Sintered YAG object and method for producing sintered YAG object

Abstract

Provided are a sintered YAG object capable of contributing to an improvement in yield and a method for producing the sintered YAG object. The sintered YAG object includes Y3Al5O12, and the whole of a surface thereof orthogonal to a light transmission direction has an average birefringence along the light transmission direction of 5.0 nm / cm or less.

Description

YAG sintered body and manufacturing method of YAG sintered body

[0001] This specification describes a YAG sintered body and a method for producing the YAG sintered body.

[0002] Yttrium and aluminum composite oxide (YAlO 12 Garnet-structured crystals composed of YAG are generally called YAG crystals and are used as oscillation media for solid-state lasers for industrial, research, and medical use, as window materials for infrared spectrometers, and for various other devices.

[0003] When the laser medium, which is one of the uses of YAG, is irradiated with excitation light, the active atoms that absorb the excitation light and become excited release energy as they return to the ground state, causing spontaneous emission and stimulated emission. At this time, the stimulated emission amplifies the light, and highly pure light is emitted as laser light.

[0004] YAG used as a laser medium, etc., can be manufactured by sintering a raw material powder containing yttrium oxide powder and aluminum oxide powder. Here, if necessary, Nd, Yb, or other rare earth elements may be doped as active atoms. In this case, the YAG sintered body obtained by sintering the raw material powder has a portion of the Y or Al in the crystal replaced by the dopant (Nd:YAG, Yb:YAG, etc.), and an optical amplification effect of wavelength, etc., according to the type of dopant is obtained.

[0005] As related technologies, for example, Patent Document 1 describes "YAG ceramics in which the proportion of GOS (Grain Orientation Spread) between 0° and 1° is 60% or more." Patent Document 2 describes "Yb:YAG semilux material made of a composite oxide of Yb-doped yttrium and aluminum, characterized in that it contains 100 atppm to 200 atppm of Si and 500 atppm to 1000 atppm of La and / or Gd as additive elements."

[0006] JP 2020-158329 A JP 2022-96133 A

[0007] The YAG sintered body is required to have a small birefringence value in the light transmission direction, because if the birefringence value in the light transmission direction is large, the birefringence will disturb the polarization, causing a decrease in the transmitted light intensity and the generation of aberrations, which will lead to, for example, a deterioration in the characteristics as a laser medium.

[0008] In the YAG sintered body manufactured by sintering the raw material powder as described above, when the birefringence value in the light transmission direction is measured on the surface perpendicular to the light transmission direction, the birefringence value tends to be smaller in the central region than in the outer edge region in many cases. For this reason, the YAG sintered body is sometimes processed to remove the outer edge region with a large birefringence value, and then the central region including the effective diameter is used as a laser medium, etc.

[0009] However, since the outer edge region with a large birefringence value in the YAG sintered body obtained by powder sintering has a wide range and the large birefringence value in the outer edge region requires the removal of the outer edge region, which reduces the yield. Therefore, the YAG sintered body after sintering is required to have a relatively small birefringence value in the light transmission direction over the entire surface perpendicular to the light transmission direction.

[0010] This specification provides a YAG sintered body that can contribute to improving yields and a method for manufacturing the YAG sintered body.

[0011] The YAG sintered body disclosed in this specification is Y3Al5O 12 and the average value of birefringence in the light transmission direction over the entire surface perpendicular to the light transmission direction is 5.0 nm / cm or less.

[0012] The method for producing a YAG sintered body disclosed in this specification is 12 The method for producing a YAG sintered body comprising the above-mentioned compound includes an annealing step of heating the sintered body obtained by sintering a raw material powder in an oxidizing atmosphere, and in the annealing step, when the sintered body is heated to a maximum temperature and then cooled, the cooling rate from the maximum temperature is set to 80°C / hr or less.

[0013] The above-described YAG sintered body and the method for manufacturing the YAG sintered body can contribute to improving the yield.

[0014] 1 is a perspective view showing a YAG sintered body of one embodiment; FIG. 2 is a plan view of the YAG sintered body of FIG. 1; FIG. 3 is a two-dimensional mapping image of the birefringence value of the YAG sintered body produced in Example 1; and FIG. 4 is a two-dimensional mapping image of the birefringence value of the YAG sintered body produced in Comparative Example 1.

