CN110467185B - Silicon material dephosphorization purification additive and purification method - Google Patents

Silicon material dephosphorization purification additive and purification method Download PDF

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CN110467185B
CN110467185B CN201910850909.9A CN201910850909A CN110467185B CN 110467185 B CN110467185 B CN 110467185B CN 201910850909 A CN201910850909 A CN 201910850909A CN 110467185 B CN110467185 B CN 110467185B
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李京伟
陈健
班伯源
史剑
孙继飞
曹佰来
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Hefei Institutes of Physical Science of CAS
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Abstract

The invention relates to a silicon material dephosphorization purification additive and a purification method. The additive is prepared by mixing one or more of cryolite, titanium-containing halide, vanadium-containing halide, alkali metal halide, alkaline earth metal halide and aluminum fluoride in any proportion. The purification method for removing phosphorus from the silicon material by using the additive comprises the following steps: heating and melting the silicon raw material, the metal medium and the additive, and uniformly stirring to carry out slagging and refining; after slagging and refining are finished, separating the obtained slag phase from the silicon alloy and then cooling the slag phase or cooling the obtained slag phase from the silicon alloy and then separating the slag phase and the silicon alloy; soaking the silicon alloy obtained after separation in an acid solution, dissolving and removing metal media in the silicon alloy, and then drying the obtained silicon material; repeating the steps for 1-4 times until the phosphorus content in the silicon material meets the purity requirement. The additive of the invention reduces the temperature of refining boron removal to 600-1300 ℃, has low energy consumption and obvious effect of removing phosphorus.

Description

Silicon material dephosphorization purification additive and purification method
Technical Field
The invention belongs to the technical field of silicon material purification, and particularly relates to a silicon material dephosphorization purification additive and a purification method.
Background
In recent years, the solar photovoltaic power generation market is rapidly increased, and the demand of high-purity solar grade silicon materials for manufacturing solar cells is also rapidly increased. In the traditional silicon material purification technology, a chemical method is always the mainstream, and the silicon material purified by the chemical method has high purity, good quality and mature technology, but the chemical method has complex purification process, is difficult to control, has serious pollution, large investment and high cost. And the chemical method is adopted to purify the silicon, and the occupation ratio of energy consumption and carbon emission in the industrial chain of solar cell production is up to more than 50%. Therefore, the development of the silicon material purification technology with low energy consumption, low emission and low cost has important significance.
As a method for effectively removing impurities in silicon, a slagging method is widely researched at home and abroad, but has the defects that slagging agents with high melting points are selected, and the temperature required by slagging refining is higher than the melting point 1414 ℃ of silicon, so that the temperature and the energy consumption are overhigh.
The patent application CN102951645A discloses a method for removing boron and phosphorus by slagging and refining, wherein slagging agents selected in the method are ferric oxide and SiO2MnO and CaF2(ii) a The iron oxide is Fe2O3、FeO、Fe3O4One of (1); the slag former and the industrial silicon are mixed according to the mass ratio of (20-26) to (5-9). Heating to 1550-1850 ℃ by using an induction furnace to carry out slagging refining, wherein the feeding mode is to melt a slagging agent firstly, then pour industrial silicon into a liquid slagging agent to carry out slagging treatment, and simultaneously introduce Ar + H into the melt2And O, repeating slagging for 8 times, and reducing the content of phosphorus to 0.5 ppmw.
Patent application CN02135841.9A discloses a high purity silicon for solar cell and a method for producing the same, which describes a slag-making process for adding lime, iron oxide and fluorite into a melt to obtain the high purity silicon for solar cell.
Patent application CN201010109835.2A discloses a method for removing boron and phosphorus impurities in industrial silicon by using rare earth oxide, wherein rare earth oxide is introduced into slag former component, and R is specific componentXOY(Y2O3、La2O3、CeO2、Sm2O3)-SiO2-BaO-CaF2And carrying out slagging for 40min under vacuum by medium frequency induction, wherein the weight ratio of slag to silicon is 1:1, and the P content is reduced from 15ppmw to 1.5 ppmw.
