JP2005219952A - Single crystal and method for producing the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method for producing a single crystal by which a uniformly balanced (homogeneous) single crystal can be easily produced by a Bridgman method. <P>SOLUTION: The method for producing the single crystal A by growing it by the Bridgman method has a filling process for filling a seed crystal 3 in the lower part of a crucible 5 and further sequentially filling a plurality of single crystal raw materials having different compositions in layers on the seed crystal 3, a melting process for arranging the crucible 5 in a vertical furnace 2 wherein a temperature gradient is formed in the vertical direction of the crucible 5, and heating and melting the single crystal raw materials into a melt 6, and a growing process for growing the single crystal A by progressively solidifying the melt 6 from a lower part toward an upper part. In the filling process, the filling is performed while changing single crystal raw materials, in each of which the ratio of an element, whose ratio decreases in comparison with the compositional ratio of an original melt in accordance with progression of growth, is enhanced, from a lower part toward an upper part in stages. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

The present invention relates to a single crystal suitably used for a piezoelectric device favorable for a SAW filter or the like and a method for producing the single crystal.

In recent years, a single crystal of La ₃ Ga ₅ SiO ₁₄ (Langasite) has a low rate of change in elastic wave propagation velocity and frequency due to temperature and a large electromechanical coupling coefficient indicating the magnitude of piezoelectricity. Research has been conducted on substrate materials for piezoelectric devices such as filters. That is, this langasite single crystal has the same temperature characteristics as quartz and has an electromechanical coupling coefficient about three times that of quartz. For this reason, Langasite single crystals have been used effectively for various applications, and one of them has been used for SAW (Surface Acoustic Wave Device) filters, which are widely used in mobile phones. Those are known (for example, see Patent Document 1).
The Czochralski method is known as a method for producing this langasite single crystal.

  In the growing method by the Czochralski method, a langasite raw material previously filled in a crucible serving as a container is placed in a langasite single crystal manufacturing apparatus, and then heated and melted. This is a method of growing a Langasite single crystal by bringing the site seed crystal into contact and then slowly pulling it up while rotating.

  In the above-mentioned Czochralski method, since a single crystal having a large diameter is gradually grown by gradually pulling a thin seed crystal in contact with the melt, a so-called shoulder in which the diameter gradually changes before reaching a predetermined diameter. Part is formed. This shoulder has become a useless part when a single crystal ingot is processed into a wafer. Also, since the shoulder is formed from a thin seed crystal, if the single crystal formed in the lower part exceeds a certain weight, it may break at the thin part, and there is a limit to lengthening the straight body part. It was happening.

Therefore, in order to solve the above problem, as another single crystal growth method, a growth method by the vertical Bridgman method (vertical temperature gradient solidification method) is used.
In the growing method by the vertical Bridgman method, a seed crystal is put in the bottom of a cylindrical platinum crucible having a thin thickness, and a raw material is put on it. Then, the crucible is placed in the furnace, the upper part of the furnace is set to a temperature equal to or higher than the melting point of the langasite, and the temperature is lowered toward the lower part of the furnace to set the temperature gradient necessary for growing the single crystal. . After setting the temperature in the furnace, the position of the crucible is set at a position where the upper part of the seed crystal and the lower part of the raw material are higher than the melting point from the vicinity of the melting point. After setting, place the crucible at this position for a predetermined time, and melt the seed crystal upper part and the raw material to remove seed crystal (crushed crystal on the seed crystal surface and attach the langasite melt to the single crystal part of the seed crystal. Do). After the seeding is completed, the crucible is slowly lowered and moved to a temperature region lower than the melting point of the langasite to cool and solidify the melt, and a single crystal can be grown according to the orientation of the seed crystal.

