YAG sintered body and method for producing YAG sintered body

Abstract

The present invention provides: a YAG sintered body which is capable of achieving a relatively low reflectance and / or uniform mechanical strength at the bonding interface between a first sintered part and a second sintered part; and a method for producing a YAG sintered body. This YAG sintered body includes a portion in which a part of a crystal of Y3Al5O12 is replaced with a dopant. The YAG sintered body has a first sintered part and a second sintered part which are bonded to each other, the first sintered part containing a dopant that is not contained in the second sintered part. On the surface of the YAG sintered body, the average diffusion distance of at least one dopant, which is contained in the first sintered part, to the second sintered part is longer than 0.010 mm in a direction that is orthogonal to the bonding interface between the first sintered part and the second sintered part.

Description

YAG sintered body and manufacturing method of YAG sintered body

[0001] This specification discloses 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 purposes.

[0003] When the oscillation medium 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] The YAG used as the oscillation medium can be produced by sintering raw material powder containing yttrium oxide powder and aluminum oxide powder. Here, neodymium, ytterbium, or other rare earth elements may be doped as active atoms, if necessary. In this case, the YAG sintered body becomes one in which the dopant replaces part of the yttrium or aluminum in the crystal (Nd:YAG, Yb:YAG, etc.), and optical amplification of wavelengths, etc., is achieved according to the type of dopant.

[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 oscillation medium may be a YAG sintered body formed by bonding a first sintered portion and a second sintered portion, each containing a different type of dopant or with or without a dopant. In order to achieve a large optical gain, it is desirable to minimize the reflectance of light at the bonding interface between the first sintered portion and the second sintered portion, so that reflection at the bonding interface between the first sintered portion and the second sintered portion is almost eliminated. Furthermore, the mechanical strength of the bonding interface between the first sintered portion and the second sintered portion may be required to be uniform. A bonding interface with uneven mechanical strength may become a starting point for cracks or other problems when subjected to external force.

[0008] This specification provides a YAG sintered body that can achieve relatively low reflectivity and / or uniform mechanical strength at the bonding interface between the first sintered part and the second sintered part, and a method for manufacturing the YAG sintered body.

[0009] The YAG sintered body disclosed in this specification is Y3Al5O 12 The YAG sintered body includes a first sintered portion and a second sintered portion bonded to each other, the first sintered portion having a dopant not contained in the second sintered portion, and the average diffusion distance of at least one dopant contained in the first sintered portion to the second sintered portion on the surface of the YAG sintered body in a direction perpendicular to the bonding interface between the first sintered portion and the second sintered portion is longer than 0.010 mm.

[0010] The method for producing a YAG sintered body disclosed in this specification is 12a first sintered portion and a second sintered portion bonded to each other, the first sintered portion containing a dopant not contained in the second sintered portion, and raw material powders being a first powder and a second powder containing yttrium oxide powder and aluminum oxide powder, respectively, the first powder containing an oxide powder for dopant not contained in the second powder; a raw material preparation step of preparing the first powder and the second powder, the first powder containing an oxide powder for dopant not contained in the second powder; a molding step of pressing and molding the first powder and the second powder in a state where they are in contact with each other at their interfaces, to obtain a molded body having a first molded portion of the first powder and a second molded portion of the second powder bonded to each other; and a sintering step of heating and sintering the molded body.

[0011] According to the above-described YAG sintered body and the method for manufacturing the YAG sintered body, it is possible to achieve a relatively low reflectivity and / or uniform mechanical strength at the bonding interface between the first sintered part and the second sintered part.

[0012] 3 is a graph showing an example of a change in the characteristic X-ray intensity (element intensity) of an arbitrary element along a direction perpendicular to the bonding interface between the first sintered portion and the second sintered portion by EPMA line analysis. A cross-sectional view along the axial direction, schematically showing a state in which a first powder and a second powder are molded to produce a molded body having the first molded portion and the second molded portion bonded to each other. A cross-sectional view along the axial direction, showing a YAG sintered body having the first sintered portion and the second sintered portion obtained by heating the molded body of FIG. 2. A cross-sectional view along line IV-IV of FIG. 3. A graph showing the results of line analysis of the YAG sintered bodies of Example 1 and Comparative Example 1. A graph showing the results of line analysis of the YAG sintered bodies of Example 2 and Comparative Example 2. A graph showing the results of line analysis of the YAG sintered bodies of Example 3 and Comparative Example 3. A graph showing the results of line analysis of the YAG sintered bodies of Example 4 and Comparative Example 4. An SE image and a BSE image of the bonding interface at the surface of the YAG sintered body of Example 1. An SE image and a BSE image of the bonding interface at the surface of the YAG sintered body of Comparative Example 1. Fig. 1 is a schematic diagram showing a method for measuring reflectance. Fig. 2 is a plan view of a YAG sintered body of one embodiment and a schematic cross-sectional view taken along line bb thereof. Fig. 3 is a graph showing the results of linear analysis of a YAG sintered body of Example 5. Fig. 4 is a graph showing the results of linear analysis of a YAG sintered body of Example 6. Fig. 5 is a graph showing the results of linear analysis of a YAG sintered body of Example 7.

