JP2853840B2 - Crucible for producing single crystal and method for producing single crystal - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a crucible for producing a single crystal, in particular, a novel crucible for producing a ferrite or oxide single crystal by the Bridgman method, and a method for producing a single crystal using this crucible. It is about.

[0002]

2. Description of the Related Art Ferrite and oxide single crystals have been conventionally produced by the Bridgman method. Production of single crystals by this Bridgman method, for example, lithium borate L
As shown in FIG. 2, a single crystal of i ₂ B ₄ O ₇ (hereinafter abbreviated as “LBO”) is manufactured by placing an LB on the bottom of a platinum cylindrical crucible 11 having a pointed cylindrical shape.
In addition to providing a platinum seed tube 12 into which an O seed crystal 13 is inserted,
The tip of the thermocouple 14 inserted into the protective tube 15 made of alumina is attached to the seed tube 12 with a platinum wire 17 and the LBO is attached to the crucible 11.
The temperature is measured by a thermocouple 14 at this time using a furnace in which the polycrystal is charged and installed in a Bridgman furnace 20.

However, in this conventional method, even if a thermocouple is inserted near the crucible, the measured values slightly differ depending on the arrangement of the crucible in the furnace, and the electromotive force indicated by the arrangement varies greatly depending on the arrangement. Can not be measured accurately,
Therefore, if crystal formation is started while the melt is not sufficiently melted or the temperature of the melt is too high, the quality of the obtained single crystal becomes poor, and it takes another month to grow the crystal. In some cases, the quality of the single crystal may be noticed afterwards, and when cooling to room temperature after growth, the disadvantage that the melt does not become single crystal due to the inaccurate electromotive force of the thermocouple may occur. Therefore, accurate temperature measurement is required for this.

Therefore, the present inventors formed a crucible using one of two metals, platinum and a platinum-rhodium alloy, which can generate a thermoelectromotive force, and attached the other metal to the crucible to form a thermoelectric crucible. As a pair, a crucible for producing a single crystal, which is characterized by having a thermoelectric thermometer function in this crucible, and a method for producing a single crystal from a melt using a bridgman using this crucible have been proposed. 3-267329
No.).

[0005]

However, in this case, since the platinum used here has a melting point of 1,744 ° C.,
The melting point of the single crystal is close to the melting point of platinum, for example, a crucible for manufacturing a single crystal such as gadolinium gallium garnet (GGG), lithium tantalate (LiTaO ₃ ), and lithium niobate (LiNbO ₃ ). However, there is a problem that the strength is reduced in a neutral atmosphere.

[0006]

SUMMARY OF THE INVENTION The present invention relates to a crucible for producing a single crystal and a method for producing a single crystal, which solves such disadvantages. The two metals capable of generating electromotive force are iridium and One selected from an iridium / rhodium alloy, two kinds of platinum / rhodium alloys having different platinum / rhodium ratios, tungsten and tungsten / rhenium alloys, and two kinds of tungsten / rhenium alloys having different tungsten / rhenium ratios. A single crystal crucible characterized by forming a crucible using the above metal, attaching another metal to the crucible to form a thermocouple, and having a function as a thermothermometer, and using this crucible And producing a single crystal from the melt by the Bridgman method.

That is, the present inventors have conducted various studies to develop a single-crystal crucible that can solve the disadvantages of the single-crystal crucible composed of platinum and a platinum-rhodium alloy that was developed earlier. Metal selected from iridium and iridium / rhodium alloys, two platinum / rhodium alloys with different platinum / rhodium ratios, tungsten and tungsten / rhenium alloys, and two tungsten / rhenium alloys with different tungsten / rhenium ratios The inventors have found that a crucible that can be used for producing various single crystals having various melting points can be obtained, and research on these various metals and their combinations has been advanced to complete the present invention. This is described in more detail below.

[0008]

The present invention relates to a crucible for producing a single crystal and a method for producing a single crystal, which comprises a crucible in the Bridgman method which is capable of generating a thermoelectromotive force, such as two metals, for example, iridium and an iridium / rhodium alloy, platinum. The crucible is made of any one of two metals selected from two kinds of platinum / rhodium alloys having different ratios of tungsten / rhodium, tungsten and tungsten / rhenium alloy, and two kinds of tungsten / rhenium alloys having different ratios of tungsten / rhenium. To produce a single crystal by the Bridgman method using this crucible, and according to this, various single crystals having various melting points Can be manufactured.

A crucible for producing a single crystal according to the present invention is made of a crucible made of any one of the two metals consisting of a combination of the aforementioned metals capable of generating a thermoelectromotive force as described above,
It is constituted by attaching another kind of metal to this. This thermoelectromotive force is the electromotive force generated in this circuit when two different metals are joined at both ends and the two contacts are kept at different temperatures, which is called the Seebeck effect. Which is used for thermocouples,
The two metals used here are iridium, an alloy of 60% iridium and 40% rhodium, an alloy of 80% platinum and 20% rhodium, an alloy of 60% platinum and 40% rhodium, platinum
Alloy of 94% and rhodium 6%, alloy of platinum 70% and rhodium 30%, tungsten and tungsten 74% and rhenium 26
%, An alloy of 5% tungsten and 95% rhenium, and a combination of an alloy of 74% tungsten and 26% rhenium are exemplified.

