High-purity Si Research Articles

Simultaneous preparation of high-purity Si and eutectic Si-Nd alloy utilizing Nd2O3-containing waste slag and diamond-wire sawing silicon waste

Nd2O3-containing waste slag (NCWS) and diamond-wire sawing silicon waste (DSSW) are important rare earth and Si secondary resources, respectively. Currently, NCWS and DSSW are recycled respectively by at least two different routes, which is not efficient and increases the burden on the environment. The present study proposed a novel technical route for preparing high-purity bulk Si and eutectic Si-Nd alloy simultaneously using NCWS and DSSW as raw materials, depending on the concept of using waste to treat waste. The new technical route has only two steps: initially, raw Si-Nd alloys were obtained by extracting Nd from NCWS utilizing DSSW as a low-cost reductant, and the impurity, oxygen, in the DSSW was effectively removed utilizing NCWS; the highest extraction rate of Nd from NCWS reached 68.3%, and the oxygen removal rate in DSSW was 99.89%; in the subsequent step, the obtained raw Si-Nd alloys were separated and purified to produce high-purity bulk Si (＞99.98%) and eutectic Si-Nd alloy (＞99%) through a physical and clean method-electromagnetic directional crystallization. This novel route is considered effective and environmentally-friendly for the sustainability of rare earth and Si resources, because no gas and liquid wastes discharged throughout the whole route, and two high value products can be prepared simultaneously using two wastes.

Plasma-Chemical Disposal of Silicon and Germanium Tetrachlorides Waste by Hydrogen Reduction

The processes of hydrogen reduction of silicon and germanium chlorides under the conditions of high-frequency (40.68 MHz) counteracted arc discharge stabilized between two rod electrodes are investigated. The main gas-phase and solid products of plasma-chemical transformations are determined. Thermodynamic analysis of SiCl4 + H2 and GeCl4 + H2 systems for optimal process parameters was carried out. Using the example of hydrogen reduction of SiCl4 by the method of numerical modeling, gas-dynamic and thermal processes for this type of discharge are investigated. The impurity composition of gas-phase and solid reaction products is investigated. The possibility of single-stage production of high-purity Si and Ge mainly in the form of compact ingots, as well as high-purity chlorosilanes and trichlorogermane, is shown.

Separation of magnesium vapor and carbon monoxide during the vacuum carbothermal reduction of MgO by employing the polycrystalline silicon cutting waste as the separation agent

With the rapid development of magnesium-based materials, the worldwide demand for magnesium has increased dramatically. Vacuum carbothermal reduction (VCR) method is a potential technology to replace the highly energy-intensive Pidgeon process for magnesium production. However, this process is limited by the bottleneck problem, e.g., the separation of magnesium vapor and carbon monoxide during the carbothermal reduction. In this paper, a new strategy for separating magnesium vapor and carbon monoxide during the VCR by employing polycrystalline silicon cutting waste (PSCW) as the separation agent is proposed. The separation mechanism of magnesium vapor and carbon monoxide by PSCW was investigated thoroughly. It is proved that the magnesium vapor can react with silica in PSCW to produce magnesium oxide, while carbon monoxide cannot react with the PSCW under the same conditions, by which the magnesium vapor and carbon monoxide was separated efficiently. The magnesium oxide was then dissolved by using hydrochloric acid to recycle Si from the reduced PSCW. The results show that a high-purity Si was obtained and its recovery rate attained 86.9%. Additionally, the magnesium used in the experiment could be recycled from the leaching solution in the form of MgCl2·6H2O and its purity attained 99.94%. Based on these, it is thus suggested that a novel process for separating magnesium vapor and carbon monoxide was achieved, which is not only beneficial for the cost reduction, but also for the environmental protection.

