Tellurium Research Articles

Computational investigation of structural, magnetic, electronic and optical properties of the cluster Mn-X6 (X=P, S, Cl, Br or Te) doped monolayer WSe2

• The Mn-S 6 doped monolayer WSe 2 under the W-rich condition is the most stable. • The Mn-S 6 , Mn-Cl 6 and Mn-Br 6 doped monolayer WSe 2 systems become magnetic half-metal. • The Mn-P 6 and Mn-Te 6 doped monolayer WSe 2 systems turn into magnetic semiconductor. • The Mn-X 6 doped monolayer WSe 2 systems exhibit red shift and enhanced absorption. We perform systematic first-principles calculations to clarify the effects of the cluster Mn-X 6 (X=P, S, Cl, Br or Te) doping on the structural, electronic, magnetic and optical properties of monolayer WSe 2 . The smaller formation energy shows that all doping systems are more stable under W-rich condition than Se-rich condition. The cluster Mn-S 6 doped monolayer WSe 2 has the smallest formation energy may be due to S and Se elements having similar electronegativity, while the maximum formation energy of the cluster Mn-Te 6 doping may be due to the lowest electronegativity of the Te element. Although pure monolayer WSe 2 is a non-magnetic semiconductor, the Mn-P 6 and Mn-Te 6 doped monolayer WSe 2 become magnetic semiconductor, while the Mn-S 6 , Mn-Cl 6 and Mn-Br 6 doped monolayer WSe 2 turn into magnetic half-metal. Compared with the pure monolayer WSe 2 , the cluster Mn-X 6 doped monolayer WSe 2 have not only a red-shift phenomenon but also an enhanced absorption in infrared and far-ultraviolet region and thus a potential application in infrared and far-ultraviolet light detectors.

Waste heat recycling of high-power lighting through chips on thermoelectric generator

A waste heat is inevitably generated in high-power lighting due to the limited efficiency of light-emitting diode (LED) chips and the non-radiative transition of phosphors. In this work, we proposed an integrated module of LED chips on thermoelectric generator (TEG) for the waste heat recycling of high-power lighting. The multi-chips were directly bonded on the hot side of TEG for heat conduction. The chip powers and temperature distribution of chips-on-TEG were investigated under different chip currents, and their output voltage, current, and power were measured. When the chip current increases from 0.4 to 1.4 A, the heat power increases from 1.7 to 9.2 W, resulting in a high temperature gradient of 219 °C for the TE elements at the chip current of 1.4 A. This enough heat energy converts to an electric power with an output voltage of 1.23 V. In addition, a low-power indicating lamp was driven by the electricity from three chips-on-TEGs without additional power consumption. Our work opens a good idea to recover the normally wasted heat from high-power lighting, which could be extended for the heat energy harvesting in many power devices.

Klein–Nishina formula and Monte Carlo method for evaluating the gamma attenuation properties of Zn, Ba, Te and Bi elements

Abstract In this work, the Klein–Nishina (K–N) approach was used to evaluate the electronic, atomic, and energy-transfer cross sections of four elements, namely, zinc (Zn), tellurium (Te), barium (Ba), and bismuth (Bi), for different photon energies (0.662 MeV, 0.835 MeV, 1.170 MeV, 1.330 MeV, and 1.600 MeV). The obtained results were compared with the Monte Carlo method (Geant4 simulation) in terms of mass attenuation and mass energy-transfer coefficients. The results show that the K–N approach and Geant4 simulations are in good agreement for the entire energy range considered. As the photon energy increased from 0.662 MeV to 1.600 MeV, the values of the energy-transfer cross sections decreased from 81.135 cm2 to 69.184 cm2 in the case of Bi, from 50.832 cm2 to 43.344 cm2 for Te, from 54.742 cm2 to 46.678 cm2 for Ba, and from 29.326 cm2 to 25.006 cm2 for Zn. The obtained results and the detailed information of the attenuation properties for the studied elements would be helpful in developing a new generation of shielding materials against gamma rays.