Through comparative analysis of the patents and documents in the phosphorus removal aspect of the prior slagging method, the types of the prior slagging agent are mainly oxides, such as CaO-SiO2,Na2O-SiO2,CaO-SiO2-CaF2,CaO-MgO-SiO2,CaO-BaO-SiO2Meanwhile, a small amount of low-melting-point compound is added in an auxiliary manner to reduce the viscosity of the melt and improve the fluidity of the melt, and the impurity removal effect on boron in silicon is far better than that of phosphorus impurity elements; collected at the above instituteThe used slagging temperature is more than 1414 ℃, the energy consumption is higher, and the future industrial application is not facilitated.
Disclosure of Invention
In order to solve the technical problems, the invention firstly provides a silicon material dephosphorization purification additive. The additive has low melting point, slag-forming refining temperature of 600-1300 ℃, low energy consumption and obvious phosphorus removal effect.
In order to realize the purpose of the invention, the invention adopts the following technical scheme:
the additive is prepared by mixing one or more of cryolite, titanium-containing halide, vanadium-containing halide, alkali metal halide, alkaline earth metal halide and aluminum fluoride in any proportion.
The preferred scheme is as follows: the titanium-containing halide is one or more of TiClx, TiBrx, TiIx and TiFx, wherein the value of x is 1-10.
The preferred scheme is as follows: the vanadium-containing halide is one of VClx, VBrx, VIx and VFx, wherein the value of x is 1-10.
The preferred scheme is as follows: the alkali metal halide comprises one or more compounds formed by alkali metal elements Li, Na, K and Rb of IA group and elements F, Cl, Br and I of VIIA group.
The preferred scheme is as follows: the alkaline earth metal halide comprises one or more compounds formed by Be, Mg, Ca, Sr and Ba of alkali metal elements in IIA group and F, Cl, Br and I of elements in VIIA group.
The preferred scheme is as follows: the vanadium-containing halide is vanadium trichloride, and the alkaline earth metal halide is calcium halide.
The invention also aims to provide a purification method for removing phosphorus from silicon materials by using the additive. The purification method comprises the following steps:
step 1, heating and melting a silicon raw material, a metal medium and the additive, uniformly stirring, and carrying out slagging refining for 2-6 hours at 600-1300 ℃;
step 2, after slagging and refining are finished, separating the obtained slag phase from the silicon alloy and then cooling the slag phase or cooling the obtained slag phase from the silicon alloy and then separating the slag phase from the silicon alloy;
step 3, soaking the silicon alloy obtained after separation in an acid solution, dissolving and removing metal media in the silicon alloy, and then drying the obtained silicon material;
and 4, repeating the step 1 to the step 3 for 1 to 4 times until the phosphorus content in the silicon material meets the purity requirement.
The further technical scheme is as follows: the proportion of the using amount of the additive to the total amount of the silicon raw material and the metal medium in the step 1 is 0.1-10.
The further technical scheme is as follows: the silicon alloy in the step 2 is one or more of silicon-aluminum, silicon-iron, silicon-calcium, silicon-gallium, silicon-titanium, silicon-manganese, silicon-tin, silicon-germanium, silicon-vanadium, silicon-copper, silicon-zinc and silicon-zirconium alloy, and the proportion of silicon in the silicon alloy is 0.1-99%.
The further technical scheme is as follows: the acid solution in the step 3 is one or more of hydrochloric acid solution, nitric acid solution, sulfuric acid solution, hydrofluoric acid solution and phosphoric acid solution.
The invention has the beneficial effects that:
the additive has the advantages of low melting point, slag-forming refining temperature of 600-1300 ℃, low energy consumption and obvious phosphorus removal effect. The purification method has the advantages of low smelting temperature, short time, capability of greatly reducing the smelting energy consumption, relatively simple process, high impurity removal rate and contribution to large-scale production. By adopting the additive and the purification method, the phosphorus content in the silicon can be reduced to 0.3ppmw after one-time slagging and refining treatment, and the removal rate can reach more than 99.78 percent.
Drawings
FIG. 1 is a flow chart of the purification method of the present invention.
