JP2818344B2 - Method and apparatus for producing oxide 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 method and apparatus for producing an oxide single crystal such as a lithium niobate single crystal.

[0002]

2. Description of the Related Art Lithium niobate is an important single crystal oxide material and is usually referred to as LiNbO ₃ . At present, almost all commercially available lithium niobate single crystals are produced by the so-called Czochralski method. In this method, a single crystal can be pulled near a so-called congruent composition (Li is 48.6 mol%). However, it is impossible at present to pull a single crystal having a composition deviating from the congruent composition due to problems such as cracks.

[0003] Lithium niobate is widely used especially as an optical material. However, due to the manufacturing restrictions described above, considerable studies have been made on the optical characteristics of lithium niobate having a congruent composition, but no optical studies have been made on compositions having a composition other than the congruent composition. Therefore, it is expected that lithium niobate having a congruent composition will be mass-produced and used as an optical device.

As a method for producing lithium niobate having a congruent composition, VTE (Vapor Transport) is currently used.
Equilibration) method is known. This method will be briefly described. First, a columnar lithium niobate single crystal is pulled up by the Czochralski method. This single crystal has a congruent composition. Next, the single crystal is annealed, a single domain treatment is performed by applying a voltage at 1175 ° C., and then the columnar material is cut to obtain a thin plate. On the other hand, a powder composed of lithium niobate having a desired composition, for example, Li ₂ O of 50 mol% is prepared, and the thin plate and the powder are sealed in a closed container.
When the inside of the closed vessel is heat-treated at a sufficiently high temperature for a sufficiently long time, the composition in the thin plate and the composition in the powder reach an equilibrium state by transport in the gas phase and solid phase diffusion.

[0005]

Lithium niobate having a congruent composition has a Curie temperature of 1146 ° C.
Then, even if the single-domain processing is performed on the single crystal, when the heat treatment is performed at a temperature higher than the Curie temperature of the single crystal, the domain of the single crystal returns to the multi-domain state again. Therefore, the heat treatment temperature must not exceed the Curie temperature of the single crystal.

[0006] In a composition in which Li ₂ O is 50 mol%, the Curie temperature of a single crystal is 1190 ° C. And as the above powder
When using lithium niobate having a composition in which Li ₂ O is 50 mol%, the Curie temperature of the single crystal is from 1146 ° C. to 1190 ° C.
Ascend towards. For this reason, conventionally, heat treatment was performed at about 1100 ° C., but it took about 500 hours for the Curie temperature of the single crystal to reach 1190 ° C.

On the other hand, in a composition in which Li ₂ O is 47.2 mol%,
The Curie temperature of the single crystal is 1090 ° C. When lithium niobate having a composition of Li ₂ O of 47.2 mol% is used as the powder, the Curie temperature of the single crystal is 1146 ° C.
To 1090 ° C. For this reason, 10
The heat treatment was performed at about 50 ° C, but it took about 800 hours for the Curie temperature of the single crystal to reach 1090 ° C.

Moreover, in the above example, the thickness of the thin plate is
The thickness is about 0.5 mm, and if the thickness is further increased, an enormous amount of time is required until the inside of the system reaches an equilibrium state. As described above, synthesizing lithium niobate having a composition outside the congruent composition requires an extremely enormous amount of time and heat, so that the production cost is high and hinders full-scale research and commercialization. Was.

It is an object of the present invention to reduce the heat treatment time in the VTE treatment of a material composed of an oxide single crystal, and to mass-produce an oxide single crystal having a desired composition in a short time. That is.

[0010]

According to the present invention, a material comprising an oxide single crystal and an oxide powder having a predetermined composition different from the composition of the single crystal are housed in a container, and the inside of the container is heat-treated. Simultaneously applying a voltage to the material and the powder, thereby changing the composition of the single crystal and forming a single domain in the single crystal. It is related to.

[0011] The present invention also relates to an apparatus for producing an oxide single crystal for changing the composition of an oxide single crystal and forming a single domain in the single crystal. An oxide powder having a predetermined composition different from that of the single crystal accommodated therein; a pair of plate-like electrodes embedded in the powder; between the pair of plate-like electrodes embedded in the powder A material comprising the single crystal,
And a member for supplying electric power to the pair of plate-shaped electrodes.

As the above-mentioned oxide, various complex oxides can be exemplified. Such composite oxides include, for example,
LiNbO _{3 and} LiTaO ₃ can be exemplified.