[0015] Hereinafter, the above-mentioned YAG sintered body and the manufacturing method thereof will be described in detail. Hereinafter, the description will be given with reference to the drawings and symbols as needed, but the symbols may be omitted.

[0016] In one embodiment, the YAG sintered body is Y3Al5O 12 This YAG sintered body contains. When the birefringence value of this YAG sintered body is measured in the direction of transmission of light such as laser light (referred to as the "light transmission direction") when used as a laser medium, for example, the average value of the birefringence value over the entire surface perpendicular to the light transmission direction is 5.0 nm / cm or less. If the average value of the birefringence value over the entire surface in the light transmission direction is small in this way, the wide central region can be effectively used as a laser medium, etc. In other words, the outer edge region that cannot be used as a laser medium, etc. and must be removed, is narrowed or almost eliminated, thereby improving yield.

[0017] To manufacture the YAG sintered body described above, the sintered body obtained by sintering the raw material powder is heated in an annealing step in an oxidizing atmosphere, and the temperature can be lowered by slow cooling at a rate of 80°C / hr or less after reaching the maximum temperature. Such slow cooling significantly reduces distortion, resulting in a YAG sintered body with a relatively small birefringence value over the entire surface perpendicular to the light transmission direction after the annealing step.

[0018] (YAG sintered body) The YAG sintered body is a composite oxide of Y (yttrium) and Al (aluminum) (Y3Al5O 12 The crystal structure of the YAG sintered body can be identified by X-ray diffraction measurement. The YAG sintered body for laser medium is this Y3Al5O12 In many cases, a part of the crystal is replaced with a dopant that becomes an active atom in the laser medium. In this case, the dopant 12 The Y and / or Al constituting part of the crystal is substituted, and the dopant is dissolved in the crystal in the form of ions.

[0019] Specific examples of the dopant include rare earth elements (i.e., at least one element selected from 16 elements consisting of Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu). Among rare earth elements, the dopant may be at least one element selected from the group consisting of Nd (neodymium), Yb (ytterbium), Er (erbium), Tm (thulium), and Ho (holmium).

[0020] Nd has a four-level energy level, which makes it easy for population inversion to occur and for laser oscillation to occur. Yb has a three-level energy level, which makes it difficult for population inversion to occur, but high-power pumping enables highly efficient and high-power laser oscillation. Er, Tm, and Ho all have a quasi-three-level energy level and are characterized by emitting light in the mid-infrared region, making them usable as eye-safe lasers.

[0021] When the YAG sintered body contains Nd, the Nd content is preferably 0.1 at% to 5 at%. When it contains Yb, the Yb content is preferably 0.1 at% to 15 at%. When it contains Er, the Er content is preferably 0.1 at% to 50 at%. When it contains Tm, the Tm content is preferably 0.1 at% to 10.0 at%. When it contains Ho, the Ho content is preferably 0.1 at% to 5 at%.

[0022] For example, in applications such as window materials for infrared spectrometers and other applications, YAG sintered bodies containing no dopants may be used. 12 The present invention also includes a YAG sintered body containing

[0023] In addition, the YAG sintered body may contain at least one element selected from the group consisting of Sc, La, Ce, Pr, Pm, Eu, Gd, Tb, Dy, Ho, Er, Tm, and Lu at a concentration below the solid solubility limit. The YAG sintered body may also contain unavoidable impurities resulting from the manufacturing process, etc. The content of the above elements, such as Nd and Yb, can be measured using glow discharge mass spectrometry (GD-MS) or inductively coupled plasma atomic emission spectrometry (ICP-AES).

[0024] When measuring the birefringence value in the light transmission direction of a YAG sintered body, the birefringence value may be larger in the outer edge region than in the central region of the surface perpendicular to the light transmission direction of the YAG sintered body. Typically, the birefringence value in the light transmission direction tends to have a distribution pattern in which it gradually increases from the central region to the outer edge region. The outer edge region of the YAG sintered body, which has a large birefringence value, is not desirable to be included as part of the laser medium, so it can be removed before use as a laser medium. Therefore, if the birefringence value of the outer edge region is large, removing it reduces the yield, and this becomes more noticeable as the outer edge region extends over a wider area.

[0025] In contrast, when the birefringence value of the YAG sintered body of this embodiment is measured in the light transmission direction, the average birefringence value over the entire surface perpendicular to the light transmission direction is 5.0 nm / cm or less. Such a small average birefringence value means that the birefringence value in the outer edge region is relatively small, and / or the outer edge region with a large birefringence value is in a relatively narrow range. This reduces or almost eliminates the outer edge region that needs to be removed before using the YAG sintered body as a laser medium. As a result, this can contribute to improving yield.