Evaluation of thermal conductivities and thermal expansion coefficients of TiSi2 and Ti5Si3 ceramics prepared from Ti- and Si-rich wastes

TiSi2 and Ti5Si3 ceramics are high-temperature coating materials that are mainly synthesized using high-purity Ti and Si. In this study, to determine the application potential of TiSi2 and Ti5Si3 ceramics prepared through Al reduction-electromagnetic directional crystallization (AR-EDC) from Ti-bearing blast furnace slag (TBFS), spent SCR catalysts (SSCs), and diamond wire saw Si powder (DWSSP) for high-temperature coating, the thermal conductivity of AR-EDC-prepared TiSi2 and Ti5Si3 ceramics was measured. In addition, the effect of dissolved W and Al on the thermal conductivities of TiSi2 and Ti5Si3 ceramics was investigated. Meanwhile, the thermal conductivities of AR-EDC-prepared TiSi2 and Ti5Si3 ceramics were compared with those of commercial TiSi2 and Ti5Si3 ceramics and typical high-temperature coating materials. Additionally, the thermal coefficient expansions of AR-EDC-prepared TiSi2 and Ti5Si3 ceramics were compared with those of typical high-temperature Ti alloys. The results showed that the heat transfer mode of TiSi2 ceramics was phonon heat transfer, while that of the Ti5Si3 ceramics was radiation heat transfer, and dissolved W and Al reduced their thermal conductivities. At the temperature range of 298–873K, the thermal conductivities of the TiSi2 and Ti5Si3 ceramics were 29–35 W/(m·K) and 6–11 W/(m·K), respectively, and their thermal expansion coefficients were 8 × 10−6–12 × 10−6 K−1 and 5 × 10−6 –10 × 10−6 K−1, respectively. These results indicate that the thermal conductivity and thermal expansion coefficient of AR-EDC-prepared TiSi2 and Ti5Si3 meet the requirements for high-temperature coating. This study shows that Ti5Si3 and TiSi2 ceramics prepared from Ti- and Si-rich wastes are promising high-temperature coating materials.

Mechano-chemical conversion of rice husk ash and gasifier-derived rice husk ash into porous silicon

Rice husk is an abundant agricultural biomass and a potential source of amorphous silica and porous silicon. To produce high-purity SiO2 and Si from rice husks, multiple steps of acid leaching to remove impurities and heat treatment to reduce residual carbon are necessary. In this study, a simple mechanochemical (magnesio-milling) experiment was conducted using an attrition mill to convert rice husk ash (RHA) and gasifier-derived rice husk ash (GRHA) into porous Si under various acid leaching (hydrochloric acid and lactic acid) and heat-treatment conditions. Three noteworthy results were obtained. First, eco-friendly lactic acid can be used instead of the harmful acid (hydrochloric acid). Next, the heat-treated GRHA was converted to Si via magnesio-milling without acid leaching. Finally, the carbon content (<0.3 wt%) of RHA and GRHA is a key factor affecting the conversion of SiO2 into Si based on elemental analysis. The purities of the Si samples prepared from RHA and GRHA, analyzed using inductively coupled plasma (ICP) mass spectrometry, were 97.66% and 95.62%, respectively. Furthermore, the porous Si prepared using RHA and GRHA can be utilized as a high value-add material such as an anode material for lithium-ion batteries and nanostructured materials.

High-Index Faceted Cu2 O@CuO Mesocrystals Act as Efficient Catalyst for Si Hydrochlorination to Trichlorosilane.

Mesocrystals (MCs) with high-index facets may have superior catalytic properties to those with low-index facets and their nanocrystal counterparts. However, synthesizing such mesocrystal materials is still very challenging because of the metastability of MCs and energetic high-index crystal facets. This work reports a successful solvothermal method followed by calcination for synthesizing copper oxide-based MCs possessing a core-shell structure (denoted as Cu2 O@CuO HIMCs). Furthermore, these MCs are predominantly bounded by the high-index facets such as {311} or {312} with a high-density of stepped atoms. When used as catalysts in Si hydrochlorination to produce trichlorosilane (TCS, the primary feedstock of high-purity crystalline Si), Cu2 O@CuO HIMCs exhibit significantly enhanced Si conversion and TCS selectivity compared to those with flat surfaces and their nanostructured counterparts. Theoretical calculations reveal that both the core-shell structure and the high-index surface contribute to the increased electron density of Cu sites in Cu2 O@CuO HIMCs, promoting the adsorption and dissociation of HCl and stabilizing the dissociated Cl* intermediate. This work provides a simple method for synthesizing high-index faceted MCs and offers a feasible strategy to enhance the catalytic performance of MCs.