According to this vertical Bridgman method, as long as the optimum conditions for growing a single crystal such as a temperature gradient are established, there is no shoulder formation, which is a problem with the Czochralski method, as described above. Since the change is smooth, there is no thermal strain stress compared to the Czochralski method, and high-quality single crystals are easily obtained. Moreover, it has the characteristic that a long single crystal can be easily grown by lengthening the full length of a furnace or a crucible.
Furthermore, in the case of growing a langasite single crystal, the composition of the stoichiometric ratio (La ₂ O ₃ (30 mol%), gallium oxide Ga ₂ O ₃ (50 mol%), silicon dioxide SiO ₂ (20 mol%)) is used. In some cases, considering the crystal structure, atoms are arranged at all positions, so that the charge balance is achieved and the langasite single crystal is in an energetically stable state. Therefore, the defect density such as oxygen vacancies is low, and a high quality langasite single crystal is obtained.
Japanese Laid-Open Patent Publication No. 10-126209 (paragraph numbers 0006-0013, FIGS. 1-4)

However, when a Langasite single crystal is grown using the above-mentioned vertical Bridgman method with the starting material composition as the stoichiometric ratio, the composition of the stoichiometric ratio (AB in the figure) matches as shown in FIG. Since it is located at a position deviated from the melt composition, a good quality langasite single crystal can be obtained from the initial stage of growth to the middle stage of growth, but when the stage is from the middle stage of growth to the final stage of growth, the liquid phase of the melt moves to the silicon-rich side. The lanthanum silicide (La ₂ Si ₂ O ₁₄ ) is precipitated at the growth end portion. When this lanthanum silligate precipitates at the end of growth, the thermal expansion differs from that of langasite, so there is a possibility of cracking due to the difference in thermal expansion between the two, and there is a risk of eroding the portion of the grown langasite single crystal. there were.

  The present invention has been made in view of such circumstances, and the object thereof is to make a uniformly balanced (uniform) single crystal and to easily manufacture the single crystal by the Bridgman method. It is to provide a method for producing a single crystal.

In order to achieve the above object, the present invention provides the following means.
The invention according to claim 1 is a method for producing a single crystal by growing the single crystal by the Bridgman method, wherein the seed crystal is filled in the lower part of the crucible and has a plurality of different compositions on the seed crystal. A filling step in which raw materials are stacked one after another, and the crucible is placed in a vertical furnace in which a temperature gradient is formed in the vertical direction of the crucible, and the single crystal raw material is heated and melted to form a melt. And a growth step of growing the single crystal by gradually solidifying the melt from below to above in the filling step, with the progress of the growth, the composition ratio of the original melt A method for producing a single crystal is provided, in which the single crystal raw material with an increased ratio of the decreasing element is filled stepwise from above to below.

In the method for producing a single crystal according to the present invention, when the melt is gradually solidified from below by the melt process and the growing process, the single crystal is adsorbed on the seed crystal and gradually grows. Here, in the filling process, the single crystal raw material with a higher ratio of elements whose ratio decreases with respect to the composition ratio of the original melt as the growth progresses is changed step by step from the seed crystal side. Therefore, as the growth of the single crystal progresses, the elements that have decreased with the progress of the single crystal are complemented one after another by the melt. In particular, the growth of a single crystal by the Bridgman method has a high temperature at the top of the melt and a low temperature at the bottom, so that convection of the melt hardly occurs, and the composition distribution of the melt depends on the position of the single crystal raw material. Therefore, it is easy to supplement the melt.
Therefore, a single crystal can be grown without causing a deviation in the composition of the melt, and foreign substances such as lanthanum silicate are not deposited at the end of the growth as in the prior art. Thereby, a crack etc. do not enter into a single crystal, and a uniformly balanced (uniform) single crystal can be easily manufactured by the Bridgman method.

  The invention according to claim 2 provides the method for producing a single crystal according to claim 1, wherein the crucible is rotated around the vertical axis during the growing step.

  In the method for producing a single crystal according to the present invention, when the single crystal is grown, the crucible is rotated, so that the melt composed of each composition can be diffused. Therefore, a more uniform single crystal without compositional irregularities can be produced.

