JPH09255494A - Production of neodymium gallium garnet single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a neodymium gallium garnet(NGG) single crystal having low dislocation content in the single crystal, small compositional fluctuation and high quality by suppressing the content of β-gallium oxide in the molten liquid of NGG below a prescribed level. SOLUTION: A neodymium gallium garnet single crystal is produced by suppressing the content of β-gallium oxide in the molten liquid of the substance to <=0.1wt.%. The number of dislocations in the obtained NGG single crystal can be decreased and a highqualaty crystal can be produced by suppessing the β-gallium oxide content in the molten liquid to <=0.1wt.%. The β-gallium oxide content in the molten liquid can be decreased to <=0.1wt.% by decreasing the β-gallium oxide content in the starting gallium oxide to <=10wt.%. The average particle diameter of the gallium oxide to be used as a raw material is preferably adjusted to <=1mm since gallium oxide having an average particle diameter of >=1mm forms a coagulum in melting to hinder the reaction with neodymium oxide and increase the ratio of β-gallium oxide rearranged from gallium oxide at a high temperature.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for producing a neodymium gallium garnet single crystal, particularly an optical isolator,
The present invention relates to a method for producing a neodymium gallium garnet single crystal which is a substrate material used for a magneto-optical sensor or the like.

[0002]

2. Description of the Related Art Neodymium gallium garnet single crystal (Nd ₃
Ga ₅ O ₁₂ ) is used as a substrate material for optical isolators and magneto-optical sensors, but the single crystal neodymium oxide and gallium oxide are weighed to a stoichiometric composition, mixed, baked and put in an iridium crucible. , Melting temperature of 1,650 ℃ or more to melt and grow single crystal by pulling method (Journal of Crystal Grouse, 12 (197
2), P.3). In order to improve the quality of this crystal, a method of shifting the composition to the neodymium oxide side (see JP-A-62-19602) and a crystal growth method by the floating zone method (FZ method) (Journal of Japan Society for Crystal Growth, 14 (1987), P.29) are known.

[0003]

Neodymium gallium garnet single crystal (hereinafter abbreviated as NGG) has been attracting attention as a substrate material for optical isolators and magneto-optical sensors. Recently, there has been a demand for higher quality of this crystal, and there is a demand for a crystal that has few dislocations and extremely small composition fluctuation. However, although NGG is an oxide single crystal having a garnet structure, neodymium ions have a large ionic radius, so it is difficult to enter the center of the dodecahedron of the garnet structure, and the melt composition is stoichiometric with respect to the crystal composition. Therefore, there is a problem that the solid-liquid region is very narrow.

Therefore, it has been proposed to improve the quality by shifting the melt composition to the neodymium side (see Japanese Patent Application Laid-Open No. 62-19602), but it is possible to obtain a uniform composition in the NGG melt. There is a drawback that it is not always kept uniform. In addition, since NGG has a small solid solution region, F
Although the crystal composition can be made uniform even by the Z method, there is a problem that it is difficult to produce an NGG single crystal having a diameter of 25 mm or more.

[0005]

In order to solve such disadvantages and problems, the present invention provides a method for producing an NGG single crystal, wherein the content of β-type gallium oxide contained in the melt of the single crystal is Is 0.1% by weight or less.

[0006]

BEST MODE FOR CARRYING OUT THE INVENTION In the production of NGG single crystal according to the present invention, the melting point of NGG single crystal is 1,650 ° C., whereas the melting point of gallium oxide is 1,740 ° C. If gallium oxide is taken into the NGG single crystal as it is, it is possible that it will be present in the melt without doing so, and composition change will occur in a minute region, and dislocation will also occur from there. On the other hand, it was considered that gallium oxide changes into β-type crystal form at high temperature to become a compound insoluble in acid and alkali. As a method for measuring β-type gallium oxide in the melt of NGG single crystal, the melt was once cooled to room temperature, a predetermined amount of solid matter was collected, and the sample was heated in concentrated hydrochloric acid at 60 ° C or higher. It can be determined by measuring the weight of the undissolved residue when dissolved. Therefore, the amount of β-type gallium oxide was measured by the above method for the melt of NGG single crystal obtained by weighing neodymium oxide and gallium oxide in a stoichiometric ratio and melting them according to the present invention. When the content of type gallium oxide is 0.1% by weight or less, the number of dislocations in the obtained NGG single crystal can be reduced, and the crystal can be made high quality.

