JPH0297492A - Production of chrysoberyl single crystal - Google Patents

Abstract

PURPOSE:To reduce a bubble inclusion by specifying the oxygen partial pressure in the system, and thereby stably occluding only trivalent Ti in chrysoberyl at the time of growing a chrysoberyl single crystal doped with trivalent Ti ion. CONSTITUTION:BeO, Al2O3, and 0.01-1wt.% Ti2O3 as trivalent Ti are mixed, and the mixture is hydrostatically pressed to obtain a green compact. A crucible contg. the green compact is placed in a Czochralski furnace, and the furnace is evacuated to <=10<-1>-Torr. A mixture of an inert gas and 0.05-1vol.% gaseous H2 or gaseous CO or the gaseous N2 or inert gas passed through a reducing agent and a dehydrating agent is introduced into the furnace to hold the oxygen partial pressure in the system at 10<-9>-10<-17>Torr. The green compact is then melted, and the melt is pulled up at ordinary pressure at a rate of 0.5-3.0mm/hr to grow a chrysoberyl single crystal.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention uses trivalent titanium as an active ion for laser oscillation.Production of chrysoberyl (Be AJ z O) single crystal doped with trivalent titanium ions Regarding the method.

[Prior Art] Solid-state lasers are small in size, have high output, are easy to maintain, and have excellent stability, so their industrial applications are expanding.

Among these, lasers that use trivalent titanium ions as active ions can achieve continuous oscillation tuning over an extremely wide range, and are expected to be applied to a variety of uses. Chrysoberyl single crystal doped with trivalent titanium was disclosed in Japanese Unexamined Patent Publication No. 8
As shown in Japanese Patent No. 2-218288, it is an extremely promising crystal. This t11 crystal has a broad absorption band centered at 500 nm, and has a 6o.

It emits light in a wide range from n11 to over 900nII,
Tunable wavelength laser oscillation that can be tuned over this wide range is expected. In this crystal, the light source is trivalent titanium ions contained within the chrysoberyl oxide. Therefore, it is necessary to grow chrysoberyl single crystals under conditions where trivalent titanium ions can exist stably.

In the same publication, chrysoberyl single crystals are grown mainly by the high-frequency heating Czochralski method, and the growth rate is 0.5 to 3.0 m/hr.

It is said that the atmosphere is preferably hydrogen gas, nitrogen gas, argon gas, or the like.

[Problems to be Solved by the Invention] However, it is technically difficult to stably fix trivalent titanium within a chrysoberyl single crystal even if these manufacturing conditions are set strictly.

Furthermore, if commercially available nitrogen or inert gas is used as the single crystal growth atmosphere gas, only a single crystal containing a large amount of tetravalent titanium ions can be produced. In this way, the single crystal with few trivalent titanium ions is 500n11
The absorption intensity in the absorption band centered on is weak (and 800 r
Since the emission intensity in the region exceeding 900 ni from v is weak, it cannot be used for laser oscillation. Furthermore, a single crystal containing a large amount of tetravalent titanium ions has a weak absorption band in the region from 600 nm to over 900 nm. Formation of an absorption band in this region is harmful to laser oscillation.

On the other hand, in the Czochralski method, the obtained +li
There is a problem that iridium, which is a crucible material, gets mixed into the crystal. Moreover, in order to produce single crystals at low cost, it is necessary to have no bubble inclusions and to pull the crystals at a high growth rate.

In view of the problems of the prior art, it is an object of the present invention to provide an inexpensive method for producing lithoberyl single crystals that stably incorporates only trivalent titanium into chrysoberyl and has fewer bubble inclusions. shall be.

[Means and effects for solving the problems] The above objects of the present invention are achieved by controlling the oxygen partial pressure to a constant state during the growth of chrysoberyl single crystals.

That is, the method for producing chrysoberyl single crystal of the present invention includes 3
A method for producing a chrysoberyl single crystal doped with valent titanium ions is characterized in that the oxygen partial pressure in the system is set to 10-9 to ro-17 or less during growth of the single crystal.

3 (ilIi) Chrysoberyl single crystals containing titanium are grown by the high-frequency heating Czochralski method or the infrared condensing floating zone method, but the high-frequency heating Czochralski method is preferably adopted in the present invention. .

In addition, the raw materials used in the production method of the present invention include beryllium oxide (BeO) and aluminum oxide (Al2
O2) and titanium oxide (m) as a luminescent ion.
(TI 203) is added. Trivalent titanium is 0 in the crystal.
．． The titanium content is preferably 1.0% by weight. If the content of titanium is less than 0.01% by weight, the fluorescence is so weak that it cannot be used practically. Furthermore, if the titanium content exceeds 1.0% by weight, segregation of rutile (Tl 02 ) occurs and the laser cannot be used.

In the present invention, this chrysoberyl single crystal is
When growing at a temperature near 870°C, the oxygen partial pressure in the system is set at 10-9 to 10-l, preferably 10-10 to 10
-17.

