JP2008074691A - Method for producing single crystal - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a method which can prevent heterogeneous precipitation forming a Ce-enriched phase, a Nd-enriched phase or the like, without lowering production efficiency, in the growth of a garnet type oxide single crystal added with a luminescent element such as Ce:GGAG or Nd:YAG. <P>SOLUTION: The single crystal 1 is pulled in such a manner that the sum of descending rate of the liquid surface of raw material melt 2 stored in crucible 4 during the pulling of the single crystal and the pulling speed of the single crystal 1 is always constant during the pulling. The measurement of the height of the liquid surface of raw material melt 2 or the measurement of weights of single crystal 1 is performed so as to calculate the descending rate of raw material melt based on the variation of the weight. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a method for producing a single crystal, and is particularly suitable for a garnet-type oxide single crystal to which a light emitting element such as Ce-added gadolinium gallium aluminum garnet (Ce: GGAG) or Nd-added yttrium aluminum garnet (Nd: YAG) is added. This relates to a manufacturing method.

  A Ce-added gadolinium gallium aluminum garnet (Ce: GGAG) single crystal is an oxide single crystal having a garnet structure containing at least Gd, Ga, Al, and O with Ce as a light emitting element, and is used for a radiation detector such as an X-ray. It is known as a scintillator material. Nd-doped yttrium aluminum garnet (Nd: YAG) single crystal is most commonly used as a solid-state laser oscillation element.

  These garnet-type oxide single crystals are grown by a so-called pulling method in which a seed crystal is immersed in a raw material melt dissolved in a crucible and then pulled while rotating. An example (schematic diagram) of an oxide single crystal pulling apparatus is shown in FIG. The raw material 2 is put into a noble metal crucible 4 such as iridium or platinum, and the noble metal crucible 4 is induction-heated by a high frequency coil 7 to melt the raw material 2. The precious metal crucible 4 is covered with a refractory 5 such as zirconia or alumina or a bubble for heat insulation. Further, since oxide single crystals are generally brittle and are likely to crack due to thermal strain, a refractory 5 such as zirconia or alumina is also provided above the noble metal crucible 4 to keep the temperature gradient within an appropriate range. Configure hot zones to keep. Further, depending on the type of oxide single crystal to be grown, a noble metal ring or an after heater (both not shown) may be provided. After adjusting the output of the high-frequency coil 7 so that the melted raw material 2 has a temperature suitable for growth, the lower end of the seed crystal 3 attached to the tip of the pulling / rotating shaft 6 is immersed and rotated while being pulled up. . The diameter of the growing single crystal is measured directly by a sensor or the like, or calculated from the weight of the grown single crystal. For example, the high frequency coil always matches the pre-programmed crystal diameter as shown in FIG. Adjust the output of. In this way, while always controlling the diameter, through the necking process from seed crystal immersion, gradually increasing the crystal diameter (shoulder formation), after reaching the target crystal diameter (straight body) While maintaining the diameter constant, it is grown up to the desired length and separated.

On the other hand, a growing method for measuring the height of the melt surface and controlling the pulling speed in accordance with the change in the height of the liquid level is disclosed in Patent Document 1, and the growing method of the pulling method that keeps the position of the liquid level constant. Is disclosed in Patent Document 2. In Patent Document 1, RBa ₂ Cu ₃ O _7-x (R is an yttrium or lanthanoid element) oxide single crystal is grown, and the melt overflows the crucible wall and overflows and the rate of lowering of the melt surface is unsatisfactory. Because it is stable, the height of the melt surface is directly measured using a sensor or the like to determine the descending speed of the melt surface, and the pulling speed is controlled in conjunction with the descending speed to stabilize the crystal shape. It is possible to control and cultivate stably for a long time. In Patent Document 2, the amount of drop of the melt surface is calculated from the weight and shape of the grown single crystal, and the crucible is pivoted so that the relative position between the melt surface and the heater is maintained throughout the entire process of single crystal growth. By pushing up in the direction, the temperature distribution in the vertical direction in the melt is prevented from changing.
JP-A-8-183698 JP-A-6-206797

For example, when growing a garnet-type oxide single crystal in which part of Gd and Y is substituted with a light emitting element such as Ce and Nd, such as Ce: GGAG and Nd: YAG, Ce ³⁺ ions and Nd ³⁺ ions are Gd ³⁺ ions. Since it is larger than the ion radius of Y ³⁺ ions, only a smaller amount than the composition of the raw material melt is taken into the crystal during crystallization. The ratio X _c / X _m between the concentration X _c of Ce ³⁺ or Nd ^{3+ in} the crystal and the concentration X _m of Ce ³⁺ or Nd ^{3+ in} the melt is called a distribution coefficient, and the above-mentioned Ce: GGAG, Nd: YAG, etc. Then, depending on the growing conditions, it is approximately 0.1 to 0.3.

