JP7243027B2 - synthetic silica glass powder - Google Patents

Description

Synthetic silica glass powder used as a raw material for quartz glass crucibles used as containers for molten silicon when manufacturing silicon wafers used in semiconductors and solar cells by the single crystal pulling method (Czochralski method (CZ method)). Regarding.

With the recent increase in diameter of silicon wafers, a quartz crucible for pulling silicon single crystals has a two-layer structure. The outer layer is a silica layer made of natural quartz powder, which has excellent high-temperature strength, and the inner layer, which is in contact with silicon melt, is a silica layer made of high-purity synthetic silica glass powder with few impurities. A typical method for producing a double-layered crucible is to deposit layers of natural silica powder and synthetic silica glass powder inside a rotating carbon mold (rotating mold) and arc-melt them.

Conventionally, in this two-layer structure crucible, it has been required that the inner layer be free of air bubbles (for example, Patent Documents 1 to 3). When the transparent glass layer on the inner surface is substantially bubble-free, there is no occurrence of delamination in the two-layer structure crucible, which has the advantage of being able to reduce the dislocation rate during pulling of the silicon single crystal. ing.

On the other hand, recently, when pulling a silicon single crystal, in order to prevent the surface vibration of the silicon melt in the crucible, which adversely affects the quality of the single crystal, the inner layer near the surface of the crucible has a volume of 0.01 to 0.2%. % air bubbles (for example, Patent Document 4), and for the purpose of dispersing external radiant heat in order to eliminate temperature unevenness of the silicon melt, a volumetric air bubble content of 0.1 is placed between the inner layer and the outer layer of the crucible. % or more has been developed (for example, Patent Document 5). Specifically, the quartz powder deposited on the inner surface of the rotating mold is heated and melted from the mold space side, and during the heating and melting, the air in the quartz powder deposition layer is sucked from the mold side to remove air bubbles. A method of generating bubbles by intermittent leakage is described. In addition, Patent Document 6 describes a method of including a certain number or more of white silica particles (hereinafter referred to as white particles) in synthetic silica glass powder as a method of partially forming air bubbles in a crucible. there is

JP-A-1-148783 Japanese Patent Application Laid-Open No. 2001-002430 JP-A-11-116388 Japanese Patent Application Laid-Open No. 2004-250304 JP 2009-084113 A JP 2014-15380 A

However, according to the studies of the present inventors, Patent Document 4 does not describe means for generating air bubbles, and in the method described in Patent Document 5, vacuuming and leaking are intermittently performed, etc. The process turned out to be cumbersome. Furthermore, in the method described in Patent Document 6, the control for producing white grains is complicated, and there is room for improvement.

The present invention has been made in view of the above problems, and an object thereof is to provide a synthetic silica glass powder capable of easily generating air bubbles in a silica glass layer obtained by melting.

In response to the above problems, the present inventors synthesized and investigated various silica glass powders, and found that when synthetic silica glass powders each containing a predetermined amount of a group of synthetic silica glass powders with different particle sizes are used, melting The inventors have found that it is possible to generate air bubbles in the subsequent silica glass layer, and have completed the present invention. That is, the gist of the present invention is as follows.

(1) A synthetic glass-silica powder containing a synthetic silica glass powder A and a synthetic silica glass powder B, wherein the particle size of the synthetic silica glass powder A is larger than 300 μm and the particle size of the synthetic silica glass powder B is 106 μm or less. Synthetic silica glass having a content of synthetic silica glass powder A of 1% by weight or more and a content of synthetic silica glass powder B of 5% by weight or more when the total amount of synthetic silica glass powder is 100% by weight. powder.
(2) The synthetic silica glass powder according to (1), wherein the synthetic silica glass powder having a diameter of 1000 µm or more accounts for 3% by weight or less of the total amount of the synthetic silica glass powder.
(3) The synthetic silica glass powder according to (1) or (2), wherein the synthetic silica glass powder A has a particle size of 425 μm or less.
(4) The synthetic silica glass powder according to any one of (1) to (3), wherein the particle size of the synthetic silica glass powder B is larger than 45 μm.
(5) A quartz crucible for pulling a silicon single crystal, using the synthetic glass silica powder according to any one of (1) to (4) as a raw material.