Assessment of ecological pollution of heavy metals in surface soils of different sites within northwest of iraq

Heavy metals pollution in surface soils of different urban areas in northwest Iraq were investigated. Correlation between screened metals’ spatial distribution (33 elements) and point and non-point pollution sources were performed. Obtained results showed that the levels of 15 elements (Hg, Ag, Cd, Sb, Sr, Ti, Mo, Rb, Sc, Zn, Ni, Cr, Cs, Te and Ca) exceeded the reference values of urban soil constituents. Higher observed levels of these metals, indicating that the urban soils of the studied areas are enriched with these contaminants. Further, higher concentrations of some “unexpected” toxic metals were detected in the studied locations. Estimated correlation coefficients of metal concentrations suggested three potential sources for soil pollution by heavy metals in the surveyed region. Different industrial activities, dominated by petroleum and petrochemical industries, are likely to be responsible for the releases of many heavy metals, e.g. Ni, Cr and Cu. Military activities were considered an important source for some toxic metals, e.g. Zr, Rb, V, and As, since these metals were observed at high levels in the studied sites. Trace metals such as Cu, Pb, Zn are found to be correlated with agricultural practices. However, the higher observed concentration of Ca in the surveyed locations can be attributed to natural processes’ impact. Overall, this research’s outcomes can be useful for the policymaking efforts dedicated to solving complex environmental problems related to soil pollution and being a guide for soil quality in northwest Iraq.

High refractive index IR lenses based on chalcogenide glasses molded by spark plasma sintering

In this work, spark plasma sintering is used to mold non conventional chalcogenide glasses of high refractive index at low temperature (<400°C). This equipment, usually used for sintering refractory materials, is presented as efficient for both densification and high precision molding of IR transparent bulks and lenses of telluride glasses. Thermo-mechanical and optical characteristics of the selected Ge25Se10Te65 glass composition were investigated showing a refractive index of 3,12@10 µm and with however a limited resistance to crystallization. Mechanical milling of raw Ge, Se, Te elements leads to a major amorphous phase with the formation of a small proportion of GeTe crystals. Remaining GeTe crystals induce a fast crystallization rate during the sintering process leading to the opacity of the material. SPS flash moldings were then performed using melt quenched glass powders to produce complex lenses. It has been found that the critical parameter to reach optimal IR transparency is mainly the powder granulometry, which should be superior to 100 µm to prevent from MIE scatterings. The possibility of producing high refractive index infrared lenses has been demonstrated even with unstable glasses against crystallization.

Theoretical prediction of electronic, transport, optical, and thermoelectric properties of Janus monolayers In2XO ( X=S,Se,Te )

The breaking of the vertical symmetry in Janus monochalcogenides gave rise to many properties that were not present in the original monochalcogenide monolayers. However, recent papers have often focused only on Janus monochalcogenides containing S, Se, and Te elements despite that O is also one of the group VI chalcogen elements. In this paper, we systematically investigate the electronic, transport, optical, and thermoelectric properties of Janus monolayers ${\mathrm{In}}_{2}X\mathrm{O}$ ($X=\mathrm{S},\mathrm{Se},\mathrm{Te}$) using first-principles calculations. Based on phonon spectrum analysis and ab initio molecular dynamics simulations at room temperature, ${\mathrm{In}}_{2}X\mathrm{O}$ monolayers were reported to be stable. Our calculations reveal that, while ${\mathrm{In}}_{2}\mathrm{SO}$ is an indirect semiconductor, ${\mathrm{In}}_{2}\mathrm{SeO}$ exhibits a direct semiconducting characteristic, and biaxial strain can lead to the semiconductor-metal phase transition in ${\mathrm{In}}_{2}\mathrm{SeO}$. Monolayer ${\mathrm{In}}_{2}\mathrm{TeO}$ is metal at equilibrium, and its metallic characteristics are prevented under biaxial strains. Calculations for transport properties show that the carrier mobilities of ${\mathrm{In}}_{2}\mathrm{SO}$ and ${\mathrm{In}}_{2}\mathrm{SeO}$ monolayers are highly anisotropic, and electron mobility of ${\mathrm{In}}_{2}\mathrm{SO}$ exceeds $3\ifmmode\times\else\texttimes\fi{}{10}^{3}\phantom{\rule{4pt}{0ex}}{\mathrm{cm}}^{2}/\mathrm{Vs}$. In this paper, the optical and thermoelectric properties of ${\mathrm{In}}_{2}\mathrm{SO}$ and ${\mathrm{In}}_{2}\mathrm{SeO}$ monolayers are also investigated and discussed in detail. Finally, the electronic properties of all four possible stacking configurations of the Janus bilayers are briefly calculated. Our findings not only contribute to a more general view of the physical properties of the Janus group III monochalcogenides but also recommend them as potential nanomaterials for applications in optoelectronic and thermal devices.

