High Sn Content Research Articles

A RECENTLY DISCOVERED TRACHYTE-HOSTED RARE EARTH ELEMENT-NIOBIUM-ZIRCONIUM OCCURRENCE IN NORTHERN MAINE, USA

AbstractReported here are geological, geophysical, mineralogical, and geochemical data on a previously unknown trachyte-hosted rare earth element (REE)-Nb-Zr occurrence at Pennington Mountain in northern Maine, USA. This occurrence was newly discovered by a regional multiparameter, airborne radiometric survey that revealed anomalously high equivalent Th (eTh) and U (eU), confirmed by a detailed ground radiometric survey and by portable X-Ray fluorescence (pXRF) and whole-rock analyses of representative rock samples. The mineralized area occurs within an elongate trachyte body (~1.2 km2) that intrudes Ordovician volcanic rocks. Geologic constraints suggest that the trachyte is also Ordovician in age. The eastern lobe (~900 × ~400 m) of the trachyte is pervasively brecciated with a matrix containing seams, lenses, and veinlets composed mainly of potassium feldspar, albite, and fine-grained zircon and monazite. Barite is locally abundant. Minor minerals within the matrix include columbite, bastnäsite, euxenite, chlorite, pyrite, sphalerite, and magnetite. The pXRF analyses of 22 samples (App. Table A1) collected from the eastern lobe demonstrate that this entire part of the trachyte is highly mineralized. Whole-rock geochemical analyses for samples from the eastern lobe document high average contents of Zr (1.17 wt %), Nb (1,656 ppm), Ba (3,132 ppm), Y (1,140 ppm), Hf (324 ppm), Ta (122 ppm), Th (124 ppm), U (36.5 ppm), Zn (689 ppm), and Sn (106 ppm). Among light REE, the highest average concentrations are shown by La (763 ppm) and Ce (1,479 ppm). For heavy REE (HREE), Dy and Er are the most abundant on average (167 and 114 ppm, respectively). No HREE-rich minerals such as xenotime have been identified; the HREE may reside chiefly in monazite and bastnäsite, and within the fine-grained zircon. Very strong positive correlations (R2) of 0.92 to 0.98 exist between Th and Zr, Nb, Y, Ce, Yb, and Sn, indicating that the radiometric data for eTh are valid proxies for concentrations of these metals in the mineralized rocks.Trachyte-hosted REE-Nb-Zr deposits like the occurrence at Pennington Mountain also are known in eastern Australia and in the south Qinling belt of Central China. Based on comparisons with these deposits, and the lack of detailed geologic mapping in the Pennington Mountain region, we suggest that other rare-metal occurrences contained in trachyte may exist elsewhere in northern Maine, and more widely in the Appalachian-Caledonian orogen where volcanic and subvolcanic trachytes have been recognized.

Effect of B on microstructure and properties of joints brazed by In-situ Ag-Cu-Zn-Sn filler metal with high Sn content

The copper brazed joints were obtained by induction brazing using in situ synthetic high Sn content silver filler metals with different B contents and the effect of element B on the wettability of filler metals and microstructure and mechanical properties of the joints were studied. With the addition of element B, the spreading area of the filler metals on the copper increases. The microstructure of the joints mainly consists of silver-based solid solution and copper-based solid solution, and the distribution of silver-based solid solution in the brazing seam becomes dispersed with the addition of B. The width of the brazing seam increases significantly with the increase in B content. Meanwhile, the B element was mainly distributed in the Ag-based solid solution. The tensile strength firstly increased and then sharply decreased with B added. The maximum average tensile strength of 206.83 MPa was obtained with a 2% addition of B and the joint fracture pattern is a brittle fracture.

Synthesis of short-wave infrared Ge1−ySny semiconductors directly on Si(100) via ultralow temperature molecular routes for monolithic integration applications

