JPH013024A - Method for manufacturing doped quartz glass - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a method for manufacturing homogeneous, large-sized doped quartz glass that can be applied to quartz laser glass, glass filters, fluorescent glass tubes, optical lenses, and the like.

[Conventional technology]

Various methods have been proposed for producing doped silica glass, but they can be broadly classified into the following three methods.

(i) Flame oxidative decomposition melting method (ii) Soot-containing vitrification method (iii) Sol-gel method [Problems to be solved by the invention] However, with the conventional methods, homogeneous and large-sized doped quartz glass has not been obtained.

The flame oxidation decomposition melting method generates striae and is difficult to scale up. Additionally, there are many drawbacks, such as extremely low conversion efficiency of raw materials and energy, and the need for special equipment. In the soot-containing vitrification method, it is difficult to control the amount and distribution of dopant added, and it is essentially impossible to produce a homogeneous glass body.

The sol-gel method allows for the homogeneous addition of dopants in liquid form at room temperature, and is theoretically the best method for producing doped glass. However, with the conventional method, bubbles and cracks are likely to occur, and it is not possible to increase the size or improve the quality.

Therefore, the obtained doped quartz glass was far from being of practical use, and had bubbles, striae, cracks, etc., and the homogeneity of the glass body remained in a fragmentary shape.

Silica glass is difficult to thermally process, and it is preferable to mold it into the desired shape in one shot in order to maintain homogeneity, but to date there has been no method that allows this.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for easily producing homogeneous, large-sized doped quartz glass and doped glass that can be applied to quartz laser glasses, glass filters, fluorescent glass tubes, optical lenses, and the like.

[Means for solving problems]

The method for producing doped quartz glass of the present invention includes a step of gelling a sol solution made of a compound containing at least an alkyl silicate, silica fine particles, and a metal element, a step of drying to create a trigel, and a step of drying the dry gel. In glass body synthesis using the sol-gel method, which consists of a step of heating dry gel to close the pores to form a glass body, the pores of the dry gel are closed using one of the following three methods.

a) Sinter in a helium atmosphere to close the pores.

b) Sintering under reduced pressure to close the pores.

C) After creating a helium atmosphere, the pressure is reduced to seal and close the pores.

[Effect]

When the sol-gel method is used, metal elements can be doped uniformly with a high Q degree. This is because the metal ions or metal compounds are vitrified while remaining homogeneously dispersed in the sol. However, the conventionally known sol-gel method, which only hydrolyzes alkyl silicate, has not been able to produce bulk glass bodies of a size that is industrially applicable.

When fine silica particles are dispersed in a solution obtained by hydrolyzing an alkyl silicate using an acidic catalyst, a porous dry gel that does not crack during drying or sintering can be produced. When the pH of the sol is adjusted to a range of 3 to 6, the polymerization rate of tetrahydroxysilane, which is a hydrolysis product, is accelerated, the network structure is strengthened, and a strong structure that is difficult to crack is formed. When this dry gel is heated to 1100° C. or higher, it becomes a transparent glass body, but the gas trapped in the closed pores generated during sintering expands due to the heat and remains in the glass body as bubbles.

Therefore, the pore-closing temperature of the porous dry gel (500
The sintering atmosphere at a temperature of 1400°C to 1400°C is important.

The gas permeability of helium in quartz glass is 8X10-'
(cc@cm-"*sec,-' ・atm-
'ak-') and oxygen exo-''(CC"
Cm"""5ec-"atm-'"k-')
and hydrogen, 6X10-"(cc@cm-' fist5e
c-'satm-' is extremely high (
Even if the gas is confined in closed pores of several hundred microns, the gas will diffuse to the surroundings and the closed pores will disappear by sintering. When the pores are closed under reduced pressure, the absolute amount of gas molecules trapped in the closed pores is small, so even when heated, they do not expand and tend to disappear. −
After creating a helium atmosphere, when the pressure is reduced to close the pores, a small amount of gas remaining in the closed pores is helium.
It is even more effective.

If the pore-closing temperature is too low, H, O, and various decomposed gases are generated in the closed pores, and become a mixed gas with the sintering atmosphere. It is necessary to control the mixing ratio and particle size of the raw silica fine particles to make the pore-closing temperature as high as possible. In the conventional sol-gel method, which only hydrolyzes alkyl silicate, foaming always occurs due to generated gas even if the sintering atmosphere is controlled.

[Example 1] Edyl silicate, absolute ethanol, water, and aqueous ammonia (29%) were mixed at a molar ratio of 1 nia, 6:4:0.08, stirred for about 5 hours, and then heated to room temperature. A fine silica particle solution with good dispersibility was prepared by aging the mixture for several days and concentrating it under reduced pressure.