Detailed Description
The technical scheme of the invention is more specifically explained by combining the following embodiments:
the silicon material dephosphorization purifying additive is prepared by mixing one or more of raw materials of cryolite, titanium-containing halide, vanadium-containing halide, alkali metal halide, alkaline earth metal halide and aluminum fluoride in any proportion. The raw material of the additive can be powder material and/or particle material.
The titanium-containing halide is one or more of TiClx, TiBrx, TiIx and TiFx.
The vanadium-containing halide is one of VClx, VBrx, VIx and VFx. The vanadium-containing halide is preferably vanadium trichloride.
Because the transition metal has multiple valence states, the value of x is a variable value, and the value of x is preferably 1-10 in the invention.
The alkali metal halide comprises one or more compounds formed by alkali metal elements Li, Na, K and Rb of IA group and elements F, Cl, Br and I of VIIA group.
The alkaline earth metal halide comprises one or more compounds formed by Be, Mg, Ca, Sr and Ba of alkali metal elements in IIA group and F, Cl, Br and I of elements in VIIA group. The alkaline earth metal halide is preferably a calcium halide.
The invention relates to a purification method for removing phosphorus from silicon materials by using the additive, which comprises the following steps:
step 1, heating and melting the silicon raw material, the metal medium and the additive, uniformly stirring, and carrying out slagging refining at 600-1300 ℃ for 2-6 hours, wherein the ratio of the consumption of the additive to the total amount of the silicon raw material and the metal medium is 0.1-10.
The silicon raw material in the step 1 can be metallurgical-grade silicon, high-grade silicon, diamond wire cutting waste silicon powder, electronic-grade silicon waste or other types of silicon tailings. The metallic medium may form an alloy with silicon, the melting temperature of the alloy being much lower than the melting temperature of silicon.
The container in the heating melting in the step 1 adopts a graphite crucible, a corundum crucible or a quartz crucible, and the heating equipment is an induction furnace, a silicon-molybdenum rod furnace, a silicon-carbon rod furnace or a resistance furnace.
The specific operation of heating and melting the silicon raw material, the metal medium and the additive in the step 1 can be implemented in two ways, wherein the first way is as follows: adding the additive into a silicon raw material and a metal medium to be heated and melted; the second way is: adding the pre-melted additive into the silicon alloy melt formed by melting the silicon raw material and the metal medium.
The stirring in the step 1 can adopt mechanical stirring or electromagnetic stirring, the mechanical stirring is carried out once every 10-30 min, and the voltage of a stirring electromagnetic field is controlled to be 0-300V when the electromagnetic stirring is adopted.
And 2, after slagging and refining are finished, separating the obtained slag phase from the silicon alloy and then cooling the slag phase or cooling the obtained slag phase from the silicon alloy and then separating the slag phase from the silicon alloy. The silicon alloy is one or more of silicon-aluminum, silicon-iron, silicon-calcium, silicon-gallium, silicon-titanium, silicon-manganese, silicon-tin, silicon-germanium, silicon-vanadium, silicon-copper, silicon-zinc and silicon-zirconium alloy, and the proportion of silicon in the silicon alloy is 0.1-99%.
Separating the obtained slag phase from the silicon alloy in the step 2, and then cooling, namely: during separation, the slag phase is directly poured out or filtered and separated. The temperature when the slag phase is directly poured out is 10 ℃ of the liquidus temperature of the silicon alloy melt; when the filtering separation slag phase is adopted, a porous alumina or porous graphite filtering container is adopted, and the diameter of a filtering hole is controlled within 3 mm. Of course, according to the different viscosity of the silicon alloy melt and the slag phase, the filtering separation can be realized by adopting an extrusion or centrifugation mode.
Cooling the obtained slag phase and the silicon alloy in the step 2, and then separating, namely: and (3) not pouring a slag phase at high temperature, solidifying the slag phase along with the silicon alloy melt at a certain cooling rate, and cutting and separating the solidified slag-containing alloy by using a diamond wire cutting machine or grinding by using a grinding wheel to remove the slag phase to obtain a silicon alloy phase after re-solidification.
