Method for manufacturing composite optical ceramic elements

Abstract

To provide a method of manufacturing a composite optical ceramic element in which degradation of the optical properties may be suppressed.SOLUTION: A manufacturing method includes a first step of preparing a first powder P1 for a first ceramics part 10 and a second powder P2 for a second ceramics part 20, containing a first transition element, a second step of arranging the first powder P1 in a first region R1 and the second powder P2 in a second region R2 to make contact between the first powder P1 and the second powder P2 to form a contact state, and a third step of forming the first ceramics part 10 and the second ceramics part 20 from each of the first and second powders P1 and P2 to form a composite PB by sintering the first and second powders P1 and P2 while maintaining the contact state.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present disclosure relates to a method for producing a composite optical ceramic element.

Background Art

[0002] Patent Document 1 describes a method for producing a composite laser element including a transparent crystal body having a laser-oscillatable region and a second crystal body bonded to the transparent crystal body. In this method, first, a compact of a powder composition that can constitute a transparent crystal body is brought into contact with a compact of a powder composition that can constitute a second crystal body. Thereafter, both compacts are heated in a temperature range of 70% to 90% of the melting point, thereby forming a bond between the transparent crystal body and the second crystal body.

Prior Art Literature

Patent Literature

[0003]

Patent Document 1

Summary of Invention

Problem to be Solved by the Invention

[0004] Meanwhile, as a laser using composite ceramics, there is known one in which a second ceramic portion containing a transition element that absorbs emitted light generated in an optical laser medium is annularly provided outside a first ceramic portion serving as a laser medium. As a method for producing such a laser, for example, there is a method in which the first ceramic portion and the second ceramic portion are produced separately, precision processing and precision polishing are performed thereon, and then they are pressure-bonded to each other.

[0005] However, in this manufacturing method, the pre-fabricated first ceramic part and the second ceramic part do not adhere sufficiently, resulting in gaps at the joint and a tendency for bonding defects to occur. Furthermore, if gaps occur at the joint (if air is interposed at the joint), the optical properties may deteriorate. In addition, in this manufacturing method, the concentration of transition elements changes rapidly at the joint between the first and second ceramic parts. This can cause a rapid thermal gradient during use, leading to thermal distortion. Therefore, in this manufacturing method, due to these problems, there is a risk of deterioration in the quality of the laser light or damage to the laser medium, resulting in a deterioration of the optical properties.

[0006] In contrast, Patent Document 1 discloses a method of bringing two compacts into contact, as described above. When bringing two compacts into contact, it is stated that in addition to a method of manufacturing each compact in advance and bringing both compacts into contact, it is also possible to manufacture only one of the compacts, load it into a container, and then fill the gap between the compact and the container with the other powder composition and pressurize it. Thus, Patent Document 1 describes that in the manufacture of a composite laser element, at least one of a laser-oscillating transparent crystalline powder composition and a second crystalline powder composition is used as a compact.

[0007] In the method described in Patent Document 1, at least one of the powder compositions of the two crystalline materials to be joined is a compacted powder, which means that voids can still occur at the joint. Furthermore, the rapid change in the concentration of transition elements at the joint, which causes a steep heat gradient and the resulting thermal strain, can be suppressed by providing a buffer region at the joint where the concentration of transition elements changes gradually. However, in the method described in Patent Document 1, it is unlikely that a sufficient buffer region will be formed for the same reason. Therefore, there is room for improvement in suppressing the deterioration of optical properties in the method described in Patent Document 1.

[0008] Therefore, the object of this disclosure is to provide a method for manufacturing a composite optical ceramic element that can suppress the deterioration of optical properties. [Means for solving the problem]

[0009] A method for manufacturing a composite optical ceramic element according to the present disclosure is a method for manufacturing a composite optical ceramic element including a first ceramic part and a second ceramic part joined to the first ceramic part, comprising: a first step of preparing a first powder for the first ceramic part that contains a first transition element and a second powder for the second ceramic part that does not contain a first transition element; a second step after the first step of placing the first powder in a first region and the second powder in a second region adjacent to the first region, and bringing the first powder and the second powder into contact at the boundary between the first region and the second region to form a contact state; and a third step after the second step of sintering the first powder and the second powder while maintaining the contact state to form the first ceramic part and the second ceramic part, respectively, and to form a composite.

