JPS60226498A - Preparation of starting material for single crystal - Google Patents

Abstract

PURPOSE:Boehmite which has been obtained from aluminum isopropoxide by the sol-gel method is treated with heat at high temperatures to obtain Al2O3 as a starting material for growing single crystals with no defects, especially free from bubbles, excellent clarity and good luster. CONSTITUTION:Aluminum isopropoxide is hydrolyzed, according to the sol-gel method, in an aqueous hydrochloric acid of 1-3pH at 10-20 deg. centigrade for 10-20hr to form boehmite (AlOOH). The product is heat treated at high temperature of 1,000-1,200 deg.C in air to give alpha-Al2O3. The alpha-Al2O3 is thoroughly mixed with Cr2O3 or the like, as a colorant, then pressed and sintered into a rod. The rod is set together with a seed crystal in a FZ furnace, heated for melting to allow the single crystal to grow at a speed of less than 4.0mm./hr.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field] The present invention is a raw material manufacturing method for growing single crystals by a floating zone method using alumina synthesized from aluminum isopropoxide by a sol-gel method.

[Prior art]

Conventionally, the floating zone method (hereinafter referred to as FZ method) has been widely used in research on new synthetic crystals because it allows crystals with new compositions to be easily synthesized in a short time. Many patents have also been issued regarding new methods of growing these crystals. However, there is little information regarding the quality of crystals, and crystals grown using this method tend to have many defects.
In particular, the bubbles that can be observed with the naked eye are large bubbles, and in crystals used for jewelry, they prevent the original light from reflecting and breaking, reducing the transparency and texture that are essential for jewelry. This is a major cause of decreasing the value of gemstones.

〔the purpose〕

The present invention is intended to solve the above-mentioned problems, and its purpose is to solve the above-mentioned problems in A-right crystals using alumina as a raw material.
The object of the present invention is to provide a method for producing a raw material for synthesizing alumina without air bubbles in the alumina grown by the FZ method using alumina that has been hydrolyzed with aluminum isopropoxide by the sol-gel method. .

〔overview〕

The present invention provides a method for growing a single crystal from a melt, in which when alumina (AAiOa) is used as the raw material powder for the melt, the alumina is hydrolyzed with aluminum isopropoxide and then heated at 1000°C to 1200°C. It is characterized in that the material treated at high temperature is used as a raw material for the FZ method.

In the hydrolysis of aluminum inpropoxide by the sol-gel method in the present invention, the TL solution used for hydrolysis is preferably an aqueous hydrochloric acid solution with a PHI to PH8. In addition, the optimal temperature for hydrolysis is between 10°C and 10°C, and below 10°C the hydrolysis will not be sufficient, and if this powder is used, the shrinkage rate will be large during sintering, and air bubbles will be formed inside. I don't like being trapped inside. Further, at temperatures above 20° C., hydrolysis proceeds rapidly, the particle size increases, and sinterability deteriorates, so the above-mentioned &I-4 is preferable.

In the present invention, 1 ml during hydrolysis is 14jL in the range of 10 to 20 hours, and if it is less than 10 hours, the hydrolysis is incomplete and the amount is 1 ml if it is over 20 hours. The above-mentioned range is desirable because it does not change even if it is more than that.

The product after hydrolysis in the present invention is
The optimum temperature for converting (&#OL+)1) into alumina by high-temperature treatment is in the range of 1000℃ to 1200℃ □Ah.
Below 1000℃, it changes to θ-alumina instead of α-alumina, and above 1200℃, it changes to α-alumina, but secondary particles are formed, the particle size increases, and sinterability decreases, so the above range is desirable.

The alumina raw material in the present invention is used for single crystal growth by the yz method. In the case of corantum crystals, alumina is the main raw material, and as a coloring agent, dichromium oxide or dichromium chloride is added for ruby, dichromium oxide and nickel oxide for pavarathia, and ferric oxide and titanium oxide are added for blue sapphire, in an alumina mortar. Mix well, pack the mixed powder into a rubber tube, and pressure mold it into a round bar shape using a rubber press. Furthermore, the molded body is sintered in an electric furnace, and F
By using the alumina raw material synthesized from the above-mentioned aluminum isopropoxide, which is used as a raw material for uniaxial high content by the Z method, it is possible to synthesize crystals without any bubbles and without affecting the hardness and TL of these colorants. Can be done.

Using the alumina raw material in the present invention, the length is 701 ul.
, straight @ = 8 wx raw material rod formed into a round rod shape is
The seed crystals are hung on the upper shaft of the device (infrared heating single crystal manufacturing device) and all the seed crystals are installed on the lower shaft.T: Isolate from the outside air with a quartz glass tube and let air flow into it.Then, heat it. , a molten body is formed between the raw material and the seeds, and both of them are simultaneously moved downward at a constant speed to grow the seed crystals.At this time, the downward movement speed, that is, the growth rate is 4. At .0 ma/H or higher, air bubbles are included in the crystal, and at 4.0 us/H, air bubbles are included in the crystal.
Less than H is desirable.