Ce: GGAG In growth of a single crystal, since ^{the Ce 3+} concentration in the crystal was grown against ^{Ce 3+} concentration in the melt as described above is different significantly, release the excess ^{Ce 3+} to melt when solidified Therefore, the Ce ³⁺ concentration in the vicinity of the solid-liquid interface is higher than the Ce ³⁺ concentration in the melt at other locations, so-called compositional supercooling occurs. When compositional supercooling is large, cell growth occurs and crystal defects such as non-uniformity of Ce ³⁺ concentration in the crystal and heterogeneous precipitation of Ce-rich phase occur.

  As methods for reducing such compositional supercooling or cell growth, there are methods such as increasing the temperature gradient at the solid-liquid interface and decreasing the pulling rate. However, when the temperature gradient at the solid-liquid interface is increased, the temperature gradient above the melt (hot zone) inevitably increases, so that thermal distortion occurs and the single crystal is easily broken during cooling. Although it is effective to reduce the pulling speed, there is a problem that the production efficiency is lowered because the growing time becomes longer. In particular, in growing a garnet-type oxide single crystal, it is necessary to set the opening angle of the shoulder portion to 90 ° or less, more preferably about 60 ° in order to prevent the introduction of defects, and it takes a lot of time to reach the straight body portion. Therefore, the reduction in the pulling speed greatly affects the production efficiency. The same can be said for these problems in the Nd: YAG single crystal.

  In Patent Document 1, since the melt rises over the crucible wall surface and overflows and the descending speed of the melt surface is unstable, the height of the melt surface is directly measured using a sensor or the like. In some cases, the lowering speed is obtained and the pulling speed is controlled in conjunction with the lowering speed. However, in the case of a garnet-type oxide single crystal, the phenomenon that the raw material melt reacts with the crucible or rises and overflows the crucible wall surface does not occur. For this reason, it is possible to stably grow for a long time so as to match the planned shape using the above method, but with Ce: GGAG single crystal, etc., if the effective pulling rate is too fast, the cell growth causes a different phase. In order to suppress compositional supercooling and cell growth, the above method alone is insufficient.

  In Patent Document 2, the crucible is pushed up so that the relative position between the heater and the liquid level of the raw material melt is always constant so that the temperature gradient in the vertical direction in the melt does not change. In addition, the oxide single crystal has lower thermal conductivity than the semiconductor single crystal, and the grown single crystal hinders heat dissipation from the melt. In the growth, the noble metal crucible is heated directly by high frequency induction heating, and the side wall of the noble metal crucible above the melt surface shows the same effect as the after heater because the raw material melt in the crucible decreases with the growth. Therefore, the temperature gradient in the vertical direction of the melt and solid-liquid interface is reduced. Therefore, in the growth of Ce: GGAG single crystal or the like, a sufficient effect for preventing compositional supercooling and cell growth cannot be obtained even if the relative position between the heater and the liquid surface of the raw material melt is kept constant. Furthermore, the growing method of Patent Document 2 requires a crucible raising mechanism, which makes the structure of the apparatus complicated and increases the cost of the single crystal growing apparatus.

  The present invention has been made in view of such problems, and an object thereof is to provide an invention that solves the above problems.

