Sn Powders Research Articles

Surface roughness and pore evolutions in multi-layer laser powder bed fusion of extra-low interstitial Ti-5Al-2.5Sn powder: A numerical study

In this paper, the three-dimensional discrete element method (DEM) and computational fluid dynamics (CFD) coupled approach was used to numerically reproduce the whole process of laser powder-bed-fusion (L-PBF) additive manufacturing (AM) of extra-low interstitial (ELI) Ti-5Al-2.5Sn powder. The effects of key parameters such as scanning strategy and hatch spacing (h) on the surface roughness (Ra) and pores during multi-layer printing are systematically investigated by characterizing the molten pool characteristics and thermal behavior upon laser motion; and the melt volume in this duration is quantified by the volume of fluid (VOF) method to demonstrate inter-layer interactions. The results show that Ra can be categorized according to the scanning directions. Along the scanning direction, the Ra is affected by the heat accumulation effect and increases as the h decreases. In this case, the Ra caused by the Marangoni effect can be reduced by increasing the melt volume at the end of the track through the layer rotation. The Ra perpendicular to the scanning direction is caused by the ripple-like surface formed by track overlap and decreases as the h decreases. For defects, the pores formed by shrinkage due to insufficient melting or by lack of fusion (LoF) due to incomplete track overlap decrease with the decrease of h. The LoF pores caused by weak inter-layer metallurgical bonding are affected by the surface morphology of the previous layer, which is increased as the h increases. The layer rotation can also reduce such LoF pores. On this basis, a quality control chart suitable for actual production is established.

Effects of the Addition of Tin Powder to Perovskite Precursor Solutions on Band Bending at PEDOT:PSS/Perovskite Interfaces in Mixed-Cation Mixed-Halide Tin Perovskite Solar Cells.

Using electron spin resonance (ESR) spectroscopy, we investigated the effects of the addition of tin (Sn) powder to perovskite layers on band bending at the perovskite surface near poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) hole-transport layers in perovskite solar cells (PSCs) involving formamidinium (FA)-methylammonium (MA)-mixed-cation I-Br-mixed-halide tin perovskites. We performed dark ESR spectroscopy measurements of a PEDOT:PSS/FA0.75MA0.25Sn(I0.75Br0.25)3 stack and of a PEDOT:PSS/Sn-powder-added FA0.75MA0.25Sn(I0.75Br0.25)3 stack. The results indicate that FA0.75MA0.25Sn(I0.75Br0.25)3 layers have significant downward band bending near PEDOT:PSS layers. Such downward band bending is unfavorable for hole selectivity and surface passivation at the interface. However, the addition of Sn powder to the tin perovskite precursor solution was found to significantly prevent the downward band bending and rather cause upward band bending, which can improve the hole selectivity and field-effect passivation quality. This can be due to prevented oxidation of perovskite layers by Sn powder addition. These findings are crucial for developing highly efficient and stable tin perovskite solar cells.

Microstructure, hardness, electrical, and thermal conductivity of SZCN solder reinforced with TiO2 and ZrO2 nanoparticles fabricated by powder metallurgy method

The microstructure and characterization of Sn–Zn–Cu–Ni (SZCN) solder alloy reinforced with TiO2 and ZrO2 nanoparticles (NPs) synthesized by powder metallurgy were investigated. Sn, Zn, Cu and Ni metallic powders were mixed mechanical by 10:1 ball to powder ratio with 300 rpm speed for 2 h. Then 0.5 wt% from nano ZrO2 or TiO2 was mixed by the same parameters with the mixed metal powder. The morphologies and microstructures development during the fabrication process was investigated by X-ray diffractometer (XRD), optical microscope (OM), and scanning electron microscope (SEM) with energy dispersive X-ray spectrometry (EDX). The results reveal an improved distribution of TiO2 or ZrO2 NPs in the SZCN matrix solder, which resulted in an improvement in its density. The analyses of microstructural demonstrated that the addition of TiO2 or ZrO2 NPs to SZCN solder results in the grain refinement of the β-Sn phase, besides the formation of Ni3Sn IMC with small size and uniform distribution. The microhardness was enhanced as a result of the addition of TiO2 or ZrO2 NPs. The experimental results showed that the SZCN-ZrO2 composite solder had the greatest hardness and stress exponent values due to its effectiveness in suppressing the growth of β-Sn grains and the pile-up of dislocations. Both the electrical and thermal conductivities were improved by incorporating TiO2 NPs compared to other solders.

