JPH0196036A - Production of doped quartz glass - Google Patents

Abstract

PURPOSE:To reduce the valency of an added metal when a glass body is synthesized by a sol-gel process by carrying out vitrification by heating in an atmosphere of a nonoxidizing gas under reduced pressure. CONSTITUTION:Sol prepd. with alkyl silicate, fine silica particles and a compd. contg. a metallic element as starting materials is converted into gel and this gel is dried. The resulting dry gel is heated at >=300 deg.C in an atmosphere of an inert gas such as He, Ar or N2, hydrogen or a reducing gas such as CO or H2S under reduced pressure. By the heating, the pores in the dry gel are sealed to obtain a glass body.

Description

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

[Conventional technology]

Although various methods have been proposed for producing doped silica glass, they can be roughly divided into the following three methods.

(i) Flame oxidative decomposition melting method (ii) Soot-mixed vitrification method (iii) Sol-gel method [Problems to be solved by the invention] The sol-gel method allows for the homogeneous addition of dopants in a liquid state at room temperature, and is logically This is the most excellent method for producing doped glass. Doped silica glass only exhibits applicable functions when the ionic valence of the added metal can be controlled. For example, Ti'', Cr'', Ce'' etc. oscillate as a laser, but Tt4+, Cr'', Ce'' do not oscillate.

In the conventional sol-gel method, the ionic valence of the metal at the time of addition is such that the fluorescence is maintained even in the sintered glass body, but it generally shifts to a higher ionic valence and has the problem of not being able to fully demonstrate its function. .

SUMMARY OF THE INVENTION The present invention aims to solve these problems, and its purpose is to provide a manufacturing method in which the ionic valence of the added metal can be controlled at a low valence.

[Means for Solving the 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, and drying the sol solution. In glass body synthesis using the sol-gel method, which consists of a step of creating a dry gel by heating the dry gel to close the pores to form a glass body, heating and vitrifying the dry gel under any of the conditions shown below. It is characterized by

a) Depressurized state b) Inert gas atmosphere such as He, Ar, N2, etc. C) Hydrogen atmosphere d) Reducing gas atmosphere such as Co, H, S, etc. By making the atmosphere oxidizing or reducing, the ionic valence of the added metal changes reversibly. When pore closure and vitrification are performed in a reducing atmosphere, the added metal shifts to a lower ionic valence and becomes stable. When pore closing and vitrification are performed in a vacuum or an inert atmosphere, even if the ionic valence of the metal at the time of addition is low, it is maintained and stable.

[Example 1] 280 mf of ethyl silicate and 190 ml of a 0.02 N hydrochloric acid aqueous solution were vigorously stirred to obtain a colorless and transparent homogeneous solution.

Separately, ethyl silica) 420mj2. 840 ml of ethanol and 170 m2 of 3N aqueous ammonia were uniformly mixed and left at room temperature for 3 days. Pure water 1 in cloudy sol
00 ml was added and then concentrated to 240 ml using a rotary evaporator. Furthermore, a 2N aqueous hydrochloric acid solution was added to adjust the pH to 4.0. The mixture was mixed with the hydrochloric acid hydrolysis solution described above and thoroughly stirred.

Next, add 7.1 ml of 1% cerous chloride aqueous solution (Ce/
3102-0.01 mol%) and 0.2% while stirring.
Normal ammonia water was added dropwise to adjust the pH to 4.2. Pour this sol into a Teflon container (inner diameter 5 C1!L x length 3
The solution was injected into a tube (0 cm), sealed tightly, and allowed to stand for 2 days.

The shrunken gel was placed in a polypropylene container (10CIIIX
40CIIIX 15CIllH), and the aperture ratio was 1.
I put a lid on the percentage. After drying at 60°C for 10 days, a rondo-shaped dry gel was produced.

In the atmosphere, the temperature is increased at a rate of 60°C/hr to 200°
The temperature was maintained at 1300°C and 1500°C for 5 hours. Transfer to the next vacuum furnace and heat at a rate of 60°C/hr while maintaining the degree of vacuum below 10-'Torr.
The temperature was raised to 0°C and held for 1 hour. Further 1250°C
and held for 1 hour. Vitrification has been completed,
The size was 2.5 cm in outer diameter and 15 cm in length.

The glass body thus obtained was colorless and transparent, and was in good condition with no striae or crystals observed. Chemical analysis revealed that this glass body contained the same amount of cerium as calculated. Moreover, it was confirmed from spectroscopic analysis that the abundance ratio of cerium ions in the glass was approximately (trivalent:quadrivalent)=(3:1).