In order to solve the above-described problems, the present invention provides a single crystal so that the sum of the descending speed of the raw material melt stored in the crucible during single crystal pulling and the single crystal pulling speed is always constant during pulling. Pull up. Thereby, heterogeneous precipitation due to compositional supercooling or cell growth can be prevented without lowering the production efficiency of single crystal growth. The growth rate _{V g} is defined as the sum of the liquid surface lowering speed Vm and the single crystal pulling speed _{V c} of the raw material melt, were grown growth velocity _{V g} at 0.5 mm / hr constant Ce: GGAG single crystal FIG. 2 and FIG. 3 show longitudinal sectional photographs of Ce: GGAG single crystals grown at a constant pulling speed Vc of 0.5 mm / hr, respectively. These were grown using an iridium crucible having an outer diameter of 100 mm, a height of 100 mm, and a thickness of 2 mm, and a single crystal having a straight body portion diameter of 60 mm and an opening angle of the shoulder portion of 60 °. When growing at a constant V _g = 0.5 mm / hr, V _c = 0.30 mm / hr at the straight body, and when V _c = 0.5 mm / hr is constant, the growing speed V _{g at the} straight body Becomes 0.82 mm / hr. When it nurtures the pulling rate _{V c} at 0.5mm / hr constant, while the out-of-phase 11 and bubbles 12 of the Ce-rich phase from about was only a 10mm entered the straight body portion is deposited, growth velocity V _{When g} is grown at a constant rate of 0.5 mm / hr, no such heterogeneous phase is precipitated.

In FIG. 4, when a single crystal having a straight body diameter of 60 mm and 85 mm is grown using a crystal shape program with a shoulder opening angle of 60 °, the growth rate V _g at the straight body part is 0.5 mm / hr. as for the case of growing at a pulling rate V _c constant and the case of growing at a growth rate V _g constant, showing the relationship between crystal diameter relative to time from the start of breeding. Here, an iridium crucible having an outer diameter of 100 mm × height of 100 mm × thickness of 2 mm is used for growing a single crystal having a straight barrel diameter of 60 mm, and an outer diameter of 150 mm × height of 150 mm × thickness of 2 mm for growing a single crystal having a straight barrel diameter of 85 mm. Each of these iridium crucibles is used. At this time, the pulling rate _{V c} constant development, in the case of _V c = 0.30mm / hr, straight body diameter 85mm For straight body 60mm diameter becomes _V c = 0.33mm / hr. Case of growing a single crystal of the straight body portion diameter 60 mm, when growing a pulling rate _{V c} at 0.30 mm / hr constant, about 6 days and half before entering the straight body from necking (158 hours), while necessary, since the growth rate _{V g} 0.5 mm / hr constant (pulling rate _{V c} of the straight body portion is 0.30 mm / hr) reaching the straight body of about 4 and a half days (112 hours) in the case of growing in step Can be shortened by two days. Further, in the case of growing a single crystal straight body diameter 85mm, when growing the pulling rate _{V c} at 0.33 mm / hr constant of about 8 and a half days before entering the straight body from necking (207 hours) required whereas, the growth rate _{V g} 0.5 mm / hr constant (pulling rate _{V c} of the straight body portion is 0.33 mm / hr) in the straight body of about 6 and a half days (155 hours) in the case of growing in The process can be shortened by 2 days.

  In order to obtain the liquid surface moving speed of the raw material melt, the height of the liquid surface is measured using a sensor or the like, and the descending speed of the raw material melt can be obtained based on the change in the liquid surface height. For example, by installing a CCD camera or the like, the liquid level height is calculated by image processing from the position of the meniscus of the raw material melt on the side of the crucible captured by the CCD camera, and the moving speed is obtained by measuring it at regular intervals. There are methods.

  As another method for obtaining the liquid surface moving speed of the raw material melt, the weight of the single crystal during pulling can be measured, and the lowering speed of the raw material melt can be obtained based on the change in the weight. A weight sensor such as a load cell is installed on the pulling / rotating shaft, and the high frequency output is adjusted so that the weight of the single crystal actually grown matches the weight change when the growth progresses in the planned shape of the single crystal to be grown. While nurturing. When the raw material melt does not overflow the crucible side surface and does not overflow like Ce: GGAG, the weight of the raw material melt is equal to the weight of the raw material melt reduced. The liquid level lowering rate can be calculated from the inner diameter of the crucible, the diameter of the single crystal, and the density of the single crystal to be grown. When performing these calculations, it is more preferable to correct the tension tension and buoyancy of the meniscus reflecting the density difference between the melt and the single crystal and the solid-liquid interface shape as needed.

  According to the growing method of the present invention, when growing a garnet-type oxide single crystal to which a light-emitting element such as Ce: GGAG single crystal or Nd: YAG single crystal is grown, a Ce-rich phase or It is possible to prevent heterogeneous precipitation such as Nd-rich phase.

  Hereinafter, the present invention will be specifically described with reference to examples. Note that the method for growing an oxide single crystal of the present invention is not limited to the following examples.

