deterioration of the elongation and strength of Cu–Sn–Ti alloy. This work uses unidirectional solidification (US) and homogenization annealing (HA) methods to regulate the volume fraction and types of IMCs in Cu–15Sn-0.3Ti alloy. The volume fraction of IMCs decreases from 20.6 % to 0.1 % after HA, and the network δ phases (Cu41Sn11) transform to fine γ phase (Cu3Sn) and CuSn3Ti5. The ultimate tensile strength (UTS) and elongation of the samples treated with HA increase by 2000 % and 94 %, respectively, and deformation twins are found in the stretched samples. The research results indicate that the elongation and UTS of Cu–15Sn-0.3Ti alloy are improved by the decrease of IMCs volume fraction and deformation twins formed during the tensile process.

Cluster-doping in silicon nanocrystals.

Creating tin-alloyed silicon nanocrystals with tailored bandgap values is a significant challenge, primarily because a substantial concentration of tin is essential to observe useful changes in the electronic structure. However, high concentration of Sn leads to instability of the silicon-tin nanocrystals. This work introduces a completely new approach to doping and the modification of the electronic structure of nanoparticles by incorporating few-atom clusters in nanocrystals, deviating from isolated atom doping or attempting alloying. This approach is exemplified via a combined theoretical and experimental study on tin (Sn) 'cluster-doping' of silicon (Si) nanocrystals, motivated by the opportunities offered by the Si-Sn system with tailored band energy. First-principles modelling predicts two noteworthy outcomes: a considerably smaller bandgap of these nanocrystals even with a modest concentration of tin compared to an equivalent-sized pure silicon nanocrystal and an unexpected decrease in the bandgap of nanocrystals as the diameter of nanocrystals increases, contrary to the typical quantum confined behaviour. Experimental verification using atmospheric pressure microplasma synthesis confirms the stability of these nanocrystals under ambient conditions. The plasma-synthesised nanocrystals exhibited the predicted atypical size-dependent behaviour of the bandgap, which ranged from 1.6 eV for 1.4 nm mean diameter particles to 2.4 eV for 2.2 nm mean diameter particles.

(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.

Multiple stages of skarnization in the world-class Zhuxi scheelite skarn deposit, South China

Although previous studies consistently revealed that the world’s largest W deposit, Zhuxi (3.44 Mt. WO3 @0.54 %) was formed by a single metallogenic stage in the Late Jurassic (∼150 Ma), this contribution identifies an unrecognized, postdate metallogenic event. After detailed field investigation, we noted that the early disseminated scheelite-bearing garnet–pyroxene massive skarn ores are crosscut by vein-type skarn ores, mainly composed of garnet, coarse-grained scheelite, and apatite. The mineral assemblage of the vein-type skarn ore is different from the scheelite-bearing veins that formed during the retrograde alteration stage. Moreover, some massive skarn ores crosscut by vein-type skarn ores have undergone obvious retrograde alteration. Given that a complete metallogenic event in skarn deposits is characterized by retrograde alteration following the prograde skarn stage, the component of the vein-type skarn ores shows affinity to that of the prograde massive skarn ores and the vein-type skarn is superimposed on both previous skarns and their retrograde altered ores, indicating another skarnization event occurred in conjunction with a new metallogenic event in the Zhuxi deposit.The studied massive and vein-type skarn scheelites are characterized by low Sr contents (usually less than 40 ppm), positive Eu anomalies (δEu = 2–105), and low Mo contents (usually less than 300 ppm); thus, the massive and vein-type skarns were both formed by reduced magmatic hydrothermal fluids, with no oxidized meteoric water that is commonly prevalent in the retrograde alteration stage. Compared to the massive skarn garnets, the vein-type skarn garnets are richer in Al and poorer in Fe, indicating lower oxygen fugacity conditions during their crystallization and arguing against the involvement of oxidized meteoric water in their formation. The vein-type skarn garnets have higher Sn contents, lower U contents, and similar W contents compared to the massive skarn garnets; thus, the massive and vein-type skarns did not form from the same hydrothermal fluid system at different evolution stages. This is because garnets crystallized from an evolved hydrothermal fluid system under lower oxygen fugacity conditions are expected to have lower Sn and W contents with higher U contents than their predecessors. The in situ U–Pb age (142.8 ± 2.4 Ma) of apatite from the vein-type skarn reveals that apart from the widely known Late Jurassic metallogenic event (∼150 Ma), within the Zhuxi deposit, an Early Cretaceous metallogenic event also occurred, and the latter has been widely identified in the other districts of the Jiangnan tungsten belt. From this multistage metallogenic event superposition, early disseminated scheelite could leach and recrystallize as larger scheelite grains, forming high-grade, world-class scheelite skarn deposits, such as the Zhuxi (3.44MtWO3) deposit and similar deposits worldwide.