[Example 1] Accurately punch 80 f of aluminum impropoxide (AA (OCH (CHsh) a) of special reagent grade (purity 99.9% or higher) in an alumina mortar. Grind it as finely as possible, add 160 square meters of an aqueous solution of PH2 hydrochloric acid, and stir well to make a sol.

Furthermore, this alumina mortar was placed in a constant temperature bath at a temperature of 15°C.
Leave it for 6 hours to completely hydrolyze it.

When the hydrolysis is completely completed, this sol-like boehmite (A7UOH) is transferred to a platinum melting vessel and heated to 110°C in an electric furnace.
Calcination is performed at 0°C for 2 hours to combine α-alumina.

The alumina 19.8F, dichromium chloride (c7CZs)
) Weigh 0.417F into an alumina mortar, add 20cc of distilled water and mix well. After drying the steamed water, the mixture was packed into a rubber tube with an inner diameter of 10 mm, sealed, and molded for about 15 minutes using a rubber press at a pressure of 1 ton/cm.Furthermore, the molding raw material rod was pressed with a platinum wire. It was suspended in an alumina tube to prevent contamination from the heater, and sintered at 1650°C for 20 hours using a box-type electric furnace.The sintered raw material rod was used to produce a ruby single crystal using an FZ apparatus. The growing conditions are shown below.

Growth rate: 2゜0 shoulder - Upper shaft rotation speed: 45 rpm Lower shaft rotation speed: 15 rpm Seed: Corundum single crystal Atmosphere: Air flow #40 A/min The crystals grown by the above method have a length of 40 wings and a diameter of It was a high-quality ruby single crystal with a round rod shape of 8.0 yen, uniformly colored throughout, and no bubbles observed even under a magnification microscope.

[Example 2] Alumina 19.8F and dichromium oxide (Cr!Os) 0.29%, which were synthesized in the same manner as in [Example 1], were accurately weighed into an alumina mortar, and a Diflon was added thereto and mixed well. A baked Mi raw material rod was made according to [Example 1] below, and the growth rate was 1.
．． A ruby single crystal was grown according to [Example 1] under the growth conditions other than 0 g/)1.

The crystal grown by the above method has a length of 40 wings and a diameter of 8+++s.
It was a round rod-shaped ruby single crystal, uniformly colored throughout, and with no bubbles observed even under a high-power microscope.

[Example 3] Alumina 19.8? synthesized in the same manner as [Example 1] Add Ron and mix well. Hereinafter, a sintered raw material rod was prepared according to [Example 1], and a blue sapphire single crystal was grown under the growth conditions according to [Example 1]. The crystal grown by the above method had a length of 40 mm and a diameter of 8 mm.

IIj round bar shape, uniformly coated in 1c7i 4 colors,
Furthermore, it was a high-quality blue sapphire single crystal with no bubbles observed even under a high-power microscope.

〔effect〕

As described above, according to the present invention, in growing a single crystal from a melt, alumina necessary for crystal synthesis is obtained by hydrolyzing aluminum isopropoxide using a sol-gel method.
By using alumina synthesized by high-temperature processing of the boehmite (AJ%00H) produced, there is no need to pay close attention to the sintering conditions of the raw material or the conditions for crystal growth.
If the growth rate is easily less than 4-0/8,
Bubble-free crystals can be synthesized. This invention is
This will have a significant effect on the productivity of artificial gemstones, and will also greatly contribute to crystal synthesis technology for electronic phase materials.

that's all

Claims (1)

[Claims] (1) In the method of growing a single crystal from a melt, the above-mentioned
When alumina (AlkzOs) is used as the raw material powder for the melt, the alumina is processed by converting aluminum isopropoxide into boehmite (AA○OH) by a sol-gel method and then treated at still temperature. A method for producing raw materials for single crystal growth. (2) The hydrolysis temperature by the sol-gel method is 11)
The method for producing a raw material for single crystal growth according to claim 1, wherein 1HJ is in the range of IO time to addition time. (8) The scope of the claim is that the still temperature treatment of boehmite (A100H) is carried out in the air at a temperature in the range of 1000°C to 1200°C! ! ! The method for producing raw materials for single crystal growth described in Section 1. (4) The method for producing a raw material for single crystal growth according to claim 1, wherein the former method for producing a IIt raw material is for single crystal synthesis by an infrared condensing floating zone method. (5) The method for producing a raw material for single crystal growth according to claim 1, characterized in that the crystallization is carried out at a growth rate of 4.0-min.