[0010] In this manufacturing method, first, a first powder containing a first transition element and a second powder having a different concentration of the first transition element than the first powder are prepared. Next, the first powder is placed in a first region and the second powder is placed in a second region, bringing the first and second powders into contact to form a contact state. Then, while maintaining this contact state, the first and second powders are sintered to form a first ceramic part and a second ceramic part from the first and second powders, respectively, thus forming a composite. In this way, when the fluid first and second powders are brought into contact, they mix with each other in the contact region, and the first transition element diffuses. Therefore, when sintered afterward, voids are less likely to form between the first and second ceramic parts, and a sufficient buffer region is formed where the concentration of the first transition element gradually changes due to the diffusion of the first transition element. Thus, it is possible to suppress the deterioration of the optical properties of the composite optical ceramic element. Furthermore, this manufacturing method eliminates the need for precise machining of the ceramic shape and precision polishing of the joint surface, as required in conventional methods, thus reducing costs. Furthermore, the statement that "the concentration of the first transition element differs from that of the first powder" in the second powder also includes cases where the second powder does not contain the first transition element.

[0011] In the method for manufacturing a composite optical ceramic element according to this disclosure, the first powder and / or the second powder may include ceramic raw material powder. The first powder and / or the second powder may be obtained by crushing pre-formed ceramics into powder, but as in this case, it may also include ceramic raw material powder. In this case, compared to the case in which crushed ceramic powder is used, the shrinkage rate during sintering is improved and the adhesion of the joint portion is increased, thereby suppressing bonding defects (such as the occurrence of voids). Therefore, it is possible to reliably suppress the deterioration of optical properties due to the occurrence of bonding defects.

[0012] In the method for manufacturing a composite optical ceramic element according to this disclosure, the second powder contains a second transition element different from the first transition element, and if the first powder contains a second transition element, the concentration of the second transition element in the first powder may be different from the concentration of the second transition element in the second powder. Thus, the first powder does not have to contain a second transition element, but if it does, the concentration of the second transition element in the first powder can be different from the concentration of the second transition element in the second ceramic part.

[0013] In the method for manufacturing a composite optical ceramic element according to this disclosure, in the second step, the first powder and the second powder may be placed in the first region and the second region, respectively, with the first region and the second region separated by a partition member, and then the partition member may be removed to form a contact state. In this way, for example, if a container containing the first region and the second region is prepared and a partition member is provided in the container, a composite optical ceramic element having a joint portion with a complex shape according to the shape of the partition member can be easily manufactured.

[0014] The method for manufacturing a composite optical ceramic element according to this disclosure may include a fourth step after the third step, in which an optical surface is formed by polishing at least one surface of the composite. In this case, a composite optical ceramic element having an optical surface can be manufactured.

[0015] In the method for producing a composite optical ceramic element according to the present disclosure, in the second step, the second powder is disposed in a second region formed in an annular shape so as to surround the first region to form a contact state, whereby a contact region between the first powder and the second powder may be formed in an annular shape. In this case, a buffer region can be formed in a direction from the inner side to the outer side of the annular contact region.

[0016] In the method for producing a composite optical ceramic element according to the present disclosure, a fifth step of compression-molding the first powder and the second powder while maintaining the contact state may be provided after the second step and before the third step. In this case, handling becomes easy.

Effects of the Invention

[0017] According to the present disclosure, it is possible to provide a method for producing a composite optical ceramic element capable of suppressing deterioration of optical properties.