Co-treatment of diamond-wire-saw silicon kerf and spent automotive catalysts for simultaneous recovery of PGMs, REEs, Zr, and high-purity Si

Spent automotive catalysts (SACs) and diamond-wire-saw silicon kerf (DWSSK) are classified as hazardous wastes. Currently, the two wastes are treated separately using unrelated approaches. More than two independent approaches are required to recover platinum group metals (PGMs), Zr and rare earth elements (REEs) from SACs, and recover Si from DWSSK, which is time-consuming and laborious. In this study, a new approach was proposed to co-treat the two wastes based on the concept of using waste treats waste: using DWSSK (∼89.85 wt% Si) as a new metal collector to extract PGMs, REEs, and Zr simultaneously from SACs to obtain a Si-VM alloy (VM: valuable metal); meanwhile, using the carrier of SACs to form molten slag to eliminate the main impurity, O, from DWSSK. The largest recovery ratios of Pd, Rh, Zr, Ce, La, and Nd from SACs were 99.50 ± 0.10%, 99.14 ± 0.14 %, 96.19 ± 0.76%, 67.18 ± 4.57%, 61.24 ± 4.93% and 47.65 ± 7.27%, respectively, and the largest removal ratio of O from DWSSK was 99.96%. After smelting, the Si-VM alloy was separated into high-purity Si and VM-containing acid solutions via acid leaching. The leaching ratios of Pd, Rh, Ce, La, Nd, and Zr were 99.78%, 98.15%, 99.93%, ∼100%, 99.76% and 99.98%, respectively. The purity of Si was upgraded from 89.85 wt% (in DWSSK) to 99.98 wt% after acid leaching. The new approach proposed in this study is considered more environmentally friendly and cost-effective than the regular approaches that treat the two wastes separately.

Oxide unlocking electron beam melting to separate boron for impurities co-removal of metallurgical grade silicon

Removing stubborn B from Si efficiently and simplifying the purification process are critical challenges that must be addressed in the manufacture of solar grade silicon (SoG-Si) via metallurgical routes. Herein, B is flexibly coupled with other impurities separation procedure, so that metallurgical grade silicon (MG-Si) is purified through simplified electron beam melting (EBM) unlocked by a few oxides (0.1 wt%). EBM fulfills three functions including promotion of oxidation, evaporation of impurities, and induction of directional solidification, giving high-temperature field, high vacuum field, and intense melt convection, which not only ensures the smooth process of B oxidation but also favors the co-removal of other impurities, obtaining high purity Si. As a result, purified Si ingot exhibits a low content of B (from 12.76 ppmw to 2.92 ppmw), and the total content of major impurities is reduced from 1217.24 ppmw to 5.66 ppmw. Significantly, pure SiO2 could more readily access the high-temperature region of Si melt during EBM, offering distinct advantages for the oxidation gas phase separation of B. This work provides an efficient and robust method for expanding ideas of B removal and simplifying metallurgical routes.

Fe2O3-modified CuO catalyst for efficient catalytic silicon hydrochlorination to trichlorosilane: Catalyst structural evolution

Catalytic hydrochlorination of Si is an effective route to manufacture trichlorosilane (TCS), the main feedstock of high-purity Si for solar cells. However, the understanding of its catalytic process is still limited. Herein, we prepared CuO catalysts modified with Fe2O3 promoter (Fe2O3-CuO) by one-step hydrothermal method and investigated their catalytic performance for producing TCS. Compared with the non-catalytic case, pure CuO catalyst, and the Fe2O3-CuO-M catalyst obtained by mechanically mixing CuO with Fe2O3, the Fe2O3-CuO catalyst exhibits the highest TCS selectivity and Si conversion. The introduction of Fe2O3 facilitates lattice oxygen migration of CuO due to the electron interactions between Fe2O3 and CuO. During the reaction, CuO transforms into CuCl2 and CuCl2·2H2O, then to CuCl. The latter is the key intermediate for forming the active CuxSi phase. This work discloses the transformation of the CuO catalyst during the Si hydrochlorination reaction, and provides new insights into the catalytic mechanism.

