JPH042700A - Production of oxide crystal thin wire - Google Patents

Abstract

PURPOSE:To continuously obtain oxide crystal thin wire without void nor variation of diameter, etc., by solidifying an oxide melt having a fixed viscosity with cooling in downward laminar flow of a cooling medium, partially melting resultant raw material wire and pulling-up resultant melt through a pipe. CONSTITUTION:Powdery oxide (e.g. lithium niobate) is melted by heating to obtain a melt 1 having <=40cp viscosity. Next, a crucible 2 is filled with said melt 1 and the melt is naturally dropped from an extruding hole 13 into downward laminar flow of a cooling medium 6, then solidified in quenching to obtain a raw material wire 11 having >=1mm diameter. Thus, said raw material wire 11 is partially heated in a heating furnace 22 and melted to form a molten part 16. Next, the melt 16 is pulled up into a pipe 18 heated higher than melting point of said oxide and the melt 16 is solidified to a thin wire having <=0.5mm diameter to afford the aimed oxide crystal wire 15.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing an oxide crystal thin wire by a melting method using a powdered oxide as a starting material.

[Prior Art] Conventionally, oxide crystal wires have been manufactured using the FZ (floating zone) method, in which the wire is locally melted by condensed heating, and the melted portion is moved relatively in the longitudinal direction of the wire, and the resistance CZ, in which the wire is pulled up by heating the raw material melt by heating or high-frequency induction heating and bringing the seed crystal into contact with the melt.
(Czochralski) method is used.

However, in these methods, the wire diameter is 0.5
It is difficult to manufacture wire rods with a diameter as small as mm or less.

As a method for manufacturing an oxide crystal thin wire with a wire diameter of 0.5 mm or less, L HP G (Laser Hea
tedPedestal Growth) method (R,S,
Felgelson, “Pullng Optica.
l Fiber”+Journal of Crystal
al Groveth, Volume 79, Ili[19-11i
80 pages, 198G) and the μmCZ method (Micro-Czochralski) method (Norlo 0hnlshl e)
tal, Japanese of Journal o
f Applied Physics, Volume 28, No. 2
No. 27B-280, February 1989).

In these methods, a rod-shaped oxide sintered or a rod-shaped large crystal of an oxide produced by the above-mentioned CZ method is used as the raw material wire. In the LHPG method, a laser beam is focused on the circumferential surface of this raw material wire to form a melted part, and a crystal thin wire is grown in this melted part. In addition, in the μ-CZ method, power is supplied to a resistance heating element made of PT or the like to generate resistance heat, and the raw material wire is locally melted by this heat to form a melted part, and crystals are formed in this melted part. Cultivate fine wire material.

[Problems to be Solved by the Invention] However, in the LHPG method, controlling the output of laser light is complicated, and it is difficult to form a stable molten zone. For this reason, it is difficult to form a crystal thin wire material with a uniform wire diameter. Further, there is a problem that wire breakage is likely to occur during manufacturing, and wires with a length of 100111 m or more cannot be formed.

On the other hand, in the μmCZ method, although it is possible to form a relatively stable molten zone compared to the LHPG method, it is difficult to control the wire diameter of the thin wire because crystals are grown at the upper end of the molten zone. There is a problem.

In addition, in both methods, a rod-shaped wire is required as the raw material wire, but if a sintered body is used as the raw material wire, it is difficult to form a rod-shaped sintered body with a uniform diameter and density. For this reason, there is a drawback that the molten zone tends to become unstable and the wire diameter of the grown crystal thin wire varies.

Further, due to voids or gas components contained in the sintered body, defects such as voids are likely to occur in the thin wire material after growth, making it difficult to produce a high-quality crystalline thin wire material.

On the other hand, if a large crystal produced by the CZ method is cut and used as a raw material wire, cracks are likely to occur within the crystal, and the manufacturing yield of the raw material wire is low, so the manufacturing cost of the oxide crystal fine wire is reduced. The problem is that it is expensive.

The present invention has been made in view of such problems, and includes:
It is an object of the present invention to provide a method for producing an oxide crystal thin wire material that has a uniform wire diameter, is free from defects such as voids, and can continuously produce high-quality oxide crystal thin wire materials at low cost.

