JP2859984B2 - 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.

[0003]

However, according to 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 indicated electromotive force is also changed every time the crucible is arranged. Due to such a large difference, the temperature cannot be measured accurately, and thus the quality of the obtained single crystal deteriorates if the melt is not sufficiently melted or the crystal formation is started with the temperature of the melt too high. I see
This may also take a month to grow the crystal and then notice a problem with the quality of the single crystal. When the crystal is grown and cooled to room temperature, the electromotive force of the thermocouple is inaccurate. Since the disadvantage that the liquid does not crystallize sometimes occurs, accurate temperature measurement is required for this.

[0004]

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 can solve such disadvantages, and which comprises platinum and platinum rhodium which can generate a thermoelectromotive force. A crucible is formed by using one of the two metals of the alloy, and the other metal is attached to the crucible as a thermocouple. The crucible has a thermoelectric thermometer function. And a crucible for producing a single crystal, and using the crucible to produce a single crystal from a melt by Bridgman.

That is, the present inventors have conducted various studies on a method for accurately measuring the temperature during the production of a single crystal in the Bridgman method. We found that if we made one of the two metals and attached this other metal to it, the crucible itself would become a thermoelectric thermometer, so we could measure this temperature accurately. The present invention has been completed. This is described in more detail below.

[0006]

The present invention relates to a crucible for producing a single crystal and a method for producing a single crystal, which is one of two metals, platinum and platinum-rhodium alloy, which can generate a thermoelectromotive force in the crucible in the Bridgman method. Make a crucible with the metal
Another type of metal is attached thereto, and a single crystal is manufactured by the Bridgman method using this crucible.

In the crucible for producing a single crystal according to the present invention, as described above, a crucible is made of one of two metals, platinum and a platinum-rhodium alloy, which can generate a thermoelectromotive force, and another metal is added thereto. It is constituted by mounting. By joining both ends of two kinds of different metals to this thermoelectromotive force, 2
The electromotive force generated in this circuit when the contacts are kept at different temperatures.This is called the Seebeck effect and is used for thermocouples. R thermocouple is platinum and platinum 87%, rhodium 13
% Of the alloy.

[0008] The crucible for producing a single crystal according to the present invention is constituted as described above, and since the crucible itself becomes a thermoelectric thermometer, the temperature can be measured accurately.
The two kinds of metals that can generate a thermoelectromotive force in the crucible are made of platinum and an alloy of 87.2% of platinum and 12.8% of rhodium.

The crucible for producing a single crystal of the present invention is made of a combination of the above-mentioned two metals, platinum and a platinum-rhodium alloy, which is used for producing a ferrite or oxide single crystal by the Bridgman method. Since it is usually made of platinum, for example, this crucible is made of platinum, and this crucible is regarded as platinum of an R thermocouple. At one end of this crucible, the above-mentioned platinum 87% and rhodium 13% At the same time as welding the fine wire of the alloy consisting of: and welding the fine platinum wire of the same material as the crucible to the other end of the crucible, take out the platinum fine wire and the platinum rhodium alloy fine wire at room temperature or at a temperature of 0 ° C. Since an electromotive force is generated between the welded end and the end taken out at room temperature due to the Seebeck effect, it is possible to accurately read the temperature at the position where the platinum-rhodium alloy fine wire is welded to the crucible. That.

In this case, when measuring the temperature of the same crucible at a plurality of locations, the thermocouple may be welded to a plurality of crucibles. In the conventional method, a platinum wire and a platinum rhodium wire are respectively placed at the same position. For welding, for example, 3
Although at least six thin wires were required to measure the temperature of the spot, in the case of the present invention, a platinum wire of the same material as the crucible only needs to be taken out from one end at one end, and this was measured 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 platinum rhodium alloy thin wire 5 at a position corresponding to a position 7 where the crystal growth is completed by pulling down the crucible 1. The fine wire 6 of the platinum-rhodium alloy is also welded to a position corresponding to the position 8 where the crucible 1 is pulled down and the single crystal growth is started. And this fine line 4,
The wires 5 and 6 are taken out of the Bridgman furnace in which the crucible 1 is installed, and 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.

[0015]

Next, examples of the present invention and comparative examples will be described. Example The apparatus shown in FIG. 1 was used, which had a diameter of 50 mm and a length of 50 mm.
The diameter of the platinum crucible 1 is 100 mm
A seed tube 2 made of platinum having a length of 5 mm and a length of 50 mm is provided, and a seed 3 of LBO to be grown is inserted into the seed tube 2.