Optimization of TLPS Bonding Process and Joint Property using Ni-Sn Paste for High Temperature Power Module Applications

Recently, as interest in eco-friendly vehicles such as electric and hybrid vehicles increases, the demand for power semiconductors, a key component, is also increasing. Power semiconductors convert, distribute, and control power and operate in harsh environments such as high temperature and high pressure. In order to ensure stable reliability in such harsh environments, research on a technology that can stably form joints even at high temperatures is essential. Transitional liquid phase (TLP) bonding was proposed as a high-temperature power semiconductor chip bonding technology, which has the advantage of forming an intermetallic compound (IMC) phase with a high melting point at the joint. However, it takes a long time to convert the joint into full IMC phase. Therefore, in this study, in order to shorten the process time, a paste was manufactured by mixing high-melting point Ni metal powder and low-melting point Sn metal power, and a joint was formed through a TLPS (Transition liquid phase sintering) bonding using the paste. Pastes of different compositions were prepared by adjusting the ratio of Ni and Sn powders. The chip and substrate were bonded through a thermocompression (TC) bonding process, and the highest shear strength was obtained at a bonding temperature of 250 ℃ for 10 min. Heat treatment was performed at 200 ℃ for up to 500 h to evaluate the high temperature long-term reliability of the joints. The Ni-Sn TLPS bonded joints remained reliable joints after a long-term aging test at a high temperature of 200 ℃.

Giant Seebeck coefficient in SnTe thin films grown by thermal evaporation using layered structure engineering

In this work, we have reported a giant Seebeck coefficient (8033 µV/K) in SnTe thin films by controlling the layered structure using post growth annealing technique. The samples used in the current study were synthesized using a vacuum tube furnace having an evaporation temperature 700 °C, base pressure 180 m Torr and source to substrate distance 7 cm. Sn and Te metal powders with an equal weight ratio were evaporated on the glass substrate to form SnTe composite. Post-growth annealing in vacuum environment was performed for different time’s duration of 1–4 h with a step of one hour. XRD analysis reveals six diffraction peaks for all samples, which correspond to different crystal planes of SnTe structure. Raman spectra exhibit the presence of specific vibrational modes associated with SnTe. Using the giant value of Seebeck coefficient and moderate electrical conductivity, a strong power factor value of 8.1 × 10−3 W m−1 K−2 was observed for optimized sample (annealed for 3 h). The strongest values of Seebeck coefficient and power factor are supposed to be the layered structure of SnTe thin films which was verified by the SEM images.

Hydrazine-Assisted Synthesis, Structures, Photoelectricity, and Photocatalysis of Ternary Mercury-Tellurostannate Hybrids with Transition-Metal Complexes.

Tellurostannates are traditionally prepared by multistep reactions using the tellurides SnTe, SnTe2, K4SnTe4, or A6SnTe6 (A = K, Rb, or Cs) as precursors, which are usually prepared by the molten reaction of alkali metals Sn and Te under harsh synthetic conditions. Differently, ternary Hg-tellurostannate hybrids [Mn(en)3]HgSnTe3(Te2) (1) (en = ethylenediamine), [Mn(dien)2]HgSnTe3(Te2) (2), and [Fe(dien)2]HgSnTe3(Te2) (3) (dien = diethylenetriamine) were synthesized by one-pot reactions using Sn and Te powders as starting materials in the presence of hydrazine under mild solvothermal conditions. In 1, HgTe3 and SnTe4 units are joined via Te-sharing to form a 1-D polymeric chain [HgSnTe3(Te2)]n2n-, while the [HgSnTe3(Te2)]n2n- chains in 2 and 3 are composed of HgTe4 and SnTe4 units. The common feature of the [HgSnTe3(Te2)2-]n chains in 1-3 is that they are constructed by both the telluride anion Te2- and the polytelluride anion Te22-. 1-3 exhibited strong photocurrent responses with current densities of 5.26, 3.38, and 3.94 μA cm-2, respectively. They showed effective photocatalytic activities for methylene blue degradation with degradation ratios in the range of 85.3-94.6% after light irradiation for 80 min. Investigation of the photocatalytic mechanism showed that •O2- radicals and h+ holes were the main active substances in the photodegradation.