Although β-type gallium oxide is produced when gallium oxide reaches a high temperature, the content of β-type gallium oxide contained in the raw material gallium oxide is 10%.
Since the content of β-type gallium oxide in the melt increases when the content is more than 10% by weight, the β-type gallium oxide in the raw material must be β-type gallium oxide in order to reduce the content of β-type gallium oxide in the melt to 0.1% by weight or less. It was found that the gallium oxide content should be 10% by weight or less.

Further, when the average particle diameter of the gallium oxide as the raw material is 1 mm or more, it does not easily react with neodymium oxide because it aggregates when it melts, and the proportion of dislocation to β-type gallium oxide at a high temperature is high. Therefore, the average particle size is 1 mm
It was confirmed that the following is recommended.

[0009]

Next, examples of the present invention and comparative examples will be described. Example 1 1,745 g of 4N neodymium oxide having a purity of 99.99% (the same applies hereinafter)
1,255 g of 4N gallium oxide were weighed out, mixed and baked at 1,000 ° C, then placed in an iridium crucible with a diameter of 100 mm and a height of 100 mm and heated to 1,650 ° C or higher by high frequency heating to melt it. .

Next, the melt was once cooled to room temperature and solidified to obtain 5.0 g of a sample, which was concentrated in 50 ml of concentrated hydrochloric acid.
The solution was heated and dissolved at 100 ° C., and the insoluble residue produced at that time was weighed to find 2.4 mg (0.048% by weight). Next, this cooled solid body is reheated to 1,650 ° C. or more to form a melt, and an NGG single crystal having a diameter of 50 mmφ and a length of 60 mm is pulled up at a pulling rate of 3 mm / hour, and a wafer for evaluation is cut out from this single crystal. When the number of dislocations in this wafer was examined by etching with hot phosphoric acid, it was only 5.

Example 2 4N gallium oxide was calcined at 1,000 ° C. to obtain 5.0 g
The sample was sampled, put in 50 ml of concentrated hydrochloric acid and dissolved by heating at 100 ° C., and the weight of the insoluble residue produced at this time was measured to be 300 mg (6% by weight). Then
1,745 g of 4N neodymium oxide and the above 4N gallium oxide
Weigh 1,255g, mix these and bake at 1,000 ℃,
This 3,000 g was put into an iridium crucible having a diameter of 100 mmφ and a height of 100 mm, and was heated to 1,650 ° C. or higher by high frequency heating to melt it.

Next, the melt was cooled and solidified to obtain a sample.
5.0g was collected, put in 50ml concentrated hydrochloric acid, dissolved by heating at 100 ℃, the weight of the insoluble residue was measured,
It was 2.7 mg (0.054% by weight).
Reheat to 650 ℃ or higher to obtain a melt, and the diameter is 50mm
A φ, 60 mm long NGG single crystal was pulled at a pulling rate of 3 mm / hour, a wafer for evaluation was cut out from this single crystal, and the number of dislocations in the wafer was examined by etching with hot phosphoric acid. It was

Example 3 After passing 4N gallium oxide through a 1 mm mesh, 1 mm
A sample below the mesh was sampled, baked at 1,000 ° C, sampled at 5.0 g, put in 50 ml of concentrated hydrochloric acid, dissolved by heating at 100 ° C, and the weight of the insoluble residue was measured. It was 320 mg (6.4% by weight). Then, 1,745 g of 4N neodymium oxide and 1,255 g of 4N gallium oxide that had been dispensed above were weighed and baked at 1,000 ° C.
This 3,000 g was put into an iridium crucible having a diameter of 100 mmφ and a height of 100 mm, and was heated to 1650 ° C. or higher by high frequency heating to melt.

Next, the melt was cooled and solidified to obtain a sample.
5.0 g was taken, put it in 50 ml concentrated hydrochloric acid, dissolved by heating at 100 ° C, and weighed the insoluble residue.
(0.042% by weight), so this solid was
Reheat to the above temperature to obtain a melt. From this, diameter 50 mmφ, length 60
mm NGG single crystal is pulled at a pulling rate of 3 mm / hour,
When a wafer for evaluation was cut out from this single crystal and etched with hot phosphoric acid, the number of dislocations in this wafer was examined, and only three were found.