A missing link between ancient and active mafic-hosted seafloor hydrothermal systems – Magmatic volatile influx in the exceptionally preserved Mala VMS deposit, Troodos, Cyprus

Reconciling observations between ancient volcanogenic massive sulfide (VMS) and actively forming seafloor massive sulfide (SMS) deposits is critical for understanding the sources and processes that govern metal enrichment in marine hydrothermal systems. For a mafic VMS deposit, the Mala VMS mound located within the Troodos ophiolite, Cyprus, is unusual as pyrite is enriched in magmatic volatile elements (Au, Cu, Te and Se), sulfide δ34S values average − 3.8‰ ± 1.9‰ (1σ, n = 28), and gypsum averages +14.5‰ ± 2.0‰ (1σ, n = 26) - in stark contrast to the bulk of Troodos VMS pyrite, which averages +4.6‰ ± 2.8‰. To date, this combination of features has only been observed in actively forming SMS deposits in immature, subduction-influenced environments and rarely in ancient VMS deposits hosted in felsic environments. Traditionally, the leaching of igneous rocks is considered as the primary source of metals in mafic VMS deposits. However, at Mala, and perhaps other active SMS deposits in mafic environments, we suggest that Au, Cu, Te and Se were initially sourced from the direct contribution of a magmatic volatile phase where SO2 underwent disproportionation, a signature that is later overprinted by reacted seawater during deposit maturation and is therefore not usually preserved in ancient analogues. Thus, the exceptional preservation of Mala provides evidence of a magmatic volatile contribution in the early stages of mafic VMS deposit formation.

Itinerant ferromagnetism mediated by giant spin polarization of the metallic ligand band in the van der Waals magnet Fe5GeTe2

We investigate near-Fermi-energy (EF) element-specific electronic and spin states of ferromagnetic van der Waals (vdW) metal Fe5GeTe2. The soft x-ray angle-resolved photoemission spectroscopy (SX-ARPES) measurement provides spectroscopic evidence of localized Fe 3d band. We also find prominent hybridization between the localized Fe 3d band and the delocalized Ge/Te p bands. This picture is strongly supported from direct observation of the remarkable spin polarization of the ligand p bands near EF, using x-ray magnetic circular dichroism (XMCD) measurements. The strength of XMCD signal from ligand element Te shows the highest value, as far as we recognize, among literature reporting finite XMCD signal for none-magnetic element in any systems. Combining SX-ARPES and elemental selective XMCD measurements, we collectively point an important role of giant spin polarization of the delocalized ligand Te states for realizing itinerant long-range ferromagnetism in Fe5GeTe2. Our finding provides a fundamental elemental selective view-point for understanding mechanism of itinerant ferromagnetism in low dimensional compounds, which also leads insight for designing exotic magnetic states by interfacial band engineering in heterostructures.