Microstructures and properties of Al2O3 dispersion-strengthened Cu10Sn oil bearings prepared by solid-liquid doping and reactive synthesis method

To modify the shortcomings of Cu10Sn oil bearing in mechanical performance, this work proposes to prepare the Al2O3 oxide dispersion strengthened (ODS) Cu10Sn oil bearings by reactive synthesis using elemental Sn and Al2O3 ODS-Cu powder, among which the uniformly doped Al2O3 ODS-Cu powder was synthesized through a solid-liquid doping of Al(NO3)3 in CuO powders followed with hydrogen reduction. The effects of Al2O3 content on the microstructure and properties of ODS-Cu powder and ODS-Cu10Sn oil bearings were investigated in details. The results showed that an increase in Al2O3 amount from 0 to 1.5 wt% leads to a decrease in the average particle size of the reduced ODS-Cu powders, and contributes to the significant improvement of radial compressive strength, and Vickers microhardness. The appropriate sintering temperature is approximately 800 °C, which can result in the evenly distributed Al2O3 and well-developed porosity in oil bearing sample after sintering. The corresponding compressive strength and microhardness of ODS1.5-Cu10Sn oil bearing can reach 305 MPa and 208 HV respectively.

Relationship between cross-sectional plane and corresponding morphology in an immiscible alloy powder with core-deviated structure

Immiscible alloy powders with core/shell structure have recently garnered considerable interest due to their excellent industrial performance. However, a frequently observed yet often overlooked feature is the presence of core-deviated structure in various cross-sectional planes of the powder. To date, limited research has been conducted on this structure and its origin, leaving the formation mechanism unclear. Gaining a comprehensive understanding of this mechanism is crucial for advancements in powder materials research. In this study, we first analyzed the solidification microstructures of Fe-68 wt.%Sn alloy powders, followed by a numerical analysis of airflow and internal temperature fields within a powder during the free-falling process. Our findings revealed that the average airflow velocity on the windward side is faster than that on the leeward side, causing the highest temperature point within the powder to shift towards the leeward side over time. This phenomenon is fundamentally linked to the formation of the core-deviated structure. Furthermore, we explored the relationship between cross-sectional planes and potential microstructures, demonstrating that the final observed structures are strongly influenced by the position and orientation of the cross-sectional plane. Additionally, the core deviation distance was theoretically predicted and found to be consistent with experimental results in Fe-68 wt.%Sn powders. This research provides valuable insights into the actual solidification process of immiscible alloy powders and contributes to the development of specialized structural materials.

Stable Inorganic Colloidal Tin and Tin-Lead Perovskite Nanocrystals with Ultralong Carrier Lifetime via Sn(IV) Control.

Inorganic tin (Sn) perovskite nanocrystals offer a promising solution to the potential toxicity concerns associated with their established lead (Pb)-based counterparts. Yet, achieving their superior stability and optoelectronic properties remains an ongoing challenge. Here, we report a synthesis of high-symmetry α-phase CsSnI3 nanocrystals with an ultralong 278 ns carrier lifetime, exceeding previous benchmarks by 2 orders of magnitude through meticulous Sn(IV) control. The nanocrystals demonstrate excellent colloidal stability, uniform monodispersity, and a distinct exciton peak. Central to these outcomes is our designed solid-liquid antioxidation suspension of tri-n-octylphosphine (TOP) and zerovalent tin (Sn(0)) that fully addresses the unique coexisting oxygen-driven and solvent-driven Sn oxidation mechanisms in Sn perovskite nanocrystal synthesis. We uncover the largely undervalued function of TOP in mitigating oxygen-driven Sn oxidation and introduce Sn(0) powder to generate a synergistic antioxidation function with TOP, significantly reducing Sn(IV)-induced defects and distortions and contributing to enhanced optoelectronic properties. Strikingly, this approach also profoundly impacts inorganic Sn-Pb perovskite nanocrystals, boosting lifetimes by 2 orders of magnitude and increasing photoluminescence quantum yield over 100-fold to 35%. Our findings illuminate the potential of Sn-based nanocrystals for optoelectronic applications.

