High-purity cerium-silicon alloy and preparation method thereof
By using suspension melting technology and high-purity argon protection, the composition and cooling process of cerium-silicon alloys were optimized, solving the problem of impurity control in high-purity cerium-silicon alloys and realizing high-purity, low-defect cerium-silicon alloys to meet the application requirements of semiconductors and high-end electronic devices.
Patent Information
- Application Number
- CN202511423764.6
- Authority / Receiving Office
- CN · China
- Patent Type
- Applications(China)
- Current Assignee / Owner
- Filing Date
- 2025-09-30
- Publication Date
- 2026-01-23
AI Technical Summary
The impurity content in existing high-purity cerium-silicon alloys is difficult to control, resulting in large deviations in cerium doping concentration and numerous crystal growth defects. This affects the quality and performance of silicon carbide crystals, especially in high-temperature growth environments where brittle compounds and gaseous impurities are easily formed, reducing device performance.
The process employs suspension melting technology, uses high-purity argon gas for protection, controls the ratio of cerium to silicon to be 60wt%–80wt% and 20wt%–40wt%, achieves a purity of ≥99.995%, controls impurities to Fe≤5ppm, Ni≤3ppm, Al≤5ppm, and gaseous impurities≤100ppm, optimizes the CeSi2 phase ratio to ≥90%, and reduces the defect rate through rapid cooling.
A cerium-silicon alloy with high purity and low defect rate was prepared, meeting the material requirements of the semiconductor and high-end electronics fields. This significantly improved the reliability and service life of the alloy and stabilized the growth process of silicon carbide crystals.
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Abstract
Description
TECHNICAL FIELD
[0001] The application belongs to the field of alloys, and particularly relates to a high-purity cerium-silicon alloy and a preparation method thereof. BACKGROUND
[0002] Silicon carbide (SiC) crystal as an important wide-bandgap semiconductor material has a wide application prospect in the fields of high-temperature, high-frequency, high-power electronic devices and optoelectronic devices due to its excellent physical and chemical properties. Rare earth metal cerium and its alloys play a key role in crystal quality control, defect inhibition and electrical and optical performance optimization due to their unique physical and chemical properties and doping effects. However, the purity, content of key sensitive impurities, alloy composition and physical form of the rare earth metal cerium and its alloys have a direct impact on the doping effect, and are important influencing factors in the growth process of silicon carbide crystals.
[0003] At present, rare earth cerium alloy, especially high-purity cerium-silicon alloy, has become the preferred dopant in the industry because its melting point, density and phase characteristics are controllable, and it is easier to diffuse uniformly and avoid local enrichment of cerium elements in the production process of silicon carbide crystals. However, due to the chaotic phase composition of cerium-silicon alloy, CeSi, CeSi2 and Ce5Si3 coexist in multiple phases, and the proportion of each phase in the cerium-silicon alloy fluctuates greatly, causing the doping concentration of cerium elements in silicon carbide crystals to deviate by more than 20%, which makes it difficult to achieve precise control of crystal performance. In addition, in the high-temperature (above 2000℃) growth environment of silicon carbide crystals, defects such as pores and micro-cracks in the cerium-silicon alloy will release impurity gases, interfere with the normal growth of the crystal, and cause problems such as unstable crystal growth interface and polytype defects.
[0004] In order to obtain high-purity, low-defect cerium-silicon alloy required for the production of silicon carbide crystals, the purity of alloy raw materials cerium and silicon must reach more than 99.99%, and the concentration of key impurities must be extremely low. Since the purity of high-purity silicon can generally reach more than 7N at present, the key to obtaining high-purity cerium-silicon alloy lies in obtaining high-purity metal cerium. However, due to the high activity of metal cerium, it is difficult to effectively control the content of key impurities such as iron, nickel and aluminum, and gas impurities, and the content of key impurities often exceeds 10ppm, and the content of gas impurities exceeds 150ppm. The cerium-silicon alloy prepared therefrom is prone to form brittle intermetallic compounds such as Ce-Fe-Si, Ce-Ni-Si and Ce-Al-Si, and Ce-O compounds. In the growth process of silicon carbide crystals, these intermetallic compounds are easily wrapped into the crystal, becoming deep level recombination centers, which causes the carrier lifetime to decrease by more than 40%, seriously affecting the switching speed and breakdown voltage of the device; and the Ce-O compound becomes the starting point for dislocation multiplication, causing the microtube density of the crystal to increase to 100 / cm 2 Therefore, the yield of silicon carbide substrates is greatly reduced. SUMMARY
[0005] (I) Invention purposes
[0006] The purpose of the present application is to provide a high-purity cerium-silicon alloy and a preparation method thereof. The method can obtain a cerium-silicon alloy with a specific phase composition, a low defect rate, and a purity of ≥4N, which can meet the stringent requirements of materials in the fields of semiconductors and high-end electronics.
