JPS63147839A - Doping method for porous glass base material - Google Patents

Abstract

PURPOSE:To dope a desired dopant into a porous glass base material coated with a capsule contg. a doping raw material at a high concn. with high efficiency even with a small amt. of the doping raw material of low vapor pressure by putting said base material into a heating device and heating the same to the m.p. of the doping raw material or above. CONSTITUTION:The pure quartz porous glass base material 6 prepd. by a vapor chemical reaction method such as VAD method is carried to the lower part of a quartz supporting bar 7. The capsule 9 which consists of a heat resistant material such as quartz and is constituted dividably vertically or laterally at need is removably mounted to the base material so as to cover the circumference of the base material and the doping raw material 8 is housed therein. An inert gas such as He is circulated in a furnace core tube 4 installed in an electrical heater 5 of the heating device 1 through a gas inlet 2 and gas outlet 3 of said tube and is heated by the heater 5 to the m.p. of the doping raw material 8 or above. The base material 6 coated with the above-mentioned capsule 9 is inserted together with the supporting bar 7 into the upper part in the tube 4 and the material 8 is evaporated so that the material 8 is taken into the base material 6.

Description

[Detailed Description of the Invention] Industrial Application Field 1 The present invention is applicable to porous glass IJ materials used in fields such as communications and optics. The present invention relates to a method of doping with a dopant.

4. Prior Art Doped quartz is widely used as a synthetic quartz base material for optical fibers, image guides, light guides, lenses, etc.

The doped quartz described above is obtained by creating a porous glass material through a vapor phase chemical reaction method and converting the porous glass CJ material into transparent glass. Set by the next step.

One of these is when creating a porous glass base material.

Synthesize the dopant with 5i07 and add it to S i0
(Prior Art 1), another method is to make a porous glass IzI material made of pure quartz into transparent vitrification in an atmosphere containing raw materials of 1. (Prior Art 2).

As prior art other than L, there are prior inventions (Special Furnace Closure 81-2).
In the method of 02230), the melting point of the dope raw material is 4. The dope material is introduced into the porous glass fJ material in a dope atmosphere maintained at about 1°, and then the temperature of the dope material in the 8 and 11 materials is maintained at a temperature below the melting point of the dope material 1. Repeat the process of 1-culm to liquefy in the molten atmosphere,
In this way, the dopant C11 doped porous glass T-I material is transformed into transparent glass.

1 Problem to be Solved by the Invention 1 As is well known, in the method of Prior Art 1, dopants such as fluorine, phosphorus, gases, reaction products, etc., which have a high vapor pressure, or neodymium, which has a high vapor pressure, In the case of a dopant with a low value, it cannot be introduced into the flame of the gas phase chemical reaction method, and the method of Prior Art 2, which was devised as a method of adding a dopant that cannot be applied in 1, has various methods. As is known from experimental examples, it is impossible to increase dope ■.

By the way, as a method of adding fluorine with high vapor pressure, the method of prior art 2, which is made into a film, uses Sio? It is often used to lower the refractive index by doping to produce depressed clad single mode optical fibers, specifically) 1e and 5iFa or SF.
A porous glass base material made of pure quartz is made into transparent glass in a mixed atmosphere with 6 and the base material is doped with fluorine.
It will only be to a certain extent.

・On the other hand, a report on neodymium (8
In this report, in an atmosphere where NdCh was vaporized at a high temperature of 1000°C or higher, pure quartz porous glass L; However, neodymium dope at this time■
The maximum value remains at 0.3wt$.

Note that the transparent vitrification of the porous glass L and I material that also serves as neodymium doping is not carried out in an atmosphere containing 100x of dope raw material vapor as in the case of general doping, but is carried out in an atmosphere in which He coexists. The doping level is correlated with the partial pressure of NdCl3 in the atmosphere described below, and the mechanism by which neodymium is doped is that NdCl:+ diffuses into the porous glass IJ material in the high-temperature NdCl3 atmosphere. As the sintering of the porous glass base material progresses, NdG
13! ll] Said 1';) It is thought that it is confined in the material.

In addition, regarding the doped quartz after sintering described in , Nd and C
According to the results of examining 41 C degrees with 1, the behavior of C1 and Nd was similar.

Considering only this point, Nd in the above atmosphere
Doping 2-Odium into the base metal by increasing the partial pressure of Cl: t1. However, when the doping rate exceeds a certain value, the partial pressure of helium decreases, and the transparency of the L material becomes insufficient.Conclusively, even in the case of 2 ohm. Dope! 11: cannot be increased.

On the other hand, in the method of the prior invention (Japanese Patent Application No. 61-202230), even if the original dope 1 has a low vapor pressure, the dope raw material is poured into the porous glass tit material by repeating 1 as described in 1111. It is said that it can be added for 1 minute.

However, in the first invention mentioned above, since the entire area inside the core tube of the electric furnace (heating furnace) is maintained in a dope atmosphere, the dope raw material is diffused in the wide dope atmosphere, and - times (
- about 2), the dope original ability 1 uptake II; is reduced.

