JPH07115861B2 - Method for manufacturing single crystal growing material - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention relates to a method for producing a growth raw material of a nonlinear optical crystal beta barium borate (β-BaB ₂ O ₄ or less, abbreviated as β-BBO) single crystal. Regarding the improvement of.

(Prior art) Using a barium borate hydrate (BaB ₂ O ₄ .4H ₂ O, hereinafter abbreviated as BBO hydrate) obtained by a chemical precipitation method as a growth raw material, a seed crystal was used. It was found that it is possible to grow β-BBO by a direct pulling method without using a flux in an ordinary high frequency furnace by using a platinum wire instead of (Japanese Patent Application No. 63-325207). The production method of the raw material used for growing is boric acid (H ₃ BO ₃ ) and barium chloride (BaCl
- the pH of the aqueous solution of 2H ₂ O) must be 12 or more, have used sodium hydroxide (NaOH) in the adjustment.

(Problems to be Solved by the Invention) Since sodium hydroxide (NaOH) was used for pH adjustment to obtain BBO hydrate by the chemical precipitation method, the precipitated BB
Sodium ion was included as an impurity in O hydrate. Sodium ions were also mixed in the grown raw material that had been dried after firing and washed, and as a result of impurity analysis of this raw material, about 1000 ppm of sodium ions were detected.
It is unavoidable that sodium ions will be mixed as impurities into the crystals grown from this material.
If such metal ions enter the crystal, the quality of the crystal deteriorates and the performance as a nonlinear optical material deteriorates.

(Means for Solving the Problem) When precipitating a hydrate of BBO from an aqueous solution of boric acid and barium chloride, an aqueous tetramethylammonium hydroxide (hereinafter abbreviated as TMAH) solution is used to adjust pH. By using the growing raw material obtained in this way without mixing metal ion impurities, which are harmful to the quality of crystals, in the precipitate, high quality β-BB containing no impurities can be obtained.
O single crystal can be grown.

(Function) In order to adjust the pH of the aqueous solution to be strongly alkaline, an alkali metal hydroxide is usually used. In order to precipitate BBO hydrate from an aqueous solution of boric acid and barium chloride, it is necessary to adjust the pH to 12 or higher. So far, sodium hydroxide was used to adjust the pH. However, according to this method, alkali metal ions are contained in the solution, the metal ions do not evaporate even when fired, and are contained as impurities in the growth raw material. However, if BBO hydrate was precipitated using TMAH to adjust the pH, the organic components would evaporate during firing, so that impurities would not be mixed into the growth material. TMAH is also used for pretreatment of semiconductor materials, and metal impurities with 1 ppb or less are easily available.
If the raw material obtained by this method is used, a high-quality β-BBO single crystal free from impurities can be obtained.

(Example) boric acid (H ₃ BO ₃₎ and barium chloride (BaCl ₂ · 4H ₂ O) 2: 1
The powder mixed in the above molar ratio was added little by little to water heated carefully so that the temperature did not exceed 50 ° C., and dissolved until just before saturation with water. Next, a concentrated aqueous TMAH solution was added little by little so that the pH became 12 or more, and BBO hydrate was precipitated. At this time, the reaction was carried out while cooling the container so that the temperature of the solution did not rise above 50 ° C (when the temperature rises above 50 ° C, the precipitate becomes amorphous). The precipitated BBO hydrate is washed, dried, transferred to a platinum container, and heated in an electric furnace for 1250
The mixture was heated to ℃ and kept at that temperature for about 3 hours, and then the electric furnace was turned off and naturally cooled to room temperature. As a result of impurity analysis of the thus obtained growth material, metal ions harmful to crystal quality were below the detection limit (0.1 ppm or less).

This raw material was kept warm with an alumina refractory material with an inner diameter of 40 mm and a depth of 40
A platinum crucible having a thickness of 1.5 mm and a thickness of 1.5 mm was heated, melted, and filled, and a platinum wire having a diameter of 1.5 mm was used in place of the seed crystal, and was grown by an ordinary high-frequency single crystal pulling apparatus. The upper part of the crucible was kept warm with a normal alumina refractory having a height of 12 cm. The growth atmosphere was in air, the platinum wire rotation speed was 14 rpm, and the pulling speed was 4 mm / hr. When the growth was tried under these conditions, a β-BBO single crystal having a straight copper portion of 8 mm and a length of 12 mm could be grown. As a result of impurity analysis of the grown crystal, metal ions were below the detection limit (0.1 ppm or less).

(Effect of the Invention) According to the present invention, when growing β-BBO from a BBO melt by a pulling method, it is possible to obtain a high-quality β-BBO single crystal growth raw material free from impurities.

Claims (1)

[Claims] 1. A barium borate hydrate (BaB ₂ O ₄ .4H ₂ O) which is a raw material when growing a beta barium borate (β-BaB ₂ O ₄ ) single crystal from a melt by a pulling method. In the production, when the target compound is produced by precipitation from an aqueous solution of boric acid (H ₃ BO ₃ ) and barium chloride (BaCl · 2H ₂ O),
A method for producing a single crystal growth raw material, which comprises using an aqueous solution of tetramethylammonium hydroxide ((CH ₃ ) ₄ NOH) for adjusting the pH.