Brief Description of Drawings

[0018] [Figure 1] FIG. 1 is a diagram showing the composite optical ceramic element according to the present embodiment. [Figure 2] FIG. 2 is a plan view more specifically showing the optical element shown in FIG. 1. [Figure 3] FIG. 3 is a diagram showing the concentration of a transition element in the optical element shown in FIG. 2. [Figure 4] FIG. 4 is a flowchart showing one step of the method for producing the optical element shown in FIGS. 1 to 3. [Figure 5] FIG. 5 is a diagram showing one step in the production direction shown in FIG. 4. [Figure 6] FIG. 6 is a diagram showing one step in the production direction shown in FIG. 4. [Figure 7] It is a diagram showing one step in the production direction shown in FIG. 4. [Figure 8] It is a diagram showing one step in the production direction shown in FIG. 4. [Figure 9] It is a diagram showing one step in the production direction shown in FIG. 4. [Figure 10]Figure 4 shows an image of an example of an optical element obtained by the manufacturing method shown. [Figure 11] Figure 11 shows another optical element manufactured by the manufacturing method according to this embodiment. [Figure 12] Figure 12 is a plan view showing an optical element according to the first modified example. [Figure 13] Figure 13 shows the concentrations of transition elements in the optical element shown in Figure 12. Figure 3(a) is a conceptual diagram showing an enlarged view of the transition element concentration distribution in region AR of Figure 2, and Figure 3(b) is a graph showing the transition element concentration distribution. Figure 13 shows the concentrations of transition elements in region CR shown in Figure 12. [Figure 14] Figure 14 shows an optical element relating to a second modified example. [Figure 15] Figure 15 shows an optical element according to a third modified example. [Figure 16] Figure 16 shows an optical element relating to another modified example. [Modes for carrying out the invention]

[0019] An embodiment will be described below with reference to the drawings. In the description of each drawing, the same or corresponding elements will be denoted by the same reference numeral, and redundant explanations may be omitted.

[0020] Figure 1 shows a composite optical ceramic element according to this embodiment. Figure 1(a) is a plan view, and Figure 1(b) is a perspective view. The composite optical ceramic element shown in Figure 1 (hereinafter referred to as "optical element") is, as an example, a laser element. The optical element 1 includes a columnar (here cylindrical) first ceramic part 10 and a cylindrical (here cylindrical) second ceramic part 20 provided so as to surround the first ceramic part 10.

[0021] The first ceramic part 10 is, for example, a laser medium and includes ceramics and a first transition element. The ceramics of the first ceramic part 10 are, for example, YAG(Y3A l5 O12 ) and the first transition element is Nd as an example. The second ceramic part 20 has the function of preventing the reflection of emitted light (suppressing parasitic oscillation) by absorbing emitted light generated in the laser medium, for example, and includes ceramics and a second transition element. The ceramics of the second ceramic part 20 are, for example, the same as the ceramics of the first ceramic part 10, for example YAG(Y3A l5 O 12 ) The second transition element is different from the first transition element, and Sm is one example.

[0022] The optical element 1 includes a first end face 1a and a second end face 1b in a direction intersecting the direction from the first ceramic portion 10 toward the second ceramic portion 20 (for example, the radial direction). The first end face 1a and the second end face 1b are, for example, surfaces along the radial direction of the optical element 1. The first end face 1a and the second end face 1b are optical surfaces having a certain optical function, such as light entry / exit surfaces and reflection surfaces in the optical element 1.

[0023] However, the optical element 1 is not limited to a laser element, but may include light-emitting bodies such as scintillators and white light sources. Furthermore, the optical element 1 may also be a light-absorbing body. Various materials can be used for the ceramics and transition elements. For example, Lu3Al5O 12 Y3(Al,Ga)5O 12 Ga3Sc2Al3O 12 Examples include oxides having a garnet structure, oxides of rare earth elements such as Sc2O3, Gd2O3, and Lu2O3, aluminum oxides such as sapphire (Al2O3) and alexandrite (BeAl2O4), fluorides such as LiSrAlF6 and LiCaAlF6, and Hf oxides such as SrHfO3.

[0024] Figure 2 is a plan view showing a more detailed optical element as shown in Figure 1. Figure 3 is a diagram showing the concentrations of transition elements in the optical element as shown in Figure 2. Figure 3(a) is a conceptual diagram showing an enlarged view of the concentration distribution of transition elements in region AR of Figure 2, and Figure 3(b) is a graph showing the concentration distribution of transition elements. As shown in Figures 1 to 3, the first ceramic part 10 and the second ceramic part 20 form a joint CP. The joint CP is formed in a cylindrical shape (here, cylindrical) similar to the outer shape of the second ceramic part 20. Here, the side surface of the second ceramic part 20 constitutes the side surface 1s of the optical element 1.