High‐Performance N‐MoSe2/P‐GeSn/N‐Ge van der Waals Heterojunction Phototransistor for Short‐Wave Infrared Photodetection

AbstractIn this work, a high‐performance two‐terminal n‐MoSe2/p‐GeSn/n‐Ge van der Waals (vdW) heterojunction phototransistor (HPT) is proposed and demonstrated for short‐wave infrared (SWIR) detection. With a high Sn content of 17.1% in the GeSn base region, the cutoff wavelength is extended to beyond 2400 nm. The substantial electron/hole injection ratio resulting from the large bandgap offset between the MoSe2 emitter and the GeSn base enables the harvesting of high photocurrent gain. A record high responsivity of 12.75 A W−1 and an excellent specific detectivity of 1.74 × 1010 Jones at 2250 nm are achieved under a collector‐emitter bias of 1.0 V at room temperature. A response time of 462 µs at 1550 nm outbalancing that of most vdW junction‐based devices is obtained for the non‐optimized devices. Those results show that the mixed‐dimensional GeSn HPT is one of the promising candidates for detection of infrared band above 2 µm.

Synthesis of High Sn Content Ge1-x-ySixSny (0.1 < y < 0.22) Semiconductors on Si for MWIR Direct Band Gap Applications.

A systematic effort has been described to grow ternary Ge1-x-ySixSny semiconductors on silicon with high Sn concentrations spanning the 9.5-21.2% range. The ultimate goal is not only to produce direct band gap materials well into the infrared region of the spectrum but also to approach a critical concentration (yc) for which further additions of Si would decrease─rather than increase─the band gap. This counterintuitive behavior is expected as a result of the giant bowing parameter in the compositional dependence of the band gap associated with the presence of Si-Sn pairs. The growth approach in this study was based on a chemical vacuum deposition method that uses Si4H10, Ge3H8, and SnD4 or SnH4 as the sources of Si, Ge, and Sn, respectively. A fixed Si concentration near x = 0.05-0.07 was chosen to focus the exploration of the compositional space. A first family of samples was grown of Ge-buffered Si substrates. For Sn concentrations y < 0.12, it was found that the samples relaxed their mismatch strain in situ during growth, resulting in high Sn content films that had relatively low levels of strain and exhibited photoluminescence signals that demonstrated direct band gap behavior for the first time. The device potential of these materials was also demonstrated by fabricating a prototype photodiode with low dark currents. The optical studies suggest that the above-mentioned critical concentration is close to yc = 0.2. As the growth temperature was lowered in an effort to reach such values, Sn concentrations as high as y = 0.15 were obtained, but the films grew fully strained with compressive levels as high as 1.7%. To increase the Sn concentration beyond y = 0.15, a new strategy was adopted, in which the Ge buffer layer was eliminated, and the ternary alloy was grown directly on Si. The much higher lattice mismatch between the Ge1-x-ySixSny layer and the Si substrate caused strain relaxation right at the film/substrate interface, and the subsequent films grew with much lower levels of strain. This made it possible to lower the growth temperatures even further and achieve a comprehensive series of strained relaxed samples with tunable Sn concentrations as high as y = 0.21 (and beyond). The latter represent the highest Sn contents in crystalline Ge1-x-ySixSny attained to date and reach the desired yc = 0.2 range. The synthesized films exhibited significant thickness, allowing a thorough determination of composition, crystallinity, morphology, and bonding properties, indicating the formation of single-phase single-crystal alloys with random cubic structures. Further work will focus on optimizing the latter samples to explore the optical and electronic properties.