[0013] The following describes in detail an embodiment of the above-mentioned YAG sintered body and a method for manufacturing the YAG sintered body. 12 Contains YAlO 12 The YAG sintered body includes a portion in which a part of the crystal is replaced by a dopant. The YAG sintered body has a first sintered portion and a second sintered portion bonded to each other, and the first sintered portion contains a dopant that is not contained in the second sintered portion. In other words, the first sintered portion and the second sintered portion differ from each other in the presence or absence and / or type of dopant.

[0014] Furthermore, in the above-mentioned YAG sintered body, the average diffusion distance of at least one dopant contained in the first sintered body to the second sintered body on its surface in a direction perpendicular to the bonding interface between the first sintered body and the second sintered body (hereinafter also referred to as the "interface-perpendicular direction") is longer than 0.010 mm. A YAG sintered body with such a long average diffusion distance can be easily obtained, for example, by employing powder sintering bonding rather than diffusion bonding during its manufacture, as described below, which effectively suppresses parasitic oscillation. Parasitic oscillation is a phenomenon in which laser oscillation occurs within a laser medium in a direction different from the intended direction of laser light extraction when the excitation energy density inside the medium becomes high. Parasitic oscillation can be suppressed by bonding a laser light-absorbing medium to the outside of the laser medium, and the smaller the reflection at the interface between them, the greater the suppression effect of parasitic oscillation. The refractive index of light at the bonding interface between the first sintered portion and the second sintered portion varies depending on the dopant type and its concentration. If the dopant contained in the first sintered portion diffuses into the second sintered portion over a distance longer than 0.010 mm, the change in refractive index is reduced. On the other hand, Fresnel reflection increases as the refractive index difference increases. Therefore, reducing the refractive index difference is expected to reduce Fresnel reflection. As a result, parasitic oscillation is efficiently suppressed, potentially increasing the optical gain of the laser. Furthermore, if the average diffusion distance of at least one dopant contained in the first sintered portion into the second sintered portion is longer than 0.010 mm, the mechanical strength of the bonding interface becomes uniform.

[0015] Manufacturing such a YAG sintered body may include, for example, a raw material preparation process, a molding process, and a sintering process, performed in this order. In the raw material preparation process, a first powder corresponding to the desired composition of the first sintered portion and a second powder corresponding to the desired composition of the second sintered portion are prepared. Here, it is important to obtain a compact having corresponding first and second molded portions by pressing the first and second powders in a state of mutual contact at the interface during the molding process. The first and second molded portions are then heated during the sintering process to bond them into the first and second sintered portions. By molding the first and second powders in the molding process and then sintering them during the sintering process, the first and second powders overlap before sintering. The dopant in either the first or second powder mixes with the other, increasing the average diffusion distance of the dopant. The average diffusion distance of the dopant is determined by parameters such as temperature, time, and initial concentration gradient.

[0016] (YAG sintered body) The YAG sintered body is mainly a composite oxide of Y (yttrium) and Al (aluminum) (Y3Al5O 12 The YAG sintered body has a first sintered portion and a second sintered portion bonded to each other.

[0017] The YAG sintered body contains Y3Al5O 12 In more detail, of the first sintered portion and the second sintered portion of the YAG sintered body, the first sintered portion contains one or more kinds of dopants, and the dopants cause the crystal structure of Y3Al5O 12 The yttrium and / or aluminum constituting part of the crystal is substituted, and the dopant is dissolved in the crystal in the form of ions.

[0018] The second sintered portion may not contain a dopant. In this case, the first sintered portion contains a dopant, while the second sintered portion does not, so the first sintered portion and the second sintered portion differ in the presence or absence of a dopant. Alternatively, if both the first sintered portion and the second sintered portion contain a dopant, at least one type of dopant contained in the first sintered portion is not contained in the second sintered portion. In this case, the first sintered portion and the second sintered portion differ from each other in the type of at least one dopant.

[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). The first sintered portion may contain such a rare earth element as a dopant.

[0020] Among rare earth elements, Nd (neodymium) has a four-level energy level system, which makes it easy for population inversion to occur and laser oscillation to occur. Yb (ytterbium) has a three-level energy level system, which makes it difficult for population inversion to occur, but high-power pumping enables high-efficiency, high-power laser oscillation. Sm (samarium) does not absorb the pumping light of Nd:YAG, but absorbs the oscillation wavelength (1064 nm), so it is used as an absorption layer for Nd:YAG. Cr (chromium) is a chromium-based material that can absorb Cr. 4+ When valence converted to Cr, it can absorb the oscillation wavelengths of Nd:YAG and Yb:YAG (1064 nm, 1030 nm), so it is used as an absorption layer for them. Furthermore, Cr is a saturable absorber, so it is used as a Q-switch. It is preferable that the first sintered portion contains Nd and / or Yb as a dopant, and the second sintered portion contains Sm and / or Cr as a dopant, or does not have any portion replaced by a dopant. Typically, the first sintered portion contains Nd, and the second sintered portion contains Sm or Cr, or does not contain a dopant. Furthermore, the first sintered portion may contain Yb, and the second sintered portion may contain Cr, or does not contain a dopant.