The crucible for producing a single crystal according to the present invention is constituted as described above. Since the crucible itself becomes a thermoelectric thermometer, the temperature can be measured accurately.
Two kinds of metals that can generate a thermoelectromotive force constituting the crucible are made of a combination of the above-mentioned metals.

The crucible for producing a single crystal according to the present invention is characterized in that
It is made of a combination of metals, but this is because the crucible used for producing ferrite and oxide single crystals by the Bridgman method is usually made of platinum, so for example, this crucible is made of iridium. And put this crucible in R
Considering that the iridium of the thermocouple, while welding the above-mentioned alloy thin wire consisting of 60% iridium and 40% rhodium to one end of this crucible, and welding the iridium thin wire of the same material as the crucible to the other end of the crucible, If both the iridium fine wire and the iridium rhodium alloy fine wire are taken out at room temperature or at a temperature of 0 ° C., an electromotive force is generated by the Seebeck effect between the end welded to the crucible and the end taken out at room temperature. The temperature at the position where the thin alloy wire is welded can be accurately read.

Further, in this case, when measuring the temperature of the same crucible at a plurality of locations, the thermocouples may be welded to the plurality of crucibles. In the conventional method, the thin wires are welded to the same positions, respectively. In order to measure the temperature at three places, at least six thin wires were required. However, in the case of the present invention, a thin wire of the same material as the crucible may be taken out at one end from a certain end, and this is taken for each measurement. Since it is not necessary to attach the wire at any of the places, if at least four fine wires are welded, the temperature can be measured at three places, and the measurement cost can be greatly reduced.

According to the present invention, a plurality of temperatures can be accurately measured as described above. However, if this measurement point is, for example, a single crystal growth start position, a temperature measurement error generated at the start of growth will be reduced. It is possible to reduce the problem of insufficient bonding between the melt and the seed crystal and melting of the seed crystal, and if this measurement point is a position where the growth end position can be determined, cooling before the growth is completed, Since the trouble that the melt does not entirely crystallize but partially crystallizes and cracks occur therefrom can be reduced, a high-quality single crystal can be easily and inexpensively obtained. The advantage of being able to do so is given.

FIG. 1 is a longitudinal sectional view of a Bridgman furnace using the crucible for producing a single crystal according to the present invention. A seed tube 2 is provided below the platinum crucible 1 in the figure, and a seed 3 of a single crystal to be grown is inserted into the seed tube 2, and a platinum thin wire is placed at an upper end of the crucible 1. 4 are welded.

The crucible 1 is welded with a thin wire 5 of an iridium rhodium alloy at a position corresponding to a position 7 where the single crystal growth is completed by pulling the crucible 1 down. The iridium rhodium alloy fine wire 6 is also welded to a position 8 where the crucible 1 is pulled down to start single crystal growth. And
The fine wires 4, 5, and 6 are taken out of the Bridgman furnace in which the crucible 1 is installed, and are wired so that the thermoelectromotive force of the fine wires 4 and 5 and the fine wires 4 and 6 can be measured.

Next, after the crucible 1 is charged with a polycrystal 10 for obtaining a target single crystal, the crucible 1 is set in a Bridgman furnace 9, and the furnace is slowly heated to a position. The crucible 1 is slowly lowered while measuring the temperatures at the positions 7 and 8 so that the temperature at the position 8 becomes the melting point of the single crystal and the temperature at the position 7 becomes, for example, 1,000 ° C. Is stopped when the temperature becomes lower than the melting point of the single crystal, the target single crystal can be obtained by taking out the single crystal after cooling to room temperature.

[0017]

Next, examples of the present invention will be described. Example 1 The apparatus shown in FIG. 1 was used, which had a diameter of 50 mm and a length of
A iridium seed tube 2 having a diameter of 5 mm and a length of 50 mm is provided at the lower end of a cylindrical crucible 1 made of iridium having a 100 mm sharp gauge and gadolinium gallium garnet (chemical formula: Gd ₃ Ga ₅₎ to be grown in the seed tube 2. O ₁₂ ) (hereinafter referred to as GGG) seed crystal 3 is inserted. The crucible 1 is welded on its upper end with an iridium thin wire 4 having a diameter of 0.5 mm and a length of 200 mm. The position 7 is 70 mm from the point of the crucible 1 and the position 8 is 20 mm from the tip of the seed tube 2. Contains iridium 60
0.5mm diameter, length 200mm made of 40% rhodium alloy
The thin wires 5 and 6 were welded, and these thin wires 4 and 5, 4 and 6 were wired so that the thermoelectromotive force could be measured.