[Means for Solving the Problems] The method for producing an oxide crystal thin wire according to the present invention uses a powdered oxide as a starting material, and heats and melts this starting material to produce a molten material with a viscosity of 40 cp or less. A process of obtaining a liquid, a process of allowing this melt to naturally fall into a downward laminar flow of a cooling medium to rapidly cool and solidify it to obtain a raw material wire with a diameter of 1 mm or more, and a process of locally heating this raw material wire to melt it. A step of forming a molten zone by pulling the melt into a pipe placed at the upper end of the molten zone and heated above the melting point of the oxide to form a thin molten zone with a diameter of 0.5 mm or less. The method is characterized by comprising a step of solidifying it into a wire rod.

[Function] In the present invention, since the powdered oxide is once melted, air bubbles in the raw material powder are degassed. Then, this melt is allowed to flow out, for example, from a hole provided in the bottom wall of the crucible, and allowed to fall naturally into the downward laminar flow of the cooling medium, where it is cooled and solidified. As a result, the melt is cooled by the cooling medium while maintaining the straightness of the natural falling flow.Moreover, since the cooling medium is a downward laminar flow, the resistance of the cooling medium to the melt falling flow is extremely small, so it solidifies. Bending and deformation of the oxide wire can be avoided, and an oxide wire with excellent straightness can be obtained. Moreover, since this raw material wire is not a sintered body but a molten and solidified one, it does not contain voids or gas components and has a uniform density.

In this case, if the viscosity of the melt exceeds 40 cp, it is difficult for the melt to maintain its straightness and fall smoothly, resulting in poor straightness of the wire. In addition, the melt tends to run out, making it difficult to stably produce the oxide wire. Therefore, the viscosity of the melt needs to be 40 cp or less.

The oxide wire produced in this way is used as a raw material wire,
This raw material wire is locally heated above its melting point to form a molten part. The melt in the melting section passes through a pipe placed at the upper end of the melting section and is pulled up and solidified, so that the resulting crystalline wire has a wire diameter approximately equal to the outer diameter of the pipe. In this case, by heating the pipe above the melting point of the oxide, the melt does not solidify when passing through the pipe and passes smoothly through the pipe. Therefore, wire breakage is reliably prevented, and oxide crystal thin wires having a diameter of 0.5 mm or less can be continuously produced.

When the diameter of the raw material wire is less than 1 mm, when the raw material wire is melted to form a fused part, it is difficult to hold the fused part on the raw material wire. For this reason, the wire diameter of the raw material wire is set to 1 mm or more.

In addition, when trying to grow a crystalline fine wire with a wire diameter exceeding 0.5 mm from a melt, it is necessary to increase the amount of melt stored in the melt zone, which increases the size of the melt zone and increases the composition and viscosity of the melt zone. It becomes difficult to maintain uniformity,
Wire breakage is more likely to occur.

For this reason, it is necessary to solidify the melt into a thin wire material with a diameter of 0.5n+n or less, for example, using a pipe with an appropriate outer diameter.

[Embodiments] Next, embodiments of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is a cross-sectional view showing an apparatus for manufacturing raw material wire used in the embodiment method of the present invention.

An outflow hole 13 is formed in the bottom wall of the crucible 2 disposed in the upper part. A cooling medium 6 is placed below this crucible 2.
A cooling medium holding container 4 containing a cooling medium is arranged. Inside this container 4, a downward laminar flow generating cylinder 5 is provided with its axis in the vertical direction. The upper end of this downward laminar flow generating cylinder 5 is lower than the liquid level of the cooling medium 6 in the container 4, and the lower part thereof is inserted through the bottom wall of the container 4 and led out downward. A packet 10 for accommodating the raw material wire 11 after solidification is installed in the lower part of the downward laminar flow generating cylinder 5.

Further, a mesh 9 is attached to a connection point between the tube 5 and a pipe connecting the lower side wall of the tube 5 and the pump 7. The cooling medium 6 is sucked from the lower part of the lower laminar flow generating cylinder 5 through a mesh 9 by a circulation pump (P) 7, and is fed under pressure to a heat exchanger (HEx) 8. After this cooling medium 6 is cooled by a heat exchanger 8, it is returned to the inside of the cooling medium holding container 4. As a result, the cooling medium 6 in the cooling medium holding container 4 enters the lower laminar flow generating cylinder 5 from its upper end, and after the cooling medium 6 flows downward inside the cylinder 5,
It is discharged from the cylinder 5 by the pump 7 and is circulated and supplied into the container 4. In this way, a downward laminar flow of the cooling medium 6 is formed within the downward laminar flow generating cylinder 5.