ADVANTAGE OF THE INVENTION According to this invention, the synthetic silica glass powder which can generate air bubbles easily in a quartz crucible can be provided. Also, a quartz crucible for pulling a silicon single crystal having bubbles can be provided.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining one flow for manufacturing synthetic silica glass powder. BRIEF DESCRIPTION OF THE DRAWINGS It is a figure explaining one flow for manufacturing synthetic silica glass powder.

Embodiments of the present invention will be described below, but the present invention is not limited to the following embodiments, and can be arbitrarily modified without departing from the gist of the present invention.

[1. Synthetic silica glass powder]
Synthetic silica glass powder is amorphous silicon dioxide particles. The synthetic silica glass powder of the present invention contains predetermined amounts of synthetic silica glass powder A and synthetic silica glass powder B, which are groups of synthetic silica glass powders having different particle sizes. Thereby, bubbles can be generated in the silica glass layer in the crucible when the quartz crucible is manufactured. By generating air bubbles in the silicon glass layer in the crucible, it is possible to prevent surface vibration of the silicon melt. In addition, it is possible to disperse external radiant heat and eliminate temperature unevenness of the silicon melt.

Here, the principle of bubble generation is considered as follows. Synthetic silica glass powder has a faster melting rate as its particle size decreases. Therefore, when a synthetic silica glass powder containing a group of synthetic silica glass powders with different particle sizes is melted, the melting rate differs depending on the particle size, and a density difference occurs between the surrounding particles during melting. When the density difference occurs, voids are generated between particles, which appear as bubbles after melting.

It is suitable that the size of the air bubbles is 0.5 mm or less in diameter. If the size of the bubbles exceeds 0.5 mm in diameter, the effect of preventing the surface vibration of the silicon melt and the effect of dispersing external radiation heat may be reduced. The size of the bubbles is considered to be determined by the size of the voids between particles caused by the density difference.

Therefore, according to the present invention, by using predetermined amounts of a group of synthetic silica glass powders having different particle sizes, the difference in melting rate during melting and the density difference caused by the difference in melting rate can be controlled to obtain an appropriate It generates air bubbles of an appropriate size.
The synthetic silica glass powder of the present invention will be described in detail below.

First, the synthetic silica glass powders A and B contained in the synthetic silica glass powder will be explained.
The particle size of the synthetic silica glass powder A is larger than 300 μm. The particle size of the synthetic silica glass powder B is 106 μm or less. Thus, when there is a difference of about 200 μm or more in particle size, the difference in melting speed becomes appropriate, and air bubbles are likely to occur.
Although the upper limit of the particle size of the synthetic silica glass powder A is not particularly limited, it is preferably 1000 μm or less, particularly preferably 425 μm or less. If the upper limit of the particle size of the synthetic silica glass powder A is 1000 μm or less, the melting rate can be appropriately maintained, and when a silica glass layer is produced using the silica glass powder, particle interfaces are less likely to remain. Therefore, it becomes easier to prevent the silica glass layer from being damaged.

Although the lower limit of the particle size of the synthetic silica glass powder B is not particularly limited, it is preferably larger than 45 μm, more preferably larger than 75 μm. If the lower limit of the particle size of the synthetic silica glass powder B is larger than 45 μm, dusting is easily prevented, and furthermore, the occupied volume of the particles themselves increases, which tends to contribute to the generation of air bubbles.

Here, "particle size" is specified by the nominal opening in the JIS standard sieve table (JIS Z8801-J1982). Therefore, in synthetic silica glass powder, for example, "particle size is larger than 300 µm" means that when sieved for 10 minutes on a sieve with a nominal opening of 300 µm in the JIS standard sieve table (JIS Z8801-J1982), it does not pass through the sieve. It is a group of synthetic silica glass powders, and "having a particle size of 106 µm or less" means a group of synthetic silica glass powders that pass through a sieve having a nominal opening of 106 µm in the JIS standard sieve table for 10 minutes. means that The same applies to other particle sizes.