[0013]

Embodiments of the present invention will be described below. In the following examples, examples in which the present invention is applied to the production of a lithium niobate single crystal will be mainly described.
First, a lithium compound and a niobium compound are mixed, calcined at, for example, 950 ° C., and calcined at 1050 ° C. Using this fired product, the columnar material having a congruent composition is pulled up at 1250 ° C. by the Czochralski method. Next, the columnar material is annealed at 1170 ° C. to remove distortion in the crystal. Next, the columnar material is cut to obtain a thin plate having a predetermined thickness.

Next, a lithium niobate powder having a predetermined composition different from the congruent composition and the above-mentioned thin plate are accommodated in a container, and the composition of the lithium niobate single crystal constituting the thin plate is changed by heat-treating the inside of the container. . 1A and 1B are cross-sectional views schematically showing a heat treatment apparatus suitable for the VTE process.

The container 20 comprises a main body 2 and a lid 1. The lid 1 is placed over the upper opening of the main body 2. The outer shape of the main body 2 is substantially cylindrical, and the upper end surface 2a of the main body 2
Edge 1d is placed. A step 1a is formed inside the edge 1d of the lid 1, and the step 1a protrudes into the space inside the container 2. The planar shape of the step portion 1a is substantially circular, and a side peripheral surface 1c is provided around the step portion 1a.

Both the upper end face 2a and the edge 1d are polished with high precision, and the parallelism between them is increased. This increases the airtightness of the inner space and removes volatile components from the container 20.
Began to escape outside. As a result, lithium became easier to maintain an equilibrium state in the gas phase in the container 20. Also, by projecting the step portion 1a into the inner space, the side peripheral surface 1c is formed.
And the inner wall 2b has become smaller. As a result, it became more difficult for the lithium component to escape from the portion where the main body 2 and the lid 1 were fitted together.

The main body 2 contains lithium niobate powder 6 having a predetermined composition. In this powder 6, a pair of flat electrodes 5
A and 5B are embedded, and the plate electrodes 5A and 5B are substantially parallel to each other and perpendicular to the bottom surface 2c. Lead wires 3A, 3A are provided on the upper ends of the flat electrodes 5A, 5B, respectively.
B is connected, and each lead wire 3A, 3B is
1e are respectively inserted and pulled out of the container 20. The lead wires 3A and 3B are connected to a power supply (not shown). The periphery of the outlets of the lead wires 3A, 3B is sealed with alumina cement 4.

A predetermined number of thin plates 7 made of a single crystal of lithium niobate having a congruent composition are embedded in the powder 6. Each thin plate 7 is arranged between a pair of flat electrodes 5A and 5B so as to be parallel to these.

Preferably, a device as shown in FIG. 1 is used to heat-treat the inside of the container 20 and to apply a voltage to the thin plate 7, thereby changing the composition of the single crystal and converting the single crystal into a single domain domain. Is formed. Such a method will be further described by taking a lithium niobate single crystal as an example.

In the conventional heat treatment schedule 11 shown in FIG. 2, the heat treatment is continued at a temperature of 1100 ° C. Also in this case, the Curie temperature _Tc of the thin plate 7 is, for example, 1146 ° C. to 11 ° C.
Going to 90 ° C, it rises over time. However, in this method, it takes a long time for the Curie temperature to reach 1190 ° C. For example, if the thickness of the thin plate is 0.5 mm, about 500 hours are required.

Next, in the case of producing a lithium niobate single crystal in which Li ₂ O is 47.2 mol%, in the conventional heat treatment schedule 12 shown in FIG. 3, heat treatment was performed at, for example, 1070 ° C. Curie temperature _Tc of single crystal of thin plate 7 is 1090 ° C
It took about 800 hours of heat treatment to reach (when the thickness of the thin plate was 0.5 mm).

On the other hand, according to the present invention, a lithium niobate single crystal having a composition other than the congruent composition can be manufactured in an extremely short heat treatment time. For example, when a thin plate 7 made of a single crystal of lithium niobate having a congruent composition is heated at 1175 ° C. and a voltage is applied to the pair of flat electrodes 5A and 5B,
It was found that the composition of the single crystal became 50 mol% of Li ₂ O within 54 hours. Moreover, even when the thickness of the thin plate is 3 mm,
These results were obtained. The reason why the VTE treatment can be promoted is that the heat treatment can be performed at a temperature equal to or higher than the Curie temperature (1146 ° C.) corresponding to the congruent composition.