The invention according to claim 3 is the method for producing a single crystal according to claim 1 or 2, wherein the single crystal is a single crystal having a Ca ₃ Ga ₂ Ge ₄ O ₁₄ type structure. provide.

In the method for producing a single crystal according to the present invention, uniformly balanced, langasite single crystal _{(La 3 Ga 5 SiO 14)} , Rangateito single crystal _{(La 3 Ga 5.5 Ta 0.5 O} 14) Ya A single crystal having a Ca ₃ Ga ₂ Ge ₄ O ₁₄ type structure which is an oxide single crystal such as a laganite single crystal (La ₃ Ga _5.5 Nb _0.5 O ₁₄ ) is easily produced by the Bridgman method. Can do.

The invention according to claim 4 is the method for producing a single crystal according to claim 3, wherein the single crystal having the Ca ₃ Ga ₂ Ge ₄ O ₁₄ type structure is a langasite single crystal. provide.

In the method for producing a single crystal according to the present invention, a uniformly balanced langasite single crystal (La ₃ Ga ₅ SiO ₁₄ ) can be easily produced by the Bridgman method.

The invention according to claim 5 provides the method for producing a single crystal according to claim 3, wherein the single crystal having the Ca ₃ Ga ₂ Ge ₄ O ₁₄ type structure is a langate single crystal. To do.

In the method for producing a single crystal according to the present invention, a uniformly balanced langate single crystal (La ₃ Ga _5.5 Ta _0.5 O ₁₄ ) can be easily produced by the Bridgman method.

The invention according to claim 6 is the method for producing a single crystal according to claim 3, wherein the single crystal having the Ca ₃ Ga ₂ Ge ₄ O ₁₄ type structure is a langanite single crystal. provide.

In the method for producing a single crystal according to the present invention, a uniformly balanced langanite single crystal (La ₃ Ga _5.5 Nb _0.5 O ₁₄ ) can be easily produced by the Bridgman method.

The invention according to claim 7 provides a single crystal manufactured by the method for manufacturing a single crystal according to any one of claims 1 to 7.
In the single crystal according to the present invention, a uniform and balanced single crystal is obtained from the initial growth stage to the final growth stage. Therefore, for example, a sound wave or the like can be propagated with high accuracy in the crystal and on the surface, and can be suitably used for applications such as mobile phone base station filters that require precision.

According to the method for producing a single crystal according to the present invention, a uniformly balanced single crystal can be easily produced by the Bridgman method. In particular, since it can be manufactured by the Bridgman method, the manufacturing cost can be reduced without the need for manufacturing.
In addition, according to the single crystal according to the present invention, a uniform and balanced single crystal can be provided from the initial growth stage to the final growth stage.

Hereinafter, an embodiment of a method for producing a single crystal of the present invention will be described with reference to FIGS. In the present embodiment, the langasite single crystal (La), which is one of the single crystals having the Ca ₃ Ga ₂ Ge ₄ O ₁₄ type structure, using the langasite single crystal manufacturing apparatus 1 shown in FIG. ₃ Ga _5.5 Nb _0.5 O ₁₄ ) A will be described.
As shown in FIG. 1 and FIG. 2, the apparatus 1 for producing a langasite single crystal includes a vertical furnace 2 capable of forming a temperature gradient in the vertical direction, and a langasite seed crystal (seed). Crystal) 3 and a crucible 5 that can be filled with a langasite raw material (single crystal raw material) 4. After the langasite raw material 4 is heated into a melt 6, the melt 6 is gradually moved upward from below. The Langasite single crystal A is grown by solidification. This manufacturing method will be described in detail later.

