Te Content Research Articles

Structural, optical, and shielding investigation of PVA/Te composite for technological applications

Using the casting process, polymeric films made of polyvinyl alcohol (PVA) including varying percentages of Te were created to form PVA/Te composite at doping concentrations of Te (0, 4.76, 13.04, 20 wt %), which denoted as PT1, PT2, PT3 and PT4 respectively. XRD results show semicrystalline nature in PT1 and PT2 however with further increasing of Te contents, a nano-crystallite Te appeared in PT3 and PT4. The absorption spectrum confirms that PT3 film is a good option to be used in UV-shielding. PT4 film shows an abrupt rise in absorption coefficient at 0.5 eV, 1.5 eV and UV regions, hence this qualifies this sample for various optical applications. The optical energy gap of the films varies between 4.94 eV and 3.32 eV for the indirect transitions and between 5.3 eV and 4.5 eV for the direct transitions, the PT4 film has the lowest values of both direct and indirect energy gaps. Several methods were used to measure the average refractive index nav value. Furthermore, the nonlinear refractive index (n2) was estimated. PT4 possesses the highest value of both nav and n2. Furthermore, the radiation shielding coefficients have been estimated according to the Phy-X/PSD online software. The sample with the highest Te concentration, PT4, has the best radiation shielding between the films under investigation. The investigated polymer with high Te weight percentage is an optical system that can be used for solar cells, optoelectronics, electronics, nonlinear optics, optical filters and for radiation shielding.

Genesis of the Sanhetun Tellurium–Gold Deposit, Northeast China: Constraints from In Situ Elemental and Sulfur Isotopic Compositions of Pyrite

The Sanhetun tellurium–gold (Te–Au) deposit, located in the Duobaoshan polymetallic metallogenic belt (DPMB) within the eastern section of the Central Asian Orogenic Belt (CAOB), is a newly discovered small-scale gold deposit. The mineralization, with a resource of ≥4 t Au, is mainly hosted in three NNE-trending alteration zones between Early Carboniferous granitic mylonite and Lower Cretaceous volcanogenic-sedimentary formations. The genesis of formation of this deposit is poorly constrained. Here, we report the results of petrographic studies, TESCAN Integrated Mineral Analyzer (TIMA), major and trace element concentrations, and in situ S isotopes of pyrite. The results show that there are four types of pyrite: coarse-grained euhedral Py1, fine-grained quartz-Py2 vein crosscutting Py1, anhedral aggregated Py3, and anhedral aggregated Py4. The pre-ore stage Py1 contains negligible Au, Te, and other trace elements and has a relatively narrow range of δ34S values ranging from −1.20 to −0.57‰. Py2 has higher concentrations of Au and Te and distinctly high concentrations of Mo, Sb, Zn, and Mn with markedly positive δ34S values of 4.67 to 14.43‰. The main-ore stage Py3 contains high Au and Te concentrations and shows narrow δ34S values ranging from −5.69 to 0.19‰. The post-ore stage Py4 displays low Au concentrations with the δ34S values ranging from 2.66 to 3.86‰. Tellurides are widespread in Py3 and Py4, consisting mainly of native tellurium, tetradymite, tsumoite, hessite, and petzite. Especially, tetradymite commonly coexists with native gold. This study highlights the role of Te–Bi–S melt as an important gold scavenger in As-deficient ore-forming fluids.

CuIn (Se,Te)2 Absorbers With Bandgaps <1 eV for Bottom Cells in Tandem Applications