Moreover, in the present invention, a single domain domain can be formed in the single crystal constituting the thin plate 7 by applying a voltage to the thin plate 7 simultaneously with the above heat treatment. Conversely, even if the heat treatment temperature exceeds the Curie temperature of the single crystal, if a voltage is applied at this time, a multi-domain domain does not occur.

As described above, the present invention provides an epoch-making method in that the conventional VTE processing and the single-domain formation of the single crystal domain are simultaneously performed. This allows
The heat treatment time of lithium niobate by the VTE method was significantly shortened, the production amount was significantly increased, and the production cost was greatly reduced. In addition, the domain of the single crystal was not multi-domain. In addition, the present invention eliminates the need for a conventional single-domain processing step.

For example, a thin plate 7 made of a single crystal of lithium niobate having a congruent composition is heated at 1175 ° C.
When a voltage was applied to the pair of flat electrodes 5A and 5B, it was found that the composition of the single crystal became Li ₂ O of 47.2 mol% within 36 hours.

The heat treatment temperature of the single crystal must be lower than the melting temperature of the single crystal, and the difference between the heat treatment temperature and the melting temperature is preferably 10 ° C. or more. When a pair of plate-like electrodes is embedded in oxide powder and a material such as a thin plate is embedded between the pair of plate-like electrodes, the magnitude of the voltage (V) is determined by the distance between the pair of plate-like electrodes ( When the value divided by (cm) is 1 V / cm or more, the material can be treated as a single domain without fail.

(Experiment 1) Hereinafter, more specific experimental results will be described. Using the heat treatment apparatus shown in FIG. 1, a lithium niobate single crystal having a congruent composition was subjected to VTE treatment. A 3 inch diameter column made of lithium niobate single crystal containing 48.6 mol% of Li ₂ O was pulled up from a Czochralski furnace to obtain a column having a length of 100 mm. This was annealed and cut by an inner peripheral blade to obtain a thin plate having a predetermined thickness.

The thin plate was optically polished on the Z surface to obtain a rectangular sample having a length of 20 mm and a width of 10 mm. The material of the flat electrodes 5A and 5B was platinum having a thickness of 1 mm. 1050 ℃
After crushing the sintered body fired in step 2 to a particle size of 250 μm or less, heat-treating it in a closed vessel at 1225 ° C for 24 hours, and then crushing the particle size to 250 μm or less, Li ₂ O is 50 mol% Powder of lithium niobate was used as powder 6. The powder 6 in the container 20 was compression-molded so that the height of the powder 6 was adjusted to 30 mm, the gap between the samples 7 was filled, and cracks caused by pyroelectricity were prevented.

The flat electrodes 5A and 5B have a diameter of 0.5
mm platinum lead wires 3A, 3B were connected, and the gap between the lid 1 and the platinum lead wires 3A, 3B was sealed with alumina cement 4.

Thus, the experiment numbers 1 to 1 shown in Table 1 were obtained.
Processing was performed under each of the eleven conditions. However, the thickness of the thin plate 7 and the heat treatment conditions were changed as shown in Table 1. Then, the Curie temperature of the single crystal after the heat treatment was measured, and a single domain determination was performed.

The heat treatment conditions and the like in Experiment Nos. 1 to 11 will be further described with reference to FIG. However, in FIG. 4, the graph 13 shows the heat treatment schedule,
14 shows a schedule of applied voltage.

The vessel 20 was placed in an electric furnace, heated at a rate of 100 ° C./hour, and reached a desired heat treatment temperature T ₁ at time t ₁ . This T1 is the heat treatment temperature shown in Table 1.
However, in Experiment Nos. 1 to 3, a two-stage heat treatment was performed. After maintaining at each heat treatment temperature for 6 hours, the voltage value was gradually increased, and a desired voltage was applied over 6 hours.

Then, the heat treatment is performed at the heat treatment temperature and time shown in Table 1. That is, t ₃ −t ₁ shown in FIG. 4 is the “heat treatment time” shown in Table 1. During this time, the experiment number
1, 2, 3, 4, 5, 7, 8, in 10, at time t ₂ T _C is 1190
° C. After the above heat treatment is completed,
The mixture was cooled to room temperature at a temperature lowering rate per hour. The time when it becomes to room temperature and t _4. Then, the applied voltage was set to OV over 3 hours after the temperature reached room temperature.

The magnitude of the applied voltage is determined by a pair of flat electrodes 5.
The voltage was set to 1 V per 1 cm of the powder interposed between A and 5B. However, the interval between the flat electrodes 5A and 5B is the same as that shown in FIG.
m shown in (a).