As shown in FIG. 1, the furnace 2 is made of super cantal, for example, formed in a cylindrical shape and capable of high-temperature heating, and has a heater 7 for heating the langasite raw material 4 inside. The heater 7 is composed of a three-zone heater divided into upper, middle and lower stages, for example, 200 mm in length. The upper stage is set to a temperature higher than the melting point of the langasite raw material 4 (for example, 1550 ° C.). Is set to be a temperature range lower than the melting point of the langasite raw material 4 (for example, 1450 ° C.). Further, the heater 7 is connected to a temperature control unit (not shown), and the temperature of each stage is controlled so as to be independent. Thereby, the furnace 2 can form a temperature gradient in the vertical direction.
In addition, a shaft member 8 that can move in the vertical direction inside the furnace 2 and that can rotate about the axis is supported by a drive mechanism (not shown) inside the heater 7. A crucible receiver 9 is connected.

The crucible 5 can be placed on the crucible receiver 9. The crucible 5 is made of a material such as platinum and has a cylindrical bottomed cylindrical shape having an opening at the top. Specifically, the crucible 5 is formed in a size of, for example, a height (L) of 200 mm, a diameter (φ) of 51 to 52 mm, and a thickness of 0.05 mm to 0.3 mm.
A tube 10 made of alumina or the like is disposed on the crucible receptacle 9 and on the outer periphery of the crucible 5 to protect the crucible 5. The tube 10 has a hole 10a at one location, and a side wall position 11 of the crucible 5 corresponding to the interface between the langasite seed crystal 3 and the langasite raw material 4 filled in the crucible 5 from the hole 10a. Thus, the thermocouple 12 is disposed so as to make point contact. The thermocouple 12 is connected to a temperature display unit (not shown) and can monitor the measured temperature.

Next, a method of manufacturing the langasite single crystal A using the thus configured langasite single crystal manufacturing apparatus 1 will be described.
First, a filling step is performed in which the langasite seed crystal 3 is filled in the lower portion of the crucible 5 and the langasite raw material 4 having a plurality of different compositions is sequentially stacked on the langasite seed crystal 3. At this time, as the growth progresses, the langasite raw material 4 having an increased ratio of elements whose ratio decreases with respect to the composition ratio of the original melt 6 is changed in a stepwise manner from below to perform filling. .
For example, in this embodiment, the langasite raw material 4 includes lanthanum oxide (La ₂ O ₃ ), gallium oxide (Ga ₂ O ₃ ) and silicon dioxide (SiO ₂ ) having different ratios, As the distance from the site seed crystal 3 increases, the langasite raw material 4 is filled so that the ratio of gallium oxide to silicon dioxide increases.

  That is, as shown in the position 0 to 20 mm from the seed crystal in FIG. 3, the powders of the lanthanum oxide (30.0 mol%), gallium oxide (50.0 mol%), and silicon dioxide (20.0 mol%) are balanced. To do. These are sufficiently mixed to obtain a mixed powder, which is molded by a press so as to be equal to or less than the inner diameter of the crucible 5, and then put into a rubber bag or the like to be evacuated to be in close contact with the rubber. Subsequently, after removing rubber | gum by an isostatic pressure rubber press etc., it calcines, for example at 1100 degreeC-1300 degreeC for 5 hours, and the pellet-shaped langasite raw material 4 is obtained.

  Similarly, the powders of lanthanum oxide, gallium oxide and silicon dioxide are respectively weighed in the remaining mol% shown in FIG. 3, and three more langasite raw materials 4 having different ratios of gallium oxide and silicon dioxide are prepared. In this embodiment, four Langasite raw materials 4 are used, but the number is not limited to four. Further, lanthanum oxide, gallium oxide and silicon dioxide are not limited to the ratios shown in FIG.

Next, as shown in FIG. 2, after the langasite seed crystal 3 (for example, 30 mm in height) is filled in the lower part of the crucible 50, the above-described pelletized langasite raw material 4 is placed on the langasite seed crystal 3. Overlay and fill. At this time, as shown in FIG. 3, according to the ratio of gallium oxide and silicon dioxide, each langasite raw material 4 is filled stepwise from the bottom to the top so as to have a predetermined distance from the langasite seed crystal 3. To do. In addition, in this embodiment, the height of each langasite raw material 4 is about 20 mm.
After filling with the langasite raw material 4, a lid 13 formed of platinum foil or the like is placed on the upper part of the crucible 5 in order to prevent contamination of dust and the like.