Next, the contents of the synthetic silica glass powders A and B will be explained.
When the total amount of the synthetic silica glass powder is 100% by weight, the lower limit of the content of the synthetic silica glass powder A is preferably 1% by weight or more, more preferably 2% by weight or more, and more preferably 3% by weight or more. It is particularly preferred to have The upper limit of the content of the synthetic silica glass powder A is not particularly limited. Since the entire synthetic silica glass powder may be difficult to melt, the amount is preferably 20% by weight or less, more preferably 15% by weight or less, and particularly preferably 10% by weight or less.

The lower limit of the content of the synthetic silica glass powder B is preferably 5% by weight or more, more preferably 10% by weight or more. Although the upper limit of the content of the synthetic silica glass powder B is not particularly limited, it is preferably 70% by weight or less, particularly preferably 65% by weight or less.
Thus, by controlling the contents of both the synthetic silica glass powders A and B within the above range, density differences due to differences in melting rates are likely to occur, and air bubbles are likely to occur. In addition, the size of the voids between particles caused by the density difference becomes appropriate, and air bubbles of appropriate size are likely to be generated.

Next, the whole synthetic silica glass powder (sometimes simply referred to as "synthetic silica glass powder") will be described. In addition to the synthetic silica glass powder A and the synthetic silica glass powder B, synthetic silica glass powder having a different particle size may be contained in the entire synthetic silica glass powder.

(1) Particle size The particle size of the synthetic silica glass powder is not particularly limited as long as the synthetic silica glass powders A and B satisfying the predetermined particle size and blending amount are contained. The proportion of particles larger than 1000 μm when expressed as % by weight is preferably 3% by weight or less, more preferably 2% by weight or less, further preferably 1% by weight or less, and most preferably 0%. % by weight. On the other hand, the ratio of the synthetic silica glass powder having a particle size of 45 μm or less is preferably 3% by weight or less, more preferably 2% by weight or less, more preferably 1% by weight, based on the total synthetic silica glass powder as 100% by weight. % or less, most preferably 0% by weight. As described above, if it is within the above range, it tends to be excellent in handleability and to be easily melted when manufacturing a crucible for manufacturing a solar cell (a crucible for pulling a silicon single crystal).

(2) Bulk Density The bulk density of the synthetic silica glass powder is preferably 1.1 g/cm ³ or more, more preferably 1.2 g/cm ³ or more, and preferably 1.5 g/cm ³ or less, more preferably It is in the range of 1.4 g/cm ³ or less. Bulk density is measured, for example, by a measuring method according to JIS-K-6720. The bulk density can be adjusted by adjusting the particle size distribution of the synthetic silica glass powder.

(3) Specific Surface Area The specific surface area of the synthetic silica glass powder is preferably 0.003 m ² /g or more, more preferably 0.01 m ² /g or more, preferably 0.5 m ² /g or less, more preferably 0 .1 m ² /g or less. Measurement of the specific surface area is performed by a gas adsorption method such as, for example, a nitrogen adsorption method.

When the specific surface area of the synthetic silica glass powder exceeds 0.5 m ² /g and is large, the properties of the porous gel derived from the raw material dry gel remain, which causes the generation of coarse bubbles during crucible formation. On the other hand, if it is less than 0.003 m ² /g, the particle size of synthetic silica glass powder usually exceeds 1000 μm, which is not preferable. By setting the specific surface area within the above range, it is possible to manufacture a crucible in which bubble formation is controlled.

(4) Content of Impurities As for the content of impurities in the synthetic silica glass powder, the total content of metal elements is preferably 1 ppm by weight or less. The impurity content is measured, for example, by the ICP-MS method (inductively coupled plasma mass spectrometry).