Toward sustainability for upcycling SoG-Si scrap by an immersion rotational segregation purification process

Recycling solar grade silicon (SoG-Si) scrap is critical for the sustainability of solar energy and fulfilling to close material loops in circular economics. A major challenge is to control trace impurities efficiently in short time for upgrading scrap to a level of SoG-Si. Here, a new immersion rotational separation purification (IRSP) process is developed to enhance trace impurities removal and the crystal growth from remelted metal by driving the rotating shear flow to improve the efficiency of solute and heat transfer. In a departure from conventional practice that forces extremely low solidification rate limited by the diffusion layer depth at approximately equilibrium solidification interface, here IRSP achieves the deep removal of impurities and the increase of solidification rate by the non-equilibrium rotating solidification interface. In the non-equilibrium solidification process caused by mold rotation, the rotating shear flow not only reduces the diffusion layer depth to improve impurity removal efficiency, but also increases the temperature gradient of the melt at the solidification front that is conducive to the increase of crystal growth rate. The new method is applicable to molten Si and the production of SoG-Si (99.9998%) has been demonstrated, which is able to improve the quality of recycled SoG-Si requiring a low energy input. It is expected that this process helps close high purity Si material loops, reduce resource consumption and the carbon footprint of the photovoltaic industry.

Development of multicomponent hybrid powders based on titanium and niobium carbides as a promising material for laser cladding

Multicomponent hybrid TiC-NbC(Zr, Si) powder was developed and manufactured by mechanosynthesis in a high-energy vibratory ball mill. High-purity fragmented TiC, NbC, Zr and Si powders were selected and mixed in a ratio of 60:15:10:15 at.%, respectively, to manufacture the above powder. Several modes of mechanosynthesis were chosen for the experiment: 3, 6, 9 and 12 hours. Scanning electron microscopy (SEM) and X-Ray diffraction (XRD) analyzes were used to study the morphology, chemical and phase compositions of the obtained TiC-NbC(Zr, Si) powder. The SEM analysis confirmed the presence of all TiC, NbC, Zr and Si components in the final powder regardless of the mechanosynthesis time. However, the XRD analysis showed that after 9 and 12 hours of mechanosynthesis, the Zr and Si diffraction lines are completely absent. This occurs due to the dissolution of the Zr and Si elements in titanium and niobium carbides. In addition, it has been established that more than 6 hours are required to synthesize finely dispersed TiC-NbC(Zr, Si) powder. The study results can be useful for optimization of the mechanosynthesis process.

Si nanoplates prepared by ball milling photovoltaic silicon sawdust waste as lithium-ion batteries anode material

High-purity Si sawdust waste from the photovoltaic industry is an available source for Si anodes of lithioum-ion batteries (LIBs), but seeking for a synthetic process featuring with low cost and industrial scale from the Si waste to nanoscale Si materials in actual applications is quite challenging. Herein, we report a highly scalable and cost-effective ball milling method that directly converts photovoltaic Si sawdust waste to Si nano-plate (BM Si) for LIBs’ anode material. In the ball milling process, a thin SiO2 layer generates on BM Si. The nanoscale size of BM Si and SiO2 layer can buffer volume change of Si anode during cycling. As a result, BM Si displays a high initial capacity of 2196 mAh/g and remains a stable capacity of 1480 mAh/g after 100 cycles at 100 mA g−1, which is higher than that of commercial Si nanoparticles.

Purifying Metallurgical-Grade Silicon to 4N with 3D Porous Structure by Integrated Metallurgy-Materials Phase Separation

Silicon (Si) is widely used in photovoltaics, semiconductors, and lithium-ion batteries but high purity is required in most applications. Conversion of metallurgical-grade Si (MG-Si) to Si with 4N purity and desired structure by an economical and environmentally friendly technique is still challenging, albeit desirable. Herein, an integrated metallurgy-materials technique is described to produce high-purity Si (99.99%) with a three-dimensional (3D) porous structure from metallurgical Si. This green and cost-effective strategy involves controllable phase separation of impurities from the Si matrix via Mg alloying, nitriding/dealloying (<800 °C), and acid etching, which can remove metallic impurities (Fe, Al, Ca, et al.) and non-metallic impurities (B, P, et al) with the efficiency of above 90% and 80% respectively. The intermediate product of Mg3N2 serves as both the pore-forming medium and impurity carrier /remover to separate impurities, improve the exposed area, and enhance dissolution of impurities. Different from conventional metallurgical processes, B and P are converted into MgB2 and Mg3P2 resulting in easy removal during phase separation. This green process is effective in purifying Si and forming a porous structure on a large scale as demonstrated by the conversion of metallurgical Si to high-purity Si. Moreover, the integrated metallurgy-materials phase separation technique can be extended to other industrial applications.

Kinetics of Magnesiothermic Reduction of Natural Quartz.