[0021] When the YAG sintered body contains Nd, the Nd content is preferably 0.1 at% to 5 at%. When the YAG sintered body contains Yb, the Yb content is preferably 0.1 at% to 15 at%. When the YAG sintered body contains Sm, the Sm content is preferably 0.1 at% to 10 at%. When the YAG sintered body contains Cr, the Cr content is preferably 0.1 at% to 3 at%. 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 or below the solid solubility limit. The contents of the above elements, such as Nd, Yb, Sm, and Cr, can be measured using GD-MS (glow discharge mass spectrometry) or ICP-AES (inductively coupled plasma atomic emission spectroscopy). In addition, the YAG sintered body may contain unavoidable impurities resulting from the manufacturing process, etc.

[0022] Although it may be difficult to visually or microscopically observe the first and second sintered portions of the YAG sintered body, a bonding interface exists between them. As described above, the first sintered portion contains a dopant that is not contained in the second sintered portion. Therefore, by checking the change in the content of this dopant on the surface of the YAG sintered body, for example, the bonding interface between the first sintered portion and the second sintered portion can be grasped. This is because the first sintered portion side of the bonding interface contains a large amount of the dopant, while the second sintered portion side contains little or almost no dopant.

[0023] In the YAG sintered body of this embodiment, the average diffusion distance of at least one dopant contained in the first sintered portion into the second sintered portion on its surface in the direction perpendicular to the interface is longer than 0.010 mm. If the average diffusion distance of the dopant contained in the first sintered portion into the second sintered portion is 0.010 mm or less, this suggests insufficient bonding, resulting in increased variation in the mechanical strength of the bonding surface and increased reflectivity at the bonding interface. From this perspective, the average diffusion distance of the dopant contained in the first sintered portion is preferably 0.020 mm or more. The average diffusion distance of the dopant contained in the first sintered portion may be 0.020 mm to 0.300 mm. If the average diffusion distance of the dopant contained in the first sintered portion is too long, there is a concern that the effective diameter will be reduced when used as an oscillation medium, etc. For this reason, the average diffusion distance of the dopant contained in the first sintered portion is preferably 0.090 mm or less, and even preferably 0.080 mm or less. As will be described later, when a pre-molding step is performed in manufacturing a YAG sintered body, the diffusion distance of the dopant in the YAG sintered body tends to be kept small to some extent as described above, compared to when the first powder and the second powder are molded as they are in their powder form. The average diffusion distance of the dopant contained in the first sintered portion is preferably 0.020 mm to 0.080 mm.

[0024] The average diffusion distance of the dopant contained in the first sintered portion is measured as follows. For a given element, such as a dopant, contained in the YAG sintered body, a line analysis is performed on the surface of the YAG sintered body along the direction perpendicular to the interface using an electron probe microanalyzer (EPMA), and the change in element intensity along the direction perpendicular to the interface is confirmed on both sides of the bonded interface, including the bonded interface. This results in a graph, as shown in Figure 1, in which the horizontal axis represents the distance along the direction perpendicular to the interface and the vertical axis represents the element intensity (characteristic X-ray intensity). Next, the element intensity in the graph is normalized so that the minimum value is 0 and the maximum value is 1. Normalization is performed using the formula: C n = (C x -C0) / (C1-C0), where C xis the element intensity at a certain distance, C is the element intensity at a reference position Ps1 where the element intensity is substantially constant at a position sufficiently far from the bonded interface position Pi toward the first sintered portion (right side in FIG. 1 ) in the direction perpendicular to the interface, and C is the element intensity at a reference position Ps2 where the element intensity is substantially constant at a position sufficiently far from the bonded interface position Pi toward the second sintered portion (left side in FIG. 1 ) in the direction perpendicular to the interface. The bonded interface position Pi refers to the position where the element intensity is half of its maximum value. Here, element intensity is generally proportional to concentration, so the vertical axis can be considered to represent the element concentration. The relationship between the element concentration c normalized to 0 to 1 and the average diffusion length can be described by the following equation (1), which includes an error function. In equation (1), x is the bonded interface position Pi, and L is the average diffusion length. The above graph is fitted using the least squares method based on equation (1) to determine the average diffusion length L. Here, the average diffusion distance L is used as an operating variable to determine the average diffusion distance L that minimizes the sum of squares of the error.