ABSTRACTThin‐film solar cells reach high efficiencies and have a low carbon footprint in production. Tandem solar cells have the potential to significantly increase the efficiency of this technology, where the bottom‐cell is generally composed of a Cu(In,Ga)Se2 absorber layer with bandgaps around 1 eV or higher. Here, we investigate CuIn(Se1 − xTex)2 absorber layers and solar cells with bandgaps below 1 eV, which will bring the benefit of an additional degree of freedom for designing current‐matched two‐terminal tandem devices. We report that CuIn(Se1 − xTex)2 thin films can be grown single phase by co‐evaporation and that the bandgap can be reduced to the optimum range (0.92–0.95 eV) for a bottom cell. From photoluminescence spectroscopy, it is found that no additional non‐radiative losses are introduced to the absorber when adding Te. However, losses occur in the final solar cell due to non‐optimized interfaces. Nevertheless, a device with 9% power conversion efficiency is demonstrated with a bandgap of 0.97 eV and , the highest efficiency so far for chalcopyrites with band gap <1 eV. Interface recombination is identified as a major recombination channel for larger Te contents. Thus, further efficiency improvements can be expected with improved absorber/buffer interfaces.

Linking the PETM and North Atlantic volcanism using tellurium in sediments

The Paleocene – Eocene Thermal Maximum (PETM) was a short period (~170 kyr) of global temperature rise starting at 55.93 Ma, which occurred during the breakup of the North Atlantic and the emplacement of the North Atlantic Igneous Province (NAIP). Recently, mercury (Hg) concentrations in sediments have been used in an attempt to connect the eruptive history of the NAIP with environmental change during this period, at a higher resolution than possible using geochronology. Here we present sedimentary tellurium (Te) as a novel proxy to further reconstruct NAIP volcanism at high resolution. We measured 45 trace elements in 401 sediment samples from 3 sections across the PETM in the northern hemisphere. All study sites exhibit an increase in Te concentrations and Te/Th ratios close to the onset of the PETM and remain high until the end of the main North Atlantic ash phase about 1 Myr later. The trace element data indicate that changes in sediment lithology or in environmental conditions do not influence sedimentary Te concentrations suggesting a volcanic source instead. We used existing age models to remove the effect of changes in sedimentation rate and calculated volcanic Te fluxes. Our Te data suggest increased volcanism in the latest Paleocene and early Eocene. This fits existing radiometric ages of the NAIP, which demonstrate that a more than 5 km thickness of lava in eastern Greenland and the Faroes was erupted within about 1 Myr between ~56 to ~55 Ma. All our study sites show similar Te flux variations across the PETM. In contrast, sedimentary mercury (Hg) profiles from these and other sites are less consistent. Tellurium in sediments may represent a useful proxy to reconstruct NAIP volcanism.

Genesis of the Kateba’asu gold deposit, Western Tianshan, China: Constraints from pyrite trace element, sulfur isotope, and quartz H-O isotopes

The Kateba’asu gold deposit, situated in the Western Tianshan of China, is one of the most significant discoveries in the world-class Tianshan gold belt. The deposit features two distinct mineralization styles. The early, subordinate skarn-type copper–gold mineralization occurs in the contact zone between monzogranite, diorite, and Silurian limestone, composed of garnet, diopside, epidote, chalcopyrite, pyrite, and gold. The later, primary lode-gold mineralization is hosted in the altered monzogranite characterized by pervasive quartz-pyrite-sericite-chlorite-K-feldspar alteration and a well-develped veining systems.Pyrite is the dominant sulfide mineral related to gold mineralization in the Kateba’asu gold deposit, with four types identified: Py0 from the early skarn copper–gold mineralization, and Py1 to Py3 from the later lode-gold mineralization. All types of pyrite are homogeneous and contain very low levels of lattice-bound gold. Py0 is euhedral and fine-grained, with relatively high Cu, Au, Co, and Ni contents, and displays a magmatic sulfur isotopic signature with δ34S ranging from 0.8 to 4.3 ‰. Py1 occurs as euhedral to subhedral, coarse-grained crystals within pyrite-quartz veins with higher concentrations of Co and Ni. Py2, which develops in the quartz-pyrite veins, is medium to coarse-grained and contains elevated levels of As, Cu, Zn, and Bi relative to Py1. Py3, found in polymetallic sulfide veins of the main lode-gold stage, is anhedral and medium to fine-grained with higher contents of As, Ag, Cu, Zn, Se, Te and lowest Co and Ni concentrations compared to Py1 and Py2. The positive correlations between Au-Te, Au-Bi, Au-Cu, and Pb-Bi across all pyrite types, along with the presence of visible gold in Py3, indicate that most gold occurs as micro-/nano-sized inclusions and as fissure gold. The δ34S values of Py1, Py2, and Py3 (7.6 to 11.8 ‰, 10.1 to 12.6 ‰, and 9.8 to 12.4 ‰, respectively) were attributed to an initial magmatic source and mixed with external sulfur subsequently from the wall rocks. The H and O isotopic compositions (δDH2O = −84.1 to −93.5 ‰; δ18OH2O = 1.8 to 6.6 ‰) of quartz from the lode-gold mineralization imply that ore-forming fluids were predominantly of magmatic origin, with a additional contribution from meteoric water. Taken together, a two-episode mineralization model was proposed for the formation of the Kateba’asu gold deposit. The early skarn mineralization stage is associated with the emplacement of diorite during the Early Carboniferous. In contrast, the subsequent lode-gold mineralization, occurring between the Late Carboniferous and Permian periods, represents a overprinted magmatic-hydrothermal gold system potentially linked to a deep-seated magmatic intrusion.