Magnetocrystalline anisotropy of interstitially and substitutionally Sn-doped MnBi for high temperature permanent magnet applications

First-principles calculations were performed to calculate the electronic structures of low temperature phase (LTP) MnBi (Mn50Bi50) and substitutionally and interstitially Sn-doped MnBi [Mn50Bi25Sn25, (Mn0.5Bi0.5)66.7Sn33.3]. Brillouin function predicts the temperature dependence of saturation magnetization M(T). Sn substitution for Bi in MnBi (Mn50Bi25Sn25) changes the magnetocrystalline anisotropy constant (Ku) from −0.202 MJ/m3 (the in-plane magnetization) for LTP MnBi to 1.711 MJ/m3 (the out-of-plane magnetization). In comparison, the Ku remains negative but slightly decreases to −0.043 MJ/m3 when Sn is interstitially doped in MnBi [(Mn0.5Bi0.5)66.7Sn33.3]. The Curie temperature (TC) decreases from 716 K for LTP Mn50Bi50 to 445 K for Mn50Bi25Sn25 and 285 K for (Mn0.5Bi0.5)66.7Sn33.3. Mn50Bi25Sn25 has a lower magnetic moment of 5.034 μB/f.u. but a higher saturation magnetization of 64.2 emu/g than (Mn0.5Bi0.5)66.7Sn33.3 with a magnetic moment of 6.609 μB/f.u. and a saturation magnetization of 48.2 emu/g because the weight and volume of the substitutionally Sn-doped MnBi are smaller than the interstitially Sn-doped MnBi. The low Curie temperature and magnetization for Sn-doped MnBi are attributed to the high concentration of Sn. Thus, future study needs to focus on low Sn-concentrated MnBi.

Microstructure evolution, strength-ductility synergy and fracture mechanisms of Cu-18Sn-0.3Ti alloy prepared using Direct Current assisted Hot Pressed sintering and conventional solution treatment

Based on micron atomized spherical Cu-18Sn-0.3Ti alloy powders, the Cu-18Sn-0.3Ti alloy with an elongation of 23.4%, an ultimate tensile strength of 507.2 MPa and a yield strength of 229.4 MPa was prepared using Direct Current assisted Hot Pressed sintering (DCHP) and conventional solution treatment. The microstructure evolution mechanism of alloy during DCHP, the strength-ductility synergy and fracture mechanisms of solution treated DCHP (ST-DCHP) samples were systematically investigated. The results show that, under the synergistic effect of Joule heat, electron wind force and external load of DCHP, dislocations were consecutively generated and consumed as the driving force of dynamic recrystallization, fine equiaxed grains and a large number of annealing twins were formed, the prior particle boundaries (PPBs) of alloy powders gradually disappeared and good sintering necks were formed, which played key roles in improving the strength of alloy. Simultaneously, the δ phase was segregated from grain boundaries to PPBs during DHCP. During the subsequent solution treatment, the phase transformation of δ phase occurred, the β, γ and ε phases which were conducive to the plastic deformation of alloy were generated inside δ phase, resulting in a change in the fracture mechanism inside powders and at sintering necks. The high fraction of high-angle grain boundaries (HAGBs) was considered as the main reason for inducing the formation of high-density deformation twins with different directions inside fine α grains, which greatly improved the ductility of alloy. The strengthening contributions of microstructure were also evaluated, and the calculated yield strength was well consistent with the experimental ones. The results provide the theoretical guidance for the preparation of Cu-Sn-Ti alloy with higher Sn content and lay a foundation for the preparation of Nb3Sn superconducting wires with higher critical current density.

Pegmatite zonation and the use of muscovite as a geochemical indicator for tin-tantalum-tungsten mineralization: Case studies from the Kalehe and Idjwi areas, Democratic Republic of Congo