[0007] (II) Technical solutions
[0008] To solve the above problems, the present application provides a high-purity cerium-silicon alloy and a preparation method thereof. The high-purity cerium-silicon alloy comprises cerium and silicon. The content of the cerium is 60wt%-80wt%, and the content of the silicon is 20wt%-40wt%. The purity of the cerium-silicon alloy is ≥99.995%. The content of impurity Fe in the cerium-silicon alloy is ≤5ppm, the content of impurity Ni is ≤3ppm, the content of impurity Al is ≤5ppm, the content of gas impurities is ≤100ppm, and the content of residual impurities is ≤10ppm. The residual impurities include transition metal elements such as Cu, Cr, V, Mn, Co, Zr, Zn, Mo, and W, and rare earth impurity elements.
[0009] Preferably, the content of cerium is 75wt%-80wt%, and the content of silicon is 20wt%-25wt%,
[0010] Preferably, the density of the high-purity cerium-silicon alloy is 3.47g / cm 3 -4.58g / cm 3 .
[0011] Preferably, the main phase of the high-purity cerium-silicon alloy is CeSi2, and the mass ratio of CeSi2 in the high-purity cerium-silicon alloy is ≥90%. Preferably, the mass ratio of CeSi2 in the high-purity cerium-silicon alloy is ≥95%. Doping with CeSi2 can make SiC crystals exhibit low resistivity characteristics, which is conducive to the stable growth of 4H-SiC and the stable crystal form. The mass ratio of CeSi2 in ordinary melting and blending technology is 80%-90%, and even lower than 75% in poor process control. The mass ratio of CeSi2 in the present application is increased to more than 95%.
[0012] Preferably, the form of the high-purity cerium-silicon alloy is any one of particles, rods, and blocks. The maximum size is 10-100mm. The maximum size refers to the maximum size in each direction, such as the maximum particle size of particles, the maximum length of rods, and the maximum edge length of blocks.
[0013] Preferably, the total defect rate of the cerium-silicon alloy is <0.1%, and the defect density of microcracks and pores is each ≤1 / cm 2Further preferably, the total defect rate of the cerium-silicon alloy is <0.05%, and the defect density of micro-cracks and pores is both ≤0.5 / cm 2 .
[0014] Preferably, the purity of the cerium is ≥99.99%, the content of impurity Fe in the cerium is ≤10ppm, the content of impurity Ni is ≤5ppm, the content of impurity Al is ≤10ppm, the content of impurity Si is ≤100ppm, the content of impurity Mg is ≤2ppm, the content of impurity Ca is ≤1ppm, the content of gas impurities is ≤100ppm, and the content of residual impurities is ≤20ppm; further preferably, the purity of the cerium is ≥99.995%, the content of impurity Fe is ≤5ppm, the content of impurity Ni is ≤3ppm, the content of impurity Al is ≤5ppm, the content of impurity Si is ≤10ppm, the content of impurity Mg is ≤1ppm, and the content of impurity Ca is ≤1ppm; the residual impurities include transition metal elements such as Cu, Cr, V, Mn, Co, Zr, Zn, Mo and W, and rare earth impurity elements.
[0015] Preferably, the surface roughness Ra of the cerium is ≤10μm, the diameter of surface micropores is ≤50μm, and the number of surface micropores is ≤5 / cm 2 The surface of the metallic cerium is smooth and clean, and no hole can be seen by naked eyes.