[0025]

[0026] The average diffusion distance of the dopant contained in the first sintered portion is determined by performing the above-described measurement method for the average diffusion distance L on the dopant. For at least one of the dopants contained in the first sintered portion, the average diffusion distance of the dopant into the second sintered portion may be longer than 0.010 mm.

[0027] The YAG sintered body may have a first sintered portion and a second sintered portion, and may have one or more other sintered portions bonded to the first sintered portion and / or the second sintered portion. In this case, the bonding mode and average diffusion distance between the first sintered portion or the second sintered portion and the other sintered portions are not particularly important.

[0028] The shape of the YAG sintered body is determined appropriately depending on the application, and can be various three-dimensional shapes, such as a cylindrical column, a rectangular column, or other columnar shapes, or a polyhedron including a cube or rectangular parallelepiped. For example, in a YAG sintered body having an overall cylindrical shape, the first sintered portion may be cylindrical, and the second sintered portion may be cylindrical, surrounding the side surface of the first sintered portion and joining the inner circumferential surface of the first sintered portion to the side surface of the first sintered portion. In this case, for example, the outer diameter of the cylindrical second sintered portion may be 25 mm to 100 mm, the diameter of the cylindrical first sintered portion may be 10 mm to 60 mm, and the thicknesses of the first sintered portion and the second sintered portion may be 5 mm to 20 mm. Furthermore, a relatively large YAG sintered body may be formed, for example, with an outer diameter of the cylindrical second sintered portion of 120 mm to 200 mm and a diameter of the cylindrical first sintered portion of 110 mm to 190 mm. However, the shapes and dimensions are not limited to those described herein.

[0029] The YAG sintered body of this embodiment may have high mechanical strength, for example, due to being manufactured by a method described below. The bending strength of the YAG sintered body is preferably 310 MPa to 370 MPa, and more preferably 340 MPa to 360 MPa. A YAG sintered body having such bending strength can be used in a high-load environment. The bending strength is measured in accordance with JIS R1601, "Test method for room-temperature bending strength of fine ceramics."

[0030] Furthermore, as will be described later, by adjusting the pressure applied during the pre-molding process and the molding process in the manufacturing method, the YAG sintered body 13 may have a shape in which either the first sintered portion 11 or the second sintered portion 12 (the first sintered portion 11 in the figure) bulges toward the other side (the second sintered portion 12 in the figure), as shown in Figure 12.

[0031] More specifically, when the illustrated YAG sintered compact 13 is cut in the thickness direction from one surface 13a where the bonding interface BI is exposed to the other surface 13b on the back side thereof, a cut surface such as that shown in Fig. 12(b) is obtained. In the case of the YAG sintered compact 13 having a cylindrical first sintered portion 11 and a cylindrical second sintered portion 12 as shown in Fig. 12, the cut surface is obtained by cutting the YAG sintered compact 13 through its central axis. In this cut surface, the bonding interface BI has a shape that bulges toward the first sintered portion 11 or the second sintered portion 12 (the second sintered portion 12 in the illustrated example) at a central portion relative to both end points E1 and E2 in the thickness direction of the bonding interface BI (the vertical direction in Fig. 12(b)).

[0032] In this case, it is preferable that the ratio (P / C) of the length P of a virtual arc VA (shown by a dashed line in FIG. 12(b)) passing through both end points E1 and E2 of the bonded interface and the center point CP on the thickness center position Pc on the above-mentioned cut surface to the linear distance C between both end points E1 and E2 of the bonded interface BI is 1.0050 or more. The virtual arc VA is an arc between both end points E1 and E2 on a circle circumscribing the triangle, with the circumcenter of the triangle having the three vertices, the end points E1, E2 and the center point CP, as its center. The ratio (P / C) of the length P of the arc VA to the linear distance C may be 1.2000 or less, more preferably 1.0100 to 1.1000, and even more preferably 1.0300 to 1.0700. By making the ratio (P / C) of the length P of the arc VA to the linear distance C relatively large, the area of ​​the bonded interface becomes large, which promotes bonding during sintering, resulting in a strong bonded interface and suppressing the occurrence of cracks at the bonded interface. Many cut surfaces are obtained depending on where the YAG sintered body 13 is cut, and it is sufficient that P / C is equal to or greater than the above-mentioned lower limit or within the above-mentioned range at at least one of these cut surfaces.

[0033] Furthermore, in at least one of the cut surfaces, the ratio (h / C) of the distance h between the midpoint MP of the line segment LS connecting the end points E1, E2 and the center point CP to the linear distance C is preferably 0.050 or more, and more preferably 0.080 or more. The advantages of a large ratio (h / C) of the distance h to the linear distance C are similar to the advantages described above when the ratio (P / C) of the length P of the arc VA to the linear distance C is large. The ratio (h / C) of the distance h to the linear distance C may be, for example, 0.200 or less, particularly 0.180 or less.