If the magnitude of the applied voltage is less than 1 V / cm, even if the thin plate 7 is heated above its Curie temperature,
Not all single crystal domains are aligned.

In Experiment Nos. 12 and 13 shown in Table 1, VTE processing was performed by a conventional VTE apparatus according to the conventional heat treatment schedule shown in FIG. The Curie temperature T _C of the single crystal was measured using a DTA device. If the domain of the single crystal is in a single domain, the "single domain determination"
Is indicated as “○”.

[0037]

[Table 1]

FIG. 5 schematically shows a phase diagram of lithium niobate. As can be seen from this phase diagram, there is a relationship shown in Table 2 between the ratio of Li ₂ O, the Curie temperature T _C and the melting temperature.

[0039]

[Table 2]

As can be seen from a comparison of Experiment Nos. 1-11 with 12, 13 according to the present invention, 1190 ° C. or 118 ° C.
A lithium niobate single crystal having a Curie temperature of 0 ° C. can be manufactured in a much shorter time than in the past.
This is because the VTE reaction is basically limited by temperature. In addition, the domain of the single crystal was well single-domained.

Also, in Experiment Nos. 1 to 11, the Curie temperature was 1 in a shorter time when the heat treatment temperature was higher.
Has reached 190 ° C. More specifically, 1150 ° C, 11
When heat treatment is performed at 60 ° C. and 1175 ° C., the heat treatment temperature is higher than the Curie temperature at the beginning of the heat treatment, but the Curie temperature eventually exceeds the heat treatment temperature and reaches 1190 ° C. For this reason, while the heat treatment temperature is higher than the Curie temperature, a predetermined voltage must be applied to perform the single-domain processing. When the Curie temperature exceeds the heat treatment temperature, the single-domain domain is maintained even when the application of the voltage is stopped.

In the congruent composition, the melting temperature is 125
The temperature is 2 ° C., and at least at this point, the heat treatment at 1150 to 1250 ° C. can promote the VTE reaction, and the higher the temperature, the better. However, when the Li ₂ O content becomes 50 mol%, the melting temperature decreases to 1200 ° C., and it is preferable to perform the heat treatment at a temperature of 1190 to 1150 ° C. at this time.

Even under the same heat treatment conditions, when the thickness of the thin plate 7 was 3 mm or 4 mm, the heat treatment time was slightly longer, and the Curie temperature after the heat treatment was 1180 ° C.
Further, it has been found that if the thickness of the thin plate 7 exceeds 5 mm, it is difficult to make the composition uniform inside.

(Experiment 2) Table 3
Experiment Nos. 21 to 31 shown in FIG. Table 3 shows the thickness of the thin plate 7, the heat treatment conditions, the Curie temperature after heat treatment, the determination of a single domain, and the heat treatment time for each example. However, unlike Experiment 1, as the powder, a powder of lithium niobate containing 47.2 mol% of Li ₂ O was used. The heat treatment conditions and the like in this experiment will be further described with reference to FIG. However,
In FIG. 6, graph 15 shows the heat treatment schedule,
Graph 16 shows the schedule of the applied voltage.

[0045] The vessel was placed 20 into an electric furnace, was raised at a rate of 100 ° C. / time, to reach a desired heat treatment temperature T2 at time t _1. This T2 is the heat treatment temperature shown in Table 3.
After maintaining at each heat treatment temperature for 6 hours, the voltage value was gradually increased and a desired voltage was applied over 6 hours.

Then, the heat treatment is performed at the heat treatment temperature and time shown in Table 3. That is, t ₃ -t ₁ shown in FIG. 6 is the “heat treatment time” shown in Table 3. After the above heat treatment was completed, the resultant was cooled to room temperature at a temperature decreasing rate of 50 ° C./hour. The time when it becomes to room temperature and t _4. Then, the applied voltage was set to OV over 3 hours after the temperature reached room temperature. Table 3
In Experiment Nos. 32 and 33 shown in FIG. 3, VTE processing was performed by a conventional VTE apparatus according to the conventional heat treatment schedule shown in FIG.

[0047]

[Table 3]

As can be seen from the above results, according to the present invention, a single crystal can be subjected to VTE processing in a short time. Also, within the scope of the present invention, the Curie temperature reaches 1190 ° C. in a shorter time when the heat treatment temperature is higher. If the heat treatment temperature T2 exceeds 1146 ° C,
It is necessary to maintain the single domain domain by continuously applying the voltage.