When this oxygen partial pressure exceeds lo-9, the absorption coefficient at the wavelength for excitation of laser oscillation, that is, around 500 nm, is small and the oscillation efficiency is low. Moreover, bubble-like inclusions occur in the single crystal, making it impossible to obtain a high-quality single crystal.

Furthermore, if this oxygen partial pressure is less than 10-17, the refractories (Zr 02 and Al2O3) forming the furnace will evaporate significantly, and Aj20x will also scatter from the melt, resulting in a large amount of Aj203 on the surface of the grown crystal. Needle-like crystals precipitate, and sometimes the seed crystals become polycrystalline before they are immersed in the melt and allowed to grow.

In this way, in the present invention, when growing a single crystal, the oxygen partial pressure in the system is set to 10-9 to zo-17, but the atmospheric gas in the system at that time is nitrogen or Examples include a mixed gas of an inert gas such as argon and hydrogen or carbon monoxide, or a mixed gas of hydrogen and carbon dioxide or carbon monoxide and carbon dioxide. Specifically, the following atmospheric gases include: It is necessary to keep the oxygen partial pressure within the above range.

(1) Add 0.1 hydrogen gas to nitrogen or inert gas
~3.0% by volume is added to obtain an oxygen partial pressure within the above range.

(2) Add 0.05 to 1.0% by volume of -carbon oxide gas to nitrogen or inert gas to obtain an oxygen partial pressure within the above range.

(3) Bring nitrogen or an inert gas to an oxygen partial pressure within the above range using a reducing agent and a dehydrating agent.

(4) Commercially available nitrogen or inert gas is passed through a reducing agent and a dehydrating agent, and then 1 to 1000 pp.
Mix li of oxygen and 0.1 to 3.0% hydrogen gas to obtain an oxygen partial pressure within the above range. Note that in any atmospheric gas composition, mixing excess hydrogen or carbon monoxide gas will cause an explosion. Therefore, the concentration of hydrogen or carbon monoxide gas should preferably be 3.0% or less.

When growing chrysoberyl single crystals under such conditions, the growth rate is generally 0.5 to 3.0 rnIR/hr.

In growing such trivalent titanium-doped chrysoberyl single crystals, the oxygen partial pressure in the system is set within the above range for the following reason.

That is, the Czochralski method is used as a method for producing laser crystals, and can produce inexpensive and high-quality crystals, as shown in, for example, alexandrite (chrysoberyl doped with trivalent chromium ions) single crystal. However, since raw materials are melted using a crucible, it is generally necessary to consider growth conditions that prevent contamination of crucible materials. For this reason, when producing alexandrite crystals, 0.1 to 2
．． About 0% oxygen gas is intentionally added to the inert gas.

On the other hand, TI''; B e AJ 204 crystal, which uses trivalent titanium ions as laser light emitting ions, can also be grown in such an atmosphere, but this is not preferable because a large amount of tetravalent titanium is mixed therein. Therefore, in the present invention, during chrysoberyl single crystal growth.

Only trivalent titanium can be effectively incorporated into the crystal by using nitrogen, an inert gas, or a mixed gas of these gases and hydrogen or carbon monoxide to keep the oxygen partial pressure in the system within the above range. This made it possible to minimize inclusions.

[Example code] Hereinafter, the present invention will be specifically explained based on Examples and the like.

Comparative Example 1 Be O with a purity of 99.99%, A with a purity of 99.999%
12O2 and Ti2O3 with a purity of 99.9% were mixed in a molar ratio of 1:1:0.01 or 0.02, and the gas in the raw materials was removed using a hydrostatic press to obtain a green compact.

Next, the green compact was introduced into an iridium crucible in a system (Czochralski furnace) under a commercially available nitrogen gas atmosphere,
After melting, it was slowly pulled up in a Czochralski furnace at a speed of 0.5 m/hr to produce a chrysoberyl single crystal. From the oxygen and water content contained in this nitrogen gas, the oxygen partial pressure in the system was calculated to be 10-5.

FIG. 1 shows the relationship between the titanium concentration of the chrysoberyl single crystal thus obtained and the absorption coefficient at 497 tv.

In addition, bubble-like inclusions were observed in the periphery of the grown crystals when the solidification rate (ratio of melt to crystal) exceeded 7.6%, and when it exceeded 19.9%. Inclusions were generated on almost the entire surface, and it could not be used for laser oscillation. Furthermore, the coefficient of incorporation of titanium ions from the melt into the crystal was estimated to be 0.07.

Example 1 Purity'! '1.99% BaO2 purity'l19.9'l
'1% A103 and 99.9% purity Tl2O3 were mixed in a molar ratio of 1=1:0.01, and the gas in the raw materials was removed using a hydrostatic press to form a green compact.

Next, the inside of the system (inside the Czochralski furnace) was set to 10T orr.
After maintaining the following vacuum, creating an atmosphere in which commercially available nitrogen gas was passed through a reducing agent, the green compact was introduced into an iridium crucible in the system, and after melting, it was heated in a Czochralski furnace.
Under normal pressure, 0. ! A chrysoberyl single crystal was produced by slowly pulling at a rate of onm/hr. The oxygen partial pressure in the system at this time was calculated to be 10-9.