After the filling process is completed, a melt process is performed. That is, as shown in FIG. 1, the crucible 5 is placed and fixed on a crucible receiver 9 disposed inside the furnace 2. After fixing the crucible 5, the tube 10 and the thermocouple 12 are installed. Then, after the shaft member 8 is driven by a drive mechanism and set so that the crucible receiver 9 is positioned at the lowermost part of the furnace 2, a mixed gas obtained by mixing oxygen with an inert gas such as argon or nitrogen gas is laminarized. In the furnace 2 so that it flows.
Next, the temperature of the heater 7 is raised by setting a temperature gradient so that the temperature increases sequentially from the lower stage to the upper stage. At this time, for example, the temperature of each heater 7 is set so as to be in a temperature range of 1480 ° C. to 1550 ° C.

After the temperature increase is completed and the internal temperature of the furnace 2 is stabilized, the shaft member 8 is driven to raise the crucible 5 at a moderate speed. At this time, as described above, since the temperature of the heater 7 is set higher as it goes to the upper part of the furnace 2, the pellet-shaped langasite raw material 4 is heated and melted to become a melt 6. At this time, since the temperature of the upper part of the crucible 5 is high and the temperature of the lower part is low, the convection phenomenon of the melt 6 does not occur.
Further, during the melt process, the crucible 5 and the shaft member 8 are simultaneously rotated at a speed of, for example, 10 to 20 rpm, and the temperature of the crucible 5 is monitored while the temperature of the side wall position 11 of the crucible 5 is monitored by the thermocouple 12. And the crucible 5 is positioned at a position where the temperature of the interface between the langasite seed crystal 3 and the langasite raw material 4 becomes a temperature stable state in the vicinity of 1496 ° C. to 1516 ° C., for example.

Next, after holding the crucible 5 at this position for several hours, a growth process is performed in which the melt 6 is gradually solidified from below to grow the langasite single crystal A.
That is, the crucible 5 is lowered at a speed of 1 mm / hr, for example, and the crucible 5 is moved to the lower part of the furnace 2 where the temperature of the heater 7 is low. Then, the temperature of the melt 6 heated in a stable state is lowered from the side of the langasite seed crystal 3 toward the upper side of the crucible 5 and from the vicinity of the side wall of the crucible 5 where the flow of heat is good. The temperature of the melt 6 starts to decrease toward the center. Thereby, the melt 6 is cooled and solidified from the vicinity of the side wall of the crucible 5 toward the center of the crucible 5, and the langasite single crystal A is adsorbed on the langasite seed crystal 3. This is sequentially repeated as the crucible 5 is lowered, and the langasite single crystal A is grown toward the top of the crucible 5.

  Here, in the filling process, the langasite raw material 4 is filled in stages so that the ratio of gallium oxide to silicon dioxide increases as the distance from the langasite seed crystal 3 increases. With the growth of A, gallium oxide is supplemented to the melt 6 one after another. Thereby, since the melt 6 does not shift to the silicon-rich side, lanthanum silicide is difficult to deposit at the end of the growth. Therefore, it is possible to prevent the occurrence of cracks and the like due to the difference in thermal expansion between the lanthanum silicide and the langasite, and it is possible to produce the langasite single crystal A that is uniformly balanced. In particular, since it can be manufactured by the Bridgman method, it can be manufactured without labor as in the Czochralski method, and the manufacturing cost can be reduced.