[0016] The second aspect of the present application provides a preparation method of the high-purity cerium-silicon alloy as described in any one of the above descriptions, and the method comprises the following steps:
[0017] The cerium with a weight percentage of 60%-80% and the silicon with a weight percentage of 20%-40% are weighed and prepared;
[0018] The prepared materials are put into a suspension smelting device for suspension smelting, and the high-purity cerium-silicon alloy is obtained after cooling, wherein, in the suspension smelting device, the vacuum is first extracted to 5×10 -4 Pa or above, then high-purity argon is filled to 0.1-0.2MPa for heat preservation, and the argon atmosphere is maintained during cooling.
[0019] Preferably, the purity of the high-purity argon is ≥99.999%, the cerium-silicon alloy melt is poured into a water-cooled copper mold for cooling during cooling, the purity of the high-purity argon is ≥99.999%, the flow rate of the argon gas during the cooling process is 5-20L / min, and the cooling rate is ≥40℃ / s, so that rapid cooling is realized. The ordinary purity argon contains oxygen and nitrogen, which can cause a small amount of oxidation and nitridation of the alloy, increase the brittleness of the alloy, cause oxidation inclusions and pore defects, and the impurity content in the high-purity argon is extremely low, which will not pollute the alloy.
[0020] Preferably, the temperature of the suspension smelting is 1650-1720℃, and the holding time of the suspension smelting is 8-15 minutes. In this temperature range, the CeSi2 phase can be better produced, and the loss of Si can be reduced. Further preferably, the temperature of the suspension smelting is 1680-1700℃, and the holding time of the suspension smelting is 10-12 minutes.
[0021] (III) Beneficial Effects
[0022] The above technical scheme of the present application has the following beneficial technical effects: the present application provides a high-purity cerium-silicon alloy and a preparation method thereof. The high-purity cerium-silicon alloy obtained by the preparation method can meet the stringent requirements of the semiconductor, high-end electronic and other fields for materials. The high-purity cerium-silicon alloy comprises cerium and silicon, the content of cerium is 60wt%-80wt%, the content of silicon is 20wt%-40wt%, the purity of the cerium-silicon alloy is ≥99.995%, the content of impurity Fe in the cerium-silicon alloy is ≤5ppm, the content of impurity Ni is ≤3ppm, the content of impurity Al is ≤5ppm, the content of gas impurities is ≤100ppm, and the content of the remaining impurities is ≤40ppm. The purity of the cerium-silicon alloy is ≥4N, the defect rate is low, the failure risk of the alloy in use is significantly reduced, the reliability and service life of the alloy are improved, the alloy has stable physical and chemical properties, the cerium-silicon alloy can be used in the fields of silicon carbide cerium doping and high-end electronic device manufacturing, and has a wide market application prospect. DETAILED DESCRIPTION
[0023] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below with specific embodiments. It should be understood that these descriptions are only exemplary and are not intended to limit the scope of the present application. In addition, in the following description, the description of well-known structures and techniques is omitted to avoid unnecessary confusion of the concept of the present application.
[0024] In order to make the purpose, technical scheme and advantages of the present application more clear, the present application will be further described in detail below with specific embodiments.
[0025] Example 1
[0026] Table 1 High-purity rare earth metal cerium composition
[0027]
[0028] As shown in Table 1, the high-purity rare earth metal cerium has a purity of 4N6, Fe content of 8 ppm, Ni content of 0.5 ppm, Al content of 6 ppm, Ca content of 0.9 ppm, Si content of 1.2 ppm, and the remaining impurities have a content of 20 ppm, and the gas impurities have a content of 65 ppm; the high-purity rare earth metal cerium is in a block shape with a size of 8-15 mm; the surface roughness Ra is less than or equal to 4.3 μm, the micro-pore diameter is less than or equal to 34.8 μm, and the number of micro-pores per unit area is less than or equal to 3 per cm 2 .
[0029] The high-purity rare earth metal cerium and 7N high-purity silicon are prepared according to the mass percentages of 77% and 23% respectively, and are placed in a crucible of a suspension smelting furnace; a vacuum pump is started to extract vacuum to 5x10 -4 Pa, heating to 1000℃ for 30 minutes, then filling high-purity argon (the purity of argon is greater than 99.999%) into the furnace to 0.15 MPa, and heating to 1690℃ for 11 minutes for suspension smelting, and after the heat preservation is completed, the alloy melt is poured into a square mold with a side length of 80 mm, and is cooled under the protection of argon atmosphere in the furnace, the argon flow is controlled to be 12 L / min, and the alloy cooling rate is 86℃ / s, and the high-purity cerium silicon alloy has the performance as shown in Table 2.