Next, add 0 to ethyl/licade so that the weight ratio is 1:1.
．． A hydrolyzed solution was prepared by adding 02N hydrochloric acid and stirring for about 2 hours while cooling with water.

Silica particles! 8.1) After adjusting the I-1 value to 15 using 2N hydrochloric acid, mix the hydrolysis solution,
Stir thoroughly until a homogeneous solution is obtained. After that, this lol
In the i liquid, Ce / S i O * = 100 P
Add a predetermined amount of cerium to cerium chloride to make pm.
76; Added overnight and continued stirring for about 1 hour. The value of p + - of this i;;lt2 was adjusted to 50 using 0.4N aqueous ammonia, and gelation was performed over about 50 minutes.

This gel body is dried in a polypropylene drying container.
3%) and dried in a constant temperature dryer kept at about 60°C for about 2 times to obtain a porous gel body that does not crack even when left in the air.

This gel body is once heated at 1000C in an oxygen/nitrogen atmosphere, and after various treatments such as promotion of synthesis reaction, dehydration, and demolition, the inside of the furnace is changed to a helium atmosphere,
It was heated to 0°C and vitrified.

The glass body thus obtained was a colorless glass body with high transparency, and was in good condition with no bubbles, striae, or crystallization. Regarding larger sizes, it was possible to produce ingots with an outer diameter of about 30 cm and a thickness of about 5 cm, and rondos with an outer diameter of about 5 cm and a length of about 1 m.

An ingot with an outer diameter of 10 cm and a thickness of 3 cm was mirror-polished in parallel, and 200 nm to 5.
Transmittance was measured in the 0 μm wavelength range, but no difference was observed at each location. When the thermal strain and refractive index distribution were measured, the homogeneity was 5×10 −′ or less. It was also confirmed from chemical analysis that almost the same amount of Ce as the charged composition was contained.

Since this glass body exhibits selective ultraviolet absorption characteristics in the wavelength range of 200 to 300 nm, it can be applied as a glass filter. Also. When excited with ultraviolet light, 350-550n
Since light emission occurs in the m wavelength range, it can be applied as a fluorescent tube by manufacturing a tube-shaped glass body.

Further, when both end faces of a glass body measuring 1 cm x f cm x 3 cm were polished into parallel planes with high accuracy and laser oscillation was attempted, stable oscillation was confirmed. The oscillation wavelength was variable in the range of 350-550 nm. Repeated oscillation was sufficient, and no deterioration was observed even after long-term use.

[Example 2] 0.0 to ethyl silicate at a weight ratio of 1:1
A hydrolysis solution was prepared by adding 2N hydrochloric acid and stirring for about 2 hours while cooling with water. M fine powder silica (Aerosil OX-50) was gradually added thereto at a molar ratio of 1:1 to ethyl silicate, and the mixture was thoroughly stirred. This sol was irradiated with 28 kHz ultrasonic waves for 2 hours while being kept at 20°C, and then subjected to a centrifugal force of 1500 G for 10 minutes, and then passed through a 1 μm filter.

Thereafter, a predetermined amount of neodymium in the form of neodymium chloride was added to this sol so that Nd/S to = 1%, and aluminum in the form of aluminum nitrate was added in an amount 15 times the mole of neodymium to give a solution of about 1%. Stirring was continued for an hour. The pH value of this sol was adjusted to 4.5 using 0.4 MK aqueous ammonia, and the sol was gelated over about 2 hours.

Transfer this gel body to a drying container with an opening ratio of about 0.3%, and dry it using a constant temperature dryer kept at about 60°C.
! A porous dry gel that does not crack even when left in the air was obtained.

This porous body was heated to 1000°C in an oxygen/nitrogen atmosphere.
Various treatments such as acceleration of the condensation reaction, dehydration, and dehydration were performed. It was heated to a maximum of 1400° C. and vitrified using a vacuum furnace while maintaining the degree of reduced pressure below ITorr.

The thus obtained neodymium- and aluminum-containing quartz glass was a highly transparent blue glass body, and was in good condition with no bubbles, striae, or crystallization. Outer diameter 6mm
When both end faces of a glass rod with a length of 75 mm were polished into parallel planes with high precision and irradiated with a He-Ne laser, the attenuation due to scattering was comparable to that of YAG. When laser oscillation was attempted, stable oscillation was confirmed.

The oscillation wavelength was 1.06 μm, and no deterioration was observed even after long-term use.