(Example 1)
Gd ₂ O ₃ 1641.73 g, Lu ₂ O ₃ 200.25 g, Ce (NO ₃ ) ₃ .6H ₂ O 72.84 g, Ga ₂ O ₃ 622.54 g, Al ₂ O ₃ 507.95 g Weighed. Next, after mixing these raw materials with a wet ball mill, they were put in an alumina crucible and fired at 1400 ° C. for 2 hours. After cooling, the raw material powder was sufficiently loosened. The obtained raw material powder was packed in a rubber tube and subjected to cold isostatic pressing at a pressure of 98 MPa to obtain a rod-shaped molded body. After 2500 g of this molded body was melted at high frequency in an iridium crucible having an outer diameter of 100 mm, a height of 100 mm, and a thickness of 2 mm, the seed crystal was immersed, and the growth rate V _{g was} constant at 0.5 mm / h (the pulling rate when growing the straight body part) V _c is a 0.30 mm / hr), the rotational speed 20～30Rpm, was single crystal growth of the straight body 60mm diameter shoulder opening angle 60 °. The growth atmosphere was nitrogen gas containing 2 vol% oxygen, and the growth direction was the <111> direction. When the straight body portion was grown 50 mm, the single crystal was separated from the raw material melt and cooled. Lowering speed Vm of the raw material melt, the weight of the single crystal during pulling any time measured by the load cell attached to the upper side of the pulling shaft was determined descending speed V _m of the raw material melt from the weight change. The _{V g = V c + V m} = 0.5mm / hr to become as pulling speed _{V c} was adjusted to cultivate.

(Example 2)
5198.81 g of Gd ₂ O ₃ , 634.11 g of Lu ₂ O ₃ , 230.65 g of Ce (NO ₃ ) ₃ .6H ₂ O, 1971.39 g of Ga ₂ O ₃ , 1608.52 g of Al ₂ O ₃ Weighed. Next, after mixing these raw materials with a wet ball mill, they were put in an alumina crucible and fired at 1400 ° C. for 2 hours. After cooling, the raw material powder was sufficiently loosened. The obtained raw material powder was packed in a rubber tube and subjected to cold isostatic pressing at a pressure of 98 MPa to obtain a rod-shaped molded body. After 9000 g of this molded body was melted by high frequency in an iridium crucible having an outer diameter of 150 mm, a height of 150 mm, and a thickness of 2 mm, the seed crystal was immersed, and the growth rate V _{g was} fixed at 0.5 mm / h (the pulling rate during straight body growth) V _c is a 0.33 mm / hr), the rotational speed 10～25Rpm, was single crystal growth of the straight body 85mm diameter shoulder opening angle 60 °. When the straight body portion was grown 50 mm, the single crystal was separated from the raw material melt and cooled. The growth atmosphere was nitrogen gas containing 2 vol% oxygen, and the growth direction was the <111> direction. The descending speed Vm of the raw material melt was obtained by calculating the liquid surface height by image processing from the position of the meniscus of the raw material melt on the side of the crucible captured by the CCD camera, and measuring it at regular intervals to obtain the moving speed. . The _{V g = V c + V m} = 0.5mm / hr to become as pulling speed _{V c} was adjusted to cultivate.

(Example 3)
1675.08 g of Y ₂ O ₃ , 39.53 g of Nd (NO ₃ ) ₃ .6H ₂ O, and 798.57 g of Al ₂ O ₃ were weighed. Next, after mixing these raw materials with a wet ball mill, they were put in an alumina crucible and fired at 1400 ° C. for 2 hours. After cooling, the raw material powder was sufficiently loosened. The obtained raw material powder was packed in a rubber tube and subjected to cold isostatic pressing at a pressure of 98 MPa to obtain a rod-shaped molded body. After 1800 g of this molded body was melted by high frequency in an iridium crucible having an outer diameter of 100 mm, a height of 100 mm, and a thickness of 2 mm, the seed crystal was immersed, and the growth rate V _{g was} fixed at 0.5 mm / h (the pulling rate during straight body growth) V _c is a 0.30 mm / hr), the rotational speed 20～30Rpm, was single crystal growth of the straight body 60mm diameter shoulder opening angle 60 °. The growth atmosphere was nitrogen gas containing 2 vol% oxygen, and the growth direction was the <111> direction. When the straight body portion was grown 50 mm, the single crystal was separated from the raw material melt and cooled. Lowering speed Vm of the raw material melt, the weight of the single crystal during pulling any time measured by the load cell attached to the upper side of the pulling shaft was determined descending speed V _m of the raw material melt from the weight change. The _{V g = V c + V m} = 0.5mm / hr to become as pulling speed _{V c} was adjusted to cultivate.