[0034] (Manufacturing Method) The YAG sintered body as described above can be manufactured by carrying out a raw material preparation step, a molding step, and a sintering step in this order.

[0035] In the raw material preparation step, a first powder and a second powder are prepared. The first powder and the second powder contain yttrium oxide powder containing Y2O3 and the like, and aluminum oxide powder containing Al2O3 and the like, respectively. As described above, the YAG sintered body to be manufactured here has a first sintered portion and a second sintered portion bonded to each other, and the first sintered portion contains a dopant not contained in the second sintered portion. The first powder and the second powder correspond to the compositions of the first sintered portion and the second sintered portion, respectively.

[0036] More specifically, the first powder contains, in addition to yttrium oxide powder and aluminum oxide powder, one or more types of dopant oxide powders that are not contained in the second powder. The second powder may be composed of yttrium oxide powder and aluminum oxide powder without containing any dopant oxide powder. Alternatively, the second powder may contain, in addition to yttrium oxide powder and aluminum oxide powder, one or more types of dopant oxide powders. In this case, the first powder contains dopant oxide powders other than the dopant oxide powder contained in the second powder.

[0037] The dopant oxide powder 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). The dopant oxide powder contained in the first powder may contain such an oxide powder of a rare earth element.

[0038] Typically, the dopant oxide powder contained in the first powder may contain an oxide of Nd such as NdO and / or an oxide of Yb such as YbO, while the dopant oxide powder contained in the second powder may contain an oxide of Sm such as SmO and / or an oxide of Cr such as CrO.

[0039] To prepare the first and second powders as raw material powders, for example, the above-mentioned yttrium oxide powder and aluminum oxide powder, and optionally a predetermined dopant oxide powder, are placed in a mixer / mill along with a medium such as alumina and a solvent such as water, and wet mixed while being milled. A dispersant may be added to suppress aggregation of the raw material powders and ensure uniform mixing. Sintering aids such as Si and MgO may also be added. The mixing time may be, for example, 4 to 6 hours. After mixing is complete, the slurry removed from the mixer / miller can be dried by spray drying or the like. This results in the raw material powders of the first and second powders. While wet mixing has been described here, dry mixing may also be used.

[0040] Prior to the molding step described below, either the first powder or the second powder may be pre-molded into a columnar, cylindrical, or other shape as needed. In the pre-molding step, pressure is applied to either the first powder or the second powder to pre-mold it into a predetermined shape. For example, when producing the YAG sintered body 13 shown in FIG. 4, the pre-molding step may be performed on only the first powder to form it into a columnar shape, but this is not limited to this.

[0041] The pressure applied to the first or second powder in the pre-molding step is preferably smaller than the pressure applied to the first and second powders in the molding step described below, specifically, less than two-thirds of the pressure applied in the molding step. This allows one of the first or second powders used in the pre-molding step to bulge toward the other powder when pressure is applied to the first and second powders in the molding step. As a result, the YAG sintered body described above may have a shape in which either the first or second sintered portion bulges toward the other.

[0042] Thereafter, the mixture is subjected to a molding step as shown in Fig. 2. In the molding step, the first powder and the second powder are placed in a mold 51 so that they are in contact with each other at their interfaces, and then pressed to be molded. This results in a molded body 3 having a first molded portion 1 and a second molded portion 2 that are joined to each other.

[0043] As an example, in the example shown in Figure 2, the second powder is arranged in a cylindrical shape surrounding the central cylindrical first powder. When a load is applied from above the first and second powders in this state, as indicated by the arrows in the figure, and uniaxial compression is performed, the first powder and the second powder become a cylindrical first molded portion 1 and a surrounding second molded portion 2, respectively, and the first molded portion 1 and the second molded portion 2 are bonded to each other at their outer and inner surfaces. In the illustrated molded body 3, the first molded portion 1 is cylindrical and located inside the cylindrical second molded portion 2. However, the arrangement of the first and second powders can be appropriately changed depending on the shape of the YAG sintered body to be manufactured.

[0044] As a molding method in the molding step, uniaxial compression, cold isostatic pressing (CIP), etc. can be adopted. In some cases, cold isostatic pressing may be further performed after uniaxial compression. The pressure and pressing time applied to the first powder and the second powder can be appropriately set in consideration of various conditions.

[0045] After the molding step, the molded body 3 is heated in a sintering step to sinter the first molded portion 1 and the second molded portion 2 included in the molded body 3. As a result, as shown in Figures 3 and 4, the first molded portion 1 of the molded body 3 becomes a first sintered portion 11, and the second molded portion 2 becomes a second sintered portion 12, thereby obtaining a YAG sintered body 13 having the first sintered portion 11 and the second sintered portion 12 bonded to each other.

[0046] In the sintering step, the compact 3 is preferably heated to a temperature of 1600°C to 1900°C for 5 to 30 hours. 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 light transmittance will decrease.