Further, in the production of the Langasite single crystal by the Bridgman method, the convection of the melt 6 basically does not occur because the upper temperature is high and the lower temperature is low, that is, the movement of the material is only by diffusion. The mixing of the melt 6 formed from each langasite raw material 4 is weak, and the composition distribution of the melt 6 tends to depend on the position of the langasite raw material 4. Therefore, the melt 6 is easily supplemented.
Furthermore, by rotating the crucible 5, the melt 6 of the langasite raw material 4 having each composition can be diffused moderately, and a langasite single crystal A having no compositional irregularity can be obtained.

  Moreover, in the said growth process, when the crucible 5 is fall | descended at the said speed and the langasite single crystal A is grown for 11 days, for example, when the crucible 5 is peeled off after completion | finish of growth, the langasite single crystal A with a straight cylinder of 80 mm You can get an ingot.

  As described above, according to the method for producing a single crystal according to the present invention, all the crucible 5 is made of the Langasite single crystal A that is easily and uniformly balanced by the Bridgman method, that is, a high-quality single crystal. A long langasite single crystal A that uses volume can be produced. Therefore, the langasite single crystal A manufactured by the method for manufacturing a single crystal according to the present invention can propagate a sound wave or the like with high accuracy in the crystal and on the surface thereof, and is portable such as W-CDMA that requires high precision. It can be suitably used for applications such as telephone base station filters.

The technical scope of the present invention is not limited to the above embodiment, and various modifications can be made without departing from the spirit of the present invention.
For example, in the above embodiment, the composition of the langasite raw material is shifted by changing the ratio of gallium oxide and silicon dioxide. However, the ratio is not limited to the ratio of gallium oxide and silicon dioxide.
Further, in the above embodiment, as one of a single crystal having a Ca ₃ Ga ₂ Ge ₄ O ₁₄ type structure, it has been described to produce the langasite single crystal is not limited to the langasite single crystal, for example, Langatate single crystal (La ₃ Ga _5.5 Ta _0.5 O ₁₄ ) or langanite single crystal (La ₃ Ga _5.5 Nb _0.5 O ₁₄ ) may be used.
In the case of producing the langate single crystal, for example, as shown in FIG. 4, each rangate raw material includes lanthanum oxide (La ₂ O ₃ ) and gallium oxide (Ga ₂ O ₃ ) and tantalum oxide (ratio of different ratios). ta 2 _{O 5)} has a, the distance from Rangateito seed crystals, the Rangateito material such that the ratio of the gallium oxide from the tantalum oxide increases may be filled into the crucible. By doing so, a uniform and well-balanced langate single crystal can be easily produced by the Bridgman method.
Note that lanthanum oxide, gallium oxide, and tantalum oxide are not limited to the ratios shown in FIG.

In the case of producing a langanite single crystal, for example, as shown in FIG. 5, each langanite raw material is composed of lanthanum oxide (La ₂ O ₃ ) and gallium oxide (Ga ₂ O ₃ ) in a different ratio. has a niobium oxide (Nb 2 _{O 5),} the distance from langanite seed crystals may be filled with langanite material into the crucible such that the ratio of the gallium oxide than niobium oxide increases. By doing so, a uniform and balanced Langanite single crystal can be easily produced by the Bridgman method.
Note that lanthanum oxide, gallium oxide, and niobium oxide are not limited to the ratio shown in FIG.

Furthermore, it is not limited to a single crystal having a Ca ₃ Ga ₂ Ge ₄ O ₁₄ type structure such as a langasite single crystal, a langate single crystal, or a langanite single crystal, and may be a single crystal.
Moreover, in the said embodiment, although the crucible was rotated and the langasite single crystal was manufactured, you may manufacture without rotating a crucible.

[Comparative example]
Next, in order to compare with the method for producing a single crystal of the present invention, a case where a langasite single crystal is produced by a conventional production method will be described.
In this comparative example, as shown in FIG. 6, during the filling process, for example, all the langasite raw materials having the same composition regardless of the distance from the langasite seed crystal, that is, lanthanum oxide, oxidation at a stoichiometric ratio. A langasite raw material formed of gallium and silicon dioxide was filled. Thereafter, the melt process and the growing process were performed by the apparatus for producing a langasite single crystal described in the above embodiment.
When a langasite single crystal was grown by this method, it was confirmed that lanthanum silligate was deposited at the end of growth and cracks were generated due to the difference in thermal expansion between the lanthanum silligate and langasite. .