INFLUENCE OF SINTERING TEMPERATURE ON THE STRUCTURAL OF Mg2Si0.3Sn0.7 ALLOY PREPARED BY POWDER METALLURGY

The efficiency of energy consumption can be improved by reducing the heat lost during the combustion process of automotive engines. By converting waste heat energy into other energy sources that can be used directly, efficiency can be achieved. Mg2Si0.3Sn0.7 is a metal alloy that has the potential to convert waste heat into power. In this research, we used the powder metallurgy method to synthesize the Mg2Si0.3Sn0.7-based alloy. A mixture of Mg, Si, and Sn powders that had been milled for 2 hours was insulated in the stainless-steel tube to avoid oxidation and combustion. Heat treatment was conducted with temperature variations of 700, 750, and 800°C for 4 hours to investigate the influence of sintering temperature on the crystal structure of the Mg2Si0.3Sn0.7-based alloy. The microstructure and formation of the material were examined using an X-ray diffractometer (XRD) and a scanning electron microscope (SEM). Based on XRD analysis, it was found that the Mg2Si0.3Sn0.7 phase and a small amount of magnesium oxide (MgO) phase have formed. Due to the phase transition from Mg2Si0.3Sn0.7 to Mg2Sn at a sintering temperature of 800°C, the cubic lattice constant -a changes from 0.6631 nm to 0.6765 nm.

Study on lap joining and characterization of tin (Sn) powder on stainless steel SS304 using microwave heating

AbstractMetal bonding via joints of low melting point materials such as zinc and tin has been technically challenging. This paper presents a unique technique for bonding small dimensions and the low melting point of materials through the microwave hybrid heating (MHH) process. Joint of stainless steel SS304 was applied to the joint with the tin (Sn) powder with the application of microwave radiation by using domestic microwave oven at 2.45 GHz of constant frequency, 200–360 W of microwave power, 120–180 s of exposure time, and 10–20 % of the epoxy rate. A developed heat chamber was used as a susceptor and insulator in the microwave hybrid heating (MHH) process. The tin powder and parent metals were strongly bonded as lap position by the microwave hybrid heating (MHH) process at 360 W of microwave power, 180 s of constant exposure time, and 20 % of the constant epoxy rate. Characterization of the joint was evaluated through microhardness and x‐ray diffraction (XRD) analysis techniques. It was found that the intermetallic compounds (phase) of nickel tin (NiSn), iron tin (Fe1.84Sn), sulfur tin (SSn), chromium tin (Cr2Sn3), chromium tin (CrSn2), and tin phosphorus (SnP) at the joint surface with highest microhardness obtained at 498.4 HV 0.05 at 360 W of microwave power.

Metallic slurry preparation and printability assessment for material extrusion additive manufacturing

Material extrusion additive manufacturing of thermoplastics is so advanced due to the tunable rheological properties and hence a suitable printability, which is deficient for metals. Even though semi-solid modification and binder indirect modification are used to realize metal extrusion printing, the uncontrollable flow behavior and the metallurgical defects make it challenging to bridge this gap. In this study, mixed powder remelting and printability assessment were first proposed for producing metallic slurry with pre-designed microstructure and suitable printability without adding fillers or polymer carriers. Specifically, the hypoeutectic Sn-Bi metallic slurry was obtained by remelting the mixed powder composed of SnBi58 powder and pure Sn powder. The microstructural characteristics at different temperatures were investigated, demonstrating the ability of microstructure predesign. Furthermore, the printability, including stability, extrudability, and buildability, was evaluated by an advanced rheometer. The combined slurry preparation and printability assessment provides a reliable method for parameters improvement to obtain the structural fidelity.

Chemical Prelithiation/Presodiation Strategies Toward Controllable and Scalable Synthesis of Microsized Nanoporous Tin at Room Temperature for High‐Energy Sodium‐Ion Batteries

AbstractPorous Sn (PSn) has aroused extensive attention as an advanced anode for sodium‐ion batteries due to its high theoretical capacity and small volume expansion. However, as a low‐melt metal, the preparation of PSn at room temperature is a difficult problem. Herein, universal chemical prelithiation/presodiation strategies are reported to rapidly synthesize PSn from commercial Sn powders at ambient temperature. The recyclable pre‐metallation solvents are selected by redox potential analysis to react with Sn to form alloy precursors in a short time. Benefiting from the application of delithiation/desodiation agents with suitable proton concentrations, PSn perfectly inherits the Sn skeleton from precursors. With this method, porous Al, Pb, Bi, and Sb are successfully produced. Finally, the half‐cell with PSn anode prepared by presodiation strategy achieves a great rate property (663 mAh g−1 at 10 A g−1) and prominent cycling performance with 71% capacity retention after 7500 cycles (502 mAh g−1) at 5 A g−1. This work may contribute to the controllable synthesis of other porous metals at room temperature.