An investigation on CdS1-xTex interface compound in CdS/CdTe hetero-junction solar cells by density functional theory (DFT)

Abstract In this study, we present the structural, optical and electronic properties of zinc blende cadmium sulfide (CdS) and cadmium telluride (CdTe) as well as the intermixed zinc blende ternary CdS1-xTex compound with the compositional variation of S and Te elements. The density functional theory (DFT) method by incorporating the Hubbard model has been utilized to comprehend the relationships between the change of band gap with respect to the molar fraction and its subsequent effects in electronic structures. A 2 × 2 × 2 supercell with 16 atoms has been employed in the molecular design structure of CdTe and CdS. The exchange-correlation potential has been calculated using GGA + U approximation as implemented in the QUANTUM ESPRESSO package along with BURAI software as graphical user interface (GUI). The obtained calculation outcomes are in reasonable agreement with the experimental results in the case of lattice constant and refractive index (n), however, results demonstrate some discrepancy in band gap estimations. The results also exhibit band gap bowing of the ternary CdS1-xTex alloy with the variation of molar fraction (x) which suggest the shrinking of the band gap to the lowest value at x = 0.5 as CdS0·5Te0.5.

A new route for preparing CdTe thin films by chemical bath deposition

Cadmium telluride (CdTe) is a binary II-VI direct band gap semiconducting material. Cadmium telluride is a promising electrochemical and photovoltaic material for thin film solar cells. It shows both p and n type conductivity. A nanocrystalline thin film of CdTe was deposited in homogeneous medium on nickel plate by chemical bath deposition method containing 0.01 M cadmium acetate and 0.02 M tellurium dioxide. The structural, compositional and optical analysis were studied by x-ray diffraction (XRD), energy-dispersive x-ray spectroscopy (EDS), scanning electron microscope (SEM), Fourier Transform infrared spectroscopy (FTIR) and Photoluminescence (PL).The diffraction peak observed at 2θ = 23.59° with (1 1 1) plane indicate the crystalline phase of CdTe film. The average crystalline size is measured to be 7 nm. Compositional analysis reveals the presence of both Cd and Te elements. The EDS Spectroscopy shows the ratio of Cd and Te is1:2 in case of as deposited film. The Photoluminescence peak is observed at 471 nm.

Burgali Epithermal Au–Ag Deposit in the Paleozoic Kedon Volcanic Belt (Northeastern Russia)

The Burgali deposit is located in the Paleozoic Kedon volcanic belt (KVB) within the Omolon cratonic terrane. The orebodies of the Burgali deposit are veined and stockwork-type. The studies of the wallrock metasomatites demonstrate that the erosional truncation of the deposit is close to minimal. The ores of the deposit are enriched in the chalcophile elements (Au, Ag, As, Sb, Te, W, Mo, and Bi) and poor in the rare earths. The rare-earth element (REE) spectra are dominated by light lanthanides. The ores are characterized as very low-sulfidation with finely disseminated mineralization, widespread occurrence of chalcedony, and widespread colloform-banded, often combined with brecciated, structures. The late quartz veins contain Lower Carboniferous coaly siltstone fragments, filled with petrified timber remains, which indicate the Carboniferous age of the ore mineralization. The ores contain widespread Au- and Te-bearing pearceite and rare minerals such as argyrodite and the selenous petrovskaite and uytenbogaardtite. The data obtained enable the Burgali deposit to be classified as low-sulfidation epithermal. The outlook for Ag and Au reserve additions is based on the further studies and exploration of the ore-bearing stockwork.

Establishment of a research workflow for occurrence state of critical metal in ore concentrate powder: A case study of the cobalt-rich sulfur ore concentrate powder from the Middle-Lower Yangtze River Valley Metallogenic Belt, China