In this work, the kinetics of natural quartz reduction by Mg to produce either Si or Mg2Si was studied through quantitative phase analysis. Reduction reaction experiments were performed at various temperatures, reaction times and Mg to SiO2 mole ratios of 2 and 4. Rietveld refinement of X-ray diffraction patterns was used to obtain phase distributions in the reacted samples. SEM and EPMA examinations were performed to evaluate the microstructural change during reduction. The results indicated that the reduction reaction rate was slower at a mole ratio of 2 than 4 at the same temperature, as illustrated by the total amount of Si formed (the percent of Si that is reduced to either Si or Mg2Si to total amount of Si) being 59% and 75%, respectively, after 240 min reaction time for mole ratios of 2 and 4. At the mole ratio of 4, the reaction rate was strongly dependent on the reaction temperature, where SiO2 was completely reduced after 20 min at 1273 K. At the lower temperatures of 1173 and 1073 K, total Si formed was 75% and 39%, respectively, after 240 min reaction time. The results of the current work show that Mg2Si can be produced through the magnesiothermic reduction of natural quartz with high yield. The obtained Mg2Si can be processed further to produce silane gas as a precursor to high purity Si. The combination of these two processes offers the potential for a more direct and low carbon method to produce Si with high purity.

Microscopic Proof of Photoluminescence from Mechanochemically Synthesized 1-Octene-Capped Quantum-Confined Silicon Nanoparticles: Implications for Light-Emission Applications

Silicon nanoparticles (SiNPs) have been explored intensively for their use in applications requiring efficient fluorescence for LEDs, lasers, displays, photovoltaic spectral-shifting filters, and biomedical applications. High radiative rates are essential for such applications, and theoretically these could be achieved via quantum confinement and/or straining. Wet-chemical methods used to synthesize SiNPs are under scrutiny because of reported contamination by fluorescent carbon species. To develop a cleaner method, we utilize a specially designed attritor type high-energy ball-mill and use a high-purity (99.999%) Si microparticle precursor. The mechanochemical process is used under a continuous nitrogen gas atmosphere to avoid oxidation of the particles. We confirm the presence of quantum-confined NPs (<5 nm) using atomic force microscopy (AFM). Microphotoluminescence (PL) spectroscopy coupled to AFM confirms quantum-confined tunable red/near-infrared PL emission in SiNPs capped with an organic ligand (1-octene). Using micro-Raman-PL spectroscopy, we confirm SiNPs as the origin of the emission. These results demonstrate a facile and potentially scalable mechanochemical method of synthesis for contamination-free SiNPs.

Chemical Analysis of High Energy Density Electrodeposited Silicon Anodes for Lithium-Ion Batteries

Implementation of high Si-content anodes (> 10% v/v%) has been difficult to achieve at the loadings and manufacturing scale required for practical lithium-ion batteries (LIBs) applications. Three-dimensionally engineered electrically conductive porous scaffolds enable low silicon coating thicknesses (10-200 nm) and provide internal free volume to reduce the impact of Si volume changes upon cycling. Yet, scalable deposition of battery-grade silicon on these complex structures remains a challenge. Herein, we report a high energy-density Si-dominant electrodeposited material (EDEP-Si) onto 3D-structured Ni scaffolds and evaluate the impact of impurities inherent to the electrodeposition process on performance by comparing the behavior of the EDEP-Si with that of high-purity amorphous Si grown via static chemical vapor deposition (CVD). The long-term cycling stability and high reversible specific capacity of EDEP-Si and CVD-Si on a silicon basis are remarkably similar and near theoretical (~2400 mAh g-1 Si-1 after 100 cycles). However, the EDEP-Si exhibits a 13% lower first cycle efficiency and reduced round-trip efficiencies over the first 10-20 cycles relative to CVD-Si. Reactions between carbon (9-11 at%) and, more importantly, oxygen (42-44 at%) in the EDEP-Si with lithium are most likely responsible for the reduced early-cycle round trip efficiencies and low capacity relative to the mass of the total deposit. Based on our observations, we suggest directions for improving the composition and properties of EDEP-Si.