The crucible 2 and the downward laminar flow generating cylinder 5 are arranged so that the melt flow 3 flowing out from the crucible 2 falls at the center position of the downward laminar flow within the cylinder 5. As a result, the melt flow 3 falling from the outflow hole 13 is solidified into the raw material wire 11 while maintaining its straightness without being disturbed.

In addition, in order to make the length of the raw material wire 11 a desired length, the raw material wire 11 is
It is preferable to provide a cutting device 12 that is configured to divide and cut into predetermined dimensions.

Next, the manufacturing process of raw material wire using the above-mentioned apparatus will be explained. Although this example uses lithium niobate having a melting point of I253°C, the raw material wire and the crystal fine wire can be produced in the same manner using other oxides.

First, the powder raw material of lithium niobate is melted using appropriate melting equipment (
(not shown) to degas the air bubbles in the raw material. The melt is then maintained at a temperature of 30 to 150° C. higher than its melting point.

Next, the pump 7 and the heat exchanger 8 are operated to generate a lower laminar flow of the cooling medium 6 in the lower laminar flow generating cylinder 5 .

Next, the outflow hole 13 is plugged and closed, and after the melt 1 is transferred to the crucible 2 and stored in a predetermined amount, when the plug is removed, the melt 1 naturally falls from the outflow hole 13. A melt flow 3 extending vertically downward is formed. This melt flow 3 enters the lower laminar flow generating cylinder 5 and solidifies while maintaining straightness in the lower laminar flow of the cooling medium 6, thereby obtaining an oxide raw material wire 11 of lithium niobate. This raw material wire 11 is stored in a bucket 10.

FIG. 2 is a cross-sectional view showing an oxide crystal thin wire manufacturing apparatus for manufacturing an oxide crystal thin wire from the raw material wire manufactured by the method described above.

The raw material wire 11 has its lower end fixed to a wire holder 19a attached to the raw material wire supply drive shaft 21, and is supported with its longitudinal direction being vertical.

Further, a pulling drive shaft 2 is provided above the supply drive shaft 21.
0 is arranged, and a bow lifting material 24 is attached to the wire holder 19b attached to this lifting drive shaft 20.

The supply drive shaft 21 and the pull-up drive shaft 20 can be moved up and down in conjunction with each other at a predetermined relative speed by respective drive devices (not shown).

A cylindrical heating furnace 22 is arranged in the passage area of the raw material wire 11 so as to surround the raw material wire 11 with its axial direction being vertical. This heating furnace 22 has a coil-shaped heating element 23 installed therein, and by supplying power to this heating element 23 from an appropriate power source and causing the heating element 23 to generate resistance heat,
The raw material wire 11 located inside the heating furnace 22 is preheated.

Inside the heating furnace 22 , a heating coil 17 for melting is disposed in a passage area of the raw material wire 11 . This heating coil 17 for melting has a wire diameter of 0.2 to 1.0 mm, for example.
This platinum wire is formed into a coil shape. Further, a resistance heating wire 25 is provided adjacently above the melting heating coil 17.
The resistance heating wire 25 is also formed by winding a platinum wire once coaxially with the melting heating coil 17.

The coil 17 and the heating wire 25 are supplied with power from a power source as appropriate, and by supplying electricity to the fill 17 and the heating wire 25 to generate resistance heat, the raw material in the area surrounded by the coil 17 and the heating wire 25 is heated. The wire rod 11 is heated to a temperature equal to or higher than its melting point and melted. The resulting molten material is held within the area surrounded by the coil 17 and the heating element 25 by surface tension using the wetting properties of the molten material, and a molten portion 16 is formed.

Further, a pipe 18 is disposed directly above the center of the fill 17 coaxially with the fill 17, that is, with its longitudinal direction being vertical. This pipe 18 is made of platinum, for example, and has an outer diameter of 0.1 to 0.5 mm and an inner diameter of 0.05 to 0.3 mm. This pipe 18 is also heated to a temperature higher than the melting point of the raw material wire 11 due to the resistance heat generation of the heating wire 25. Since the pipe 18 is disposed in contact with the upper end of the melting section 16 in this manner, the melt in the melting section 16 permeates through the pipe 18 and rises to the upper end of the pipe 18 according to the capillary principle.