(Comparative Example 1)
Gd ₂ O ₃ 1641.73 g, Lu ₂ O ₃ 200.25 g, Ce (NO ₃ ) ₃ .6H ₂ O 72.84 g, Ga ₂ O ₃ 622.54 g, Al ₂ O ₃ 507.95 g Weighed. Next, after mixing these raw materials with a wet ball mill, they were put in an alumina crucible and fired at 1400 ° C. for 2 hours. After cooling, the raw material powder was sufficiently loosened. The obtained raw material powder was packed in a rubber tube and subjected to cold isostatic pressing at a pressure of 98 MPa to obtain a rod-shaped molded body. After 2500 g of this molded body was melted by high frequency in an iridium crucible having an outer diameter of 100 mm, a height of 100 mm, and a thickness of 2 mm, the seed crystal was immersed, and the pulling speed V _{c was} constant at 0.5 mm / h (growth speed during straight body part growth) V _g is 0.82 mm / hr), as the rotational speed 20～30Rpm, was single crystal growth of the straight body 60mm diameter shoulder opening angle 60 °. The growth atmosphere was nitrogen gas containing 2 vol% oxygen, and the growth direction was the <111> direction. When the straight body portion was grown 50 mm, the single crystal was separated from the raw material melt and cooled.

(Comparative Example 2)
Gd ₂ O ₃ 1641.73 g, Lu ₂ O ₃ 200.25 g, Ce (NO ₃ ) ₃ .6H ₂ O 72.84 g, Ga ₂ O ₃ 622.54 g, Al ₂ O ₃ 507.95 g Weighed. Next, after mixing these raw materials with a wet ball mill, they were put in an alumina crucible and fired at 1400 ° C. for 2 hours. After cooling, the raw material powder was sufficiently loosened. The obtained raw material powder was packed in a rubber tube and subjected to cold isostatic pressing at a pressure of 98 MPa to obtain a rod-shaped molded body. After 2500 g of this molded body was melted by high frequency in an iridium crucible having an outer diameter of 100 mm, a height of 100 mm, and a thickness of 2 mm, the seed crystal was immersed, and the pulling speed V _{c was} constant 0.30 mm / h (growth speed during straight body growth) V _g is the 0.5 mm / hr), the rotational speed 20～30Rpm, was single crystal growth of the straight body 60mm diameter shoulder opening angle 60 °. The growth atmosphere was nitrogen gas containing 2 vol% oxygen, and the growth direction was the <111> direction. When the straight body portion was grown 50 mm, the single crystal was separated from the raw material melt and cooled.

(Comparative Example 3)
5198.81 g of Gd ₂ O ₃ , 634.11 g of Lu ₂ O ₃ , 230.65 g of Ce (NO ₃ ) ₃ .6H ₂ O, 1971.39 g of Ga ₂ O ₃ , 1608.52 g of Al ₂ O ₃ Weighed. Next, after mixing these raw materials with a wet ball mill, they were put in an alumina crucible and fired at 1400 ° C. for 2 hours. After cooling, the raw material powder was sufficiently loosened. The obtained raw material powder was packed in a rubber tube and subjected to cold isostatic pressing at a pressure of 98 MPa to obtain a rod-shaped molded body. The compact 9000g outside diameter 150 mm, height 150 mm, after high-frequency heating in an iridium crucible in a thickness of 2 mm, a seed crystal is immersed, growth velocity during the pulling rate _V c 0.5 mm / hr constant (straight body foster V _g is 0.76 mm / hr), as the rotational speed 10～25Rpm, was single crystal growth of the straight body 85mm diameter shoulder opening angle 60 °. The growth atmosphere was nitrogen gas containing 2 vol% oxygen, and the growth direction was the <111> direction. When the straight body portion was grown 50 mm, the single crystal was separated from the raw material melt and cooled.