[0047] In the above description, the first and second powders are subjected to powder sinter bonding. This powder sinter bonding is a method of bonding unsintered first and second powders together by compacting them and then sintering them. By performing powder sinter bonding, the dopant in either the first or second powder is mixed with the other powder in advance, thereby increasing the average diffusion distance of the dopant. When the YAG sintered body 13 is manufactured in this manner, it is believed that high mechanical strength is achieved at the bonded portion between the first sintered portion 11 and the second sintered portion 12, making it possible to use the YAG sintered body 13 in high-load environments. Furthermore, this embodiment eliminates the need for high-precision polishing of the bonding surfaces when bonding the first and second sintered portions, which are manufactured separately. This reduces labor and costs.

[0048] Next, the above-mentioned YAG sintered body was prototyped and its effects were confirmed, which will be described below. However, the description here is merely for illustrative purposes and is not intended to be limiting.

[0049] <Test Example 1> (Examples 1 to 3) A predetermined raw material powder was subjected to powder sintering bonding to produce a YAG sintered body in which a cylindrical first sintered portion and a cylindrical second sintered portion, both of which had a diameter of 1 inch and a thickness of 14 mm, were bonded together at their bottom surfaces.

[0050] As raw material powders, first and second powders containing YO powder, AlO powder, and predetermined oxide powder for dopant, respectively, were prepared. In each of Examples 1 to 3, the first and second powders contained the predetermined oxide powder for dopant so as to obtain the dopant species and addition amounts shown in Table 1.

[0051] The first powder was preliminarily molded, and then the first powder and the second powder were placed in a mold with their interfaces in contact with each other and cold-pressed, followed by CIP molding at 176 MPa, to obtain a molded body having a first molded portion and a second molded portion bonded to each other.

[0052] Next, the above compact was heated at a temperature of 1750° C. for 20 hours to produce a YAG sintered body having a cylindrical first sintered portion and a cylindrical second sintered portion on the outer periphery, which were joined together.

[0053] Example 4 was substantially the same as Examples 1 to 3, except that a cylindrical YAG sintered body was produced by powder sinter bonding, in which the first sintered portion was cylindrical and the second sintered portion was bonded to the periphery of the first sintered portion, as shown in Figures 3 and 4. The outer diameter of the second sintered portion was 4 inches, the diameter of the first sintered portion was 2 inches, and the thicknesses of the first sintered portion and the second sintered portion were 10 mm.

[0054] Example 5 was substantially the same as Examples 1 to 3, except that a cylindrical YAG sintered body was produced by powder sinter bonding, in which the first sintered portion was cylindrical and the second sintered portion was bonded to the periphery of the first sintered portion, as shown in Figures 3 and 4. The outer diameter of the second sintered portion was 60 mm, the diameter of the first sintered portion was 30 mm, and the thicknesses of the first sintered portion and the second sintered portion were 10 mm.

[0055] Example 6 was substantially the same as Examples 1 to 3, except that a cylindrical YAG sintered body was produced by powder sinter bonding, in which the first sintered portion was cylindrical and the second sintered portion was bonded to the periphery of the first sintered portion, as shown in Figures 3 and 4. The outer diameter of the second sintered portion was 100 mm, the diameter of the first sintered portion was 70 mm, and the thicknesses of the first sintered portion and the second sintered portion were 10 mm.

[0056] Example 7 was substantially the same as Examples 1 to 3, except that a rectangular tubular YAG sintered body was produced by powder sinter bonding, with the first sintered portion being a rectangular parallelepiped and the second sintered portion being bonded to the periphery of the first sintered portion. The length and width of the outer periphery of the second sintered portion were each 140 mm, the length and width of the outer periphery of the first sintered portion were each 110 mm, and the thickness of the first sintered portion and the second sintered portion were 10 mm.

[0057] Comparative Examples 1 to 3 In Comparative Examples 1 to 3, Y2O3 powder, Al2O3 powder, and predetermined oxide powder for dopant were prepared so as to have the same dopant species and addition amounts as in Examples 1 to 3, respectively.

[0058] The first and second powders were separately cold-pressed and then CIP-molded at 176 MPa. This resulted in a first molded portion and a second molded portion that were not bonded to each other. The first and second molded portions were then separately heated at 1750°C for 20 hours to produce separate first and second sintered portions. The first and second sintered portions each had a rectangular prism shape measuring 10 mm in length, 15 mm in width, and 10 mm in thickness.

[0059] Then, after grinding the joining surfaces (bottom surfaces) of the first sintered portion and the second sintered portion to be joined, the first sintered portion and the second sintered portion were brought into contact with each other at their joining surfaces, and then subjected to a pressure of 70 kgf / cm 2 The resulting sintered body was heated at 1100°C for 30 minutes under a pressure of 1000 kJ / cm2, and sintered while bonding the bonding surfaces together. This resulted in a YAG sintered body in which the first sintered part and the second sintered part were bonded together. Bonding the first sintered part and the second sintered part together after obtaining them in this way is referred to as diffusion bonding here.