We report the synthesis of Ge1−ySny films containing 6%–13% Sn directly on Si(100) for monolithic integration applications, circumventing the use of conventional Ge-buffer layers. The films are produced in a gas source molecular epitaxy chamber at ultralow temperatures of 185–210 °C and a pressure of 10−5 Torr by the reactions of pure vapor Ge4H10 and SnD4 or SnH4 without carrier gases. Very small amounts of Si, incorporated via the Si4H10 precursor, can be used to improve the structural properties. All samples were characterized by XRD, RBS, IR-ellipsometry, AFM, and TEM, indicating the formation of monocrystalline single-phase films with relatively low defectivity and flat surfaces. A notable highlight is that the residual strains of the alloy layers are much lower compared to those grown on Ge buffers and can be further reduced by rapid thermal annealing without decomposition, indicating that growth on bare silicon should produce bulklike, high Sn content alloys that cannot be accessed using Ge buffers. N-type analogs of the above samples doped with phosphorus were also produced using P(SiH3)3 as the in situ dopant precursor. The results collectively illustrate the potential of our chemistry-based method to generate good quality Ge1−ySny layers directly on large area Si wafers bypassing Ge buffers that typically lead to complications such as multiple hetero-interfaces and epitaxial breakdown at high Sn concentrations.

Improvement in tensile strength of extruded Mg–5Bi alloy through addition of Sn and its underlying strengthening mechanisms

Through an investigation of the microstructure and mechanical properties of extruded Mg–5Bi– x Sn (BT5 x, x = 0, 2, 4, and 6 wt%) alloys, this study demonstrates that the addition of Sn to an Mg–5Bi binary alloy significantly improves the tensile strength of the extruded alloy. All the extruded alloys exhibit a typical basal fiber texture and a partially dynamically recrystallized (DRXed) microstructure consisting of fine DRXed grains and coarse unDRXed grains. As the Sn content increases from 0 wt% to 6 wt%, the average size of the DRXed grains decreases from 4.2 to 2.8 μm owing to the increase in the amount of precipitates via their grain-boundary pinning effect. The extruded B5 and BT52 alloys contain numerous Mg 3 Bi 2 precipitates, but their size and number density are smaller and higher, respectively, in the latter alloy. Numerous Mg 2 Sn precipitates as well as Mg 3 Bi 2 precipitates are present in the extruded BT54 and BT56 alloys, and the number density of the Mg 2 Sn precipitates is higher in the latter alloy because of its higher Sn content. The addition of 2 wt% Sn to the B5 alloy significantly improves the yield strength (YS) and ultimate tensile strength (UTS) of the extruded alloy—by 76 and 57 MPa, respectively. This drastic improvement is the combined outcome of enhanced grain-boundary hardening, precipitation hardening, and solid-solution hardening effects induced by the refined DRXed grains, numerous precipitates, and Sn solute atoms, respectively. The further addition of 2 wt% or 4 wt% Sn to the BT52 alloy leads to moderate increments in the YS and UTS of the extruded alloy. Specifically, each addition of 2 wt% Sn increases the YS and UTS by ~26 and ~20 MPa, respectively, which is attributed mainly to the additional precipitation hardening effect induced by the Mg 2 Sn precipitates.

Combined mica and apatite chemical compositions to trace magmatic-hydrothermal evolution of fertile granites in the Dachang Sn-polymetallic district, South China

Tin mineralization in the Dachang Sn-polymetallic district, South China, is inferred to be associated with the Late Cretaceous Longxianggai pluton, which is primarily composed of porphyritic and equigranular (from medium-grained, to medium- to fine-grained, and then fine-grained textures) biotite granites. However, the magmatic and post-magmatic evolution that may exert an essential role in determining metal fertility of granitic intrusions remains poorly constrained. A comprehensive investigation on chemical compositions of mica (magmatic biotite and hydrothermal muscovite) and apatite in the Longxianggai biotite granites is employed to trace magmatic-hydrothermal processes and their potential role in the formation of fertile granites and hydrothermal Sn mineralization.Magmatic biotite shows variable compositions from Fe-biotite to protolithionite in the porphyritic and equigranular granites. Increasing AlVI and Mn, and decreasing Mg and Ti with increasing XFe in biotite from the porphyritic to medium-grained, and then medium- to fine-grained granites are consistent with compositional variation trends expected during magmatic differentiation, accompanying with progressive enrichment of Li, F, Rb, Cs, Nb, Ta, W and Sn. However, an obvious depletion of Sn, Nb and Cl occurs in magmatic biotite from the more evolved fine-grained granite, with hydrothermal muscovite containing higher Sn and lower Nb contents. Tin depletion in biotite possibly reflects preferential portioning of Sn in Cl-bearing fluids exsolved from the differentiated granitic magmas prior to biotite crystallization. Likewise, the decoupling of Nb with Ta in biotite may attribute to extraction of Nb by exsolved fluids to form secondary Nb-rich rutile and CGMs (columbite-group minerals) in the granite matrix. The relatively high mobility/solubility of Nb in fluids compared to Ta is also consistent with elevated Nb/Ta ratios in hydrothermal muscovite. Compared with apatite in the porphyritic granite, apatite in the medium- to fine-grained granite generally develops fluid inclusions and micro-fractures/pores (often filled with quartz, zircon and monazite), and possesses tetrad REE patterns with variable Eu anomalies, in favor of its crystallization in fluid-saturated fractionated melts. The mineralogical data indicate that equigranular granites have experienced a higher degree of magmatic fractionation than porphyritic granites, with fluid exsolution occurring in late stage of granite solidification. The prolonged fractional crystallization followed by late fluid exsolution may play an important role in hydrothermal mineralization in the Dachang district. A compilation of mica and apatite elemental compositions from Dachang and other Sn-W-related granites demonstrates that high Sn contents and high Fe/(Fe + Mg + Mn) ratios in magmatic biotite, and elevated F, Fe, Mn and Sn contents in apatite, could be geochemical indicators for granitic rocks with high Sn-W mineralization potential.