When the impurity content of the synthetic silica glass powder is equal to or less than the upper limit of the above range, when a quartz crucible for pulling a silicon single crystal is produced using the synthetic silica glass powder as a raw material, silicon is extracted from the quartz crucible for pulling a silicon single crystal. Contamination can be prevented by suppressing the elution of metal elements into the melt and the silicon single crystal.
The lower limit of the impurity content is generally about 10 weight ppb. It is not very practical to reduce impurities to less than 10 weight ppb, and analysis at the 1 weight ppb level is very difficult.

(5) Content of silanol groups Furthermore, the content of silanol groups (Si—OH) in the particles of the synthetic silica glass powder is preferably 5 ppm by weight or more, more preferably 20 ppm by weight or more, as the concentration of silanol groups. preferably 200 ppm by weight or less, more preferably 100 ppm by weight or less. The concentration of silanol groups can be measured, for example, by infrared spectrophotometry (infrared spectroscopy) and is expressed as the weight ratio of hydroxyl groups (OH groups) to the particle weight.

By setting the content of silanol groups (Si—OH) in the particles of the synthetic silica glass powder to at least the lower limit of the above range, the generation of air bubbles based on water (water vapor) generated by dehydration condensation of the silanol groups is controlled to an appropriate amount. While controlling, the firing time during the production of synthetic silica glass powder can also be prevented from being excessively long. By keeping the content of silanol groups (Si—OH) in the particles of the synthetic silica glass powder below the upper limit of the above range, excessive generation of bubbles is prevented, and at the same time, durability such as deformation of the crucible at high temperatures is improved. exacerbation can be prevented.

[2. Method for producing synthetic silica glass powder]
The synthetic silica glass powder of the present invention can be produced by a known method, preferably by a sol-gel method using alkoxysilane as a raw material. The sol-gel method is known, for example, in the literature (Sameo Sakuhana, "Science of the Sol-Gel Method"). method.
Basically, the hydrolysis reaction of alkoxysilane is performed using reaction (A) according to the following reaction formula (a).

Tetraalkoxysilane is preferable as the raw material alkoxysilane. Further, it is preferable to use a raw material that has been purified by distillation in advance, so that SiO ₂ with high purity can be produced.
(RO) ₄ Si + 2H ₂ O → SiO ₂ + 4ROH (a)

In the above reaction formula (a), R represents an alkyl group, and preferably has 1 to 4 carbon atoms. groups are preferred.

An example of a manufacturing flow diagram of the synthetic silica glass powder of the present invention is shown in FIGS. As shown in FIG. 1, the synthetic silica glass powder of the present invention undergoes a hydrolysis step (step 1) for hydrolyzing alkoxysilane, a pulverization step (step 2) for pulverizing wet gel, and drying the pulverized wet gel. It is manufactured through a drying step (step 3) performed and a firing step (step 4) of firing the dry gel.

Alternatively, the synthetic silica glass powder of the present invention, as shown in FIG. After the drying step (step 13) for drying and the firing step (step 14) for firing the dry gel, a classification step (step 15) for classifying the fired synthetic silica glass powder may be performed.
Each process will be described in detail below. In the following description, the case of using tetraalkoxysilane as the alkoxysilane will be described.

<Hydrolysis reaction (reaction (A))>
In the hydrolysis reaction, the raw material tetraalkoxysilane is subjected to the hydrolysis reaction of reaction (A) described above, and can be carried out by reacting tetraalkoxysilane with water according to a known method. Here, the hydrolyzate of tetraalkoxysilane is called "wet gel".

At this time, organic solvents such as alcohols, ethers, and ketones compatible with the by-produced alcohol may be mixed as necessary. For example, alcohols include methanol, ethanol and propanol, ethers include diethyl ether, and ketones include acetone.

However, as the hydrolysis reaction progresses, the alkoxy group bonded to silicon is liberated as alcohol, so if the reaction solution is in a uniform state before gelation (formation of wet gel), that is, the hydrolysis rate In the case of a raw material containing an alkoxy group (for example, a methoxy group) having a large molecular weight, it is practically possible to produce without any problem without adding an alcohol or the like.