[0026] In order to further improve the yield, the average value of the birefringence in the light transmission direction over the entire surface of the YAG sintered body perpendicular to the light transmission direction is preferably 5.0 nm / cm or less, more preferably 2.5 nm / cm or less, and even more preferably 2.0 nm / cm or less. Although there is no particular problem with the average value of the birefringence over the entire surface being too small, it may be, for example, 0.01 nm / cm or more, typically 0.1 nm / cm or more.

[0027] The birefringence value of a YAG sintered body in the light transmission direction can be measured using a birefringence measurement device, such as the two-dimensional birefringence evaluation system WPA-200 manufactured by Photonic Lattice Co., Ltd. More specifically, to obtain the birefringence value of the YAG sintered body in the light transmission direction, the YAG sintered body is set in the birefringence measurement device, and two-dimensional mapping (two-dimensional distribution) data of the birefringence value perpendicular to the light transmission direction is obtained. The measurement wavelength can be 523 nm. The numerical data obtained by the birefringence measurement device is analyzed using analysis software (Photonic Lattice Co., Ltd.'s WPA-View) after applying a spike noise removal filter. Note that no processing or correction other than spike noise removal is performed. This allows the birefringence value at each position to be determined, and by calculating the average value for the entire surface, the average birefringence value over the entire surface can be obtained. When measuring birefringence values ​​using a birefringence measurement device, the field of view can be set to satisfy the following conditions for the number of measurement points: Φ60 mm sample: ≧14 data / mm 2 □106mm sample: ≧5 data / mm 2

[0028] For example, as shown in Figure 1, the YAG sintered body 1 may have a cylindrical or disc-like shape as a whole. In this case, if the axial direction along the central axis CA of the cylinder or disc is the light transmission direction, the circular end faces, such as perfect circles, ovals, or ellipses, located outside the axial direction correspond to the surfaces 2 and 3 referred to here. Alternatively, although not shown, if the YAG sintered body has a prismatic shape as a whole and the axial direction of the prismatic column is the light transmission direction, the end faces of polygonal shapes, such as rectangles, in the axial direction correspond to the surfaces. Such end faces are often flat.

[0029] As shown in FIG. 2 , the central region Rc (also referred to as the “90% central region”) occupies 90% of the surface 2 of the YAG sintered body 1 perpendicular to the light transmission direction, and the outer peripheral region Re (also referred to as the “10% outer peripheral region”) occupies the remaining 10%. The average birefringence value in the light transmission direction in the 90% central region Rc is preferably 2.0 nm / cm or less, more preferably 1.0 nm / cm or less. In many cases, the central region has a smaller birefringence value than the outer peripheral region. However, if the average birefringence value in the 90% central region Rc is calculated without considering the 10% outer peripheral region Re, the deterioration of the polarization degree can be effectively suppressed. The average birefringence value in the 90% central region Rc may be, for example, 0.01 nm / cm or more, typically 0.1 nm / cm or more.

[0030] For example, if the surfaces 2 and 3 of the YAG sintered body 1, which are perpendicular to the light transmission direction, are circular, the shape of the 90% central region Rc will be a concentric circle similar to the shape of the surfaces 2 and 3, with an area of ​​90% of the circular shape, as shown by the imaginary lines in Figure 2. Alternatively, if the shape of the surfaces is a polygon, including a square or rectangular shape, the 90% central region will be a polygon similar to the shape of the surfaces, have the same center, and have an area of ​​90% of the polygon. By measuring the birefringence value at each position on the surface using a birefringence measurement device, the average value of the birefringence value in the 90% central region can be determined.

[0031] The surface area of ​​the YAG sintered body perpendicular to the light transmission direction is not particularly limited, and here, YAG sintered bodies of various sizes are included. On the other hand, in this embodiment, even if the surface area of ​​the YAG sintered body is relatively large, it may be possible to sufficiently reduce the birefringence value over the entire surface. The surface area of ​​the YAG sintered body perpendicular to the light transmission direction is, for example, 2827 mm 2 ~17671mm 2 , typically 3848 mm 2 ~11,310 mm 2 The area of ​​the 90% central region may be relatively large, for example, 2544 mm 2~10112mm 2 , typically 3464 mm 2 ~10179mm 2 The diameter of the 90% central region may be taken as the effective diameter.