[0030] Table 2 Composition of high-purity cerium silicon alloy
[0031]
[0032] The cerium silicon alloy is detected, and the defect rate is 0.03%, the main defect density such as micro-cracks and pores is 0.3 per cm 2 ; the phase analysis shows that the mass percentage of CeSi2 phase is 98.5%, and the mass percentage of Ce3Si2 phase is 1.5%; the form is a block shape, and the maximum size is 78.4 mm.
[0033] Comparative Example 1
[0034] Table 3 Composition of high-purity rare earth metal cerium
[0035]
[0036] As shown in Table 3, the high-purity rare earth metal cerium has a purity of 4N6, Fe content of 8 ppm, Ni content of 0.5 ppm, Al content of 6 ppm, Ca content of 0.9 ppm, Si content of 1.2 ppm, and the total content of other impurities is 20 ppm, and the gas impurities have a content of 65 ppm; the high-purity rare earth metal cerium is in a block shape with a size of 8-15 mm; the surface roughness Ra is less than or equal to 4.3 μm, the micro-pore diameter is less than or equal to 34.8 μm, and the number of micro-pores per unit area is less than or equal to 3 per cm 2 .
[0037] The high-purity rare earth metal cerium and 7N high-purity silicon are prepared according to the mass percentages of 77% and 23% respectively, and are placed in a crucible of a vacuum melting furnace; a vacuum pump is started to vacuumize to 5x10 -4 Pa, heated to 1000℃ for 30 minutes, then high-purity argon is filled into the furnace to 0.15MPa, heated to 1720℃ for 15 minutes for melting, after the heat preservation is over, the alloy melt is poured into a square mold with a side length of 80mm, cooled under the protection of argon atmosphere in the furnace, the argon flow is controlled to be 12L / min, and the alloy cooling rate is 86℃ / s, to obtain a cerium-silicon alloy ingot. After the cerium-silicon alloy is cooled, it is broken into granular form.
[0038] Table 4: Parameters of cerium-silicon alloy
[0039]
[0040] The cerium-silicon alloy is detected, and the defect rate is 0.15%, the main defect density such as microcrack and pore is 1.4 / cm 2 ; the phase analysis shows that the mass percentage of CeSi2 phase is 88%, and the mass percentage of Ce3Si2 phase is 12%; the form is granular, and the maximum size is 24mm. Compared with example 1, the comparative example 1 uses ordinary vacuum melting process, the melting temperature is higher, the heat preservation time is longer, which leads to more Si burning loss, and the prepared cerium-silicon alloy has higher defect rate, lower CeSi2 phase mass percentage, and worse alloy performance.
[0041] Example 2
[0042] Table 5: Composition of high-purity rare earth metal cerium
[0043]
[0044] As shown in Table 5, the purity of high-purity rare earth metal cerium is 4N6, the content of Fe is 8ppm, the content of Ni is 0.5ppm, the content of Al is 6ppm, the content of Ca is 0.9ppm, the content of Si is 1.2ppm, the total content of other impurities is 20ppm, and the content of gas impurities is 65ppm; it is in block form, the size is 8-15mm; the surface roughness Ra is ≤4.3μm, the micropore diameter is ≤34.8μm, and the number of micropores per unit area is ≤3 / cm 2 .
[0045] The high-purity rare earth metal cerium and 7N high-purity silicon are prepared according to the mass percentages of 77% and 23% respectively, and are placed in a crucible of a vacuum melting furnace; a vacuum pump is started to vacuumize to 5x10 -4Pa, heated to 1000 ℃ for 30 minutes, then the furnace filled with high purity argon to 0.15 MPa, heated to 1650 ℃ for 8 minutes for suspension smelting, after the end of the heat preservation alloy melt poured into the side length of 80 mm square mold, in the furnace under the protection of argon atmosphere cooling, control argon flow is 12 L / min, alloy cooling rate of 86 ℃ / s, get cerium silicon alloy ingot. After the cerium silicon alloy cooled, cut into a cuboid of 40 mm wide, 75 mm long, by forging, extrusion molding.