Note that the fill 17, the resistance heating wire 25, and the pipe 18 are not limited to those molded from platinum as described above, but they must be able to be used in this temperature range.

Next, a process of manufacturing the oxide crystal fine wire 15 from the raw material wire 11 using the above-described apparatus will be described.

First, the lower end of the lithium niobate raw material wire 11 formed by the apparatus shown in FIG. 1 is fixed to the wire holder 19a of the apparatus shown in FIG. The raw material wire 11 is arranged so as to fit into the coil 17. Then, the heating element 23 is energized to preheat the raw material wire 11 in the heating furnace 22 . Further, the heating coil 17 for melting is energized to melt the raw material wire 11 locally.

As a result, a melted portion 16 is formed in a region surrounded by the coil 17. Furthermore, the resistance heating wire 25 is also energized to heat the pipe 18 to a temperature equal to or higher than the melting point of the raw material wire 11 . As a result, the melt rises within the pipe 18 and reaches the upper end of the pipe 18.

Next, the pulling drive shaft 20 is lowered, and the pulling material 2
The lower end of pipe 4 is brought into contact with the melt at the upper end of pipe 18. Thereafter, the supply drive shaft 21 and the pulling drive shaft 20 are raised at a predetermined relative speed. Then, the melt in the melting section 16 passes through the pipe 18 and exits the pipe to cool down, and the lithium niobate crystal fine wire 15 having a wire diameter determined by the outer diameter of the pipe 18 is continuously obtained.

This lithium niobate crystal thin wire 15 is carried out above the heating furnace 22 by the lifting of the pulling drive shaft 20. On the other hand, the raw material wire 11 is continuously supplied into the heating furnace 22 from below by raising the supply drive shaft 21. In this way, the raw material wire 11 of lithium niobate is transferred to the coil 17.
The melted portion 16 is reduced in diameter by the pipe 18 to a desired wire diameter, and the melt is pulled up from the upper end of the pipe 18 and solidified.

Thereby, the lithium niobate crystal thin wire material can be continuously manufactured.

Next, the results of actually manufacturing a lithium niobate crystal thin wire material using the method of this example will be explained.

A platinum crucible 2 having an outflow hole 13 with a diameter of 4 mm on the upper bottom wall of the salmon is used, and after plugging the outflow hole 13, the raw material powder of lithium niobate is placed in the crucible 2 of the apparatus shown in FIG. The mixture was heated and melted to a viscosity of 40 cp, and further degassed under reduced pressure. Thereafter, the stopper was removed, and the melt 1 was allowed to fall naturally into the lower laminar flow of the cooling medium 6. At this time, the cutting device 12 cut the melt flow 3 every 10c+n. As a result, a raw material wire 11 having a diameter of 1 mm was obtained. Then,
The second pipe is equipped with a platinum pipe 18 with an outer diameter of Q and 3 mm.
Using the apparatus shown in the figure, this raw material wire 11 is processed to have a diameter of 0.
A 3 mm lithium niobate crystal wire was manufactured.

As a result, it was possible to obtain a lithium niobate crystal thin wire having a uniform diameter of 0.3 mm.

The viscosity of the melt in the actual difference old Lux crucible 2 was adjusted to 20 cp, and the raw material wire 1 with a diameter of 5 mm was prepared in the same manner as in Example 1.
I got 1. Next, platinum pipe 1 with an outer diameter of 0.5+nm
A lithium niobate crystal wire having a diameter of 0.5 n+m was produced from this raw material wire 11 using the apparatus shown in FIG.

As a result, it was possible to obtain a lithium niobate crystal fine wire having a uniform diameter of 0.5 mm.

A raw material wire 11 having a diameter of 1 mm was obtained in the same manner as in Example 1. Next, using the apparatus shown in FIG. 2 from which the pipe 18 has been removed, a diameter of 0.5 m is obtained from this raw material wire 11.
A lithium niobate crystal thin wire material of m was manufactured.

As a result, the diameter of the lithium niobate crystal thin wire varied greatly within the range of 0.3 to 0.5 mm.

Adjust the viscosity of the melt in the pot 2 to 45 cl),
A raw material wire was produced in the same manner as in Example 1.

However, this raw material wire had a diameter of 3.5 mm, was deformed and had poor straightness, and could not be installed in the apparatus shown in FIG. 2. Therefore, it was not possible to produce a crystalline fine wire material.