(Comparative Example 4)
5198.81 g of Gd ₂ O ₃ , 634.11 g of Lu ₂ O ₃ , 230.65 g of Ce (NO ₃ ) ₃ .6H ₂ O, 1971.39 g of Ga ₂ O ₃ , 1608.52 g of Al ₂ O ₃ Weighed. Next, after mixing these raw materials with a wet ball mill, they were put in an alumina crucible and fired at 1400 ° C. for 2 hours. After cooling, the raw material powder was sufficiently loosened. The obtained raw material powder was packed in a rubber tube and subjected to cold isostatic pressing at a pressure of 98 MPa to obtain a rod-shaped molded body. After 9000 g of this molded body was melted by high frequency in an iridium crucible having an outer diameter of 150 mm, a height of 150 mm, and a thickness of 2 mm, the seed crystal was immersed, and the pulling speed V _{c was} constant 0.33 mm / h (growth speed during straight body growth) V _g is the 0.5 mm / hr), the rotational speed 10～25Rpm, was single crystal growth of the straight body 85mm diameter shoulder opening angle 60 °. The growth atmosphere was nitrogen gas containing 2 vol% oxygen, and the growth direction was the <111> direction. When the straight body portion was grown 50 mm, the single crystal was separated from the raw material melt and cooled.

(Comparative Example 5)
1675.08 g of Y ₂ O ₃ , 39.53 g of Nd (NO ₃ ) ₃ .6H ₂ O, and 798.57 g of Al ₂ O ₃ were weighed. Next, after mixing these raw materials with a wet ball mill, they were put in an alumina crucible and fired at 1400 ° C. for 2 hours. After cooling, the raw material powder was sufficiently loosened. The obtained raw material powder was packed in a rubber tube and subjected to cold isostatic pressing at a pressure of 98 MPa to obtain a rod-shaped molded body. The compact 1800g outer diameter 100 mm, height 100 mm, after high-frequency heating in an iridium crucible in a thickness of 2 mm, a seed crystal is immersed, growth velocity during the pulling rate _V c 0.5 mm / h constant (straight body foster V _g is 0.82 mm / hr), as the rotational speed 20～30Rpm, was single crystal growth of the straight body 60mm diameter shoulder opening angle 60 °. The growth atmosphere was nitrogen gas containing 2 vol% oxygen, and the growth direction was the <111> direction. When the straight body portion was grown 50 mm, the single crystal was separated from the raw material melt and cooled.

  Table 1 summarizes the presence / absence of heterogeneous precipitation in Examples 1 to 3 and Comparative Examples 1 to 5 and the time required from the start of growth to the straight body part. In Comparative Examples 1, 3, and 5 grown at a constant pulling speed Vc of 0.5 mm / hr, Ce-rich phase and heterogeneous phase of Nd-rich phase were precipitated, whereas the growth was carried out at a constant growing speed of Vg 0.5 mm / hr. In Examples 1 to 3, the heterogeneous phase does not precipitate, and the time required to reach the straight body portion can be extended by less than one day. On the other hand, in Comparative Example 2 grown at a constant pulling speed Vc of 0.30 mm / hr and Comparative Example 4 grown at a constant Vc of 0.33 mm / hr, no Ce-rich phase or Nd-rich phase was precipitated. Compared with 2 and 2, it takes about 2 days to reach the straight body part, and the production efficiency is lowered.

It is the schematic of the growth apparatus of an oxide single crystal. It is a longitudinal cross-sectional photograph of the Ce: GGAG single crystal grown by one Embodiment of this invention. It is the longitudinal cross-sectional photograph and SEM photograph of Ce: GGAG single crystal grown by the conventional method. It is the figure which showed the relationship between the growth time and the single crystal diameter in one Embodiment of this invention and the conventional method. It is a figure explaining the structure of the pulled single crystal.

Explanation of symbols

1: oxide single crystal 2: raw material melt 3: seed crystal 4: noble metal crucible 5: refractory 6: pulling / rotating shaft 7: high frequency coil 11: heterogeneous phase of Ce rich phase 12: bubbles

Claims (4)

The single crystal is pulled so that the sum of the lowering speed of the raw material melt stored in the crucible during the pulling of the single crystal and the pulling speed of the single crystal is always constant during the pulling. Production method. The method for producing a single crystal according to claim 1, wherein the height of the liquid surface of the raw material melt is measured, and the descending speed of the raw material melt is determined based on the change in the liquid surface height. The method for producing a single crystal according to claim 1, wherein the weight of the single crystal during pulling is measured, and the descending speed of the raw material melt is determined based on the change in the weight. The method for producing a single crystal according to any one of claims 1 to 3, wherein the single crystal is a garnet single crystal containing Ce as a light emitting element and containing at least Gd, Al, Ga and O.