Mobilization of tin during continental subduction-accretion processes

Abstract Major tin (Sn) deposits within the Variscan orogen are closely related to 325–270 Ma postkinematic granites that intruded the metamorphic rocks of the former precollisional accretionary wedge of the Gondwana margin. In the Erzgebirge (Germany), some of these metasedimentary rocks have high Sn contents (locally more than 1000 ppm Sn). We report cassiterite (SnO2) U-Pb ages of 395–365 Ma and high Sn contents in prograde biotite in these metasedimentary rocks. These data demonstrate that Sn was already introduced into these rocks during accretion and prograde metamorphism. Mobilization of Sn from sedimentary source rocks during prograde fluid loss in a subduction-accretion setting represents an important process of pre-enrichment of sedimentary source rocks that upon partial melting may produce Sn-enriched melts. The large-scale metamorphic mobilization of Sn, documented here for the first time, highlights the possible importance of metamorphic Sn enrichment in accretionary complexes, thereby explaining the spatial distribution of major Sn districts within the Variscan orogen.

Gesn Alloys: From Optical to Electrical Pumped Lasers

Internet of Things applications, including medical diagnostics, imaging and industrial process controls, pollution monitoring or real-time motion control, push the extension of the Si photonics towards mid-infrared range.In recent years, group IV SiGeSn-based optoelectronic devices including light emitting, detectors, modulators, and CMOS devices have been developed. The main advantage of SiGeSn is the bandgap tunability in the range between 1.5 to 5 µm via Si and Sn compositions. Remarkably, the GeSn binary alloy becomes a direct bandgap semiconductor at a relative low Sn content of about 7-8 at.% opening the quest for the realization of monolithically integrated laser sources on Si. In this direction, from the first laser emission proof in 2015 remarkable progress has been done. Supported by epitaxial growth success, processing technology, and cavity design, the laser emission of optically pumped was continuously increased from 80K to 270K. The main role here was played by increasing the Sn content up a concentration of 17 at.%.The next major improvement came from layer transfer technology allowing defect engineering and heat management. Their combination made possible room temperature lasing. However, the real life application requires low laser threshold. Here the use of multiple quantum wells based on SiGeSn/GeSn heterostructures and strain engineering allow a remarkable threshold reduction to values of about 1 kA/cm2. Interestingly, modeling shows that the very epitaxial challenging of having high Sn contents can be reduced by band structure engineering via introducing tensile strain and, in addition, larger gains are possible compared with high-Sn strain free layers. The optical laser spectrum at 0 °C for a GeSn layer under 1 % biaxial tensile strain is shown in Fig 1a.The next step is the realization of an electrical pumped GeSn laser. The first data indicate that both waveguide and microdisk cavities can be electrically pumped leading to low temperature laser emission. The effect of the geometry and strain relaxation of under-etched cavities on the laser emission is under study. Figure 1b shows an exemplary spectrum and current-in light-out (LI) curve for a device with a SiGeSn/GeSn heterostructure taken at 50 K. Figure 1

(Digital Presentation) Low Temperature Formation of Binary and Ternary Group-IV Poly-Layers Via Sn-Nanodots Nuclei