As a result, when trying to increase the dopant z degree in the porous f↓glass lJ material to a predetermined f〆1, a large amount of dope raw material is required, and it is necessary to repeat I to incorporate the dope raw material.
] The number of degrees increases.

In view of the problem described in 1-1, the present invention aims to provide a method that can efficiently dope a quartz-based porous glass base material with a dope material having a small amount of z5. It is.

Step 1 for solving the problems In order to achieve the intended purpose, the doping method according to the present invention:
Covering the porous glass base material with capsules containing dope raw materials,
The porous glass C7 material covered by the capsule is heated to a temperature higher than the melting point of the dope raw material. The dope raw material in the capsule described in I- is evaporated by heating it by placing it in a heating device whose temperature is maintained at .

The method is characterized in that the evaporated dope raw material is doped into a porous glass base material.

゛Example, l゛゛゛゛゛　゛゛゛゛゛゛゛　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　To! and explain.

4, the heating device (electric furnace) 1 is a gas heater [12
, a quartz-made furnace core tube 4 having a gas outlet [13], and an electric heater 5 provided for a part of the furnace core tube 4 for external use.

1- The porous glass base material 6 made of pure quartz that is processed through the heating device 1 is produced through a vapor phase chemical reaction method such as the VAD method; is supported by a support rod 7 made of quartz.

A capsule 9 having both a container function for accommodating the dope raw material 8 and a cover function for covering the porous glass I''k material 6 is attached to the support rod 7 at the removal port ff+&.

The capsule 8 is made of a thermal material such as quartz, and has a structure that can be divided downwardly or horizontally.

As shown schematically in the figure, for example, when the capsule 9 has a structure that can be divided into lower parts, the upper part 9a is attached to the outer periphery of the support rod 7 by screws, pins, etc. The one member 9b is attached to the lower end of the upper member 9d in one step, such as by screwing or fitting.

When processing the porous glass IJ material 6 through the heating device 1 described in , a step of incorporating the dope J3:trout '+ into the porous glass IJ material 6, and a step of incorporating the dope J3: Trout'+ into the porous glass IJ material 6. The process of solidifying the raw material and the process of oxidizing the dope raw material in the porous glass It material 6 are repeated as many times as necessary,
After that, a step of converting the porous glass base material 6 into transparent glass is carried out.

Each of these steps will be explained below.

At the stage of "taking the dope raw material into the porous glass base material 6," helium is supplied as an inert gas into the furnace core tube 4 of the heating device 1, and the inside of the furnace core tube 4 is heated by the electric heater 5. Kagaru core/i? A porous glass rat material 6 covered with a capsule 9 containing a dope raw material 8 is inserted into the upper part of the chamber 4 via a support rod 7.

Thereafter, the porous glass fit material 6 and the capsule 9 inside the furnace core tube 4 are lowered in a rotating state and transferred to a high temperature region within the furnace core tube 4 .

In this way, the dope raw material 8 in the capsule 9 is heated above its melting point and evaporated, and the inside of the capsule S becomes a dope atmosphere. The dope material is taken into the pores.

After the 1-p raw material 8 is incorporated into the porous glass lrJ material 6 in this way, step 1 of solidifying the dope raw material 8 in the porous glass base material 6 is continued.
．． In this case, the porous glass base material 6 may be pulled up and rapidly transferred to a low temperature region (below the melting point of the dope original material 18) in the furnace tube 4, thereby removing the dope original material in the porous glass material 6. 18 is cooled and precipitated (solidified) to a solidified state.

When the dope raw material 8 in the porous glass 1 and the J material 6 is solidified, the dope raw material 8 in the capsule S is cooled to a temperature at which it will not be oxidized by outside air, and then the lower part 9b of the capsule 9 is replaced with the upper part of the capsule. The lower member 9b is removed from the furnace core tube 4 together with the dope raw material 8.

Next, one culm of oxidizing the dope raw material 8 in the porous glass I material 8 is carried out, but at this time, oxygen is supplied into the furnace core tube 4 to maintain the inside of the furnace core tube 4 in an oxidizing atmosphere. , and the dope raw material 8 in the porous glass base material 6 is oxidized in a temperature range below the melting point of the dope raw material 8.

Through this oxidation step, the original dope 18 in the porous glass material 6 is completely fixed in an oxide state.

Hereinafter, the dope raw material oxidation process is repeated as many times as necessary to add the desired number of dopants to the porous glass material 6 in the steps 1--Introducing the dope raw material and solidifying the dope raw material.

Regarding the dope raw material intake process, porous glass I
Since the J material 6 is covered with the capsule 9,
'I + tA' I + tA The partial pressure of the contents inside the capsule S increases,
Dope raw material intake per time into porous glass 1q material: 11. There are many.

Therefore, 1. Even if each of the above-mentioned steps is repeated, the number of repetitions is small and the number of times of repetition is small, and the use of the 1.-p original '1 can also be reduced.