[0046] Table 6 cerium silicon alloy parameters
[0047]
[0048] Cerium silicon alloy by testing, the defect rate is 0.09%, the main defect density of microcracks, porosity, etc. 0.9 / cm 2 ; phase analysis shows that the mass of CeSi2 phase is 94.5%, and the mass of Ce3Si2 phase is 5.5%; the shape is rod-shaped, and the maximum size is 85 mm. The raw materials and smelting process of example 2 and example 1 are the same, but the parameter control is general, which does not belong to the preferred process parameters, resulting in insufficient reaction of Ce and Si, and higher defect rate of the prepared alloy and lower mass of CeSi2 phase.
[0049] Example 3
[0050] Table 7 high purity rare earth metal cerium composition
[0051]
[0052] As shown in table 7, the purity of high purity rare earth metal cerium is 4N7, the content of Fe is 6 ppm, the content of Ni is 0.3 ppm, the content of Al is 4.1 ppm, the content of Si is 0.9 ppm, the content of Ca is 0.3 ppm, and the content of the rest of the impurities is 18 ppm, and the content of gas impurities is 49 ppm; blocky, size 8-13 mm; surface roughness Ra≤4.1 μm, micropore diameter ≤32.4 μm, the number of micropores per unit area ≤3 / cm 2 .
[0053] The high purity rare earth metal cerium and 7N high purity silicon are prepared according to the mass percentage of 75% and 25% respectively, and put into the suspension smelting furnace crucible; start the vacuum pump to vacuum to 5×10 -4 Pa, heated to 1000 ℃ for 30 minutes, then the furnace filled with high purity argon to 0.15 MPa, heated to 1650 ℃ for 8 minutes for suspension smelting, after the end of the heat preservation alloy melt poured into the side length of 80 mm square mold, in the furnace under the protection of argon atmosphere cooling, control argon flow is 12 L / min, alloy cooling rate of 86 ℃ / s, get cerium silicon alloy ingot.
[0054] Table 8 Ce-Si alloy parameters
[0055]
[0056] The Ce-Si alloy was detected to have a defect rate of 0.04%, and the density of main defects such as microcracks and pores was 0.3 per cm 2 ; the phase analysis showed that the mass ratio of CeSi2 phase was 98.4%, and the mass ratio of Ce3Si2 phase was 1.6%; the form was blocky, and the maximum size was 75.3 mm.
[0057] Comparative Example 2
[0058] Table 9 High-purity rare earth metal cerium composition
[0059]
[0060] As shown in Table 9, the high-purity rare earth metal cerium had a purity of 4N2, Fe content of 10 ppm, Ni content of 4.9 ppm, Al content of 8.5 ppm, Si content of 2.1 ppm, Ca content of 0.9 ppm, and the balance of impurities of 53.6 ppm, gas impurity content of 138 ppm, in the form of block, size of 13-21 mm, surface roughness Ra≤9.9 μm, micropore diameter ≤48.1 μm, and the number of micropores per unit area ≤5 per cm 2 .
[0061] The high-purity rare earth metal cerium and 7N high-purity silicon were prepared according to the mass percentages of 75% and 25%, respectively, and were placed in the crucible of the suspension smelting furnace; the vacuum pump was started to vacuum to 5x10 -4 Pa, heated to 1000°C for 30 minutes, then high-purity argon was filled into the furnace to 0.15 MPa, and the temperature was raised to 1680°C for 11 minutes for suspension smelting, and after the holding was completed, the alloy melt was poured into a square mold with a side length of 80 mm, and cooled under the protection of argon gas atmosphere in the furnace, with the argon gas flow controlled at 12 L / min, and the alloy cooling rate was 88°C / s. After the Ce-Si alloy was cooled, it was broken into granular form.
[0062] Table 10 Ce-Si alloy parameters
[0063]
[0064] The Ce-Si alloy was detected to have a defect rate of 0.09%, and the density of main defects such as microcracks and pores was 0.7 per cm 2Phase analysis shows that the mass fraction of CeSi2 phase is 93.5%, and the mass fraction of Ce3Si2 phase is 6.5%; the morphology is granular, and the maximum size is 22 mm. The melting process and parameters and cooling rate of Comparative Example 2 and Example 3 are the same, but the purity of the raw material cerium metal is lower, resulting in high impurity content of the prepared alloy, more inclusions and defects, and lower mass fraction of CeSi2 phase.