A catalyst is not essential for this reaction, but an acid such as hydrochloric acid, acetic acid, hydrofluoric acid, or sulfuric acid, or an alkali such as aqueous ammonia may be used as a catalyst in some cases. The water used for hydrolysis is preferably ultrapure water or the like in order to obtain the target synthetic silica glass powder with higher purity. The amount of water to be used is not particularly limited as long as the hydrolysis reaction proceeds, but practically, it is generally added in excess of the theoretical amount (twice the molar amount of tetraalkoxysilane).

In order to keep the time required for gelation and the time required for coarse pulverization within appropriate ranges, the molar ratio of tetraalkoxysilane to water is 1:2 to 1:10, preferably 1:3 to 1:8. More preferably, it is practical to set it in the range of 1:4 to 1:7. If the amount of water is extremely high, not only does it take a long time to gel, but it also takes time for the wet gel to reach a hardness suitable for the pulverization process after gelation, and in some cases, the excess water must be evaporated. In addition, inconveniences such as the need for a drying step, which will be described later, may occur. On the other hand, if the amount of water is too small, hydrolysis will not proceed sufficiently, and therefore gelation will not occur sufficiently. Since the hydrolysis reaction proceeds almost completely once a uniform solution of tetraalkoxysilane and water is formed, the solution can be allowed to stand still until the solution gels and integrates.

The conditions for the hydrolysis reaction and gelation vary depending on the raw materials used, but are usually 20 minutes to 10 hours under conditions of a temperature of 20 to 100° C. and a pressure of normal pressure to 0.2 MPa. Gelation of the hydrolyzate proceeds in several hours even at room temperature and can be accelerated by heating, so the gelation time can be adjusted by adjusting the temperature conditions.

In addition, in order to facilitate handling in the pulverization treatment, after the hydrolysis reaction, a coarse pulverization treatment may be performed in which the wet gel is roughly pulverized to a size of several cm. Although the method of coarse pulverization is not limited, for example, the wet gel in the hydrolysis container after the hydrolysis reaction is placed under reduced pressure to cause cracks in the gel, and the hydrolysis container containing the wet gel is rotated or rocked. By doing so, the gel can be pulverized.

<Grinding>
The wet gel obtained by the hydrolysis of tetraalkoxysilane contains by-product alcohol and unreacted water. It is preferable to grind the wet gel at this stage in order to control the particle size of the final product. Here, a wet gel obtained by pulverizing is referred to as "pulverized wet gel".

During pulverization, wet gel is brittle and fine powder is likely to be generated. Shorter times and the use of a single-pass continuous grinder are preferred. The residence time is preferably within 1 minute, and the type of crusher is, for example, a high-speed rotary mill (hammer mill, pulverizer, etc.) of a type that crushes by impact and shear by rotating hammers, blades, pins, etc. at high speed. is preferably used. Among them, a screen mill having a built-in screen (perforated plate) for classifying the pulverized material inside the pulverizer is preferable. The pore diameter of the perforated plate is 0.5-5 mm, more preferably 0.8-3 mm.

In addition, in order to reduce or prevent the contamination of metal components during the pulverization operation, use a mesh pulverizer in which the wet gel is pressed against a mesh made of synthetic resin or the like and passed through the mesh of the mesh. can be done. When using this type of pulverizer, the mesh size and residence time may be selected in the same manner as above.

<Drying>
Next, the wet gel after pulverization is dried to remove alcohol and water contained in the gel. Drying of the pulverized wet gel is usually done batchwise. Here, what dried the wet gel is called "dry gel."

The dried gel (dry gel) is washed with pure water, etc., if necessary, to remove the solvent and catalyst used for hydrolysis, as well as the organic components derived from the alkoxy groups generated by hydrolysis. can be done.

In addition, in order to make the gel easier to handle during the baking treatment, and for the purpose of suitably adjusting the final particle size distribution range by classification after the baking treatment, the dry gel is preliminarily dried after the drying treatment as necessary. can be classified into

<Firing>
A dry gel after drying is generally porous, and is therefore unsuitable as a raw material for forming a glass layer such as a crucible. Therefore, it is preferable that the obtained dry gel is heated and sintered to be densified to obtain a non-porous synthetic silica glass powder.