Catalytic properties and stability of nickel–tin powder alloys in the process of electrochemical hydrogen evolution from alkali solution

Ni–Sn powder alloys with a nickel content from 24.4 to 78.5 at.% and from 30.6 to 55.1 at.%, respectively, were synthesized chemically and electrochemically for the use as catalysts for the hydrogen electrochemical reduction (HER) in alkali solution. It was established that the catalytically active surface area of chemically synthesized powders was larger in comparison with electrochemically obtained ones. Ni24.4Sn75.6 powder alloy has the largest surface area. It was found that catalytic properties of chemically synthesized powders increased in the row Ni24.4Sn75.6 < Ni78.5Sn21.5 < Ni. Electrochem ically obtained alloys are inefficient as HER catalysts. It was found that Ni24.4Sn75.6 alloy is characterized by the greater re tention of catalytically active surface area during exploitation in alkali solution in comparison with Ni and Ni78.5Sn21.5 alloy.

The effect of adding Sn on the mechanical properties and microstructure of the titanium

Ti-XSn (X = 0, 5, 10, 15) (wt. %) alloys were prepared by blending TiH2 and Sn powder compact extrusion. The effect of adding tin (Sn) on the microstructure and mechanical properties of titanium has been investigated by optical microscopy and tensile tests. The lamellar thickness (10 to 6.6 µm) of the Ti reduced after adding Sn and according to the Hall-Petch equation the yield strength (548.2 to 801.3 MPa) and microhardness (233.2 to 310 HV) of the Ti is increased with increasing the tin (Sn) content.

Microstructural and thermal evaluation of the formation of tin–tellurium (Sn[sbnd]Te) alloy by ball milling process

A mechanically induced phase transition in tin‑tellurium (SnTe) system and its dependence on the milling time of the masses of metastable SnTe phase(s) produced during ball milling have been investigated. The synthesis approach involves top-down ball milling of elemental Sn and Te powders in an argon environment with a milling time of 1 to 5 h at a low ball milling speed of 300 RPM. The SnTe solid solution forms as particles, resulting in large masses due to the ball milling operation. Ball milling of initial micron-sized powders of Sn and Te resulted in a homogenized nano-sized powder mixture. This mechanical mixture of Sn and Te powders exhibiting intermediate phases with a crystal structure similar to that of elemental Sn and Te were detected in the ball-milled mixtures at various milling times, which resulted in a stable phase that ultimately transformed into a SnTe solid solution. Morphological and structural modifications at different stages of ball milling were investigated through X-ray diffraction, field emission scanning electron microscopy, transmission electron microscopy, differential scanning calorimetry, dynamic light scattering, density measurement, and surface analysis. Subsequently, dense pellets were fabricated by spark plasma sintering from synthesized SnTe solid-solution powders produced by ball milling for 5 h. The sintered samples showed excellent structural integrity with densities of up to 6.35 g/cm3. It is to be noted that the formation of large quantities of uniform SnTe powder alloy produced by ball milling is reported for the first time in this study. These findings could be extended in the future to prepare bulk quantities of many solid solutions of the elements of the same periodic group.

Synthesis and H2S Gas-Sensing Properties of SnO2/ZnO Core/Shell Structure

In the study, SnO2/ZnO core/shell nanowires were synthesized through the two-step processes. First, SnO2-core nanowires were synthesized from Sn powder source at 750 oC by a chemical vapor deposition method (CVD). The ZnO shell was then deposited on SnO2 nanowires by a DC sputtering method. The morphological and crystal structures of the grown SnO2/ZnO core/shell nanostructures were investigated by emission scanning electron microscopy (SEM), field-emission scanning electron microscopy (FESEM), and X-ray diffraction (XRD). The results indicated a successful synthesis of the SnO2/ZnO core/shell nanowires with the thickness of the ZnO shell ranging from 5 nm, 10 nm, and 15 nm. The H2S gas sensing properties of the SnO2/ZnO core/shell structure sensors were then investigated, and results pointed out that the sample with a shell thickness of 10 nm showed an effective response and recovery to H2S gas in the concentration range 0.25 ppm - 2.5 ppm at the temperature range of 300 oC, 350 oC, 400 oC. The optimal working temperature of the sensor was found at 350 oC, where the sensor has a response of 7.8 towards 2.5 ppm. The selectivity of the sensor at 350 oC was also studied. These findings suggest that the sensor could have potential applications in detecting traces of H2S gas in the medical, food, and environmental fields.