长江中下游成矿带作为我国矿床学研究程度和矿产利用技术水平最高的成矿带之一，大部分矿床中除了主要成矿元素铜、金、铁和硫等，还伴生潜在可利用的关键金属资源镉、钴、硒、碲和铼等。由于目前矿山主要选矿回收铜、铁、硫、铅、锌、金和银等主要矿种，在不改变选矿工艺的条件下，矿山产品矿精粉中关键金属的分布特征和可利用性是当前关键金属资源利用的核心问题之一。本文对成矿带内玢岩型铁矿床、矽卡岩型铁矿床、矽卡岩型铁铜矿床、矽卡岩型铜金矿床、斑岩型铜金矿床和角砾岩筒型铜金矿床等六类矿床的矿山产品（铜金粉、硫精粉、铁精粉和金精粉）进行了系统化学成分分析，发现目前的矿山产品中关键金属元素含量普遍不高，但矽卡岩型铁矿床中的龙桥铁矿床硫精粉中富集钴，具有综合回收利用钴资源的潜力。在此基础上，本次工作利用综合矿物分析技术（TIMA），扫描电镜（SEM）和激光剥蚀-等离子体质谱仪（LA-ICP-MS）三种测试方法，系统开展了富钴硫精粉中钴的赋存状态研究。结果表明，龙桥硫精粉中钴矿物为辉砷钴矿、铁硫砷钴矿和硫铜钴矿，分别占硫精粉中总钴含量的9.93%、0.64%和0.01%。黄铁矿晶格中类质同象形式产出的钴占总量的81.97%，此外还有7.46%的钴赋存在其他矿物中。通过对比研究，初步建立了矿精粉中关键金属元素赋存状态的研究方法流程，为矿精粉中钴的回收利用提供了依据。;The Middle-Lower Yangtze River Valley Metallogenic Belt is one of the metallogenic belts with well-studied economic geology research and comprehensive mineral utilization technology in China. In addition of the main ore-forming elements Cu, Au, Fe and S, most deposits are associated with potentially available critical element resources, such as Cd, Co, Se, Te and Re. At present, the mines processed and recovered Cu, Fe, S, Pb, Zn, Au, Ag and other major products. Without changing the mineral process, the key problems in the utilization of critical element resources are the understanding of the occurrence of critical metals in ore concentrations. We have conducted a systematic chemical composition analysis of the mine products (i.e., copper concentrate powder, sulfur concentrate powder, iron concentrate powder and gold concentrate powder) of six types of deposits in the metallogenic belt, including apatite-magnetite Fe deposit, skarn Fe deposit, skarn Fe-Cu deposit, skarn Cu-Au deposit, porphyry Cu-Au deposit and breccia-hosted Au deposit. It is found that the contents of critical elements (Cd, Co, Se, Te and Re) in those mine products are generally low, except Co enriched in sulfur concentrate powder of Longqiao skarn iron deposit, which has the possibility of recovery and utilization of cobalt resources. In this study, the occurrence of cobalt in Co-rich sulfur concentrate powder was analyzed by Tescan Integrated Mineral Analyzer (TIMA), Scanning Electron Microscope (SEM) and Laser Ablation Inductively Coupled Plasma Mass Spectrometry (LA-ICP-MS). The analyses results show that the cobalt independent minerals in Longqiao sulfur concentrate powder are cobaltite, glaueodot and carrollite, which account for 9.93%, 0.64% and 0.01% of the total cobalt in sulfur concentrate powder, respectively. The amount of cobalt occurs as isomorphic form in pyrite lattice accounts for 81.97% of the total. In addition, 7.46% of cobalt exists in other unknown minerals. Research workflow of critical elements deportments in ore concentrate powder is established initially, which provides a theoretical basis for the recovery and utilization of cobalt in ore concentrate powder.

Three-dimensional tellurium and nitrogen Co-doped mesoporous carbons for high performance supercapacitors.