[0025] In the optical element 1, a buffer region 30 is formed in which the concentration A of the first transition element gradually decreases in the direction from the first ceramic portion 10 toward the second ceramic portion 20 (here, the direction from the radial center toward the outside) (see graph GA). Also in the optical element 1, a buffer region 30 is formed in which the concentration B of the second transition element gradually decreases in the direction from the second ceramic portion 20 toward the first ceramic portion 10 (here, the direction from the radial outside toward the center) (see graph GB). The buffer region 30 is formed in a cylindrical shape (here, cylindrical) around the junction CP, for example.

[0026] In other words, the junction CP can be defined as the point where the concentration A of the first transition element and / or the concentration B of the second transition element fall below a certain value (e.g., half value), and the region surrounding the junction CP can be defined as the buffer region 30. Note that the length over which the concentration A of the first transition element and the concentration B of the second transition element fall to a certain value does not need to be the same (but they may be). In this case, the length L30 of the buffer region 30 based on the concentration A of the first transition element and the length L30 of the buffer region 30 based on the concentration B of the second transition element do not need to be the same (but they may be).

[0027] The overall dimensions (width, in this case diameter) of the optical element 1 in a plan view are, for example, about 25 mm to 100 mm, of which the width of the second ceramic portion 20 is, for example, about 5 mm. The length L30 (radial length) of the buffer region 30 is, for example, 100 μm or more. The ratio of the length L30 of the buffer region 30 to the overall dimensions of the optical element 1 in a plan view can be, for example, 0.1% or more.

[0028] Next, the method for manufacturing the optical element 1 described above, that is, the method for manufacturing the composite optical ceramic element according to this embodiment, will be explained. Figure 4 is a flowchart showing one step in the manufacturing method of the optical element shown in Figures 1 to 3. As shown in Figure 4, in this manufacturing method, first, a first powder which will be the basis of the first ceramic part 10 and a second powder which will be the basis of the second ceramic part 20 are prepared (step S1: first step).

[0029] In this process S1, first, a first powder is prepared, which is a raw material mixture powder containing a first transition element. To this end, raw material powders of ceramics and the first transition element are weighed in appropriate ratios. Next, additives such as binders are added to the raw material powders, and a slurry is prepared by wet grinding and mixing. Subsequently, the slurry is dried and dry-ground. This yields a first powder, which is a raw material mixture powder of ceramics containing a first transition element. In other words, the first powder contains ceramic raw material powder. Meanwhile, a second powder is prepared by the same process, which is a raw material mixture powder containing a second transition element different from the first transition element. Here, the second powder does not contain a first transition element. That is, the concentration of the first transition element in the second powder is 0%, unlike in the first powder. Also, the second powder, like the first powder, contains ceramic raw material powder. The order in which the first powder and the second powder are prepared does not matter. Furthermore, raw material powder refers to the raw materials that will become the target ceramics after sintering (mixed). As an example, YAG(Y3Al5O 12The raw materials for the ceramics are Y2O3 and Al2O3, with Nd2O3 as an example of a first transition element raw material and Sm2O3 as an example of a second transition element raw material. Here, the first powder does not contain the second transition element (Sm), i.e., the concentration of the second transition element in the first powder is 0%.

[0030] Here, if necessary, a step of granulating the first powder and / or the second powder may be performed. Granulation increases the fluidity of each powder and makes the particle size of each powder uniform, so that the powders mix more easily when they come into contact with each other. The particle size (average secondary particle size) of the first powder and the second powder is preferably 1 μm or more and 50 μm or less. A particle size of 1 μm or more is preferable because it improves the fluidity of each powder. Also, a particle size of 50 μm or less is preferable because it increases the transparency of the molded product. By controlling the particle size, the fluidity of each powder and the length of the buffer region can be adjusted.