The titanium concentration of the chrysoberyl single crystal thus obtained and 497n! Figure 1 shows the relationship between the absorption coefficients in 1.

Example 2 BaO with a purity of 99.99% Al with a purity of 99.999%
2O2 and Tl2O3 with a purity of 9969% in a molar ratio of 1
:1:0.005 ratio, and the gas in the raw materials was removed using a hydrostatic press to obtain a green compact.

Next, after creating a mixed gas atmosphere in the system (inside the Czochralski furnace) of commercially available nitrogen gas and adding 0.5% by volume of hydrogen gas, a green compact was introduced into the iridium crucible in the system,
After melting, in a Czochralski furnace under normal pressure, 0.71WI
A chrysoberyl single crystal was produced by slowly pulling at a rate of t/hr. The oxygen partial pressure within the system at this time was calculated to be 10-12.

FIG. 1 shows the relationship between the titanium concentration of the chrysoberyl single crystal thus obtained and the absorption coefficient at 497 nm.

Furthermore, the grown crystal had no bubble-like inclusions at all, and the titanium ion uptake coefficient was 0.24.

Therefore, it has been found that even if the molar ratio of the titanium concentration in the raw material is small, a single crystal with a sufficiently high concentration without inclusions can be obtained.

Furthermore, as can be seen from the results in FIG. 1, Examples 1 and 2 have 497
It shows a high absorption at na+, especially Example 2 shows a significantly high absorption.

[Effects of the invention] As explained above, when growing chrysoberyl single crystals,
The production method of the present invention, in which the oxygen partial pressure in the system is kept within a certain range, provides the following effects.

(1) Since most of the titanium ions taken into the crystal become trivalent titanium ions, the absorption coefficient in the laser excitation wavelength range increases and the excitation efficiency increases.

<2) In addition, since the amount of titanium ions taken into the crystal from the melt (partition coefficient) increases, it is easy to manufacture crystals containing a high concentration of trivalent titanium ions, and impurities in the melt (in this crystal, titanium Since the amount of ions) can be reduced, the generation of inclusions due to compositional supercooling phenomenon can be prevented.

(3) Since oxidation of the iridium crucible can be prevented in principle, the amount of iridium inclusions accompanying the crystal can be reduced.

Therefore, the present invention is suitably used as a method for producing a chrysoberyl single crystal containing trivalent titanium, and the obtained single crystal is used for applications such as a solid-state laser host.

[Brief explanation of the drawing]

FIG. 1 is a graph showing the relationship between the titanium concentration and the absorption coefficient at 497 nm of chrysoberyl single crystals obtained in Examples 1 to 2 and Comparative Example 1. Patent applicant Mitsui Kinzoku Mining Co., Ltd. Agent Patent attorney Tatsuo Ito Agent Patent attorney Tetsuya Ito Draft procedure amendment 4. Yoshi, Director General of the Patent Office, December 3, 1988 1) Statement of the case 1988 Patent Application No. 249256 2, Name of the invention Method for producing chrysoberyl single crystal 3, Person making amendment case Relationship with Patent Applicant Address: 2-1-1 Nihonbashi Muromachi, Chuo-ku, Tokyo Name (618) Mitsui Kinzoku Mining Co., Ltd. Representative: Kosanbe Mashima 4, Agent: 105 Address: 2 Toranomon, Minato-ku, Tokyo 8-1-6, ``Claims column'' and ``Detailed description of the invention column'' in the specification to be amended. 7. Contents of the amendment 1. The claims are corrected as shown in the attached sheet. 2. Specification M, page 4, line 10 <7) “10-9~to-
+7 or below is corrected to ``WorlO-9~10-17 J.'' 3. In the first line of page 6 of the same book, ``The seed crystal reacts with the evaporated substance, and the seed crystal is corrected to J.'' 4. The same book. “Commercially available nitrogen gas” on page 1O, lines 4-6
... After melting, change ``to'' to ``Introduce the green compact into the iridium crucible in the system, maintain the atmosphere in which commercially available nitrogen gas is passed through the reducing agent A, and melt the raw material.'' correct. 5. In the same book, page 10, line 19 to page 11, line 2, "After melting commercially available nitrogen gas...", replace "commercially available nitrogen gas... after melting" with "a green compact is introduced into an iridium crucible in the system, and commercially available nitrogen gas is The gas is passed through the reducing agent and the raw material is melted,
” is corrected. Attached Patent Claim: ``1) A method for producing a chrysoberyl single crystal doped with trivalent titanium ions, characterized in that the oxygen partial pressure in the system is set to 10-9 to 10-17 during growth of the single crystal. A method for producing chrysoberyl single crystals.

Claims (1)

[Claims] 1) A method for producing a chrysoberyl single crystal doped with trivalent titanium ions, characterized by setting the oxygen partial pressure in the system to 10^-^9 to 10^-^1^7 during growth of the single crystal. A method for producing cresoberyl single crystal.