[0065] Comparative Example 3
[0066] Table 11 Composition of high-purity rare earth metal cerium
[0067]
[0068] As shown in Table 11, the high-purity rare earth metal cerium has a purity of 4N, Fe content of 10 ppm, Ni content of 4.2 ppm, Al content of 8.5 ppm, Si content of 2.1 ppm, Ca content of 0.9 ppm, and the balance of impurities of 70 ppm, gas impurity content of 258 ppm, in block shape, size of 13-21 mm, surface roughness Ra≤10.9 μm, micropore diameter≤48.7 μm, and micropore number per unit area≤5 / cm 2 .
[0069] The high-purity rare earth metal cerium and 7N high-purity silicon were prepared according to the mass percentages of 75% and 25% respectively, and were placed in the crucible of the suspension melting furnace; the vacuum pump was started to vacuum to 5×10 -4 Pa, heated to 1000℃ for 30 minutes, then high-purity argon was filled into the furnace to 0.15 MPa, and the temperature was raised to 1680℃ for 11 minutes for suspension melting. After the holding period, the alloy melt was poured into a square mold with a side length of 80 mm, and cooled under the protection of argon gas in the furnace, with the argon gas flow controlled at 12 L / min, and the alloy cooling rate was 88℃ / s. After the cerium-silicon alloy was cooled, it was cut into a cuboid with a width of 40 mm and a length of 75 mm, and was formed by forging and extrusion.
[0070] Table 12 Parameters of cerium-silicon alloy
[0071]
[0072] The cerium-silicon alloy was detected, and the defect rate was 0.14%, and the main defect density such as microcracks and pores was 1.8 / cm 2Phase analysis shows that the mass percentage of CeSi2 phase is 85.6%, and the mass percentage of Ce3Si2 phase is 14.4%; the morphology is rod-shaped, and the maximum size is 88 mm. The melting process and parameters and cooling rate of Comparative Example 3 and Example 3 are the same, but the purity of the raw material cerium is further reduced, and the content of gas impurities is significantly increased, resulting in high impurity content of the prepared alloy, more inclusions, a significant increase in porosity defects, and a lower mass percentage of CeSi2 phase.
[0073] Example 4
[0074] Table 13 Composition of High-purity Rare Earth Metal Cerium
[0075]
[0076] As shown in Table 13, the purity of high-purity rare earth metal cerium is 4N5, the content of Fe is 9.2 ppm, the content of Ni is 2.1 ppm, the content of Al is 5.9 ppm, the content of Si is 3.8 ppm, the content of Ca is 0.9 ppm, and the content of the remaining impurities is 20 ppm, and the content of gas impurities is 70 ppm; it is in block shape, the size is 10-15 mm; the surface roughness Ra is ≤6.8 μm, the micropore diameter is ≤42.1 μm, and the number of micropores per unit area is ≤5 / cm 2 .
[0077] High-purity rare earth metal cerium and 7N high-purity silicon were prepared according to the mass percentages of 75% and 25%, respectively, and were placed in the crucible of the suspension melting furnace; the vacuum pump was started to vacuum to 5x10 -4 Pa, heated to 1000℃ for 30 minutes, then high-purity argon was filled into the furnace to 0.15 MPa, and the temperature was raised to 1680℃ for 10 minutes for suspension melting, and after the holding was completed, the alloy melt was poured into a square mold with a side length of 80 mm, and cooled under the protection of argon gas in the furnace, with the argon gas flow controlled at 12 L / min, and the alloy cooling rate was 88℃ / s, to obtain a cerium-silicon alloy ingot.
[0078] Table 14 Parameters of Cerium-silicon Alloy
[0079]
[0080] The cerium-silicon alloy was detected, and the defect rate was 0.03%, and the main defect density such as microcracks and pores was 0.2 / cm 2 ; phase analysis shows that the mass percentage of CeSi2 phase is 98.5%, and the mass percentage of Ce3Si2 phase is 1.5%; the morphology is block-shaped, and the maximum size is 74.8 mm.