And 3, soaking the silicon alloy obtained after separation in an acid solution, dissolving and removing the metal medium in the silicon alloy, and then drying the obtained silicon material. The acid solution is one or more of hydrochloric acid solution, nitric acid solution, sulfuric acid solution, hydrofluoric acid solution and phosphoric acid solution, and the concentration, temperature and other process parameters of the acid solution can be determined by referring to the known technology in the field, so that the silicon alloy can be dissolved.
And 4, repeating the step 1 to the step 3 for 1 to 4 times until the phosphorus content in the silicon material meets the purity requirement. The phosphorus content in the silicon material is detected by adopting an inductively coupled plasma emission spectroscopy technology.
The difference between the invention and the traditional silicon material dephosphorization purification is described as follows:
the melting point of the traditional oxide additive (slagging agent) is above 1400 ℃, and the invention has the advantages that: the selected low-melting-point additive can reduce the slagging temperature from 1500 ℃ to below 1300 ℃, the slagging temperature is 600-1300 ℃, the temperature is lower than the operating temperature of oxidation slagging refining in the prior art, the energy consumption is obviously reduced, and meanwhile, the additive provided by the invention has good fluidity, is beneficial to removing impurities, has a relatively simple process and is beneficial to large-scale production.
In the traditional oxidation slagging process, the temperature is limited by the fact that the melting point of silicon is too high (1414 ℃), in order to ensure that the silicon is completely melted, the slagging refining temperature is required to be higher than 1414 ℃, and the patent provides a silicon alloying mode to reduce the temperature of a silicon melt in the slagging process, so that the low-temperature melting refining of the silicon is realized.
The traditional oxidation slagging dephosphorization effect is poor, multiple times of refining purification are often needed, the low-temperature non-oxide additive adopted by the method can realize high-efficiency phosphorus removal, and the single phosphorus removal rate is far higher than the effect of oxidation slagging dephosphorization, so that the method has the advantage of being different from the traditional oxidation slagging.
The melting point of the traditional oxide additive is higher than the density of silicon melt, so that the silicon melt floats on a slag phase, the slag and silicon are not favorably mixed, the surface of the silicon melt is easily oxidized, and a large amount of oxidized slag is generated. The density of the non-oxide additive provided by the patent is lower than that of silicon melt, so that slag can be ensured to float on the silicon melt, and therefore the silicon melt is prevented from being oxidized due to contact with air, the loss of silicon is reduced, and the yield of silicon is improved.
The non-oxide additive provided by the invention has the characteristic of volatility, and can volatilize phosphorus impurity elements in the silicon alloy from silicon melt by utilizing the characteristic of self volatilization, so that the aim of removing impurities is fulfilled, and the additive is also an advantage which is not possessed by the traditional oxide additive.
The non-oxide additive provided by the invention can not only utilize the volatility characteristic of the additive, but also utilize the chemical reaction between phosphorus and the additive to ensure that the phosphorus enters the additive in the form of a certain specific compound, thereby achieving the purpose of removing impurities.
By adopting the low-temperature non-oxide additive, the content of phosphorus in the silicon raw material can be reduced to 0.3ppmw through refining treatment, the removal rate can reach more than 99.78 percent, and meanwhile, the refining temperature is low, so that the energy consumption can be obviously reduced, and the low-cost purification of silicon is facilitated.
Example 1
Putting 25g of silicon powder and 75g of aluminum block into an alumina crucible, then adding 100g of cryolite particles, putting the crucible into a resistance furnace, raising the temperature to 900 ℃ at a constant speed, keeping the temperature for 2h, stirring the mixture once by using a quartz rod every 30min, and cooling to room temperature at the speed of 0.01 ℃/min after the silicon alloy and the slag former are completely melted uniformly. And longitudinally splitting the solidified sample by using a diamond cutting machine, separating the slag former at the top from the silicon alloy at the lower part, soaking the silicon alloy in a hydrochloric acid solution to dissolve an aluminum matrix to obtain a large-size silicon wafer, and drying the silicon wafer by adopting a filtering, washing and drying mode. The phosphorus content of the dried silicon wafer is analyzed by ICP-OES sample dissolution, and the obtained result is shown in Table 1.