Metallization of carbon-fibre reinforced composites via a metal-epoxy biphasic sublayer and low-pressure cold spraying

This study investigates the suitability of a sublayer-assisted low-pressure cold spraying for metallizing Carbon Fibre-Reinforced Polymer (CFRP) composites. The metal-based polymeric sublayer consists of a Cu-based epoxy sublayer, made of Cu spherical micron-sized powders and an epoxy phase, and which is embedded onto the CFRP composite surface using a vacuum moulding process. Then, a cold spray deposition onto the sublayer is performed to generate a coating. Different cold spray powders (copper, aluminium, zinc, and tin) were used to explore the optimal coupling powder/sublayer/CFRC substrate under different spraying conditions. The Cu powders require a high velocity so that they are difficult to be compatibilized with the CFRC structure without an erosion during the cold spray deposition. Soft powders like Al, Zn and Sn can lead to an onset of coating formation via the bonding of these powders onto the embedded sublayer. The Sn powders generate an adhesion onto the Cu-epoxy embedded sublayer via a metal-to-epoxy bonding (Sn-to-epoxy zone) and a metal-to-metal bonding (Sn-to-Cu), under the gas working condition of 9 bars and 25 °C. As conclusion, the present work demonstrates the feasibility of a sublayer-assisted cold spray process to metallize a CFRC structure partly made of metal-to-metal bonding.

Effect of Graphene Nanosheets on the Microstructure and Mechanical Properties of Sn-20Bi Solder.

The application of Sn-Bi series solder is limited due to the brittleness of Bi phase. Sn-20Bi solder with less Bi element content has great research prospects, but it needs modification to make it a substitute for traditional Sn-Pb solder. In this article, we mixed graphene nanosheets with nanometer Sn powder by means of ultrasonic oscillation, and Sn-20Bi-qGNS (q = 0.01, 0.02, 0.04, 0.06, and 0.1 wt.%) solder alloys were prepared by the melt-casting method. The effects of graphene nanosheets (GNSs) on the microstructure, physical properties, mechanical properties, and corrosion resistance of solder alloys were investigated. Scanning electron microscopy, energy dispersive spectroscopy, X-ray diffraction, and X-ray photoelectron spectroscopy were used to determine the microstructural morphology and composition. The results showed that the melting point, density, and wettability of the solder decreased slightly with the addition of GNSs. The addition of GNSs as a second phase refined the solder structure and improved the tensile strength of the molten Sn-20Bi composite solder to 99.6 MPa, while elongation decreased with the addition of GNSs. Furthermore, GNSs prevented the MC Sn-20Bi-qGNSs/Cu intermetallic compound layers' growth by interfering with atomic diffusion and grain boundary movement. In addition, the addition of 0.02 wt.% GNSs enhanced the shear strength of MC Sn-20Bi solder joints to 46.3 MPa. The electrochemical experimental results show that the surface corrosion products of MC Sn-20Bi-qGNSs under 3.5% NaCl solution were Sn3O(OH)2Cl2, with MC Sn-20Bi-0.01GNSs exhibiting the best corrosion resistance.

The role of copper in the formation of the Nb3Sn superconducting phase

Nb3Sn has been widely used in high magnetic field facilities due to its excellent superconducting properties. Moreover, copper has become an indispensable constituent element in the fabrication of Nb3Sn superconductors. However, the role of copper in the formation of the Nb3Sn phase is still not thoroughly understood. In this work, Nb–Sn–Cu ternary samples with different molar ratios of copper were prepared by sintering elemental Nb, Sn and Cu mixed powders, and the effect of copper on the formation of the Nb3Sn phase was systematically investigated. It was found that the addition of copper had a significant effect on the formation of Nb3Sn. When the amount of added copper was small, the formation of the Nb3Sn phase was efficiently promoted with the aid of the liquid phase, and a high-purity sample of Nb3Sn could be formed by the transition from the Nb–Sn binary phases. However, at the same time, the bulk samples with a low ratio of copper possessed poor compactness due to the pressure build-up and tin burst generated by the liquid phase during heat treatment. With increasing copper content, the promotion effect became relatively weaker. More high melting temperature Cu–Sn phases were formed, and Nb3Sn was gradually formed by solid-state diffusion between Nb and the Cu–Sn matrix. Finally, it was found that the sample of Nb:Sn:Cu = 3:1:3 (mol. %) with a grain size of 70–120 nm possessed the highest critical current density due to its high phase purity and fine grain size of Nb3Sn.