Anomalous tellurium enrichment associated with gold mineralization: A mineralogical and isotopic study of the Yongxin Te-Au deposit, northeast China

The Yongxin tellurium-gold (Te-Au) deposit, a large epithermal deposit in the Duobaoshan polymetallic metallogenic belt (DPMB) within eastern section of the Central Asian Orogenic Belt (CAOB), is mainly hosted by syenogranite and mylonite. However, the Te-Au occurrence, precipitation mechanism and genesis in this deposit remain elusive. In this study, pyrite, the primary host of Te-Au mineralization, was studied utilizing multiparametric techniques such as scanning electron microscope (SEM), electron probe microanalysis (EPMA), in-situ laser ablation-inductively coupled plasma mass spectrometry (LA-ICP-MS) and femtosecond laser ablation coupled multi-collector inductively coupled plasma mass spectrometry (fs LA-MC-ICP-MS). The results show that there are three generations of pyrite termed here as Py1, Py2 and Py3. The coarse euhedral Py1 and fine vein Py2 contain negligible to low contents of Te and Au, whereas the anhedral aggregated Py3 with porosity and grain boundary (GB) shows the highest concentrations of Te and Au. Representative LA-ICP-MS profiles show that Te-Au occurs either as solid solution in the Py1 and Py2 or submicroscopic Au-Ag-Te-Bi inclusions, electrum and native gold in Py3. Thermodynamic data of telluride and sulfide show that the Te-Au was deposited under relatively oxidizing conditions with values of log f Te2 ranging from −15.2 to −11.2 and log f S2 from −16.7 to −12.1. at 200 °C. We infer that fluid mixing and fluid-rock interaction were the dominant mechanisms that triggered the precipitation of Te-Au in the Yongxin Te-Au deposit. Geochemical and geochronological data indicate that the likely source of Te is Te-rich oceanic sediments originating from the Western Pacific Plate. Pyrite and telluride from the gold deposits can be potential targets for Te exploration in the DPMB.

A study on microstructure evolution of MCrAlY coatings after thermal aging in Te environment

The effects of thermal exposure on tellurium (Te) diffusion behavior in MCrAlY coatings were investigated at 800 °C in Te vapor. The results showed that the diffusion depth of Te in MCrAlY coatings gradually increased with the exposure time, and the dense Cr3Te4 layer formed on the coating surface in the initial stage was no longer continuous, especially under aging conditions with higher Te concentration. The high Cr content of the coating promoted the solid phase transition of the surface reaction product from Cr3Te4 to Cr7Te8, and resulting in the formation of large α-Cr phase either within or beneath the reaction layer during long aging processes. As a result of this phase transition, excess Te atoms were released from Cr3Te4 and continued to diffuse into the coating. Te did not exhibit obvious intergranular diffusion characteristics within the coating. When it encountered Y, it was captured by Y and formed a YTe phase. After aging for 3000 h, Te was distributed throughout the coating, and numerous voids were formed at the interface between the coating and the substrate. These two factors deteriorated the plasticity and adhesion of the coating. Results from molten salt corrosion tests indicated that the high content of Cr and Al in the coating, as well as high densities of grain boundaries providing diffusion pathways, reduced the corrosion resistance of the coating to molten salt.