TABLE 1 content Change before and after P-slagging smelting in raw Material
Raw material silicon (ppmw) After purification (ppmw) Removal Rate (%)
Impurity of P 64 0.96 98.5
Example 2
Placing 30g of silicon powder and 70g of aluminum blocks in an alumina crucible, then adding a mixture of 30g of cryolite particles and 30g of calcium fluoride powder, placing the crucible in a resistance furnace, raising the temperature to 1000 ℃ at a constant speed, keeping the temperature for 3h, stirring the mixture once by using a quartz rod every 30min in the middle until the silicon alloy and the slag former are completely and uniformly melted, and then cooling the mixture to room temperature at the speed of 0.01 ℃/min. And longitudinally splitting the solidified sample by using a diamond cutting machine, separating the slag former at the top from the silicon alloy at the lower part, soaking the silicon alloy in a hydrochloric acid solution to dissolve an aluminum matrix to obtain a large-size silicon wafer, and drying the silicon wafer by adopting a filtering, washing and drying mode. The phosphorus content of the dried silicon wafer is analyzed by ICP-OES sample dissolution, and the obtained result is shown in Table 2.
TABLE 2 content Change before and after P-slagging smelting in raw Material
Raw material silicon (ppmw) After purification (ppmw) Removal Rate (%)
Impurity of P 64 0.3 99.53
Example 3
Putting 70g of silicon powder and 130g of aluminum block into an alumina crucible, then adding 30g of calcium chloride, putting the crucible into a resistance furnace, raising the temperature to 1050 ℃ at a constant speed, keeping the temperature for 2h, stirring the mixture once by using a quartz rod every 30min in the middle, and cooling to room temperature at the speed of 0.01 ℃/min after the silicon alloy and the slag former are completely melted uniformly. And longitudinally splitting the solidified sample by using a diamond cutting machine, separating the slag former at the top from the silicon alloy at the lower part, soaking the silicon alloy in a hydrochloric acid solution to dissolve an aluminum matrix to obtain a large-size silicon wafer, and drying the silicon wafer by adopting a filtering, washing and drying mode. The phosphorus content of the dried silicon wafer is analyzed by ICP-OES sample dissolution, and the obtained result is shown in Table 3.
TABLE 3 content Change before and after P-slagging smelting in raw Material
Raw material silicon (ppmw) After purification (ppmw) Removal Rate (%)
Impurity of P 235 1.1 99.53
Example 4
Putting 37.5g of silicon powder and 112.5g of aluminum blocks into an alumina crucible, then adding a mixture of 30g of sodium chloride and 30g of calcium chloride powder, putting the crucible into a resistance furnace, raising the temperature to 900 ℃ at a constant speed, keeping the temperature for 6 hours, stirring the mixture once by using a quartz rod every 30 minutes in the middle until the silicon alloy and the slag former are completely and uniformly melted, and then cooling the mixture to room temperature at the speed of 0.01 ℃/min. And longitudinally splitting the solidified sample by using a diamond cutting machine, separating the slag former at the top from the silicon alloy at the lower part, soaking the silicon alloy in a hydrochloric acid solution to dissolve an aluminum matrix to obtain a large-size silicon wafer, and drying the silicon wafer by adopting a filtering, washing and drying mode. The phosphorus content of the dried silicon wafer is analyzed by ICP-OES sample dissolution, and the obtained result is shown in Table 4.
TABLE 4 content Change before and after P-slagging smelting in raw Material
Raw material silicon (ppmw) After purification (ppmw) Removal Rate (%)
Impurity of P 235 0.8 99.65
Example 5
Putting 70g of silicon powder and 130g of aluminum block into an alumina crucible, then adding a mixture of 30g of aluminum fluoride and 30g of calcium chloride, putting the crucible into a resistance furnace, heating to 1200 ℃ at a constant speed, keeping the temperature for 6h, stirring once by using a quartz rod every 30min in the middle until the silicon alloy and the slagging agent are completely and uniformly melted, and then cooling to room temperature at the speed of 0.01 ℃/min. And longitudinally splitting the solidified sample by using a diamond cutting machine, separating the slag former at the top from the silicon alloy at the lower part, soaking the silicon alloy in a hydrochloric acid solution to dissolve an aluminum matrix to obtain a large-size silicon wafer, and drying the silicon wafer by adopting a filtering, washing and drying mode. The phosphorus content of the dried silicon wafer was analyzed by ICP-OES dissolution, and the results are shown in table 5.