Next, we investigated its fluorescence characteristics and found that it effectively generates fluorescence with excitation light of 325 nm, and its emission wavelength range is 350 nm.
It covers a wide range from nm to 550 nm, and the fluorescence lifetime is about 1
It was found that it was 20 nanoseconds. Furthermore, when we tried laser oscillation, it was confirmed that it oscillated stably. Moreover, repeated oscillation was sufficiently possible, and no deterioration was observed even after long-term use.

〔Example〕

0.0 to ethyl silicate so that the weight ratio is 1:1.
A hydrolysis solution was prepared by adding 2N hydrochloric acid and stirring for about 2 hours while cooling with ice.

There, ultrafine powdered silica (Aerosil 0X-50
) was gradually added to the ethyl silicate in a molar ratio of 1:1, 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 europium in the form of europium nitrate was added to this sol so that Eu/S io =0.1%, and stirring was continued for about 1 hour. The pH value of this sol is set to 0.
, Adjust to 4.5 using 4-standard ammonia water, and make about 2
It took a while to gel.

This gel body is transferred to a drying container with an open area ratio of about 0.3%, and dried in a constant temperature dryer kept at about 60°C in about 2 weeks. A high quality dry gel was obtained.

This porous body was heated for 1000 minutes in an oxygen/nitrogen mixed atmosphere.
After heating to a temperature of 1,400°C and performing various treatments such as promoting condensation reactions, dehydration, and removal of organic matter, the inside of the furnace was changed to a helium atmosphere, and the mixture was heated to a maximum of 1,400°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. The abundance ratio of europium ions in the glass was approximately (bivalent:trivalent)=(3:1). Can be used as a glass filter.

[Example 3] A predetermined ff1 (Ti/5i
A sol solution containing titanium (Oz = 2%) in the form of tripropoxytitanium was prepared and gelled, dried, and heated to 500°C using the same procedure. Hydrogen mixed gas (Hz/He=5%) was introduced into the furnace and heated to a maximum of 1300°C to vitrify it.

Spectroscopic analysis revealed that almost all of the titanium ions in the glass thus obtained were in a trivalent state. It was also confirmed that even when heated to 1800°C and held for 10 minutes, the ion valence remained trivalent.

When we investigated the fluorescence characteristics, the emission wavelength was 600 nm to 11
000n over a wide range. Outer diameter 3cm, length 2
When a 0 cm glass body was used as an alexandrite laser amplifier, effective amplification was measured, and the glass body can be used as a laser amplifier material.

[Example 4] A predetermined amount (Cr/SiO□
A sol solution containing chromium (=0.1%) in the form of dichromic nitrate was prepared, and gelation, drying, and
Heating was performed up to 1000°C. The inside of the furnace was changed to a carbon monoxide atmosphere and heated to a maximum of 1400°C to vitrify it.

The chromium-containing quartz glass thus obtained has a green color but is highly transparent, and spectroscopic analysis revealed that almost all of the chromium-containing quartz glass is in a trivalent state. Outer diameter 6mm length 75mm
When we attempted laser oscillation by high-precision parallel plane polishing of both end faces of various parts of the glass body, 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.

[Example 5] Europium was added in the same manner as in Example 2, and 1000
It was heated to °C to form a porous body. The inside of the furnace was changed to a hydrogen sulfide atmosphere and the temperature was raised from 1000°C to 1200°C, then 0. 1400°C while maintaining the degree of decompression below ITorr
The temperature rose to . Almost all of the europium in the glass was in a divalent state.

Even when heated to 1750°C and held for 20 minutes, the ionic valence of europium remained divalent. 300～
Since it exhibits selective ultraviolet absorption characteristics in the 400 nm wavelength range, it can be used as a glass filter.

Although the embodiments have been described above regarding several types of atmospheric gases, the types of gases are not limited to any particular element.

〔Effect of the invention〕

As described above, according to the present invention, there is 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 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 to close the pores to form a glass body, by heating and vitrifying under any of the conditions shown below, the ionic valence of the added metal can be reduced to a low valence. I was able to control it.

a) Depressurized state b) Inert gas atmosphere such as He, Ar, N, etc. C) Hydrogen atmosphere d) Reducing gas atmosphere such as CO, H2S, etc.

Claims (1)

[Claims] 1) A step of gelling a sol solution made of a compound containing at least an alkyl silicate, fine silica particles, and a metal element, a step of drying to create a dry gel, and a step of heating the dry gel. A method for producing doped quartz glass, which comprises synthesizing a glass body using a sol-gel method, which comprises a step of closing the pores to form a glass body, and vitrifying the glass body by heating under any of the following conditions. a) Depressurized state b) Inert gas atmosphere such as He, Ar, N_2, etc. c) Hydrogen atmosphere d) Reducing gas atmosphere such as CO, H_2S 2) Heating under any of the conditions a) to d) above for 300
A method for manufacturing doped quartz glass according to claim 1, characterized in that the manufacturing method is carried out at a temperature of .degree. C. or higher.