Polycrystalline group-IV alloys, such as Si1-xGex, Ge1-xSnx, and Si1-x-yGexSny, have attractive benefits for thermoelectric generators which can directly convert heat energy into electricity with less environmental impact. Grain boundaries in the polycrystalline material can successfully reduce thermal conductivity which is essential to operate the thermoelectric devices under temperature difference [1]. Besides, mass differences between component elements of the alloy contribute to modulate phonon characteristics [2].In terms of the synthesis of the polycrystalline group-IV alloys, it has been challenging to realize crystallization, which typically needs high temperature annealing, simultaneously with controlling composition, especially Sn content which is limited by low solid solubility into Ge and Si as 1 at.% and 0.1 at.%, respectively, under equilibrium condition [3].As one of the solutions to obtain the polycrystalline group-IV alloys having high Sn content, using crystalline Sn nanodots as nuclei is effective for the growth of crystalline alloys at low temperature. The low temperature growth, which is the growth far away from the equilibrium, enables introduction of Sn more than its solubility limit [4].Amorphous Sn layer deposited on SiO2 substrate can be easily transformed into crystalline Sn nanodots by just applying an annealing in vacuum. We demonstrated the formation of polycrystalline Ge1-xSnx and Si1-xSnx alloys by deposition of Ge and Si on the Sn nanodots at the substrate temperature of 150 °C and 225 °C, respectively [5,6]. Adatoms, namely Ge and Si, were alloyed with the Sn nanodots acting as crystal nuclei. However, we found that Ge preferentially reacts with Sn nanodots when Si and Ge are simultaneously deposited on the Sn nanodots. In this case, Si remains as amorphous, meaning the effect of nucleus for the low temperature crystallization is not effective for Si if Ge exists. This result suggests that Si has to be crystallized prior to Ge.One can notice that the polycrystalline Si1-xSnx can be formed by the Sn nanodots mediated formation process as mentioned above. Therefore, we have proposed the 2-step formation process consisting of poly-Si1-xSnx crystallization and Ge alloying with the poly-Si1-xSnx which can be considered as a virtual substrate [6]. Using the 2-step formation process, whole deposited region was successfully crystallized with alloying Si, Ge, and Sn. The estimated Si and Sn content in the as-grown polycrystalline Si1-x-yGexSny layer were as high as 10.8% and 3.5%, respectively. The impact of introduction of Sn on phonon characteristics will be discussed at the presentation if time allows.Acknowledgements: This work was supported by JSPS KAKENHI Grant Number JP18K13786 and 21K04137 from the Japan Society for the Promotion of Science.