Compositionally Graded MoS2xTe2(1-x)/MoS2 van der Waals Heterostructures for Ultrathin Photovoltaic Applications.

van der Waals heterojunctions utilizing two-dimensional (2D) transition-metal dichalcogenide (TMD) materials have emerged as focal points in the field of optoelectronic devices, encompassing applications in light-emitting devices, photodetectors, solar cells, and beyond. In this study, we transferred few-atomic-layer films of compositionally graded ternary MoS2xTe2(1-x) alloys onto metal-organic chemical vapor deposition-grown molybdenum disulfide (MoS2) as p- and n-type structures, leading to the creation of a van der Waals vertical heterostructure. The characteristics of the fabricated MoS2xTe2(1-x)/MoS2 vertical-stacked heterojunction were investigated considering the influence of tellurium (Te) incorporation. The systematic variation of parameter x (i.e., 0.8, 0.6, 0.5, 0.3, and 0) allowed for an exploration of the impact of Te incorporation on the photovoltaic performance of these heterojunctions. As a result, the power conversion efficiency was enhanced by approximately 6 orders of magnitude with increasing Te concentration; notably, photoresponsivities as high as ∼6.4 A/W were achieved. These findings emphasize the potential for enhancing ultrathin solar energy conversion in heterojunctions based on 2D TMDs.

Electrical and thermal transport properties of Cr2Se3-Cr2Te3 solid-solution alloy system and estimation of optimal thermoelectric properties

Cr2Se3 is a layered narrow-bandgap semiconductor with a low lattice thermal conductivity of ∼1 W/mK, which can be considered as a potential thermoelectric material. A solid-solution alloy system with Cr2Te3 can be designed to manipulate the electrical and thermal transport properties. In this study, a series of Cr2Se3-Cr2Te3 solid-solution alloys (Cr2(Se1-xTex)3, x = 0, 0.33, 0.5, 0.67, 0.83, and 1) were synthesized, and their electrical and thermal transport properties were investigated. Regarding the electrical transport properties, the power factor (∼0.35 mW/mK2) of Cr2Se3 gradually and significantly decreased as the Te content (x) increased owing to the significant decrease in the Seebeck coefficient that resulted from the large increase in the carrier concentration. Regarding the thermal transport properties, the total thermal conductivity increased with x as a result of the large increase in the electrical conductivity, despite the continuous decrease in the lattice thermal conductivity. Consequently, the thermoelectric figure of merit (zT ∼ 0.20) of Cr2Se3 gradually and significantly decreased to 0.009 for Cr2Te3 at 700 K; thus, no enhancement of zT was observed from the experimental results of simple solid-solution alloying. On the other hand, the thermoelectric quality factors of the solid-solution compositions for x = 0.33–0.83 were found to be enhanced compared to that of the Cr2Se3 sample, implying that zT could be further enhanced by optimizing the carrier concentration. Indeed, enhanced zT values were estimated based on a single parabolic band model for the solid-solution compositions with x = 0.33–0.83 if the carrier concentration was optimized to ∼1019 cm−3, which was found to be owing to the increased nondegenerate and weighted mobility (inferring weaker carrier–phonon interaction). Therefore, it is suggested that the solid-solution alloying approach could provide a feasible strategy to enhance the thermoelectric performance by reducing carrier-phonon interaction when further combined with carrier concentration optimization.