1. After dopant is added to the porous Karasu IzI material s as described above, a step is carried out to make the porous Karasu 747 material 6 transparent. At the same time, the inside of the furnace tube 4 is maintained at a transparent vitrification temperature, and the porous glass preform 6 is vitrified into transparent glass in this transparent vitrification atmosphere.

Thus, a transparent 1y1 glass matrix, ie, doped quartz 71) is obtained.

Next, specific examples of the method of the present invention and comparative examples thereof will be explained.

Specific example Porous glass/1 material is pure 5 made by VAD method.
Made of 102, outer diameter 30IIlfflφ, length 100
mm, and the average density is 0.35 g/cm3.

Such a porous glass nl material is supported by a quartz support rod.

The dope raw material consists of NdCl3, and the amount used is 20g.
It is.

The dope raw material is placed in a capsule, and the capsule containing the dope raw material forms a porous crow n? Covered the outer periphery of the material.

Dope! ! : (The capsule containing the material and the porous Karasumi upper material covered by it were placed in a furnace core tube (within 90 mA) in an atmosphere of He: 5 alternations/min.
After inserting them into a temperature range of 100°C or higher within mmφ and length 100100O, they were heated to 1000°C at a heating rate of 5°C/ff1in, held for 60 minutes, and NdCl
3 Haki was taken into the pores of porous glass material 2.

During the dope raw material solidification process, the porous glass IJ material after the Kitaki process is rapidly transferred to a temperature range of 400°C or less in the furnace tube, and the NdC1 diffused into the porous glass material is
One base of Qi was solidified.

During the dope raw material oxidation process, by removing the lower part of the capsule from its upper part, NdCl:
6 out of the reactor core tube, and then
A porous glass II material is placed in a temperature range of 50 to 750°C, oxygen is supplied at a rate of 10 cubic meters/min into the furnace tube, and porous glass CJ material is placed in the oxidizing atmosphere at a rate of 3.
This was held for 0 minutes, thereby oxidizing NdCl3 in the nT material to Nd2O3.

Hereinafter, the dope raw material taking-in step, the dope raw material solidification step, and the dope raw material oxidation step were repeated twice.

Transparent vitrification: At the same time, the porous glass I:J material after adding the dopant (Nd20t) by repeating each step in 1-1 was placed in a furnace tube heated to 1550°C and 100$He. By heating in a transparent vitrification atmosphere for a predetermined time, the porous glass IJ material was transformed into transparent vitrification.

When we measured the composition c degree and composition distribution of the transparent glass m material obtained from the example L silica, that is, doped quartz, we found that the average dopant concentration (Nd203e degree) was 1.ol$, and Nd2O3 was uniformly distributed in the radial direction. chlorine was not detected.

As is clear from these results, in this specific example, j,
1-
A sufficient amount of dopant addition i+1- is ensured.

In the specific example, we have described an example in which Nd2 (h) is used as a dopant, but it can also be used in other specific examples in which a metal oxide is doped using a low vapor pressure dope material such as CeCl3 or AlCl3. .

Similar to the comparative example, the porous Karas IzJ material and NdCb described above were placed in a reactor core tube in a He atmosphere, and these were
After holding at 000°C for 60 minutes, immediately heat to 1550°
Warm to 51C, s1/1. The porous glass It material was made into transparent glass.

The transparent glass fJ material obtained in this comparative example, that is, the doped quartz, was doped with only 20 t of Nd or 200 ppl of In.

In the case of one bite of this ratio, the porous glass 1: sintering occurs immediately when the partial pressure of NdC 1: taken into the pores of the upper material becomes the same as the partial pressure of NdC 1: in the doped atmosphere. Therefore, it is thought that 1.-Punt was added earlier or less.

1゛Effect of the invention 1 As explained in 1-1 below, when using the method of the present invention, the porous glass II material is doped 1! ：(Cover with 1 capsule containing 1 ml of dope, and put the material into a heating device whose temperature is maintained above the melting point of the dope raw material listed in J-). By heating, the dope raw material inside the capsule is evaporated, and the evaporated dope raw material is doped into the porous glass IJ material, so it is possible to use not only commonly used dope raw materials but also dope raw materials with low vapor pressure. Even if there is a dopant, it is possible to add the dopant into the AT sealing material with high efficiency and high concentration without using multiple dope raw materials.

[Brief explanation of the drawing]

The figure is a diagram 1J1 schematically showing an embodiment of the method of the present invention. 1... Heating device 4... Furnace tube 5 of the heating device... Electric heater 6 of the heating device... Porous glass lzI material 7... ... Porous glass base material support 8 ...
・Dope raw material 9... Capsule

Claims (1)

[Claims] Covering the porous glass base material with capsules containing dope raw materials,
The porous glass base material covered with the capsule is placed in a heating device kept at a temperature higher than the melting point of the dope raw material and heated, thereby evaporating the dope raw material inside the capsule and the evaporated dope raw material. A doping method for a porous glass base material, which comprises doping into a porous glass base material.