(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

Hydrogen-Assisted Molecular Beam Epitaxy of SiGeSn

Since its first synthesis in 2003 [1], the ternary alloy semiconductor SiGeSn has seen an increasing interest due to its unique properties in the field of Group-IV semiconductors [2–6]. SiGeSn not only allows the decoupling of its bandgap and lattice-constant by what it is predestined for the epitaxy of strain-reduced heterostructures on the Si platform. Furthermore, SiGeSn becomes a direct bandgap semiconductor at high Sn concentrations. Considering these properties, SiGeSn is an attractive material system for optoelectronic applications. An exemplary heterojunction optoelectronic device is the single confinement heterostructure laser diode, the still missing key component for the monolithic integration of the optical on-chip communication on Si.However, one of the greatest challenges faced by many Group-IV researchers is the epitaxy of SiGeSn bulk alloys with high crystal quality. The temperature induced segregation of Sn results in interstitial Sn atoms and subsequently in acceptor-like defect states, as it was already reported for GeSn [7].In this work, we show the molecular beam epitaxy (MBE) of SiGeSn structures under Hydrogen ambient. First of all, we determined the concentration of the acceptor-like defect states of undoped SiGeSn NA,defect on the basis of capacitance-voltage (C-V) measurements of SiGeSn pin diodes. Furthermore, we investigated Hydrogen-assisted epitaxy as an approach for the reduction of the acceptor-like defect states.All epitaxy experiments were performed in a 6” MBE system, where Si, Ge and Sn are used as matrix materials and B and Sb as dopants respectively. In particular, we investigated the influence of molecular (H2) as well as atomic (H) Hydrogen on the epitaxy process and therefore the quality of the grown structures. For this purpose, the MBE system was upgraded with a Hydrogen atom beam source for the generation of an atomic Hydrogen flux.Since the Sn segregation is affected mostly by the substrate temperature, this critical growth parameter is measured in-situ using an infrared pyrometer, which allows the observation of the dynamic processes on the sample surface [8] and the precise control of the substrate temperature at TSub = 200 °C during the SiGeSn epitaxy.All SiGeSn structures are based on Ge virtual substrates (Ge-VS) on Si(001) [9], followed by a 400 nm thick additional Ge buffer layer. In order to fulfil lattice matching of SiGeSn on Ge, a constant ratio of Si and Sn of Si/Sn = 3.67 was kept for all structures. The Sn concentration was varied in the range of 5 % < cSn < 10 %. For material characterization, 300 nm thick undoped SiGeSn layers were grown on this substrate layer stack (see Fig. 1a). A detailed characterization of the crystallinity and the surface roughness was performed using X-ray diffraction (XRD) and atomic force microscopy (AFM), respectively. The comparison of AFM micrographs of SiGeSn layers, grown with and without Hydrogen assistance (see Fig. 1b) show a clear reduction of the surface roughness due to Hydrogen assisted epitaxy.In order to determine NA,defect, C-V measurements on SiGeSn pin diodes (see Fig. 1c) were performed. The diode layer structure, also based on the previously described substrate layer stack, starts with a 400 nm thick p-doped SiGeSn bottom layer with an acceptor concentration of NA = 5x1019 cm-3, followed by an 300 nm thick undoped SiGeSn layer and a closing 200 nm thick n-doped SiGeSn top layer with a donor concentration of ND = 5x1019 cm-3. Subsequently, pin diodes were fabricated using a single mesa process consisting of four basic steps: Mesa structuring using inductive coupled plasma reactive ion etching (ICP-RIE) with HBr, mesa passivation with plasma enhanced chemical vapor deposition (PECVD) grown SiO2, oxide window opening using RIE with CHF3 and metallization using sputtered Al. An exemplary device can be seen in the scanning electron microscopy (SEM) image in Fig. 1d.The SiGeSn pin diodes were electrically characterised by means of C-V measurements using a Keithley 4200 semiconductor characterisation system. For further evaluation, the C-V characteristics of the pin diodes show linear behaviour when plotted on a C-2-V-scaled diagram (Fig. 1e). Under the assumption of a strongly asymmetric pn junction, (ND >> NA,defect), the slope m of the C-2-V characteristics is proportional to NA,defect. In this manner, we determined NA,defect for several SiGeSn pin diodes in dependence of the alloy composition. The results, as shown in Fig. 1f, show an acceptor-like defect concentration between 1017 cm-3 < NA,defect < 1018 cm-3, which is comparable with results reported by other groups for GeSn [7].In our presentation, we will discuss Hydrogen-assisted epitaxy as a promising approach for improving the SiGeSn crystal quality. Figure 1

(Invited) Optoelectronic Quantum Information Processing: An All-Group IV Integrated Platform

Achieving coherent optical photon-to-spin conversion is a long-sought-after strategy for surmounting current fundamental limits in optical schemes that hinder the long-distance distribution of entanglement. Moreover, photon-to-spin interfaces are also essential for a direct mapping of the quantum information encoded in photon flying qubits to stationary spin processors. However, the lack of scalable materials offering an efficient interaction with optical photons along with optimal spin properties remains a formidable obstacle hindering the development of these quantum technological components. With this perspective, this presentation will discuss strategies to address these challenges by leveraging the degrees of freedom offered by group IV (Si)GeSn semiconductors, namely strain and composition, to tailor the electronic structure and eventually fulfill these prerequisites. These innovative systems do not only have the potential to enable coherent photon-to-spin interfaces, but because of their compatibility with the semiconductor industry they will also offer scalability, manufacturability, and cost-effectiveness.We will show that this family of semiconductors provide an additional flexibility to control the charge carrier states and achieve a selective confinement of holes. The latter benefit from a quiet quantum environment that has been at the core of increasingly reliable quantum processors and memories. However, most if not all available experimental studies of two-dimensional gas systems have been thus far focused on heavy-hole (HH) states. This is attributed to the nature of the heterostructures currently available (e.g, Ge/SiGe, InGaAs/GaAs), where compressive strain lifts the valence band degeneracy and leaves HH states energetically well above the light-hole (LH) states. We will demonstrate that tensile strained Ge/GeSn quantum wells alleviate these limitations and allow to selectively confine LH provided the strain is higher than 1%. This requires strain relaxed, high Sn content GeSn buffer layers to be used to grow Ge quantum wells with LH ground state, high g-factor anisotropy, and a tunable splitting of the hole subbands. The optical and electronic properties of these low-dimensional systems will be described and discussed. Spin injection and coherent control will also be addressed. Additionally, qubit designs exploiting the ability to engineer LH states and the Ge large spin-orbit coupling allowing fast all-electrical spin-manipulation schemes will also be presented and discussed.