[0031] Next, as shown in Figure 5(a), a container Q is prepared (step S2). The container Q includes, for example, an outer container Q1 which is a mold, and an inner container Q2 which is inserted and removed from inside the outer container Q1. The outer container Q1 is formed in the shape of a box with one end open. The inner wall surface of the outer container Q1 defines the shape of the side surface 1s of the optical element 1. Therefore, the inner wall surface of the outer container Q1 has an outer shape similar to the outer shape of the optical element 1 (in this case, the outer shape of the second ceramic part 20). In this case, the inner wall surface of the outer container Q1 is cylindrical.

[0032] The inner container Q2 is formed in a cylindrical shape with both ends open. The shape of the inner container Q2 defines the outer shape of the first ceramic part 10 and the shape of the joint part CP. Therefore, in this case, the inner container Q2 is formed in a cylindrical shape. The inner container Q2 is made thinner than the outer container Q1 and can be made from, for example, paper, resin film, metal film, metal plate, etc. The inner container Q2 is positioned spaced apart from the inner wall surface of the outer container Q1. As a result, the container Q is formed with a first region R1 inside the inner container Q2 and a second region R2 between the inner container Q2 and the outer container Q1.

[0033] In other words, the inner container Q2 is a partition member that separates the first region R1 and the second region R2 in the container Q. The first region R1 is formed in a columnar (cylindrical) shape corresponding to the first ceramic portion 10, and the second region R2 is formed in a cylindrical (tubular) shape that surrounds the first region R1, corresponding to the second ceramic portion 20.

[0034] The thickness of the inner container Q2 (partition member) is, for example, about 0.1 mm to 1 mm. If the thickness of the inner container Q2 is 0.1 mm or more, the distance between the first region R1 and the second region R2 becomes larger, making it easier for the first powder and the second powder to mix when the inner container Q2 is removed, and a boundary region of sufficient length is formed, which is preferable. If the thickness of the inner container Q2 is 1 mm or less, when the inner container Q2 is removed, the shapes of the first region R1 and the second region R2 are more easily maintained near the boundary between the first powder and the second powder (the interface does not become rough), which is preferable.

[0035] The inner container Q2 (partition member) divides the first region R1 and the second region R2 vertically (in the direction of gravity). By dividing the first region R1 and the second region R2 vertically, when the inner container Q2 (partition member) is removed, the powders mix more easily at the boundary region between the first and second powders compared to when the partition member divides the first region R1 and the second region R2 perpendicular to the vertical direction.

[0036] In the subsequent step, as shown in Figure 5(b), the second powder P2 prepared in step S1 is placed in the second region R2 (step S3: second step). The second powder P2 is in powder form and has fluidity. Therefore, upon being introduced into the second region R2 in step S3, the second powder P2 temporarily takes on a shape similar to that of the second region R2 as a whole.

[0037] In the subsequent step, as shown in Figure 6(a), the first powder P1 prepared in step S1 is placed in the first region R1 (step S4: second step). The first powder P1 is in powder form and has fluidity. Therefore, when the first powder P1 is introduced into the first region R1 in step S4, it temporarily takes on a shape similar to the shape of the first region R1 as a whole. Thus, in steps S3 and S4, the first powder P1 and the second powder P2 are placed in the first region R1 and the second region R2, respectively, with the first region R1 and the second region R2 separated by the inner container Q2. Note that the order of steps S3 and S4 is not limited.

[0038] In the subsequent step, a molded body containing the first powder P1 and the second powder P2 is formed (step S5: second step). Step S5 will be explained in more detail. In step S5, first, as shown in Figures 6(a) and (b), the inner container Q2 separating the first region R1 and the second region R2 is removed, thereby bringing the first powder P1 and the second powder P2 into contact at the boundary between the first region R1 and the second region R2 and forming a contact state.

[0039] This creates a contact area Pa between the first area R1 and the second area R2. The contact area Pa is formed in a cylindrical shape (in this case, cylindrical) similar to the inner container Q2. In the contact area Pa, the first powder P1 and the second powder P2 are dispersed and partially mixed with each other. Thus, steps S3 to S5 above bring fluid powders into contact with each other.