Crystal growth and characterization of Fe1+δSe1-xTex (0.5 ≤ x ≤ 1) from LiCl/KCl flux

An eutectic LiCl/KCl flux method in a horizontal configuration has been used to grow a series of homogeneous Fe1+δSe1-xTex single crystals of high quality with 0.5 ≤ x ≤ 1. Compared with previously used melt-growth method, the stable crystallization process in LiCl/KCl flux below their peritectic temperatures results in better homogeneity and crystalline perfection identified by energy dispersive spectrometer and x-ray diffraction. The interstitial Fe value δ remains small within 0.5 ≤ x ≤ 0.85 where the superconducting temperature TC is not sensitive to the Te content with sharp superconducting transition widths ΔTC < 1 K and a maximum of TC = 14.3 K at x = 0.61. The value δ starts to increase quickly accompanied by a deviation of linear behavior of crystal lattice parameters as well as the broadening of ΔTC = 2.1 K at x = 0.91, then suddenly rises up to δ > 0.1 followed by the disappearance of superconductivity and emergence of antiferromagnetic order at x ≥ 0.96. We also observed a metallic to semiconducting transition in the normal state resistivity of Fe1+δSe1-xTex with increasing Te content which is related to a localized electronic state induced by the interstitial Fe. The interstitial Fe value δ might be a key physical parameter to understand various properties of Fe1+δSe1-xTex system.

DFT study of optoelectronic and thermoelectric properties of pure and doped double perovskite Cs2SnI6 for solar cell applications

The global need of energy is raising day by day. To meet this demand double perovskites (DPs) can play a vital role for energy conversion devices. In this letter, we formulated and examined lead-free defect perovskites using a combination of tellurium and tin, denoted as Cs2Sn1-xTexI6 (0, 0.25), utilizing density functional theory which include structural, optical and thermal behavior. Both the optimized volume and lattice parameter exhibit a linear increase with the Te content in Cs2Sn1-xTexI6 (CsSnTeI). The negative value of formation energy for both pure and doped materials along with their Poisson and Pugh ratio confirm the stability of these materials. The band structure analysis reveals its semiconducting behavior, with the band gap expanding proportionally to the increased Te concentration with band gap value of pure (1.20 eV) and doped 91.43 eV) double perovskites. Optical characteristics, including the dielectric function and absorption coefficient, were also analyzed. To expose their potential use of Cs2Sn1-xTexI6 (0, 0.25) in thermoelectric devices, temperature dependent thermoelectric features are investigated reveal that suitability of these materials for energy conversion purposes.

Genesis of the Jianbeigou Gold Deposit on the Southern Margin of the North China Craton: Insights from Fluid Inclusions, H‐O‐S Isotopes, and Pyrite in situ Trace Element Analyses

AbstractThe Jianbeigou gold deposit is a typical lode gold deposit in the Qinling metallogenic belt, located on the southern margin of the North China Craton. Three stages of the hydrothermal process can be distinguished, including the quartz ± pyrite, quartz‐polymetallic sulfide, and quartz‐carbonate ± pyrite stages. From the early to late stages, the homogenization temperatures of primary fluid inclusions are 281–362°C, 227–331°C, and 149–261°C, respectively. The corresponding salinities estimated for these fluids are 3.9–9.9 wt%, 0.4–9.4 wt%, and 0.7–7.2 wt% NaCl equiv. Combined with laser Raman spectroscopy data, the ore‐forming fluid belongs to a H2O‐CO2‐NaCl ± CH4 system with medium–low temperature and salinity. The δ18Ofluid and δD values for the quartz veins are –1.0‰ to 6.0‰ and –105‰ to –84‰, respectively, which indicates that the ore‐forming fluid is of mixed source, mainly derived from magma, with a contribution from meteoric water. Pyrite has been identified into three generations based on mineral paragenetic sequencing, including Py1, Py2, and Py3. The pyrites have δ34S sulfur isotopic compositions from three stages between 3.7‰ and 8.4‰, indicating that sulfur mainly originated from magma. Te, Bi, Sb, and Cu contents in pyrite were all high and showed a strong correlation with Au concentrations. Native gold and the Au‐Ag‐Bi telluride minerals were formed concurrently, and the As concentration was low and decoupled from the Au content. Therefore, Te, Bi, Sb and other low‐melting point chalcophile elements play an important role for gold mineralization in arsenic‐deficient ore‐forming fluid. Combined with the geological setting, evolution of pyrite, and ore‐fluids geochemistry, we propose that the Jianbeigou deposit can be classified as a magmatic–hydrothermal lode gold deposit. Gold mineralization on the southern margin of the North China Craton is related to Early Cretaceous magmatism and formed in an extensional setting.