Gesn Bonding Technology for Integrated Laser-on-Chip Photonics

With the numerous recent demonstrations of germanium-tin (GeSn) semiconductor lasers, this material has become the strongest candidate for the realization of photonic-integrated circuits (PICs). However, the high defect density of this material often results in high lasing thresholds, making them undesirable for real-world applications. Furthermore, the low-thermal budget of high Sn content (>9 at.%) GeSn makes it exceptionally hard to grow onto other materials without introducing point defects. Herein, we present a novel method of directly combining GeSn with other materials through low-temperature wafer bonding. Through this technique, we can reduce the harmful high defect density and improve the lasing performance. To cater to the low thermal budget, we optimized the bonding processes which is critical in preventing Sn segregation to the surface. Through this method, we provide compelling evidence for the enhancement in photoluminescence in GeSn. Additionally, this technique can be extended to fabricate new material stacks, presenting unforeseen opportunities in other fields such as non-linear photonics.

Age and evolution of the Nanyangshan rare-metal mineralized pegmatite revealed by cassiterite U-Pb geochronology and tourmaline chemistry

Determing the age and precise bulk composition of pegmatites is challenging due to 1) the metamictization of zircon grains and 2) their coarse grain size and heterogeneity. Cassiterite and tourmaline are common in pegmatites and in the case of the former can be used to date pegmatites and while the latter can be used to monitor petrogenesis. This study presents in situ cassiterite U-Pb dating and tourmaline geochemical and B isotopic data from the Nanyangshan Li-Be-Nb-Ta-Rb-Cs-Sn mineralized pegmatite in the North Qinling terrane of China to investigate their age and petrogenesis. The Nanyangshan pegmatite host abundant spodumene, lepidotite, beryl, cassiterite, columbite and tourmaline and can be roughly divided into black tourmaline (Tur B)-cassiterite and pink tourmaline (Tur P)-spodumene bearing phases. Most of the cassiterite are homogenous in appearance although some (<10 %) have core-rim structures. The cassiterite crystals mainly yielded U-Pb ages of ∼ 410 Ma, although the the rims yielded ages of ∼ 370 Ma. Both Tur B and Tur P are rich in Li and are elbaites, with Tur B closer to shorl and Tur P to elbaite. Clear correlations exist between some trace elements (Li and Sn) with major elements (Na/(Na + X□) in the tourmalines, indicating the potential crystal chemical effects on their incorporation. The boron isotopes of the tourmalines vary from −19.36 ‰ to −15.91‰ and decrease from Tur B to Tur P. This implies the boron in the Nanyangshan pegmatite was mainly derived from partial melting of metasedimentary souce rocks with the variation likely caused by fractionation. Tur P is closely associated with spodumene and has higher concentratios of Li, Be, Nb, Ta whereas the Tur B is closely associated with cassiterite and has higher concentrations of Sn, suggesting that tourmaline chemistry could be a reliable geological record of the environment and useful exploration tool.

Unexpected effect of pre-aging prior to extrusion on microstructure and mechanical properties of extruded Mg–8Sn–6Zn–0.1Mn alloy