[0032] The birefringence value described above is obtained by dividing the value by the thickness T of the YAG sintered compact 1 to be measured, and means a value per unit thickness. The thickness T of the YAG sintered compact 1 can be measured using a vernier caliper. Furthermore, for example, when the areas of the front and back surfaces perpendicular to the light transmission direction are different from each other, the smaller of the two surfaces is used as the surface referred to here. The birefringence value is measured using the birefringence measurement device described above, with the YAG sintered compact 1 set so that light transmits through the smaller surface.

[0033] (Manufacturing Method) The YAG sintered body as described above can be manufactured by carrying out the steps of mixing raw materials, molding, sintering, and annealing in this order. The annealing step is particularly important.

[0034] In the raw material mixing step, yttrium oxide powder containing Y2O3 etc., aluminum oxide powder containing Al2O3 powder etc., and oxide powder for dopant are prepared and mixed to obtain raw material powder. Each oxide powder preferably has a purity of 4N or higher and a particle size in the range of 0.3 to 10 μm, but is not limited thereto.

[0035] The dopant oxide powder is appropriately selected depending on the composition of the YAG sintered body to be produced, and may contain, for example, an oxide of a rare earth element (i.e., at least one element selected from 16 elements consisting of Sc, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu). Among the rare earth elements, the dopant oxide powder preferably contains at least one oxide selected from the group consisting of Nd, Yb, Er, Tm, and Ho, specifically, Nd oxide such as Nd2O3, Yb oxide such as Yb2O3, Er oxide such as Er2O3, Tm oxide such as Tm2O3, and / or Ho oxide such as Ho2O3.

[0036] The mixing may be performed wet by adding the yttrium oxide powder, aluminum oxide powder, and dopant oxide powder to a ball mill or other mixer / pulverizer together with media such as alumina and a solvent such as water, and grinding the mixture. A dispersant may be added to suppress aggregation of the raw material powders and ensure uniform mixing. Sintering aids such as SiO2 and MgO may also be added. The mixing time may be, for example, 4 to 20 hours. After mixing is complete, the slurry removed from the mixer / pulverizer may be passed through a sieve as necessary and then dried by spray drying or the like. This results in the raw material powder. Note that although wet mixing has been described here, dry mixing may also be used.

[0037] In the compacting step, the raw material powder is compressed by uniaxial compression, cold isostatic pressing (CIP), or the like to be compacted into a predetermined shape, such as a cylindrical, disk-shaped, or rectangular column-shaped compact. In some cases, cold isostatic pressing may be further performed after uniaxial compression. The pressure and time for applying pressure to the raw material powder can be appropriately set in consideration of various conditions.

[0038] The compact obtained in the molding step is heated as necessary to remove moisture and organic components, and then subjected to the sintering step. In the sintering step, the compact is preferably heated to a temperature of 1600°C to 1900°C for 5 to 30 hours in a reduced pressure atmosphere such as a vacuum. If the heating temperature is too low or the heating time is too short, there is a concern that the density will not increase sufficiently. On the other hand, if the heating temperature is too high or the heating time is too long, there is a possibility that the translucency will decrease.

[0039] In the sintering step, hot isostatic pressing (HIP) may be further performed under the following conditions: an inert gas atmosphere such as Ar gas, a heating temperature of 1650°C to 1750°C, and a pressure of about 150 MPa. After the sintering step, a sintered body is obtained.

[0040] The subsequent annealing step is carried out for the purposes of oxidizing the dopant that has been reduced in the sintering step and replenishing the oxygen in the sintered body that has become deficient due to the sintering step.

[0041] In the annealing process, the sintered body is heated to a maximum temperature in an oxidizing atmosphere such as air, and then cooled. It is essential to reduce the cooling rate from the maximum temperature to 80°C / hr or less. This is because it has been newly discovered that by reducing this cooling rate, the strain in the YAG sintered body obtained after the annealing process is significantly reduced, resulting in a YAG sintered body with a small birefringence value across the entire surface. Here, the cooling rate from the maximum temperature must be 80°C / hr or less, and can be kept constant during the cooling process, or it can be changed during the cooling process.