Substitution of an isovalent Te-ion in SnSe thin films for tuning optoelectrical properties

In present work, SnSe1-xTex thin films with varying Te concentrations were deposited on glass substrate through thermal evaporation technique. SnSe1-xTex thin films were characterized using X-ray diffraction (XRD), atomic force microcopy (AFM), X-ray photoelectron spectroscopy (XPS), UV–Vis NIR spectroscopy and room-temperature hall measurements technique. XRD patterns revealed that all the samples had a polycrystalline orthorhombic structure. Additionally, a low level of Te impurity improved the crystalline quality of the SnSe thin films. AFM images showed a noticeable alteration in the surface structure of the SnSe thin films caused by Te doping. UV–Vis NIR spectroscopy was employed to assess the optical characteristics of SnSe1-xTex thin films, revealing a variation in the optical band gap energy (Eg) between 1.75 and 1.89 eV, attributed to Te doping. The Hall effect measurement revealed n-type conductivity, and the carrier concentration decreased as the Te dopant concentration increased, corresponding to a decrease in antisite SnSe defects. The experimental findings suggest that adding a moderate amount of Te is a beneficial method for enhancing the optical and electrical properties of SnSe films. Furthermore, the Schottky device parameters of the Ag/SnSe1-xTex/Al:ZnO structure were established by analyzing the temperature-dependent Current-Voltage (I–V-T) characteristics through the thermionic emission current transport mechanism.

Enhancement of the response speed of CIGS-based photodetector by Te-doping

Cu(In,Ga)Se2 (CIGS) based devices are promising candidates for high performance photodetector applications. The present work investigated the effects of Te-doping on the properties of CIGS layers and studied the performance of photodetectors (PDs) fabricated on these films. The films were vacuum evaporated on glass substrates and their morphological, structural and optical properties were evaluated after an annealing step at 550ºC. Morphological data indicated that undoped CIGS films had non-uniform surface features with large grains separated by nanoparticles. Addition of 6.6 % Te improved the morphology and yielded a smoother layer. Further increase in Te concentration showed appreciable reduction in surface feature size and shape. X-ray diffraction patterns showed that increasing the Te amount in CIGS caused a shift in the XRD peaks towards smaller angles pointing to replacement of Se atoms by Te. Peak splitting at higher Te samples suggested a graded structure with Se and Te amounts changing through the thickness of the film. Raman analysis demonstrated formation of CuInGa(Se,Te)2 (CIGST) compound. According to Tauc’s approximation, CIGS films with and without Te atoms possessed two energy band gaps of Eg1 and Eg2 that were in the ranges of 1.10–1.28 eV and 1.16–1.36 eV, respectively. Electrical data obtained from photodetector devices showed a responsivity of 4.44×10−1 A/W and a detectivity of 8.01×107 Jones for Te-free material, while the rise/fall times were measured as 34/148 ms. A much faster response speed of 19/20 ms was reached for devices fabricated on films with 10.2 % Te. This work demonstrated, for the first time, the fabrication low-cost and high-performance metal-semiconductor-metal (MSM) type CIGST-based PDs.

High Ductility and Excellent Thermoelectric Performance in Te-Stabilized Cubic Ag2TexS1-x Solid Solutions.