Laboratory Study on the Formation of Endogenous CaO‐Containing Inclusion in Gear Steel SCr420H during the Simulated LF Refining Process without Ca Treatment

The individual effect of Ca‐containing ferrosilicon, MgO crucible, and slag–steel refining on the formation of endogenous CaO‐containing inclusion in steel is investigated by contrast experiments. Experiments using Ca‐containing ferrosilicon are compared with the effect of high basicity slag and MgO crucible on inclusions compared to experiments with high purity Si. It is found that the influence of Ca‐containing ferrosilicon has a noticeable impact on endogenous CaO‐containing, while slag–steel reaction and MgO refractory mainly increase the (MgO) in inclusion. When Ca‐containing ferrosilicon is added after Al deoxidation, Al2O3 and MgO–xAl2O3 inclusions with low MgO content are modified into CaO‐containing inclusions preferentially, and [Mg] supplied by MgO refractory reacts mainly with (Al2O3) in inclusions in the subsequent refining process. Ca‐containing ferrosilicon addition before Al deoxidation is helpful in reducing Ca content in the steel. The dissolution of refractory in slag has a significant effect on slag–steel reaction by changing slag composition. Under the effect of slag and MgO refractory, MgO‐saturated spinel and MgO form in steel during the whole process. Herein, Ca‐containing ferrosilicon is a significant contributor to endogenous CaO‐containing inclusions during the simulated ladle furnace refining process without Ca treatment.

Design of Refining Slag Based on Structural Modifications Associated with the Boron Removal for SoG-Si.

Solar grade silicon (SoG-Si) is the core material of solar cells. The removal of boron (B) has always been a challenge in the preparation of high purity Si. Slag refining has always been considered as one of the effective methods to remove B, but the design of refined slag has been limited by the cognition of the relationship between slag structure and impurity removal, and can only rely on the apparent basicity and oxygen potential adjustment of slag based on a large number of conditional experiments. In order to clarify the B removal mechanism of slag refining from Si, nuclear magnetic resonance (NMR) and Raman vibrational spectroscopy were used to investigate in detail the behavior and state of B and aluminum (Al) in the SiO2–CaO–Al2O3–B2O3 slag. The role of the degree of B–Si cross linking on the B activity in slag was highlighted by comparing the partition ratio (LB) between slag and Si. Q2 structural unit of slag is an important site for capturing B. BO4 (1B, 3Si) species is the main form of connection between B and silicate networks, which determines the activity of B in the slag. The addition of Al2O3 into SiO2–CaO slag can change the relative fraction of Q2 and BO4 (1B, 3Si). Increasing Al2O3 content from 0 to about 20 wt% can lead to the overall increase of Q2 population, and a tendency to decrease first and then increase of BO4 (1B, 3Si) fraction under both basicity conditions (0.6 and 1.1). When Al2O3 content is less than 10 ± 1 wt%, the decrease of BO4 (1B, 3Si) population plays a major role in deteriorating the connectivity between B and aluminosilicate network, which leads to a higher activity of B. When the Al2O3 content is greater than 10 ± 1 wt%, B is incorporated into the silicate network more easily due to the formation of more Q2 and BO4 (1B, 3Si), which contributes to a rapid decline in activity of B in slag.

Characterization of SiC and Si3N4 inclusions in solar cell Si scraps and their motion at the Si/slag interface

The separation of SiC and Si3N4 inclusions from solar cell Si scraps to the slag phase during slag refining is essential to the recovery and production of high-purity Si. This study characterized the SiC and Si3N4 inclusions in solar cell Si scraps, which formed large clusters with complex shapes. According to the experimental and theoretical investigations, the inclusions with large diameters were found to be conducive to passing through the Si/slag interface and then being retained in the slag phase. The favorable conditions such as positive overall wettability, high operating temperature, low viscosity slag, and prolonged-time can promote the small inclusion removal from molten Si scraps.

Crystal Phases and Chemical Stabilities of YSi&amp;lt;sub&amp;gt;2&amp;lt;/sub&amp;gt; Powders Fabricated from Low and High Purity Si and Y Powders

Y-Si compounds with the composition of Y:Si = 1:2 were fabricated using Yttrium and Silicon raw powders with low and high purity in various atmospheres and temperatures. Although the latest Y-Si phase diagram shows that the α- and β-YSi2 phases are the stable phases for the stoichiometric composition of Y:Si = 1:2, the current experimental results suggest that the high temperature phase with the hexagonal structure, β-Y3Si5, would be the stable phase for this composition, and that the high temperature phase with the orthorhombic structure, β-YSi2, would be the meta-stable phase with high oxygen impurity content. It was demonstrated that YSi2 powders possess much superior chemical stability than Yttrium metal. It was found that the best dispersing solvent was 2-propanol for YSi2 powder.