Comparative Example 1 4N neodymium oxide 1,745 g and 4N gallium oxide 1,255 g
Weigh this, mix it, and bake at 1,200 ° C, then put it in an iridium crucible with a diameter of 100 mmφ and a height of 100 mm, heat it by high frequency heating to 1,650 ° C or higher to melt it, and once cool it to solidify. A 5.0 g sample was taken, placed in 50 ml of concentrated hydrochloric acid, dissolved by heating at 100 ° C., and the weight of the insoluble residue was measured to be 6.0 mg (0.12% by weight).

Next, the solid body is heated again to 1,650 ° C. or higher to form a melt, and N having a diameter of 50 mmφ and a length of 60 mm is formed from the melt.
A GG single crystal was pulled at a pulling rate of 3 mm / hour, an evaluation wafer was cut out from this single crystal, and the number of dislocations was found by etching with hot phosphoric acid to find 30 dislocations.

Comparative Example 2 4N gallium oxide was calcined at 1,200 ° C.
Take a sample of this, put it in 50 ml of concentrated hydrochloric acid, and
It was dissolved by heating at ℃, and the weight of the insoluble residue was measured.
It was 00 mg (12% by weight). Then, 1,745 g of 4N neodymium oxide and 1,255 g of the above 4N gallium oxide were weighed, mixed and baked at 1,200 ° C., and 3,000 g of this was put in an iridium crucible having a diameter of 100 mmφ and a height of 100 mm,
It was heated to over 1,650 ℃ by high frequency heating and melted.

Next, this is once cooled and solidified,
Take 5.0g sample and put it in 50ml concentrated hydrochloric acid, 1
The weight of the insoluble residue was measured by heating and melting at 00 ℃.
It was 7.2 mg (0.144% by weight).
It is heated to 1,650 ℃ or higher to form a melt, and the diameter is 50mm.
A φ, 60 mm long NGG single crystal was pulled at a pulling rate of 3 mm / hr, a wafer for evaluation was cut out from this single crystal, and the number of dislocations in this wafer was examined by etching with hot phosphoric acid. It was

Comparative Example 3 4N gallium oxide having a size larger than 1 mm mesh was taken out through a 1 mm mesh and calcined at 1,200 ° C., and 5.0 g of a sample was taken from this, which was added to 50 ml of concentrated hydrochloric acid. The mixture was put in, dissolved by heating at 100 ° C., and the weight of the insoluble residue at this time was measured to be 1,200 mg (24% by weight). Then, 1,745 g of 4N neodymium oxide and 1,255 g of the above 4N gallium oxide were weighed and mixed to obtain 1,250
After calcination at ℃, 3,000g of this was put into an iridium crucible having a diameter of 100 mmφ and a height of 100 mm, and heated to 1650 ° C or higher by high frequency heating to melt.

Next, this was once cooled and solidified to obtain 5.0 g of a sample, which was put in 50 ml of concentrated hydrochloric acid and dissolved by heating at 100 ° C., and the weight of the insoluble residue was measured. 0.16% by weight). The solid body is heated again to 1,650 ° C or higher to form a melt, and the diameter of 50
An NGG single crystal of mmφ and a length of 60 mm was pulled at a pulling rate of 3 mm / hour, and a wafer for evaluation was cut out from this single crystal,
When the number of dislocations in this wafer was examined by etching with hot phosphoric acid, there were 50 or more.

[0021]

EFFECTS OF THE INVENTION According to the present invention, high-quality NG having a small number of transitions can be obtained by achieving micro homogenization in the melt.
A G single crystal can be obtained.

Claims (3)

[Claims] 1. A method for producing a neodymium gallium garnet single crystal, wherein the content of β-type gallium oxide contained in the melt of the single crystal is 0.1 wt% or less. Manufacturing method. 2. The method for producing a neodymium gallium garnet single crystal according to claim 1, wherein the content of β-type gallium oxide contained in gallium oxide which is a raw material of the single crystal is 10% by weight or less. 3. The method for producing a neodymium gallium garnet single crystal according to claim 1, wherein gallium oxide which is a raw material of the single crystal has an average particle diameter of 1 mm or less.