[0060] Comparative Example 4 A YAG sintered body was manufactured in substantially the same manner as in Comparative Examples 1 to 3, except that the shape of the YAG sintered body was a square pillar with a length of 19 mm, a width of 15 mm, and a thickness of 10 mm.

[0061] (Evaluation) As described above, the YAG sintered bodies manufactured as described above were subjected to linear analysis of elemental intensity along a direction perpendicular to the bonding interface on the surface and tests to measure bending strength. The fitting results of the linear analysis for Example 1 and Comparative Example 1, Example 2 and Comparative Example 2, Example 3 and Comparative Example 3, and Example 4 and Comparative Example 4 are shown in Figures 5 to 8, respectively. The fitting results of the linear analysis for Examples 5 to 7 are also shown in Figures 13 to 15, respectively. Figure 5 also shows the linear analysis results, and since the fitting curves generally match the linear analysis results, it is believed that good fitting is possible using the aforementioned method. The average diffusion distance of dopants in the YAG sintered bodies is shown in Table 1.

[0062] For reference, secondary electron (SE) images and backscattered electron (BSE) images taken by a scanning electron microscope (SEM) of the bonding interfaces on the surfaces of the YAG sintered bodies of Example 1 and Comparative Example 1 are shown in Figures 9 and 10, respectively. In Comparative Example 1, the bonding interface can be clearly confirmed in the BSE image as shown in Figure 10, whereas in Example 1, the bonding interface is blurred in the BSE image as shown in Figure 9, confirming a significant difference in the bonding interfaces.

[0063] The bending strength was also measured for each of the YAG sintered compacts of Example 4 and Comparative Example 4. In the bending strength measurement test, a fixed-type four-point bending test (upper and lower support radii of 3 mm, upper support distance of 10 mm, lower support distance of 30 mm) was used as the support, and an INSTRON 5988 400 kN testing machine (using a 5 kN load cell) was used as the testing device. The test speed was 0.5 mm / min (crosshead speed control). The measurement was performed on 15 samples taken from the YAG sintered compact. As a result, for the YAG sintered compact of Comparative Example 4, the measured values ​​of the 15 samples were the average value (215 MPa) ± 149 MPa, while for the YAG sintered compact of Example 4, the measured values ​​of the 15 samples were the average value (340 MPa) ± 28 MPa, indicating small variation in bending strength. This shows that powder sinter bonding makes it easier to obtain a YAG sintered body with uniform mechanical strength across the entire bonding surface compared to diffusion bonding.

[0064] The reflectance of each YAG sintered body in Example 1 and Comparative Example 1 was also measured. Specifically, as shown in FIG. 11, a laser beam (650 nm, approximately 5 mW, linearly polarized) was irradiated onto a bonded sample of the YAG sintered body, and the intensity of the reflected light at the bonded interface of the bonded sample was measured using an optical power meter (Thorlabs S130C). The intensity of the reflected light when reflected off quartz glass under similar conditions was used as the reference, and the percentage of that was taken as the reflectance (%). As a result, the reflectance of the YAG sintered body in Comparative Example 1 was 0.035%, while that of the YAG sintered body in Example 1 was sufficiently low at 0.002% or less. Therefore, it is believed that if a YAG sintered body is manufactured by powder sintering bonding, the reflectance of the bonded interface can be reduced more than when manufactured by diffusion bonding.

[0065]

[0066] <Test Example 2> In Examples 1 to 4 of Test Example 2, cylindrical YAG sintered bodies were manufactured in which the first sintered portion was cylindrical and the second sintered portion was joined to the periphery of the first sintered portion in substantially the same manner as in Example 4 of Test Example 1 described above, except for the dopant type and its addition amount. Furthermore, in Examples 5 to 7 of Test Example 2, YAG sintered bodies were manufactured in which the second sintered portion was joined to the periphery of the first sintered portion in the same manner as in Examples 5 to 7 of Test Example 1 described above. Here, the pressure applied to the first powder during pre-molding was 2 / 3 or less of the pressure applied during subsequent molding in Examples 1 to 3 and 5 to 7, and was greater than 2 / 3 in Example 4.

[0067] Since all of the YAG sintered bodies obtained in Examples 1 to 4 were manufactured in substantially the same manner as Example 4 of Test Example 1, it is estimated that the average diffusion distance of the dopant in the first sintered portion and the average diffusion distance of the dopant in the second sintered portion were similarly longer than 0.010 mm. Furthermore, since all of the YAG sintered bodies obtained in Examples 5 to 7 were manufactured in the same manner as Examples 5 to 7 of Test Example 1, it is estimated that the average diffusion distance of the dopant in the first sintered portion and the average diffusion distance of the dopant in the second sintered portion were similarly longer than 0.010 mm.