[0081] Example 5
[0082] Table 15 Composition of High-purity Rare Earth Metal Cerium
[0083]
[0084] As shown in Table 15, the high-purity rare earth metal cerium has a purity of 4N5, Fe content of 9.2 ppm, Ni content of 2.1 ppm, Al content of 5.9 ppm, Si content of 3.8 ppm, Ca content of 0.9 ppm, and total content of other impurities of 20 ppm, in the form of a block with a size of 10-15 mm; the surface roughness Ra is less than or equal to 6.8 μm, the micro-pore diameter is less than or equal to 42.1 μm, and the number of micro-pores per unit area is less than or equal to 5 / cm 2 .
[0085] The high-purity rare earth metal cerium and 7N high-purity silicon are prepared in a mass percentage of 75% and 25% respectively, and are placed in a crucible of a suspension smelting furnace; a vacuum pump is started to draw a vacuum to 5x10 -4 Pa, heating to 1000°C for 30 minutes, then filling high-purity argon into the furnace to 0.15 MPa, and heating to 1680°C for 10 minutes for suspension smelting, and after the holding period, pouring the alloy melt into a square mold with a side length of 80 mm, and cooling under the protection of an argon atmosphere in the furnace, with the argon flow controlled at 10 L / min, and the alloy cooling rate being 54°C / s. After the cerium-silicon alloy is cooled, it is broken into granular form.
[0086] Table 16: Parameters of the cerium-silicon alloy
[0087]
[0088] The cerium-silicon alloy is detected to have a defect rate of 0.09%, and the main defect density of micro-cracks and pores is 0.9 / cm 2 ; phase analysis shows that the mass percentage of the CeSi2 phase is 91.8%, and the mass percentage of the Ce3Si2 phase is 8.2%; the form is granular, and the maximum size is 25 mm. The raw materials, smelting process, and smelting parameters used in Example 5 and Example 4 are the same, but the cooling rate is reduced, resulting in the generation of more impurity phases during the solidification process (the mass percentage of the CeSi2 phase is significantly reduced from 98.5% to 91.8%, the mass percentage of the impurity phase Ce3Si2 is increased from 1.5% to 8.2%, the defect rate is increased from 0.03% to 0.09%, and the micro-crack and pore defect density is increased from 0.2 / cm 3 to 0.9 / cm 3 .
[0089] Example 6
[0090] Table 17: Composition of high-purity rare earth metal cerium
[0091]
[0092] As shown in Table 17, the high-purity rare earth metal cerium has a purity of 4N5, an Fe content of 9.2 ppm, an Ni content of 2.1 ppm, an Al content of 5.9 ppm, an Si content of 3.8 ppm, a Ca content of 0.9 ppm, and a total content of other impurities of 20 ppm, in a block shape with a size of 10-15 mm; a surface roughness Ra of ≤6.8 μm, a micropore diameter of ≤42.1 μm, and a number of micropores per unit area of ≤5 / cm 2 .
[0093] The high-purity rare earth metal cerium and 7N high-purity silicon are prepared in a mass percentage of 75% and 25%, respectively, and are placed in a crucible of a suspension smelting furnace; a vacuum pump is started to draw a vacuum to 5x10 -4 Pa, heating to 1000℃ for 30 minutes, then filling high-purity argon into the furnace to 0.15 MPa, heating to 1680℃ for 10 minutes for suspension smelting, and after the holding period, pouring the alloy melt into a square mold with a side length of 80 mm, cooling under the protection of an argon atmosphere in the furnace, with an argon flow rate controlled at 17 L / min, and an alloy cooling rate of 125℃ / s. After the cerium-silicon alloy is cooled, it is cut into a cuboid with a width of 30 mm and a length of 70 mm, and is forged and extruded into a shape.