Next, in this crucible 1, a polycrystalline GGG 10
The crucible 1 was set in the Bridgman furnace 9 after charging 1,000 g, and then the gas atmosphere was changed to a nitrogen atmosphere containing 2% of oxygen, and the furnace was heated. So that the temperature at position 7 is 1,85 ° C
After adjusting the temperature to 0 ° C., the crucible was lowered at a speed of 5 mm / hr, and the temperature at the lowering position 7 was read.
When it was determined that all of the GGG in the crucible became a single crystal when the temperature reached 1,750 ° C. or lower, which is the melting point of G, for example, 1,600 ° C., the single crystal was taken out from the crucible 1 after cooling to room temperature. Transparent GGG without any polycrystals
Was obtained.

Example 2 The apparatus shown in FIG. 1 was used, which had a diameter of 50 mm and a length of
A seed tube 2 made of a 94 mm rhodium 6% platinum alloy having a diameter of 5 mm and a length of 50 mm is provided at the lower end of a crucible 1 made of a 94 mm rhodium 6% platinum alloy with a 100 mm cylindrical gauge. The seed crystal 3 of manganese zinc single crystal ferrite is inserted therein.
This crucible 1 has a diameter of 0.5 mm and a length of 200 m at its upper end.
m of platinum 94% rhodium 6% alloy fine wire 4 is welded.
0.5mm diameter, 200mm long thin wires 5 and 6
And the thin wires 4 and 5, 4 and 6 were wired so that the thermoelectromotive force could be measured.

Next, 101,000 g of polycrystalline manganese zinc ferrite is charged into the crucible 1, and the crucible 1 is set in a Bridgman furnace 9, and then the furnace is heated in the atmosphere to make the position 8. So that the temperature reaches the melting point of 1,650 ° C,
After adjusting the temperature at position 7 to 1,750 ° C,
The crucible is lowered at a speed of 5 mm / hr, and the temperature at the falling position 7 is read. When the temperature reaches 1,650 ° C. or less, which is the melting point of the ferrite, for example, 1,500 ° C., all the manganese zinc ferrite in the crucible is single crystal. After cooling to room temperature and taking out a single crystal from the crucible 1, a single crystal of manganese zinc ferrite without any polycrystal was obtained.

Example 3 In Example 2, the crucible 1, the seed tube 2, and the fine wire 4 were made of platinum.
Under the same conditions as in Example 2 except that the wire 5 and the wire 6 were made of an alloy of 60% platinum and 40% rhodium were made of alloy of 80% rhodium 20%, and the single wire was made of manganese zinc ferrite polycrystal by the Bridgman method. When the crystal was produced, the obtained single crystal was a transparent manganese zinc ferrite single crystal without any polycrystal.

Examples 4 and 5 In Example 1, G was measured by the Bridgman method under the same conditions as in Example 1 except that instruments and parts made of the materials shown in Table 1 were used.
When a GGG single crystal was produced using GG polycrystal as a raw material, the obtained single crystal was a transparent single crystal without any polycrystal.

[0023]

[Table 1]

[0024]

The present invention relates to a crucible for producing a single crystal and a method for producing a single crystal, wherein the two metals capable of generating a thermoelectromotive force are iridium and an iridium / rhodium alloy, platinum as described above. Selected from two kinds of platinum / rhodium alloys having different tungsten / rhodium ratios, tungsten and tungsten / rhenium alloys, and two kinds of tungsten / rhenium alloys having different tungsten / rhenium ratios, and a crucible using one of these metals To form
It is characterized by having a function of a thermocouple as a thermocouple by attaching another metal to the crucible, but according to this, the crucible itself becomes a thermocouple,
Since the temperature can be measured accurately, the single crystal can be easily obtained by growing a single crystal with reference to this temperature.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a Bridgman furnace using a crucible of the present invention.

FIG. 2 is a longitudinal sectional view of a Bridgman furnace using a conventionally known crucible.

[Explanation of symbols]

1,11 ·· Platinum crucible 2,12 ·· Seed tube 3,13 ·· Seed crystal 4 ··· Platinum fine wire 5,6 ·· Platinum rhodium alloy fine wire 7 ··· End point of single crystal growth 8 Starting point for single crystal growth 9, 20 Bridgeman furnace 10 Polycrystalline body 14 Thermocouple 15 Alumina protective tube 17 Platinum wire 19 ..Thermocouple tips

Claims (2)

(57) [Claims] 1. Two kinds of metals capable of generating an electromotive force are iridium and an iridium / rhodium alloy, two kinds of platinum / rhodium alloys having different platinum / rhodium ratios, tungsten and a tungsten / rhenium alloy, and different tungsten / rhenium ratios. Selected from two tungsten / rhenium alloys, forming a crucible using one of these metals, attaching the other metal to the crucible to form a thermocouple,
A crucible for producing a single crystal, characterized in that it has a function as a thermometer. 2. A method for producing a single crystal, comprising producing a single crystal from a melt by the Bridgman method using the crucible according to claim 1.