Pre-aging prior to extrusion (AE), aiming to achieve high strength without sacrificing ductility, has shown considerable potential in Mg-Sn alloys containing low content of Zn element. For Mg–8Sn–6Zn–0.1Mn alloy containing high contents of Sn and Zn elements, however, an unexpected decrease in mechanical properties after AE treatment is observed and comprehensively investigated in this paper. We demonstrate that after pre-aging treatment, the size and volume fraction of bulk Mg2Sn particles are not decreased as expected, but some fine particles are segregated around the bulk Mg2Sn phases due to high contents of Sn and Zn in this alloy. The bulk phases are prone to facilitate the occurrence of particle-stimulated nucleation and continuous dynamic recrystallization mechanisms during extrusion. Since pre-aging treatments produce a high number of fine particles, these particles exert a pinning or drag effect on grain boundaries, inhibiting the nucleation of dynamic recrystallization, which reduce the volume fraction of dynamic recrystallized grains (DRXed). Unexpectedly, solution-extruded (SE) alloy has finer and higher volume fraction of DRXed grains than AE alloy. Additionally, the fine particles produced by dynamic precipitation in SE alloy are densely distributed and smaller than those in AE alloy. The coarse particles in AE alloy serve as the crack initiation sites under external force, and reduce the ductility of the alloy. Consequently, SE alloy with excellent strength-ductility synergy can be attributed to a combination of refinement of grain structure and fine densely distributed particles.

Enhanced photoluminescence of GeSn by strain relaxation and spontaneous carrier confinement through rapid thermal annealing

In this work, the structural evolution and photoluminescence (PL) of 200 nm pseudomorphic Ge 0.9338 Sn 0.0662 on Ge (001) substrate grown by low-temperature molecular beam epitaxy (MBE) after rapid thermal annealing (RTA) is studied. Under RTA at 350 °C or lower, the GeSn film is coherently strained on Ge substrate. As RTA temperature further increases, gradual strain relaxation of GeSn is enabled by generation of misfit dislocations and threading dislocations. As RTA temperature reaches 550 °C or beyond, Sn segregation occurs along with strain relaxation. The PL intensity of annealed samples is enhanced compared to that of as-grown sample probably due to improved crystal quality and strain relaxation (for RTA at> 350 °C) of GeSn. The sample annealed at 500 °C exhibits highest PL intensity due to formation of a Sn-component-graded (SCG) heterojunction with highest Sn content in surface region resulted from interdiffusion of Ge and Sn. The formation of SCG heterojunction renders spontaneous confinement of optically pumped carriers in the surface region and enlarges occupation probability of carriers in Γ valley. Additionally, the carrier confinement in the surface region reduces self-absorption of GeSn and suppresses nonradiative recombination near the GeSn/Ge interface. The results manifest that RTA is an appropriate approach to improve the light emitting property of GeSn grown by low-temperature MBE. • Strain relaxation of pseudomorphic GeSn on Ge is realized by rapid thermal annealing. • A Sn-component-graded heterojunction is formed after rapid thermal annealing. • The light emitting property of GeSn is dramatically enhanced.

Novel High-Tin Bronze and Nb3Sn Multifilamentary Wires

We developed a method for manufacturing a high Sn concentration bronze material with high ductility. The high-Sn bronze was used to produce multifilamentary wires, and their characteristics were evaluated. To increase the Sn content of the bronze and ensure ductility, the δ-phase (Cu <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">41</sub> Sn <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">11</sub> ), which is a eutectoid when the Sn content is greater than the Cu-Sn solid-solution limit, was replaced with a ternary compound by the addition of Ti. The compound was further refined by hot forging to develop ductility. In this study, 1615-filament wires were produced using the high Sn concentration bronze and a commercial bronze for comparison. Each wire was heat treated with different conditions, and their superconducting properties were evaluated. The area ratio of the Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn phase was higher with the high-Sn bronze alloy irrespective of the heat-treatment temperature. The critical current density was improved for the high-Sn bronze for heat treatment at 625 °C or lower, but when the treatment was performed at 650 °C, the Ti concentration in the Nb <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">3</sub> Sn phase exceeded 2.0at% and the upper critical magnetic field deteriorated dramatically.

Hot isostatic pressing of Cu–15Ni–8Sn alloy with suppressed Sn macro-segregation and enhanced mechanical properties

Sn macro-segregation and coarse grains easily occur in the conventional casting process of the Cu–15Ni–8Sn alloy with a high Sn content. Here, hot isostatic pressing (HIP), an advanced powder metallurgy technique, was introduced to explore feasibility in alleviating or eliminating such defects. The gas–atomized powder with high homogeneity of composition was used, which was solidified rapidly. The microstructural evolution, mechanical properties, deformation mechanisms and strengthening mechanisms were deeply and systematically revealed and discussed. Nearly fully dense samples were fabricated by HIP with no Sn macro-segregation, and simultaneous strength-plasticity enhancement was obtained. The content of harmful discontinuous precipitation colonies was controlled to only ∼3.11 vol%. This was attributed to the fine grain size of the powder and the preferential complete recrystallization process during the HIP. That is, the γ nucleation sites were occupied by numerous grain boundaries provided by fine grains, and the driving force of γ growth was consumed by recrystallization. Furthermore, enhanced mechanical properties were related to the Sn macro-segregation suppression, grain refinement (∼11.0 μm), dislocation density continuous increase, and dispersion distribution of γ precipitates, etc. These encouraging findings validate the advantages and potential of HIP in the fabrication of Cu–15Ni–8Sn alloy with enhanced mechanical properties for structural applications.