[0094] Table 18: Parameters of the cerium-silicon alloy
[0095]
[0096]
[0097] The cerium-silicon alloy is detected to have a defect rate of 0.19%, a density of main defects such as microcracks and pores of 3.8 / cm 2 ; phase analysis shows that the mass percentage of the CeSi2 phase is 95.0%, and the mass percentage of the Ce3Si2 phase is 5.0%; the morphology is rod-shaped, with a maximum size of 74 mm. The raw materials, smelting process, and smelting parameters used in Example 6 and Example 4 are the same, but the cooling rate is too fast, resulting in a sharp increase in the temperature difference between the surface and the interior of the alloy during solidification, a significant increase in the defect rate (from 0.03% to 0.19%, and a density of microcrack and pore defects from 0.2 / cm 3 to 3.8 / cm 3 ), and a slight decrease in the mass percentage of the CeSi2 phase (from 98.5% to 95.0%). In summary, the high-purity rare earth metal cerium of the present application has a very high purity and a smooth and clean surface, and the cerium-silicon alloy prepared therefrom performs excellently in terms of defect rate, phase, and organizational morphology, and can meet the application requirements of high-end fields.
[0098] It should be understood that the foregoing detailed description of the application, rather than limiting the application, is intended to explain and describe the current implementation of the application. Therefore, any modification, equivalent replacement or improvement made without departing from the spirit and scope of the application should be included in the protection scope of the application. In addition, the appended claims of the application are intended to cover all changes and modifications falling within the scope and boundary of the appended claims, or the equivalent form of such scope and boundary.
Claims
1. A high purity cerium-silicon alloy, characterized by, The high-purity cerium-silicon alloy comprises cerium and silicon, the content of cerium is 60wt%-80wt%, the content of silicon is 20wt%-40wt%, the purity of the cerium-silicon alloy is ≥99.995%, the content of impurity Fe in the cerium-silicon alloy is ≤5ppm, the content of impurity Ni is ≤3ppm, the content of impurity Al is ≤5ppm, the content of gas impurities is ≤100ppm, and the content of residual impurities is ≤40ppm.
2. The high purity cerium silicon alloy of claim 1, wherein, The high-purity cerium-silicon alloy has a density of 3.47 g / cm 3 ~ 4.58 g / cm 3 .
3. The high purity cerium silicon alloy of claim 1, wherein, The main phase of the high-purity cerium-silicon alloy is CeSi2, and the mass ratio of CeSi2 in the high-purity cerium-silicon alloy is ≥90%.
4. The high purity cerium silicon alloy of claim 1, wherein, The high-purity cerium-silicon alloy is in any one of granular, rod-shaped and block-shaped forms.
5. The high purity cerium silicon alloy of claim 1, wherein, The total defect rate of the cerium-silicon alloy is <0.1%, wherein the defect density of microcracks and pores is both ≤1 / cm 2 .
6. The high purity cerium-silicon alloy as claimed in claim 1, characterized in that, The purity of cerium is ≥99.99%, the content of impurity Fe in the cerium is ≤10ppm, the content of impurity Ni is ≤5ppm, the content of impurity Al is ≤10ppm, the content of impurity Si is ≤100ppm, the content of impurity Mg is ≤2ppm, the content of impurity Ca is ≤1ppm, the content of gas impurities is ≤100ppm, and the content of residual impurities is ≤20ppm.
7. The high purity cerium silicon alloy of claim 1, wherein, The cerium has a surface roughness Ra≤10 μm, a surface micropore diameter ≤50 μm, and a surface unit micropore number ≤5 / cm 2 .
8. A method for producing a high-purity cerium-silicon alloy as claimed in any one of claims 1 to 7, characterized in that, The method comprises: cerium with a weight percentage of 60%-80% and silicon with a weight percentage of 20%-40% are weighed and prepared; The ingredients are put into a suspension smelting device for suspension smelting, and a high-purity cerium-silicon alloy is obtained after cooling, wherein in the suspension smelting device, vacuum is first extracted to 5×10 -4 Pa or above, high-purity argon is then filled to 0.1-0.2 MPa for heat preservation, and an argon atmosphere is maintained during cooling.
9. The method of claim 8, wherein the high purity cerium-silicon alloy is prepared by the steps of: The purity of the high-purity argon is ≥99.999%, the flow rate of the argon during the cooling process is 5-20L / min, and the cooling rate is ≥40℃ / s. 10. The method of claim 8, wherein the high purity cerium-silicon alloy is prepared by the steps of: The suspension smelting temperature is 1650-1720℃, and the suspension smelting holding time is 8-15 minutes.