When a glass body with an outer diameter of 3 cm and a length of 20 cm was used as an amplifier for a YAG laser, effective amplification was measured, making it possible to apply it as an amplifier material for a YAG laser.

[Example 3] A predetermined amount (Eu/S r
O! A sol solution was prepared by adding europium (=0.08%) in the form of europium 61 acid, and gelation and drying were performed using the same procedure.

The obtained dry gel was heated at 850° in an oxygen/nitrogen atmosphere.
Heated to C. After heating to 850° C. using a vacuum furnace and reducing the pressure to ITorr or less, helium gas was introduced to return the pressure to atmospheric pressure, and the pressure was further reduced to ITorr or less. Thereafter, without maintaining this degree of reduced pressure, it was heated to a maximum of 1350°C to vitrify it.

The europium-containing quartz glass thus obtained was 30
It exhibited selective ultraviolet absorption characteristics in the wavelength range of 0 to 400 nm, and no difference in absorption characteristics was observed between different parts of the glass body. It is a homogeneous glass body without bubbles, etc., and has a good refractive index distribution of 1X10-6 or less, so it can be applied as a glass filter.

[Example 4] A predetermined fl (T i /
A sol solution to which titanium (SiO+ = 2%) was added in the form of tetrapropoxytitanium was prepared and gelled, dried, and heated to 800° C. using the same procedure. The obtained porous body was heated to a maximum of 1350° C. in a vacuum furnace to vitrify it while maintaining the degree of vacuum at 0 and I Torr or less.

Both surfaces of a titanium-containing quartz glass having an outer diameter of 10 cm and a thickness of 3 cm were mirror-polished in parallel, and the thermal strain and refractive index distribution were measured, and the homogeneity was 5×10 −′ or less. The thermal expansion coefficient was measured in the range of 0 to 1200°C, but no difference was observed at each location.

There are no bubbles, striae crystals, etc., and it can be applied to highly reliable optical lens materials.

Furthermore, the homogeneity of the silica glass containing titanium added in the form of ultrafine particles of Chikunia instead of tetrapropoxytitanium was very high, and the same measurement showed a value of 6×10 −1 .

[Example 5] A predetermined amount (Cr/SiO,
A sol solution containing chromium (=0.1%) in the form of dichromic nitrate was prepared, gelled, dried, and 1% by the same procedure.
Heating was performed to ooo°C. The obtained porous body is
0.000°C After reducing the pressure to ITorr or less, helium gas was introduced to return the pressure to atmospheric pressure, and the pressure was further reduced to ITorr or less. From then on, while maintaining this degree of decompression, the maximum
It was heated to 350°C to vitrify it.

The chromium-containing quartz glass thus obtained was green in color, highly transparent, and homogeneous with no internal foreign substances such as air bubbles.Both end surfaces of a glass rod with an outer diameter of 6 mm and a length of 75 mm were precisely parallelized. After polishing the surface and attempting laser oscillation, stable oscillation was confirmed. The oscillation wavelength was variable in the range of 600 to 850 nm, and no deterioration was observed even after long-term use.

Since it is not difficult to increase the size to about 30 cm x 30 cm x 1 cm, application to slab type laser glass is also possible.

〔Effect of the invention〕

As described above, according to the present invention, there is a step of gelling Sol '60, which is made of a compound containing at least an alkyl silicate, silica fine particles, and a metal element, a step of drying to create a dry gel, and a step of drying the dry gel. In glass body synthesis using the sol-gel method, which consists of a step of heating and closing the pores to form a glass body, by closing the pores of the dry gel using one of the following methods,
An easy method for producing homogeneous, large-sized doped quartz glass, which can be applied to quartz laser glass, glass filters, fluorescent glass tubes, optical lenses, etc., has been provided.

a) Sinter in a helium atmosphere to close the pores.

b) Sintering under reduced pressure to close the pores.

C) After creating a helium atmosphere, the pressure is reduced to sinter and close the pores.

that's all Applicant: Seiko Epson Corporation

Claims (1)

[Claims] A step of gelling a sol solution made of a compound containing at least an alkyl silicate, silica fine particles, and a metal element, and a step of drying to create a dry gel.
In glass body synthesis using a sol-gel method consisting of a step of heating the dry gel to close the pores to form a glass body,
A method for producing doped quartz glass, characterized in that the pores of the dry gel are closed using one of the following three methods. a) Sinter in a helium atmosphere to close the pores. b) Sintering under reduced pressure to close the pores. c) After creating a helium atmosphere, the pressure is reduced to sinter and close the pores.