The stabilization at low temperatures of the Ag2S cubic phase could afford the design of high-performance thermoelectric materials with excellent mechanical behavior, enabling them to withstand prolonged vibrations and thermal stress. In this work, we show that the Ag2TexS1-x solid solutions, with Te content within the optimal range 0.20 ≤ x ≤ 0.30, maintain a stable cubic phase across a wide temperature range from 300 to 773 K, thus avoiding the detrimental phase transition from monoclinic to cubic phase observed in Ag2S. Notably, the Ag2TexS1-x (0.20 ≤ x ≤ 0.30) samples showed no fractures during bending tests and displayed superior ductility at room temperature compared to Ag2S, which fractured at a strain of 6.6%. Specifically, the Ag2Te0.20S0.80 sample demonstrated a bending average yield strength of 46.52 MPa at 673 K, significantly higher than that of Ag2S, whose bending average yield strength dropped from 80.15 MPa at 300 K to 12.66 MPa at 673 K. Furthermore, the thermoelectric performance of the Ag2TexS1-x (0.20 ≤ x ≤ 0.30) samples surpassed that of both InSe and pure Ag2S, with the Ag2Te0.30S0.70 sample achieving the highest ZT value of 0.59 at 723 K. These results indicate substantial potential for practical applications due to enhanced durability and thermoelectric performance.

Structural and optical properties of CdTe thin film nanoparticles prepared using chemical bath deposition technique with different Te concentration

Abstract The CdTe thin films with different Te concentration were grown by chemical bath deposition technique using glass substrates. The prepared thin films were characterized by X-ray diffraction (XRD), Raman spectroscopy, UV–Visible diffuse reflectance spectroscopy, photoluminescence (PL). The X-ray diffraction (XRD) analysis shows that the prepared thin films are polycrystalline in nature with Zinc blend structure. Decrease in the intensities of XRD peak for decreasing the Te concentration. The characteristic phonon modes of CdTe thin film nanoparticle confirmed by Raman spectra analysis. Optical absorption studies shows that direct transition with decrease in band gap energy with decreasing the Te molar concentration. Green emission was observed for prepared CdTe thin films excited with 325 nm.

Mesozoic orogenic gold metallogenesis at the Bangong–Nujiang suture belt, central Tibet: Constraints from pyrite textures, composition and sulfur isotope of the Shangxu gold deposit

Pyrite is a good carrier to provide gold within a hydrothermal mineralization system. Under prograde metamorphism, recrystallization of sedimentary and diagenetic pyrite and transformation of pyrite into pyrrhotite in a metamorphic terrane lead to the release of trace elements from the pyrite carrier into an upward migrating liquid phase carrier. In this case study, we report the in situ trace element and δ34S compositions of the pyrite from four different stages, which chronologically comprise sedimentary Py1, diagenetic Py2, metamorphic Py3a, Py3b and hydrothermal Py4a, Py4b, Py5, and the dominant sulfides from the hydrothermal stage at Shangxu, an Early Cretaceous turbidite-hosted orogenic gold deposit in the middle Bangong–Nujiang suture belt (BNSB) in central Tibet, in order to decipher the ore-forming material source and the metallogenesis of the Mesozoic orogenic gold mineralization in the BNSB. Concentrations of trace elements, i.e., Au, Co, Cu, Zn, Mo, Ag, Sb, Te, Hg, Tl, Pb and Bi, that are easy to dissolve during pyrite recrystallization, show a general progressive decline from Py1 to Py4b (excepting in Py3b and Py4a, which have a sudden rise in trace element composition) and a plunge in Py5, indicating that Py1 and Py2 supply the parent source minerals for mineralization, and that the main ore-forming stage are contemporary with the deposition of Py3b and Py4a, ending up with the precipitation of Py5. The δ34S values of pyrite narrow from −46.7 ‰–19.3 ‰ (Py1, Py2), through −7.6 ‰–0.2 ‰ (Py3a, Py3b), to − 3.6 ‰–5.7 ‰ (Py4a, Py4b) and −7.7 ‰–5.6 ‰ (Cp, Gn), indicating that a probable coeval seawater sulfate sulfur source for Py1 and Py2 (by bacterial sulfate reduction), and an inherited sulfur source from Py1 and Py2 for Py3 and Py4. We highlight that contributions from the magmatic materials to the hydrothermal gold mineralization are limited at Shangxu, and the widely distributed Lower–Middle Jurassic pyrite-rich turbidite of the Mugagangri Group is a highly potential primary source rock for the regional gold mineralization.