Tellurium-doped mesoporous carbon composite materials (Te/NMC) have been prepared by a facile intercalation method in the presence of nitrogen-doped mesoporous carbon (NMC) with tellurium powder, for the first time. The effects of the co-doped N and Te in the mesoporous carbon matrix on the physical/chemical properties and capacitance performances were investigated via the use of various characterization methods and electrochemical studies. The as-prepared NMC and Te/NMC materials were found to mainly be composed of mesopores and maintained the 3D hierarchical graphite-like structure with lots of defect sites. By intercalation of Te atoms into the NMC materials, 2.12 at% (atom%) of Te was doped into NMC and the specific surface area of Te/NMC (261.07 m2 g−1) decreased by about 1.5 times compared to that of NMC (437.96 m2 g−1). In electrochemical measurements as a supercapacitor (SC) electrode, the Te/NMC based electrode, even with its lower porosity parameters, exhibited a higher capacitive performance compared to the NMC-based electrode. These results for Te/NMC arise due to the pseudo-capacitive effect of doped Te and the increase in the capacitive area available from the formation of interconnections in the mesoporous carbons through Te–O bonds. As a result, the synergetic effect of the Te and N atoms enables Te/NMC to exhibit the highest specific capacitance of 197 F g−1 at a current density of 0.5 A g−1. Moreover, remarkable long-term cycling stability with the retention of more than 95% of the initial capacitance is observed for Te/NMC at a current density of 5 A g−1 and also for 1000 charge–discharge cycles.

Effect of element Te on alterations of microstructure and mechanical property of nickel-based superalloy Inconel 718 through alloy infiltration

Alloying elements have significant effects on material physical and mechanical properties. The present work studies the effect of element Te on the alterations of microstructure and mechanical property of nickel-based superalloy Inconel 718. Te was diffused into the surface layer of treated samples with a new alloy infiltration method. The microstructure and element distribution within the modified layer were tested and quantitatively characterized with scanning electron microscopy (SEM) and energy dispersive X-ray spectroscopy (EDS). The depth of infiltration layer presented an approximately linear relationship with the treating temperature range from 700 °C to 900 °C. Furthermore, the mechanical property of the modified layer was evaluated through nano-indentation experiments. The results show that the Te infiltration into the surface layer of Inconel 718 presents a gradient distribution from the outmost surface to the matrix, and it results in a substantial weakening of the modified layer. A gradual decrease in nano-hardness was detected from the surface to the matrix, and the nano-hardness value of infiltration layer was weakened by 31% for the Te infiltration treatment at 900 °C. The underlying weakening mechanism of Te on the superalloy Inconel 718 was revealed. Te element penetrates along the grain boundary leading to the formation of new intercrystalline phases. Consequently, the grain boundary is “opened” which causes the embrittlement of grain boundaries and weakening of the treated surface. This study can not only help to understand the influence of alloying elements on the variation of material properties, but also provide guidance for design of material compositions.

Effects of increasing dietary zinc sulfate fed to primiparous ewes: I. Effects on serum metabolites, mineral transfer efficiency, and animal performance

ABSTRACT Objective The objective of this research was to determine the effects of increasing Zn concentrations during late gestation on serum metabolites, serum mineral element transfer efficiency ratios (TE), and ewe and lamb performance in a semi-extensive management system. Materials and Methods Commercial white-face (WF; n = 23) and black-face (BF; n = 24) ewes (age ≈18 mo; BW 87.48 ± 8.37 kg) were sorted into breed-type groups and within groups ranked by BW and randomly divided into 3 dietary supplement treatment groups along the rank: CON (n = 13, 40 mg/kg Zn, ≈1 × NASEM recommendations), Zn500 (n = 19, 500 mg/kg Zn, ≈4 × NASEM recommendations), and Zn1000 (n = 15, 1,000 mg/kg Zn, ≈7 × NASEM recommendations). Treatments were administered in pelleted alfalfa (0.45 kg/ewe per day) fortified with Zn sulfate to increase Zn concentrations fed from 87.5 ± 8.9 d of gestation until parturition. Results and Discussion Maternal treatment did not affect ewe BW change throughout the experiment, nor serum metabolites, mineral element TE, or progeny performance through weaning (P ≥ 0.06). However, ewe greasy fleece weight the following year was greater for Zn500 than Zn1000 ewes (4.13 ± 0.18 kg vs. 3.48 ± 0.19 kg; P = 0.03) but did not differ between CON and the other treatments (3.68 ± 0.22 kg; P ≥ 0.22). The most marked effects were observed between breeds where Zn TE of WF ewes and lambs (264.3 ± 23.2) was approximately twice that of BF ewes and their lambs (165.4 ± 19.7; P Implications and Applications The results suggest feeding Zn supplemented from Zn sulfate beyond current NASEM recommendations from d 87 of gestation until parturition had minimal beneficial effects on fine-wool or meat-type ewes and lambs. Breed differences observed in serum mineral element concentrations (Fe and Zn) and related TE of the neonatal lamb may provide insights into adaptive trace mineral supplementation strategies based on breed type and related levels of production.