TABLE 5 content Change before and after P-slagging smelting in raw Material
Raw material silicon (ppmw) After purification (ppmw) Removal Rate (%)
Impurity of P 235 0.52 99.78
Example 6
Placing 2g of silicon powder and 180g of gallium block in an alumina crucible, then adding 25g of vanadium trichloride and 55g of calcium chloride mixture, placing the crucible in a resistance furnace, raising the temperature to 900 ℃ at a constant speed, keeping the temperature for 2h, stirring once by using a quartz rod every 30min in the middle, and cooling to room temperature at the speed of 0.01 ℃/min after silicon alloy and slagging agent are completely melted uniformly. And longitudinally splitting the solidified sample by using a diamond cutting machine, separating the slag former at the top from the silicon alloy at the lower part, soaking the silicon alloy in a hydrochloric acid solution to dissolve an aluminum matrix to obtain a large-size silicon wafer, and drying the silicon wafer by adopting a filtering, washing and drying mode. The phosphorus content of the dried silicon wafer was analyzed by ICP-OES dissolution, and the results are shown in table 6.
TABLE 6 content Change before and after P-slagging smelting in raw Material
Raw material silicon (ppmw) After purification (ppmw) Removal Rate (%)
Impurity of P 235 1.65 99.30
Example 7
30g of silicon powder and 70g of aluminum block are placed in an alumina crucible, and 1000g of TiCl is added4The crucible is placed in a resistance furnace, the temperature is raised to 600 ℃ at a constant speed, the temperature is kept for 4 hours, a quartz rod is used for stirring once every 30 minutes in the middle, and after the silicon alloy and the additive are completely and uniformly melted, the crucible is cooled to the room temperature at the speed of 0.01 ℃/min. And longitudinally splitting the solidified sample by using a diamond cutting machine, separating the additive at the top from the silicon alloy at the lower part, soaking the silicon alloy in a hydrochloric acid solution to dissolve an aluminum matrix to obtain a large-size silicon wafer, and drying the silicon wafer by adopting a filtering, water washing and drying mode. The phosphorus content of the dried silicon chip is analyzed by adopting ICP-OES sample dissolution, and the obtained result is shown inTable 7.
TABLE 7 content Change before and after P-slagging smelting in raw Material
Raw material silicon (ppmw) After purification (ppmw) Removal Rate (%)
Impurity of P 235 0.9 99.62
Example 8
Putting 30g of silicon powder and 70g of iron block into an alumina crucible, then adding 10g of vanadium trichloride, putting the crucible into a resistance furnace, raising the temperature to 1000 ℃ at a constant speed, keeping the temperature for 4h, stirring once by using a quartz rod every 30min in the middle, and cooling to room temperature at the speed of 0.01 ℃/min after silicon alloy and additives are completely melted uniformly. Longitudinally splitting the solidified sample by using a diamond cutting machine, separating the additive at the top from the silicon alloy at the lower part, soaking the silicon alloy in a hydrochloric acid solution to dissolve an iron matrix to obtain a large-size silicon wafer, and drying the silicon wafer by adopting a filtering, water washing and drying mode. The phosphorus content of the dried silicon wafer was analyzed by ICP-OES dissolution, and the results are shown in table 8.
TABLE 8 content Change before and after P-slagging smelting in raw Material
Raw material silicon (ppmw) After purification (ppmw) Removal Rate (%)
Impurity of P 235 1.1 99.53
Example 9
Putting 1g of silicon powder and 180g of tin blocks into an alumina crucible, then adding 100g of sodium chloride, putting the crucible into a resistance furnace, raising the temperature to 1050 ℃ at a constant speed, keeping the temperature for 3h, stirring the mixture once by using a quartz rod every 30min in the middle, and cooling the mixture to room temperature at the speed of 0.01 ℃/min after the silicon alloy and the additive are completely melted. And longitudinally splitting the solidified sample by using a diamond cutting machine, separating the additive at the top from the silicon alloy at the lower part, soaking the silicon alloy in a hydrochloric acid solution to dissolve a tin matrix to obtain a large-size silicon wafer, and drying the silicon wafer by adopting a filtering, water washing and drying mode. The phosphorus content of the dried silicon wafer was analyzed by ICP-OES dissolution, and the results are shown in table 9.