Composition-Structure-Property links in rocksalt AgMnGeSbTe high-entropy alloys: Insights from experiments and deep learning potential atomic simulations

High-entropy alloys (HEAs), particularly AgMnGeSbTex, are emerging as notable thermoelectric materials with excellent structural stability and tailored electronic properties. This study investigates these alloys through both experimental and computational methods. Thin films of AgMnGeSbTex with varying Te content (x = 1–4) were produced using magnetron co-sputtering on glass substrates. Structural analysis showed a transition from α-Ag2Te to a high-entropy rocksalt structure with increased Te content, with x = 4 yielding the optimal structure. Enhanced electrical properties, such as conductivity and Seebeck coefficient, were observed in the rocksalt films x = 3 and x = 4. Atomistic simulations using a deep learning potential (DLP) highlighted the importance of atomic size differences in mechanical behavior, with specific compositions showing increased ductility. Heating simulations revealed phase changes and amorphization at melting points. This research advances the understanding of the composition-structure–property relationships in high-entropy rocksalt alloys, with the x = 4 film showing promising thermoelectric potential. This study demonstrates the effectiveness of combining experimental and simulation approaches in exploring complex high-entropy systems for knowledge-driven materials design.

Sequentially Regulating Potential‐Determining Step for Lowering CO2 Electroreduction Overpotential over Te‐Doped Bi Nanotips

Electrocatalytic conversion of CO2 into formate is recognized an economically‐viable route to upgrade CO2, but requires high overpotential to realize the high selectivity owing to high energy barrier for driving the involved proton‐coupled electron transfer (PCET) processes and serious ignorance of the second PCET. Herein, we surmount the challenge through sequential regulation of the potential‐determining step (PDS) over Te‐doped Bi (TeBi) nanotips. Computational studies unravel the incorporation of Te heteroatoms alters the PDS from the first PCET to the second one by substantially lowering the formation barrier for *OCHO intermediate, and the high‐curvature nanotips induce enhanced electric field that can steer the formation of asymmetric *HCOOH. In this scenario, the thermodynamic barrier for *OCHO and *HCOOH can be sequentially decreased, thus enabling a high formate selectivity at low overpotential. Experimentally, distinct TeBi nanostructures are obtained via controlling Te content in the precursor and TeBi nanotips achieve &gt;90% of Faradaic efficiency for formate production over a comparatively positive potential window (‐0.57 V to ‐1.08 V). The strong Bi‐Te covalent bonds also afford a robust stability. In an optimized membrane electrode assembly device, the formate production rate at 3.2 V reaches 10.1 mmol h‐1 cm‐2, demonstrating great potential for practical application.

Optical Properties of GeSe1−xTex Chalcogenide Materials Promising for on‐Chip Low and Ultra‐Low Loss Reconfigurable Photonics and Nonlinear Devices

The highly promising linear and nonlinear optical properties of innovative thin films of GeSe1–xTex chalcogenide materials in the amorphous as‐deposited state, and after crystallization, are revealed here. These innovative alloys bridge the gap between two families of materials: chalcogenide glasses (GeSe) and phase‐change materials (GeTe). Their unique optical properties make them attractive candidates for reconfigurable and nonlinear photonic applications in the infrared. In this context, it is shown how, by varying the Te content of GeSe1–xTex thin films, it is possible to tailor their linear and nonlinear optical properties to optimize them for a wide range of innovative applications.