The upper end of the crucible 1 has a diameter of 0.
A 5 mm, 200 mm long platinum wire is welded. At a position 7 70 mm from the tip of the crucible 1 and a position 8 20 mm from the tip of the seed tube 2, an alloy of 87% platinum and 13% rhodium is used. The thin wires 5 and 6 having a diameter of 0.5 mm and a length of 200 mm were welded, and these thin wires 4 and 5, 4 and 6 were wired so that the thermoelectromotive force could be measured.

Next, 300 g of LBO polycrystal is charged into the crucible 1 and the crucible 1 is set in the Bridgman furnace 9 and then the furnace is heated. The temperature at the position 8 is the melting point of LBO.
After adjusting the temperature at 917 ° C and the temperature at position 7 to 1,000 ° C, lower the crucible at a speed of 0.5 mm / hour and read the temperature at position 7 during the descent. This is the melting point of LBO. When the temperature reached 917 ° C or less, for example, 900 ° C, it was judged that all the LBO in the crucible had become a single crystal. When the single crystal was taken out from the crucible 1 after cooling to room temperature, no polycrystal was found. No clear LBO single crystals were obtained.

Comparative Example Next, for comparison, a single crystal of LBO was manufactured using the conventional crucible furnace 11 shown in FIG. The crucible used here
11 is 50 mm in diameter, like the crucible 1 used in the embodiment,
This is a pointed cylindrical platinum tube with a length of 100 mm and a platinum seed tube with a diameter of 5 mm and a length of 50 mm with an LBO seed 13 inserted at its lower end in the same manner as the crucible 1 of the embodiment. There are twelve.

However, the temperature measurement in this case is performed by a known thermocouple, and therefore includes a thin wire of an alloy consisting of 87% platinum and 13% rhodium having a diameter of 0.5 mm and a length of 200 mm. A thermocouple 14 with a 0.5 mm diameter, 200 mm length of platinum wire welded to the end of a platinum wire is inserted into an alumina protective tube 15, and this end 16 is attached to the seed tube 12 with a platinum wire 17,
The thermocouple 14 was taken out of the Bridgman furnace 20 and wired so as to measure the electromotive force.

Next, 300 g of LBO polycrystal was charged into the crucible 11, the crucible 11 was set in a Bridgman furnace 20, and the furnace was heated.
After lowering the crucible at a speed of 0.5 mm / hour, and lowering the crucible by 100 mm because the distance between position 19 and position 18 at the end of growing is 100 mm, Judging that all of the LBO polycrystals 21 in the crucible had become single crystals, cooled to room temperature over 12 hours and took out the single crystal from crucible 11 after cooling. However, cracks were generated from here because they contained polycrystals. In this case, since the wire of the thermocouple 14 which was tying the seed crystal 13 was loose and shifted from the position 18, the seed crystal and the melt were not attached, and the crystal became polycrystalline from the peak. .

[0021]

The present invention relates to a crucible for producing a single crystal and a method for producing a single crystal, which comprises one of two metals, platinum and platinum-rhodium alloy, which can generate a thermoelectromotive force as described above. The crucible is formed by using a metal of the type described above, and another metal is attached to the crucible to have a thermocouple function as a thermocouple. It becomes a thermoelectric thermometer,
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 7,19 ·· End point of single crystal growth 8・ ・ 18 ・ ・ Start point of single crystal growth 9,20 ・ ・ Bridgeman furnace 10 ・ ・ ・ ・ Polycrystalline 14 ・ ・ ・ ・ Thermocouple 15 ・ ・ ・ ・ Alumina protective tube 17 ・ ・ ・ ・ Platinum wire

──────────────────────────────────────────────────続 き Continuing from the front page (72) Inventor Toshihiko Nagao 2-13-1 Isobe, Annaka-shi, Gunma Prefecture Shin-Etsu Chemical Co., Ltd. Precision Functional Materials Research Laboratories (58) Field surveyed (Int.Cl. ⁶ , DB name) C30B 11/00 C30B 35/00

Claims (2)

(57) [Claims] A crucible is formed using one of two metals, platinum and a platinum-rhodium alloy, which can generate a thermoelectromotive force, and the other metal is attached 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.