TABLE 9 content Change before and after P-slagging smelting in raw Material
Raw material silicon (ppmw) After purification (ppmw) Removal Rate (%)
Impurity of P 235 1.0 99.57
Example 10
Putting 693g of silicon powder and 7g of copper block into an alumina crucible, then adding 200g of aluminum fluoride, putting the crucible into a resistance furnace, raising the temperature to 1300 ℃ at a constant speed, keeping the temperature for 3h, stirring once by a quartz rod every 30min in the middle, and cooling to room temperature at the speed of 0.01 ℃/min after the silicon alloy and the additive are completely melted uniformly. And longitudinally splitting the solidified sample by using a diamond cutting machine, separating the additive at the top from the silicon alloy at the lower part, soaking the silicon alloy in a hydrochloric acid solution to dissolve a copper matrix to obtain a large-size silicon wafer, and drying the silicon wafer by adopting a filtering, water washing and drying mode. The phosphorus content of the dried silicon wafer was analyzed by ICP-OES dissolution, and the results are shown in table 10.
TABLE 10 content Change before and after P-slagging smelting in raw Material
Raw material silicon (ppmw) After purification (ppmw) Removal Rate (%)
Impurity of P 235 1.2 99.49
The above is only a part of the embodiments of the present invention, and the above embodiments can be used to illustrate: when the additive is composed of any one of the raw materials of cryolite, titanium-containing halide, vanadium-containing halide, alkali metal halide, alkaline earth metal halide and aluminum fluoride, the low-temperature slagging, smelting and phosphorus removal of the silicon raw material can be realized. Certainly, because the physical and chemical properties of the cryolite, the titanium-containing halide, the vanadium-containing halide, the alkali metal halide, the alkaline earth metal halide and the aluminum fluoride are close, two or more than two raw materials are mixed in any proportion to be used as the additive, and the low-temperature slagging, smelting and phosphorus removal of the silicon raw material can also be realized.

Claims (2)

1. A method for removing and purifying phosphorus from silicon materials is characterized by comprising the following steps: placing 2g of silicon powder and 180g of gallium block in an alumina crucible, then adding 25g of vanadium trichloride and 55g of calcium chloride mixture, placing the crucible in a resistance furnace, heating to 900 ℃ at a constant speed, keeping the temperature for 2h, stirring once by using a quartz rod every 30min in the middle, and cooling to room temperature at the speed of 0.01 ℃/min after silicon alloy and a slagging agent are completely melted uniformly; and longitudinally splitting the solidified sample by using a diamond cutting machine, separating the slag former at the top from the silicon alloy at the lower part, soaking the silicon alloy in a hydrochloric acid solution to dissolve an aluminum matrix to obtain a large-size silicon wafer, and drying the silicon wafer by adopting a filtering, washing and drying mode.
2. A method for removing and purifying phosphorus from silicon materials is characterized by comprising the following steps: 30g of silicon powder and 70g of aluminum block are placed in an alumina crucible,1000g of TiCl are then added4Placing the crucible in a resistance furnace, raising the temperature to 600 ℃ at a constant speed, keeping the temperature for 4 hours, stirring the crucible once by using a quartz rod every 30 minutes until the silicon alloy and the additive are completely and uniformly melted, and then cooling the crucible to room temperature at the speed of 0.01 ℃/min; and longitudinally splitting the solidified sample by using a diamond cutting machine, separating the additive at the top from the silicon alloy at the lower part, soaking the silicon alloy in a hydrochloric acid solution to dissolve an aluminum matrix to obtain a large-size silicon wafer, and drying the silicon wafer by adopting a filtering, water washing and drying mode.
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