Room Temperature Lasing in GeSn Microdisks Enabled by Strain Engineering

AbstractThe success of GeSn alloys as active material for infrared lasers could pave the way toward a monolithic technology that can be manufactured within mainstream silicon photonics. Nonetheless, for operation on chip, lasing should occur at room temperature or beyond. Unfortunately, despite the intense research in recent years, many hurdles have yet to be overcome. An approach exploiting strain engineering to induce large tensile strain in micro‐disk made of GeSn alloy with Sn content of 14 at% is presented here. This method enables robust multimode laser emission at room temperature. Furthermore, tensile strain enables proper valence band engineering; as a result, over a large range of operating temperatures, lower lasing thresholds are observed compared to high Sn content GeSn lasers operating at similar wavelength.

Thermoelectric Performance of Sn and Bi Double-Doped Permingeatite

In this study, mechanical alloying was performed to synthesize permingeatite Cu3Sb1-x-ySnxBiySe4 (0.02 ≤ x ≤ 0.06 and 0.02 ≤ y ≤ 0.04) doped with Sn and Bi. Hot pressing was subsequently conducted to achieve dense sintered bodies. When the Bi content was constant, the carrier concentration increased with the Sn content, but the mobility decreased owing to the increased carrier concentration. In contrast, when the Sn content was constant, the carrier concentration and mobility were not significantly affected by the Bi content. Higher electrical conductivity was observed in specimens with a higher Sn content or lower Bi content; consequently, Cu3Sb0.92Sn0.06Bi0.02Se4 exhibited the highest electrical conductivity. The Seebeck coefficient increased with temperature, and it is inferred that the permingeatite doped with Sn/Bi does not undergo an intrinsic transition until 623 K. In contrast to the electrical conductivity, a higher Seebeck coefficient was obtained in the specimens with a lower Sn content or higher Bi content; consequently, Cu3Sb0.94Sn0.02Bi0.04Se4 exhibited the highest Seebeck coefficient. Cu3Sb0.92Sn0.06Bi0.02Se4 exhibited the maximum power factor, depending on the electrical conductivity and Seebeck coefficient. The electronic thermal conductivity was not significantly affected by temperature, but the lattice thermal conductivity decreased as the temperature increased. However, the thermal conductivity decreased with increasing temperature. Sn doping effectively reduced the lattice thermal conductivity, whereas Bi doping effectively reduced the electronic thermal conductivity; consequently, Cu3Sb0.94Sn0.02Bi0.04Se4 exhibited the lowest thermal conductivity. Finally, the highest dimensionless figure-of-merit of 0.75 was achieved at 623 K by Cu3Sb0.92Sn0.06Bi0.02Se4.

Fe-based sintered matrix for diamond tools: microstructure, mechanical performance and crack initiation and propagation characteristics

To design Fe-Cu-Sn-Ni metal binders for diamond tools and optimize the performance of binders, Fe-based binders were prepared by hot-press sintering method using Fe powder, Cu powder, Sn powder and Ni powder as the raw materials. The phase constitution, microstructure, mechanical properties and crack formation were evaluated. Results showed that Fe-based matrixes are composed of Cu3Sn intermetallic compounds and several solid solutions, such as α-Fe, γ(Fe,Ni), and Cu13.7Sn. The relative high Sn content can increase the hardness of the sintered bulk samples and significantly reduce the bending strength. With the increase of Ni content, the hardness increases gradually, while the bending strength increases firstly and then decreases. The cracks initiate from brittle Cu3Sn intermetallic phases and quickly propagate in the brittle phases or along the interface between Cu3Sn intermetallic compounds and γ(Fe,Ni) phases. The propagation of crack can be impeded by Cu13.7Sn solid solution.