It is sectional drawing which shows one Embodiment of the manufacturing apparatus of the langasite single crystal used with the manufacturing method of the single crystal which concerns on this invention. FIG. 2 is a cross-sectional view of a crucible used in the apparatus for producing a langasite single crystal shown in FIG. 1 such that the ratio of gallium oxide to silicon dioxide increases on the langasite seed crystal as the distance from the langasite seed crystal increases. It is the figure which showed the state which filled the langasite raw material sequentially. It is a figure explaining the filling process in the case of growing a langasite single crystal, Comprising: It is the figure which showed an example of the composition ratio of the langasite raw material according to the position from a langasite seed crystal. It is a figure explaining the filling process in the case of growing a rangate single crystal, and is a figure showing an example of a composition ratio of a rangate raw material according to a position from a langate seed crystal. It is a figure explaining the filling process in the case of growing a langanite single crystal, Comprising: It is the figure which showed an example of the composition ratio of the langanite raw material according to the position from a langanite seed crystal. It is a figure explaining the conventional filling process in the case of growing a langasite single crystal, Comprising: It is the figure which showed an example of the composition ratio of a langasite raw material. It is an image figure of the binary system phase diagram which compared the case where a Langasite single crystal is grown with a stoichiometric composition, and the case where it grows with a consistent dissolution composition.

Explanation of symbols

A Langasite single crystal (single crystal having a Ca ₃ Ga ₂ Ge ₄ O ₁₄ type structure)
2 Furnace 3 Langasite seed crystal (seed crystal)
4 Rangasite raw material (single crystal raw material)
5 crucible
6 Melt

Claims (7)

A method for producing a single crystal by growing the single crystal by the Bridgeman method,
Filling a seed crystal at the bottom of the crucible and filling the seed crystal with a plurality of single crystal raw materials having different compositions sequentially;
Placing the crucible in a vertical furnace in which a temperature gradient is formed in the vertical direction of the crucible, and melting the single crystal raw material into a melt by heating and melting;
A growth step of growing the single crystal by gradually solidifying the melt from below to above,
In the filling step, as the growth progresses, the single crystal raw material having a higher ratio of elements whose ratio decreases with respect to the composition ratio of the original melt is gradually changed from below to fill. A method for producing a single crystal characterized by the above. In the manufacturing method of the single crystal of Claim 1,
The method for producing a single crystal, wherein the crucible is rotated around the vertical axis during the growing step. In the manufacturing method of the single crystal of Claim 1 or 2,
The method for producing a single crystal, wherein the single crystal is a single crystal having a Ca ₃ Ga ₂ Ge ₄ O ₁₄ type structure. In the manufacturing method of the single crystal of Claim 3,
The method for producing a single crystal, wherein the single crystal having the Ca ₃ Ga ₂ Ge ₄ O ₁₄ type structure is a langasite single crystal (La ₃ Ga ₅ SiO ₁₄ ). In the manufacturing method of the single crystal of Claim 3,
The method for producing a single crystal, wherein the single crystal having the Ca ₃ Ga ₂ Ge ₄ O ₁₄ type structure is a langate single crystal (La ₃ Ga _5.5 Ta _0.5 O ₁₄ ). In the manufacturing method of the single crystal of Claim 3,
A method for producing a single crystal, wherein the single crystal having the Ca ₃ Ga ₂ Ge ₄ O ₁₄ type structure is a laganite single crystal (La ₃ Ga _5.5 Nb _0.5 O ₁₄ ). A single crystal produced by the method for producing a single crystal according to claim 1.

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