Composition-segmented BiSbTe thermoelectric generator fabricated by multimaterial 3D printing

Abstract Segmented thermoelectric generators (TEGs) comprising multiple TE elements can operate over a large thermal gradient without inherent conversion efficiency (ZT) losses of materials. However, despite excellent theoretical efficiencies, the performance of actual segmented TEGs are critically affected by several challenges related to material incompatibility and limited design flexibility in conventional fabrication processes. Herein, we report the multi-material 3D printing of composition-segmented BiSbTe materials by the sequential deposition of all-inorganic viscoelastic TE inks containing BixSb2-xTe3 particles, tailored with Sb2Te42− chalcogenidometallate binders. The peak ZTs of the 3D-printed materials controllably shifted from room temperature to 250 °C by composition engineering of BixSb2-xTe3 particles. We fabricated the optimally designed TEG comprising the 3D-printed, composition-segmented tri-block Bi0.55Sb1.45Te3/Bi0.5Sb1.5Te3/Bi0.35Sb1.65Te3 TE leg, which extends the peak ZTs and satisfies full compatibility across the entire temperature range, realizing a record-high efficiency of 8.7% under the temperature difference of 236 °C. Our approach offers a promising strategy to optimize segmented TEGs.

Fractionation of highly siderophile and chalcogen elements in the lower oceanic crust: Insights from the troctolites of the Alpine-Apennine Jurassic ophiolites

The present study aims at investigating the role of reactive porous flow in the fractionation of highly siderophile (HSE: Os, Ir, Ru, Rh, Pt, Pd, Au and Re) and chalcogen (S, Se, Te) elements during construction of the lower oceanic crust in (ultra-)slow spreading ridges. At this purpose, we analyzed the whole-rock HSE and chalcogen elements, and Re-Os isotopes in olivine-rich troctolites embedded within large-scale gabbroic sequences from the Alpine-Apennine Jurassic ophiolites. Leucotroctolites and chromitites associated with the olivine-rich troctolites were also investigated. The olivine-rich troctolites have initial γOs ranging from +0.2 to +5.9. Their primitive mantle-normalized patterns are characterized by a slight enrichment of Os over Ir, and an increase from Ir to Ru, Rh, Pt, Pd and Au, nearly flat Au-Te-Se-S, and weak Re depletion with respect to S. This HSE and chalcogen element, and Os isotopic signature was acquired in response to sulfide segregation, which was most likely triggered by reaction between an olivine-rich matrix and migrating MORB-type melts. The chromitite layers occurring within the olivine-rich troctolites exhibit high concentrations of platinum group elements (PGE: Os, Ir, Ru, Rh, Pt and Pd). Formation of the chromitites might produce melts depleted in PGE that reactively migrated within the olivine-rich matrix, and ultimately locally led to olivine-rich troctolites characterized by a slight increase of the PGE/chalcogen element fractionation. The leucotroctolites differ from associated olivine-rich troctolites in the lower concentrations of HSE and chalcogen elements, with subparallel primitive mantle-normalized patterns but slightly higher Se/Te values. The crystallization of the olivine-rich troctolites might release HSE and chalcogen elements-depleted melts that reacted with an olivine + plagioclase crystal mush to form the leucotroctolites. Alternatively, formation of the leucotroctolites involved a process of reacting melt flow characterized by a low melt/crystal matrix ratio, which led to a relatively low proportion of trapped melt and related sulfides. At (ultra-)slow spreading ridges, the crystallization of sulfides in high-Mg# lower crustal rocks may exert a significant control in shaping the HSE and chalcogen element signature of erupted basalts.