[0042] From the viewpoint of further reducing distortion in the YAG sintered body, the temperature drop rate from the maximum temperature is preferably 75°C / hr or less. On the other hand, if the temperature drop rate is too slow, the annealing step takes a long time and productivity decreases, so the temperature drop rate from the maximum temperature is preferably 30°C / hr or more, particularly 50°C / hr or more.

[0043] The above-mentioned temperature drop rate may be continued until the temperature of the sintered body drops from the maximum temperature to room temperature, or may be continued until the temperature drops to a range of 600°C to 900°C. In this case, the temperature of the sintered body can be maintained within the temperature range of 600°C to 900°C for 5 to 10 hours. When the temperature is maintained during the temperature drop, the temperature inside the sintered body becomes uniform, and distortion can be further removed. After the temperature is maintained, the temperature drop rate can be increased to some extent, as described below. Therefore, if the temperature is maintained within the above-mentioned temperature range, the sintering process can be shortened. Furthermore, from the viewpoint of uniform heating of the sintered body, a holding time of 5 to 10 hours is preferable.

[0044] If the temperature is held in this way during the temperature drop, the temperature of the sintered body can be lowered to room temperature at any desired temperature drop rate after the temperature drop. This is because the temperature drop rate below 600°C to 900°C does not have a significant effect on the YAG sintered body. After the temperature is held, the temperature drop rate can be set to 150°C / hr to 300°C / hr, for example, or natural cooling can be used.

[0045] The maximum temperature reached in the annealing step can be, for example, 1300°C to 1500°C. If the maximum temperature is too low, the reduced dopant may not be oxidized, while if it is too high, transparency may be affected and devitrification may occur. The maximum temperature may be maintained for, for example, 5 to 30 hours. The annealing step is primarily performed to oxidize the dopant reduced in the preceding sintering step, so the maximum temperature is set to a certain degree. Furthermore, by adjusting the rate of temperature reduction from the maximum temperature as described above, it is possible to achieve the primary objective of reducing the dopant while also reducing distortion.

[0046] As mentioned above, the YAG sintered body produced after the annealing process has a surface area perpendicular to the light transmission direction of, for example, 2827 mm 2 ~17671mm 2 Even in the case of such a large YAG sintered body, by being manufactured by the above-mentioned manufacturing method, the birefringence value in the light transmission direction becomes relatively small over the entire surface perpendicular to the light transmission direction.

[0047] Next, a YAG sintered body was produced as a prototype and its effects were confirmed, which will be described below. However, the description here is for illustrative purposes only and is not intended to be limiting.

[0048] Example 1: Y2O3 powder, Al2O3 powder, and Yb2O3 were prepared and mixed to obtain a raw material powder so that the dopant content was 1.0 at%. This raw material powder was molded by cold pressing and then subjected to CIP to obtain a compact. The compact was then heated to sinter the powder, obtaining a sintered body.

[0049] The sintered body was then annealed in an air atmosphere. As shown in Table 1, the sintered body was heated to a maximum temperature of 1500°C for 10 hours, and then cooled to room temperature at a rate of 50°C / hr. This resulted in a cylindrical YAG sintered body with a diameter of 60 mm and a thickness of 12 mm.

[0050] (Example 2) A YAG sintered body was manufactured in substantially the same manner as in Example 1, except that during annealing, the temperature of the sintered body was held at 600°C for 5 hours while it was being cooled from the maximum temperature, and then the temperature was lowered to room temperature at a rate of 300°C / hr.

[0051] (Example 3) Example 3 was almost the same as Example 1, except that the shape of the YAG sintered body was changed to a rectangular columnar YAG sintered body having a square end face with a side length of 106 mm and a thickness of 7 mm.

[0052] Example 4 A YAG sintered body was produced in substantially the same manner as in Example 1, except that the temperature was lowered from the maximum temperature at 75° C. / hr during annealing.

[0053] Example 5 A YAG sintered body was produced in substantially the same manner as in Example 2, except that the temperature was maintained at 900° C. during the temperature drop and the maintenance time was set to 10 hours during annealing.

[0054] Comparative Example 1 A YAG sintered body was produced in substantially the same manner as in Example 1, except that the temperature was lowered from the maximum temperature at 300° C. / hr during annealing.

[0055] Comparative Example 2 A YAG sintered body was produced in substantially the same manner as in Example 3, except that the temperature was lowered from the maximum temperature at 300° C. / hr during annealing.