The firing method is not particularly limited, but in order to keep the purity of the synthetic silica glass powder high, it is possible to fill the powder into a crucible made of quartz and heat it in an air or inert gas atmosphere as necessary. preferable. The firing temperature is generally 1000 to 1300° C., and the firing time is generally about 10 to 100 hours.

<Classification>
The synthetic silica glass powder obtained through the drying and firing steps described above contains 1% by weight or more of the synthetic silica glass powder A having a particle size larger than 300 μm in the synthetic silica glass powder, and synthetic silica having a particle size of 106 μm or less. If it contains 10% by weight or more of the glass powder B, it can be used as it is, but if not, it needs to be classified. Classification can be performed using a screen having pore sizes corresponding to the upper and lower limits of the desired particle size of the synthetic silica glass powder.
The synthetic silica glass powder of the present invention can be obtained by adjusting the pore size to be classified or by adjusting the mixing ratio of the silica glass powder classified by each pore size. Specifically, a plurality of meshes including a mesh with a pore size of 300 μm and a mesh with a pore size of 106 μm are used in a vibrating sieve, and the silica glass powder that has passed through each mesh is recovered. Then, it is obtained by mixing predetermined amounts of each recovered silica glass powder. The classification is preferably carried out so that the particle size of the entire synthetic silica glass powder is 1000 μm or less.

[3. Quartz crucible for pulling silicon single crystal]
The synthetic silica glass powder of the present invention can be applied to a quartz crucible for pulling silicon single crystals. By using the synthetic silica glass powder of the present invention and melting the silica glass powder during production of the crucible, a quartz crucible for pulling a silicon single crystal having bubbles in the silica glass layer can be obtained.

A quartz crucible for pulling a silicon single crystal is used, for example, for pulling a single crystal of silicon by the Czochralski method, and is used as a container for molten silicon containing polycrystalline silicon and melted by heating. .

The synthetic silica glass powder of the present invention may be used in the whole (entire part) of the quartz crucible for pulling silicon single crystals, but in order to generate bubbles in specific parts of the quartz crucible for pulling silicon single crystals, conventional The synthetic silica glass powder of the present invention may be used together with the raw material silica glass powder of (1), and the silica glass powder may be melted after filling a specific portion with the synthetic silica glass powder of the present invention. The part where the synthetic silica glass powder of the present invention is used in a quartz crucible for pulling a silicon single crystal is not particularly limited. It may be used in the outer layer of the outer surface of the , it may be used in an intermediate layer between the inner layer and the outer layer, or it may be used in a specific position in each layer.

When manufacturing a quartz crucible for pulling a silicon single crystal, by partially using the synthetic silica glass powder of the present invention, bubbles can be formed at desired sites. As a result, the quartz crucible for pulling a silicon single crystal can be given a function corresponding to the location of the bubble, and a quartz crucible capable of producing a silicon single crystal of better quality can be produced.

As an example, when filling the inner surface of a mold with conventional raw material silica glass powder, the synthetic silica glass powder of the present invention is filled at a position corresponding to the portion of the inner surface of the crucible in contact with the surface of the silicon melt to obtain silica glass. Powder can be melted. As a result, by containing bubbles on the inner surface of the crucible inner layer at the position where the surface of the silicon melt will be, the vibration of the surface of the silicon melt is suppressed compared to the conventional crucible manufactured from synthetic silica glass powder. can be expected.
Alternatively, when laminating and filling a plurality of silica glass powders including a conventional raw material silica glass powder, the synthetic silica glass powder of the present invention can be laminated on the intermediate layer of the crucible to melt the silica glass powder. . As a result, by having air bubbles in the intermediate layer inside the crucible wall surface, external radiant heat during crucible heating is dispersed, A reduction in the temperature unevenness of the silicon melt can be expected.

As described above, by using the synthetic silica glass powder according to the present invention as a raw material, it is possible to manufacture a crucible for manufacturing a solar cell (a crucible for pulling a silicon single crystal). Applications of the powder are not limited to this.