Tellurium in Late Permian‐Early Triassic Sediments as a Proxy for Siberian Flood Basalt Volcanism

AbstractWe measured the concentrations of trace elements in Late Permian to Early Triassic sediments from Spitsbergen. High mercury concentrations in sediments from the level of the Permo‐Triassic Mass Extinction (PTME) at this location were previously attributed to the emplacement of the Siberian Traps Large Igneous Province and used to link the timing of volcanism with the record of environmental change and extinction in these sediments. We investigated the use of the moderately to highly volatile, siderophile elements Ni, Zn, Cd, Sb, Te, Re, and Tl as proxies for the intensity of Siberian volcanism. These trace elements, like Hg, have high concentrations in volcanic gas compared to crustal rocks. Tellurium is highly enriched at the PTME, and Te/Th ratios increase by a factor of ∼20 across the PTME, similar to the variation in Hg/total organic carbon (TOC) in the same samples. Te/Th and Hg/TOC values imply that Siberian volcanism initiated at the onset of the PTME, coincident with the start of the δ13Corganic excursion and abrupt warming. Based on Te and Hg, most Siberian volcanism occurred between the two phases of the PTME boundary (a period of less than 100 ky), but also continued into the Early Triassic. The duration of Siberian volcanism inferred from Te/Th and Hg/TOC is shorter than that indicated by recent high‐precision U‐Pb ages of Siberian intrusive and extrusive rocks. Te concentrations and Te/Th ratios in sediments represent a useful new proxy for volcanism, which can be used to link the marine sedimentary record with large volcanic events on land.

Controlling Ag3Sn Plate Formation and Its Effect on the Creep Resistance of Sn–3.0Ag–0.7Cu Lead-Free Solder by Adding Minor Alloying Elements Fe, Co, Te and Bi

Preventing the formation of large platelets of Ag3Sn intermetallic compounds (IMCs) during solidification of solder joints has become a significant challenge in the design of Sn–Ag–Cu lead-free solder alloys. Large platelets of Ag3Sn are generally considered as undesirable as their presence can create solidification defects and causes mechanical property anisotropy. In the present work, the synergetic effects of adding 0.1 wt% of Fe, Co, Te and 2 wt% Bi to Sn–3.0Ag–0.7Cu (SAC 307) solder are studied in terms of the growth of large platelets Ag3Sn IMCs and the resulting alloy’ creep resistance as well as their thermal behavior. Although minor Fe, Co, Te and Bi alloying elements addition causes large increase in the degree of undercooling from 3.4 to 22.3 °C with maintaining the pasty range and melting temperature at the same levels, the modified SAC307–FeTeCoBi alloy exhibits considerable increase in creep resistance (~ 10 times) and large fracture life-time than SAC (307) solder at same stress levels and testing temperatures. This is attributed to the transition of Ag3Sn IMCs from large platelets into fine needle-like morphology and formation of new (Cu,Co)6Sn5, FeSn2, SnTe IMCs and Bi particles, which could provide more obstacles for dislocation movement at the interphase boundaries.

Improvement of thermal stability and phase change behavior of Ge2Sb2Te5 thin films by Calcium doping

The crystallization behaviors, thermal stabilities, and the amorphous/crystalline structures of Calcium (Ca) doped Ge2Sb2Te5 (GST) phase change films have been studied. It was found that, the thermal stability is deteriorated and two-step crystallization behavior is accelerated in GST doped with a small amount of Ca (less than 3.6 at.%), but the thermal stability is increased and two-step crystallization behavior is suppressed apparently in the more Ca-doped GST. Moreover, we found Ca does not bond with the elements of Sb and Te, implying Ca can be considered as the impurity atom in doped GST films. Together with the vacancy concept in rapid phase transition mechanism, the change of the thermal stability could be explained well in Ca-doped GST films. The Ca6.4(GST)93.6 film with moderate Ca doping, which has better thermal stability and faster phase transition speed in Ca-doped GST films, is suggested as a potential candidate material for phase change application.