[0056]

[0057] (Evaluation) For each of the above YAG sintered compacts, the birefringence value in the light transmission direction was measured according to the method described above using a two-dimensional birefringence evaluation system WPA-200 manufactured by Photonic Lattice Co., Ltd. as the birefringence measurement device. Here, the axial direction of the cylindrical or prismatic YAG sintered compact was defined as the light transmission direction. The results are shown in Table 2. For reference, two-dimensional mapping images of the birefringence value for the YAG sintered compact of Example 1 are shown in Figure 3, and two-dimensional mapping images of the birefringence value for the YAG sintered compact of Comparative Example 1 are shown in Figure 4.

[0058]

[0059] As can be seen from Tables 1 and 2, in Examples 1 to 5, in which the cooling rate from the maximum temperature reached during annealing during production was slow, the YAG sintered bodies were relatively large in size, but the average value of the birefringence value over the entire surface was sufficiently small. Furthermore, the average value of the birefringence value in the 90% central region was even smaller. Therefore, it is recognized that the YAG sintered bodies of Examples 1 to 5 can be used as a laser medium over a wide central region of the surface, and that it is not necessary to remove a large portion of the outer edge region.

[0060] In Comparative Examples 1 and 2, the rate of temperature drop from the maximum temperature reached during annealing was fast, so the average values ​​of the birefringence values ​​of the YAG sintered body over the entire surface and the 90% central region were both large.

[0061] From the above, it was suggested that the above-mentioned YAG sintered body and the method for manufacturing the YAG sintered body may be able to improve the yield.

[0062] 1 YAG sintered body 2, 3 Surface perpendicular to the light transmission direction CA Central axis Rc Central region Re Outer edge region T Thickness

Claims

1. A YAG sintered body containing Y3Al5O 12 wherein the average value of the birefringence value in the light transmission direction over the entire surface orthogonal to the light transmission direction is 5.0 nm / cm or less.

2. The YAG sintered body according to claim 1, wherein the average value of the birefringence value in the light transmission direction in the central region occupying 90% of the area of the surface orthogonal to the light transmission direction is 2.5 nm / cm or less.

3. The YAG sintered body according to claim 2, wherein the average value of the birefringence value in the light transmission direction in the central region occupying 90% of the area of the surface orthogonal to the light transmission direction is 2.0 nm / cm or less.

4. The area of the central region occupying 90% of the area is 2544 mm 2 to 10112 mm 2 The YAG sintered body according to claim 2 or 3, wherein the YAG sintered body is as described above.

5. The area of the surface orthogonal to the light transmission direction is 2827 mm 2 to 17671 mm 2 The YAG sintered body according to any one of claims 1 to 3, wherein the YAG sintered body is as described above.

6. The Y3Al5O 12 is Y3Al5O in which part of the crystal is replaced by a dopant, 12 and the YAG sintered body according to any one of claims 1 to 3, which is used as a laser medium.

7. The YAG sintered body according to claim 6, wherein the dopant is at least one selected from the group consisting of Nd, Yb, Er, Tm, and Ho.

8. A method for manufacturing a YAG sintered body containing Y3Al5O 12 The method includes an annealing step of heating a sintered body obtained by sintering raw material powder in an oxidizing atmosphere. In the annealing step, when cooling the sintered body after heating it to the maximum temperature reached, the cooling rate from the maximum temperature reached is set to 80 °C / hr or less. A method for manufacturing a YAG sintered body.

9. The method for manufacturing a YAG sintered body according to claim 8, wherein in the annealing step, after reducing the temperature of the sintered body from the maximum temperature reached at the rate of temperature decrease, the temperature is maintained within the range of 600°C to 900°C for 5 to 10 hours.

10. The method for manufacturing a YAG sintered body according to claim 8 or 9, wherein in the annealing step, the maximum temperature reached is 1300°C to 1500°C.

11. The Y3Al5O 12 is Y3Al5O in which part of the crystal is replaced by a dopant, 12 and the method for manufacturing a YAG sintered body according to claim 8 or 9, wherein the YAG sintered body is used as a laser medium.

12. The method for manufacturing a YAG sintered body according to claim 11, wherein a YAG sintered body is manufactured, in which the dopant is at least one selected from the group consisting of Nd, Yb, Er, Tm, and Ho.

13. The area of the surface orthogonal to the light transmission direction is 2827 mm 2 to 17671 mm 2 The method for producing a YAG sintered body according to claim 8 or 9, which produces a YAG sintered body having the above dimensions.

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