The central part of the Karagwe-Ankole Belt (KAB) in the Great Lakes area of Central Africa is rich in various rare and strategic elements. The area north of Kalehe and Idjwi island within the Sud-Kivu Province of eastern Democratic Republic of the Congo (DRC) contains Nb, Ta, Sn and W mineralization hosted in pegmatites and quartz veins that are related to leucogranite intrusions. In this work, two granite-pegmatite fields were studied: the Bugarula field in the northern part of Idjwi island and the Kalehe field, along the west coast of Lake Kivu, with a view to determine the co-genetic link between different pegmatites and leucogranites in these regions. Based on mineralogical assemblages, five pegmatite zones were identified, occurring with some spatial overlap, but with an overall increasing distance from the inferred parental granite: 1) albite pegmatites, 2) two-mica pegmatites, 3) muscovite pegmatites, 4) beryl-bearing Nb–Ta–Sn mineralized pegmatites and 5) tourmaline-bearing Nb–Ta–Sn mineralized pegmatites. Muscovite compositions were analyzed from each zone and used to calculate pegmatite fractionation trends by using Rayleigh fractionation modelling. The model uses published partition coefficients (Kd) and measured contents of K, Rb and Cs in muscovite. Muscovites from the consecutive pegmatite zones in both the Bugarula and Kalehe pegmatite fields record a continuous fractionation trend, indicating a co-genetic magmatic evolution. A parental leucogranitic composition of 3.6 wt% K2O, 8 ppm Cs and 300 ppm Rb was iteratively determined to yield a best fit fractionation trend with the data. This composition is within the range of exposed leucogranites sampled in this study, which average at 4.2 wt% K2O, 7 ppm Cs and 400 ppm Rb (n = 12). It should be noted that individually, none of the sampled leucogranites gave satisfactory fractionation trajectories that would suggest a direct co-genetic link between them and the pegmatites. In the Idjwi granite-pegmatite field, the degree of fractionation with respect to the inferred parental leucogranite ranges from 20% to 99% for the least fractionated and most evolved Nb–Ta–Sn mineralized pegmatites, respectively. In the Kalehe area, fractionation values also range from 22% up to 99% for the least fractionated and most evolved (mineralized) pegmatites, respectively. Muscovites from mineralized pegmatites of zones 4 and 5 show high concentrations of Nb, Ta and Sn. As such, we show that muscovite compositions in these pegmatites provide a powerful tool to track Nb–Ta, Sn (and W) enrichment and potential mineralization. These high degrees of fractionation associated with the enrichment in economically interesting elements are similar to reported values for pegmatite fields elsewhere in the Karagwe-Ankole Belt.

Effect of Sn on corrosion resistance of Ti-Cu-Ni amorphous coating

Ti50Cu35-XNi15SnX (X = 5,6,7, wt%) Ti-based amorphous composite coatings were prepared on TA1 by atmospheric plasma spraying. The phase and microstructure were analysed by X-ray diffractometerand scanning electron microscope. The obtained cross-section image of the titanium-based amorphous composite coating confirmed the successful preparation of the amorphous coating. The phase analysis results indicated that an increase in Sn content resulted in a decrease in the amorphous content of the coating. The electrochemical results revealed a significant improvement in the corrosion resistance of the coating compared to the TA1 substrate, consequently enhancing the service life of the electronic material. When the Sn content was 5 wt%, the minimum current density of the coating reached 8.62 × 10-6 A/cm2, and the corrosion rate was 16 times lower than that of the TA1 substrate. As the Sn content increased, the current density of the coating increased from 8.62 × 10-6 A/cm2 to 5.08 × 10-5 A/cm2. Overall, the corrosion resistance of the coating exhibited a downward trend. This observation could be attributed to the decrease in amorphous content caused by the higher Sn content, resulting in a reduction in the corrosion resistance of the coating.

Joining mechanism, microstructure, and mechanical properties of AZ31/6061 joint prepared by pouring fusion welding process assisted with Zn-xSn brazing filler

In this study, AZ31/6061 dissimilar metal joints were manufactured using pouring fusion welding assisted with Zn-xSn brazing filler, and the process, microstructure and mechanical properties of Mg/Al joint were investigated. During welding, the addition of molten Zn-xSn brazing filler completely isolates the direct contact of Mg/Al, preventing the formation of Mg-Al intermetallic compounds. As the Sn content changes, the microstructure of the joints also changes. When the Sn content is 25 wt.%, the microstructure of the AZ31 side is dominated by Mg-Al-Zn ternary eutectic structure, Al6Mg11Zn11, (β-Zn + MgZn2), Al-Zn-Sn (SS), Sn (SS) and Mg2Sn. And the microstructure of the 6061 side is dominated by Al-Zn-Sn (SS), β-Zn, Al-Zn-Sn (SS), and Sn (SS). The width of the Mg-Al-Zn ternary eutectic structure layer decreases with the increase of Sn content. In addition, high Sn content and high heat input promote the formation of Mg2Sn, and large amounts of Mg2Sn are generated with Zn-40Sn interlayer. The average microhardness of the joint gradually decreases with the increase of Sn content. However, the shear strength of the joint first increases and then decreases, and the shear strength of the joint with the Zn-25Sn interlayer is the highest, which is 50.60 MPa. Fracture mode is cleavage fracture.