[0068] For each of the YAG sintered bodies in Examples 1 to 7, the ratio (P / C) of the length P of the arc VA to the linear distance C described above and the ratio (h / C) of the distance h between the midpoint MP of both end points E1 and E2 and the center point CP to the linear distance C were measured. Furthermore, the presence or absence of cracks at the bonding interface of each YAG sintered body was confirmed. The results are shown in Table 2.

[0069] As shown in Table 2, in Examples 1 to 3 and 5 to 7, the pressure during pre-molding was set to 2 / 3 or less of the pressure during molding, which resulted in large P / C and h / C, whereas in Example 4, the pressure during pre-molding was set to more than 2 / 3 of the pressure during molding, which resulted in small P / C and h / C. Furthermore, the YAG sintered bodies of Examples 1 to 3 and 5 to 7 were found to have sufficiently suppressed cracking at the bonding interface compared to the YAG sintered body of Example 4.

[0070]

[0071] From the above, it has been suggested that the above-mentioned YAG sintered body and the manufacturing method of the YAG sintered body may be able to achieve a relatively low reflectivity and / or uniform mechanical strength at the bonding interface between the first sintered part and the second sintered part.

[0072] REFERENCE SIGNS LIST 1 First molding section 2 Second molding section 3 Molded body 11 First sintered section 12 Second sintered section 13 YAG sintered body 51 Mold L Average diffusion distance Pi Bonding interface position Ps1, Ps2 Reference position

Claims

1. Y3Al5O 12 A YAG sintered body including a portion of a crystal of YAG sintered body replaced with a dopant, the YAG sintered body comprising a first sintered portion and a second sintered portion bonded to each other, the first sintered portion having a dopant not contained in the second sintered portion, and an average diffusion distance of at least one dopant contained in the first sintered portion to the second sintered portion on the surface of the YAG sintered body in a direction perpendicular to a bonding interface between the first sintered portion and the second sintered portion is longer than 0.010 mm.

2. The YAG sintered body according to claim 1, wherein the first sintered portion contains a rare earth element as the dopant.

3. The YAG sintered body according to claim 2, wherein the first sintered portion contains Nd and / or Yb as the dopant, and the second sintered portion contains Sm and / or Cr as the dopant or has no portion replaced by the dopant.

4. A YAG sintered body as described in claim 1 or 2, wherein the first sintered portion is cylindrical, and the second sintered portion is cylindrical and surrounds the periphery of the first sintered portion and is joined to the first sintered portion.

5. A YAG sintered body as described in claim 1 or 2, wherein, in a cut surface obtained by cutting in the thickness direction from one surface to the other surface on which the bonding interface between the first sintered portion and the second sintered portion is exposed, the bonding interface has a shape that bulges toward the first sintered portion or the second sintered portion at a central portion relative to both end points in the thickness direction of the bonding interface, and the ratio (h / C) of a distance h between the midpoint of a line segment connecting both end points of the bonding interface and a center point on the thickness center position of the bonding interface to a linear distance C between both end points of the bonding interface on the cut surface is 0.050 or more.

6. Y3Al5O 12 a first sintered portion and a second sintered portion bonded to each other, the first sintered portion containing a dopant not contained in the second sintered portion, the first powder and the second powder containing yttrium oxide powder and aluminum oxide powder, respectively, as raw material powders, the first powder containing an oxide powder for dopant not contained in the second powder, a raw material preparation step of preparing the first powder and the second powder, the first powder containing an oxide powder for dopant not contained in the second powder, a molding step of pressing the first powder and the second powder in a state of being in contact with each other at the interface and forming a molded body having a first molded portion of the first powder and a second molded portion of the second powder bonded to each other, and a sintering step of heating and sintering the molded body.

7. The method for producing a YAG sintered body according to claim 6, wherein the dopant oxide powder of the first powder contains an oxide powder of a rare earth element.

8. A method for producing a YAG sintered body as described in claim 7, wherein the oxide powder for dopant of the first powder contains an oxide of Nd and / or an oxide of Yb, and the oxide powder for dopant of the second powder contains an oxide of Sm and / or an oxide of Cr, or the second powder does not contain an oxide powder for dopant.

9. The method for producing a YAG sintered body according to claim 6 or 7, wherein in the sintering step, the molded body is heated to a temperature of 1600° C. to 1900° C. for 5 hours to 30 hours.

10. A method for producing a YAG sintered body as described in claim 6 or 7, wherein in the molding step, the first powder is arranged in a cylindrical shape, and the second powder is arranged in a cylindrical shape surrounding the first powder.

11. A method for producing a YAG sintered body as described in claim 6 or 7, further comprising a pre-molding step of applying a pressure to the first powder or the second powder after the raw material preparation step and before the molding step, wherein the pressure in the pre-molding step is 2 / 3 of the pressure applied to the first powder and the second powder in the molding step.

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