When the content of Li ₂ O is 47.2 mol%, the melting temperature of the single crystal becomes 1230 ° C., so that the heat treatment can be performed at a heat treatment temperature of 1220 ° C. or less. Further, as in this experiment, in order to obtain a composition having a composition of Li ₂ O of 47.2 mol%, heat treatment was conventionally performed at a Curie temperature of 1090 ° C. or less, for example, 1050 ° C. In addition, since the VTE process is substantially limited by temperature, conventionally, as shown in Experiment No. 32, it took a very long time. In this regard, the effect of the present invention is even greater.

In the same manner as above, 47.6 mol of Li ₂ O was added.
%, 48.0 mol%, 49.0 mol%, 49.4 mol%, 49.8 mol%
Using lithium niobate powder 6 having the following composition, single crystals of each composition were produced according to the present invention. And it was confirmed that single crystals of each composition can be mass-produced.

(Experiment 3) Lithium tantalate single crystal was
Manufactured according to the invention. This manufacturing process is described in Experiment 1.
Followed. However, the material of the thin plate 7 was a lithium tantalate single crystal having a congruent composition (Li ₂ O: 48.3 mol%). As the powder 6, a lithium tantalate powder containing 50.0 mol% of Li ₂ O was used. The heat treatment temperature was 1480 ° C., the applied voltage was 2 V / cm, and a voltage was applied in the Z-axis direction of the single crystal. As a result, the Curie temperature reached 646 ° C. after 30 hours. Table 4 shows the relationship between the ratio of Li ₂ O and the melting temperature and Curie temperature of the single crystal.

[0052]

[Table 4]

FIG. 7 shows a phase diagram of lithium tantalate. In this phase diagram, the abscissa indicates mol% of tantalum. The Curie temperature Tc of a lithium tantalate single crystal is considerably lower than its melting temperature.

In the case of lithium tantalate, when heat treatment is performed in the range of melting temperature to melting temperature −100 ° C.,
The effect of promoting the VTE process is great. In the case of lithium tantalate single crystal, since the Curie temperature is extremely low compared to the melting temperature, conventionally, it is difficult to change the composition by performing VTE treatment without multi-domain of the domain.
It was almost impossible.

(Experiment 4) Lithium tantalate single crystal was
Manufactured according to the invention. This manufacturing process is described in Experiment 1.
Followed. However, the material of the thin plate 7 was a lithium tantalate single crystal having a congruent composition. As powder 6
A lithium tantalate powder containing 47.0 mol% of Li ₂ O was used.
The heat treatment temperature was 1480 ° C., the applied voltage was 2 V / cm, and a voltage was applied in the Z-axis direction of the single crystal. As a result, the Curie temperature reached 574 ° C. after 30 hours.

When an optical waveguide was formed on the substrate using the samples manufactured in Experiments 1 to 4 above, a suitable optical waveguide substrate having a small light propagation loss and a small variation was obtained. Was done. The size of the sample is not particularly limited. For example, a wafer having a diameter of 1 to 4 inches can be processed, and several wafers can be processed at a time.

In the present invention, the VTE process and the single domaining process can be simultaneously advanced by, for example, an apparatus as shown in FIG. However, among the components shown in FIG. 8, the same components as those shown in FIG. 1 are denoted by the same reference numerals.

In the heat treatment apparatus shown in FIG. 8, each thin plate 7 is embedded so as to be substantially perpendicular to the bottom surface 2c and the surface 1b of the step portion 1a. The flat electrode 5C is connected to the lead wire 3A, and the flat electrode 5D is connected to the lead wire 3B. Flat electrode 5C, 5D
Are buried almost parallel to the bottom surface 2c and the front surface 1b.

In order to make the lithium niobate single crystal into a single domain, it is necessary to apply a voltage in the Z-axis direction. Therefore, when the positional relationship between the flat electrodes 5A and 5B and the thin plate 7 is as shown in FIG. 1, the Z plate can be easily processed. On the other hand, in the case of performing a single domaining process on an X plate having an X axis perpendicular to the main surface, which is suitable for optical waveguide use, a Z axis exists in the thin plate 7. Therefore, as shown in FIG. 8, the thin plate 7 is arranged perpendicular to the plate electrodes 5C and 5D, and is arranged such that the Z axis of the thin plate 7 substantially coincides with the voltage application direction. It is preferable that the thin plate 7 and the flat electrodes 5C and 5D are similarly arranged on the Y plate.