Hereinafter, the present invention will be described using examples. However, the present invention is not limited to this.

Synthetic silica glass powders according to Examples 1 to 3 and Comparative Examples 1 and 2 were produced according to the method described above. The synthetic silica glass powders according to Examples 1 to 3 and Comparative Examples 1 and 2 were classified in advance to remove synthetic silica glass powder having a particle size larger than 1000 μm.

(Measurement of particle size)
The particle size of the synthetic silica glass powder produced was measured by shaking for 10 minutes with a multi-stage sieve shaker having meshes with openings of 425 μm, 300 μm, 212 μm, 150 μm, 106 μm, 75 μm, and 45 μm. The weight of the flour on each screen was calculated from the difference between the weight and the total weight of the screen and flour. Table 1 shows the relationship between the particle size of the synthetic silica glass powder calculated from the opening of the mesh and the content (% by weight) (the content is rounded off to the second decimal place).

(Method for measuring the number of bubbles in molten glass)
The number of bubbles when the manufactured synthetic silica glass powder was melted to form a glass layer was examined. The method is as follows.
First, 45 g of synthetic silica powder was weighed into a graphite crucible with a capacity of 50 cc, and the surface was flattened by tapping. Then, this graphite crucible was heated in a vacuum heating furnace at 1780° C. for 1 hour and then cooled to obtain a columnar silica fused glass ingot. Bubbles in the obtained ingot were observed using a magnifying glass, and the number of bubbles having a diameter of 0.5 mm or less formed in the transparent glass layer in a bubble-free state was counted. It was confirmed that no bubbles exceeding 0.5 mm in diameter were generated in Examples 1 to 3 and Comparative Examples 1 and 2.

When the synthetic silica glass of Examples 1-3 was used, air bubbles were generated. Also, the size of the air bubbles was appropriate. On the other hand, in the synthetic silica glass of Comparative Examples 1 and 2, no bubbles were generated.

Claims (5)

A method for producing synthetic silica glass powder for quartz crucibles containing synthetic silica glass powder A and synthetic silica glass powder B,
The particle size of the synthetic silica glass powder A is larger than 300 μm,
The synthetic silica glass powder B has a particle size of 106 μm or less,
When the total amount of the synthetic silica glass powder is 100% by weight,
The content of the synthetic silica glass powder A is 1 wt% or more and 15 wt% or less ,
The content of the synthetic silica glass powder B is 10 % by weight or more ,
The manufacturing method is
a. obtaining a tetraalkoxysilane hydrolyzate by hydrolysis of the tetraalkoxysilane;
b. pulverizing the tetraalkoxysilane hydrolyzate to obtain a pulverized product;
c. obtaining a dry gel by drying the pulverized product;
d. calcining the dry gel to obtain a calcined dry gel; and e. classifying the fired dry gel;
including
A method for producing a synthetic silica glass powder for a quartz crucible, wherein the firing is performed in an air or inert gas atmosphere. 2. The method for producing synthetic silica glass powder according to claim 1, wherein the proportion of the synthetic silica glass powder having a particle size of greater than 1000 [mu]m is 3% by weight or less with respect to the total amount of the synthetic silica glass powder. 3. The method for producing synthetic silica glass powder according to claim 1, wherein the synthetic silica glass powder A has a particle size of 425 [mu]m or less. The method for producing synthetic silica glass powder according to any one of claims 1 to 3, wherein the particle size of said synthetic silica glass powder B is larger than 45 µm. Synthetic glass silica powder for a quartz crucible containing synthetic silica glass powder A and synthetic silica glass powder B,
The particle size of the synthetic silica glass powder A is larger than 300 μm,
The synthetic silica glass powder B has a particle size of 106 μm or less,
When the total amount of the synthetic silica glass powder is 100% by weight,
The content of the synthetic silica glass powder A is 1 wt% or more and 15 wt% or less,
The content of the synthetic silica glass powder B is 10% by weight or more,
Synthetic glass silica powder for quartz crucibles.

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