L1ken1 A sintered wire with a diameter of 1IllI11 is used as the raw material wire, and the second
A lithium niobate crystal thin wire having a diameter of 0.3 mm was manufactured using the apparatus shown in the figure.

As a result, the wire diameter of the lithium niobate crystal thin wire material varied and air bubbles were included in the crystal.

A raw material wire was produced in the same manner as in Example 1 except that no downward laminar flow was generated in the apparatus shown in FIG. 1. However, this raw material wire had poor straightness and could not be installed in the apparatus shown in FIG.

Therefore, it was not possible to produce a crystalline fine wire material.

Ratio μm In the apparatus shown in FIG.
A raw material wire rod having a diameter of 0.8 mm was manufactured in the same manner as in Example 1 except that the diameter of the wire rod 3 was 1.5 mm. Then,
A lithium niobate crystal thin wire having a diameter of 0.3 mm was manufactured using the apparatus shown in FIG.

As a result, since the diameter of the raw material wire was small, a stable molten zone could not be obtained and wire breakage occurred.

A raw material wire rod having a diameter of 2.5 mm was produced in the same manner as in Example 1 of the L revision supervision team. Next, using the apparatus shown in FIG. 2 equipped with a platinum pipe having an outer diameter of 1 mm, a diameter of 1. A lithium niobate crystal thin wire material of 0 mm was manufactured.

As a result, the amount of melt stored in the melting zone increased, the viscosity of the melt became unstable, and wire breakage occurred.

As described above, in both Examples 1 and 2 according to the present invention, lithium niobate crystal thin wire materials with uniform diameters could be manufactured. On the other hand, when manufacturing raw material wire, the viscosity of the melt is set to 4
In Comparative Example 2, in which the flow rate was as high as 5 cT), and in Comparative Example 4, in which no downward laminar flow was generated, it was not possible to produce a raw material wire that could be used to produce a fine wire. In addition, Comparative Example 1 in which no pipe was used, Comparative Example 3 in which a sintered wire was used as the raw material wire, Comparative Example 5 in which the diameter of the raw material wire was small, and Comparative Example 6 in which the melt was pulled up by increasing the wire diameter. In either case, the wire diameter fluctuated greatly or wire breakage occurred, making it impossible to produce a crystal thin wire material with a desired uniform diameter and long length.

[Effects of the Invention] As explained above, according to the present invention, after a raw material wire is produced by cooling and solidifying an oxide melt having a predetermined viscosity in a downward laminar flow of a cooling medium, this raw material wire is By melting locally and pulling the melt through a pipe to produce thin wire rods with a predetermined wire diameter, we can continuously produce thin oxide crystal wire rods with no defects such as voids and with suppressed diameter fluctuations. can be manufactured.

[Brief Description of the Drawings] Fig. 1 is a sectional view showing an apparatus for producing a raw material wire rod used in an embodiment method of the present invention, and Fig. 2 is a sectional view showing a production apparatus for a raw material wire rod used in an embodiment method of the present invention. FIG. 2 is a cross-sectional view showing the device. 1; melt, 2; crucible, 3; melt flow, 4; cooling medium holding container, 5; lower laminar flow generating cylinder, 6; cooling medium, 7; pump, 8; heat exchanger, 9; mesh, 10 ;packet, 11
raw material wire, 12; cutting device, 13; outflow hole, 15; crystal thin wire, 16; melting section, 17; heating coil, 18; pipe, 19a. 19b; Wire rod holder, 20; Driving shaft for pulling, 21;
Drive shaft for supplying raw material wire, 22; Heating furnace, 23; Heating element,
24; Pulling material, 25; Resistance heating wire

Claims (1)

[Claims] (1) The process of using a powdered oxide as a starting material and heating and melting this starting material to obtain a melt with a viscosity of 40 cp or less, and allowing this melt to fall naturally into a downward laminar flow of cooling medium. a step of obtaining a raw material wire having a diameter of 1 mm or more by rapidly cooling and solidifying the raw material wire; a step of locally heating and melting the raw material wire to form a molten part; The melt is pulled up into a pipe heated above the melting point of the oxide, and the melt is poured into a pipe with a diameter of 0.5 m.
1. A method for producing an oxide crystal thin wire, comprising a step of solidifying the wire into a thin wire with a diameter of m or less.