In a 128 ° Y plate suitable for a surface acoustic wave (SAW) substrate, a 128 ° Y axis appears perpendicular to the main surface of the thin plate 7. Therefore, even if the thin plate 7 is installed as shown in FIG. 1, a considerable part of the magnitude of the voltage is applied in the Z-axis direction, and a small amount is applied in the Y-axis direction. Therefore, by applying a voltage slightly larger than that for performing the single-domain processing on the Z plate and compensating for a decrease in the applied voltage in the Z-axis direction, the single-domain processing can be performed without any problem.

[0061]

As described above, according to the present invention, the heat treatment time of the oxide single crystal by the VTE method is significantly reduced. Therefore, it becomes possible to mass-produce an oxide single crystal having a desired composition. In addition, since a voltage is applied to the material together with the heat treatment, the domain of the single crystal is not multi-domain.

[Brief description of the drawings]

1A is a cross-sectional view showing a state in which a thin plate 7 is subjected to VTE processing in a container 20, and FIG. 1B is a cross-sectional view taken along the line Ib-Ib in FIG. 1A.

FIG. 2 is a graph showing a conventional heat treatment schedule.

FIG. 3 is a graph showing a conventional heat treatment schedule.

FIG. 4 is a graph showing a heat treatment schedule and a voltage application schedule according to an example of the present invention.

FIG. 5 is a phase diagram of lithium niobate.

FIG. 6 is a graph showing a heat treatment schedule and a voltage application schedule according to an example of the present invention.

FIG. 7 is a phase diagram of lithium tantalate.

FIG. 8 is a cross-sectional view showing a state in which the thin plate 7 is subjected to VTE processing in the container 20.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Lid 2 Main body 3A, 3B Lead wire for power supply 5A, 5B, 5C, 5D A pair of flat-plate electrodes 6 Oxide powder having a predetermined composition 7 Thin plate made of oxide single crystal 11, 12, 13, 15 heat treatment schedules 14, 16 voltage application schedule 20 container T _C Curie temperature T1, T2 heat treatment temperature

────────────────────────────────────────────────── ─── Continuation of front page (56) References JP-A-5-85897 (JP, A) JP-A-6-172078 (JP, A) JP-A-57-140400 (JP, A) JP-A-58-58 151399 (JP, A) JP-A-63-35498 (JP, A) JP-A-63-35499 (JP, A) JP-A-63-35500 (JP, A) JP-A-63-218599 (JP, A) JP-A-1-103999 (JP, A) F. Bordui, et al. , "Preparation of characterisation of off-consistent lithium niobate cry stals," J. Am. Appl. Phys. , 15 Jan. 1992, Vol. 71, No. 2, p. 875-879 Y. S. Luh, et al. , "Stoichiometric LiNbO3 single-crystal fibers for non-in-ear optical applications," J. Am. Cryst. See Growth, 1987, Vol. 85, p. 264 -269 (58) Field surveyed (Int. Cl. ⁶ , DB name) C30B 28/00-35/00 CA (STN)

Claims (6)

(57) [Claims] 1. A material comprising a single crystal of an oxide and a powder of an oxide having a predetermined composition different from the composition of the single crystal are accommodated in a container. A method for producing an oxide single crystal, comprising applying a voltage to a powder, thereby changing the composition of the single crystal and forming a single domain in the single crystal. 2. The method for producing an oxide single crystal according to claim 1, wherein said material is embedded in said powder. 3. The method for producing an oxide single crystal according to claim 1, wherein said heat treatment temperature is lower than a melting temperature of said single crystal. 4. The method for producing an oxide single crystal according to claim 3, wherein a voltage is applied to said material when said heat treatment temperature exceeds the Curie temperature of said single crystal. 5. A pair of plate-like electrodes are buried in the powder, the material is located between the pair of plate-like electrodes, and the magnitude of the voltage (V) is adjusted by the pair of plate-like electrodes. 3. The method for producing an oxide single crystal according to claim 2, wherein a value obtained by dividing the distance (cm) between the electrode-like electrodes is 1 V / cm or more. 6. A method for changing the composition of an oxide single crystal and forming a single domain domain in said single crystal.
An apparatus for producing an oxide single crystal, comprising: a container; an oxide powder contained in the container and having a predetermined composition different from that of the single crystal; a pair of plate-like electrodes embedded in the powder; An oxide single crystal manufacturing apparatus, comprising: a material made of the single crystal, which is buried in the powder and located between the pair of plate electrodes; and a member for supplying power to the pair of plate electrodes. .