[0040] Next, as shown in Figure 7(a), in step S5, while the contact state between the first powder P1 and the second powder P2 has been established as described above, compression molding is performed by pressing the entire first powder P1 and the second powder P2 with the pressurizing member Q3 to form a molded body PA in which the first powder P1 and the second powder P2 are integrated (see Figure 7(b) for the molded body PA) (fifth step). As a result, the first powder P1 and the second powder P2 are integrated while maintaining the contact state, making them easier to handle in subsequent steps. Note that in this step of pressing the entire first powder P1 and the second powder P2, "cold isostatic pressing (CIP)" may be performed as needed to increase the density of the molded body PA.

[0041] In the next step, as shown in Figure 7(b), the molded body PA formed in step S5 is placed in a predetermined heating device D1 and heated (step S6). This removes and degreases any organic substances and other additives contained in the molded body PA (i.e., the first powder P1 and the second powder P2) (calcination is performed).

[0042] Next, as shown in Figure 8(a), the molded body PA that has gone through step S6 is placed in a predetermined heating device D2 (step S7: third step). Then, as shown in Figure 8(b), the molded body PA is fired to form the first ceramic part 10 from the first powder P1 and the second ceramic part 20 from the second powder P2, thereby forming the composite PB (step S7: third step) (main firing). As described above, the contact state between the first powder P1 and the second powder P2 is maintained in the molded body PA. Therefore, in step S7, the first powder P1 and the second powder P2 are sintered while maintaining the contact state between the first powder P1 and the second powder P2, thereby forming the first ceramic part 10 and the second ceramic part 20 from the first powder P1 and the second powder P2, respectively, and forming the composite PB. Note that heating devices D1 and D2 may be the same device or different devices.

[0043] Subsequently, as shown in Figure 9, an optical surface is formed by polishing at least one surface of the composite PB formed in step S7 (step S8: fourth step). Here, the first end surface 1a and the second end surface 1b, which are optical surfaces, are formed by polishing both end surfaces of the composite PB in a direction intersecting the direction from the first ceramic part 10 to the second ceramic part 20. This gives rise to the optical element 1. An image of an example of the optical element 1 obtained as described above is shown in Figure 10. In the optical element 1 shown in Figure 10, YAG is used as the ceramic for the first ceramic part 10 and the second ceramic part 20, Nd is used as the first transition element, and Sm is used as the second transition element.

[0044] In this embodiment, the second ceramic portion 20 has the function of preventing reflection of emitted light (suppressing parasitic oscillation) by absorbing the emitted light generated in the first ceramic portion 10 due to the effect of Sm, which is a second transition element. Although significant heat is generated in the second ceramic portion 20 due to the absorption of emitted light, a sufficiently long buffer region 30 is formed, so that thermal distortion due to a steep heat gradient can be reliably suppressed when the optical element 1 is in use.

[0045] Figure 11 shows another optical element manufactured by the manufacturing method according to this embodiment. Figure 11(a) is a plan view image, Figure 11(b) is a magnified image of region BR in Figure 11(a), and Figure 11(c) is a graph showing the concentration distribution of transition elements. Each graph in Figure 11 shows the concentration measurement results at the six points shown in Figure 11(b). As shown in Figure 11, it can be seen that a buffer region of several hundred μm to about 1 mm is formed near the interface between the first ceramic part 10 and the second ceramic part 20, such that the relative concentration of transition elements (Sm or Nd) gradually decreases or increases as you move from one side of the first ceramic part 10 and the second ceramic part 20 to the other side.

[0046] As described above, in the manufacturing method according to this embodiment, first, a first powder P1 containing a first transition element and a second powder P2 not containing a first transition element (in this case, containing a second transition element) are prepared. Next, the first powder P1 is placed in a first region R1 and the second powder P2 is placed in a second region R2 to bring the first powder P1 and the second powder P2 into contact and form a contact state. Then, while maintaining this contact state, the first powder P1 and the second powder P2 are sintered to form a first ceramic portion 10 and a second ceramic portion 20, respectively, from the first powder P1 and the second powder P2, thereby forming a composite PB.

[0047] In this way, when the fluid first powder P1 and the second powder P2 are brought into contact, they mix with each other in the contact region Pa, and the first transition element diffuses. Therefore, when sintered afterward, voids (defects) are less likely to occur between the first ceramic part 10 and the second ceramic part 20, and a buffer region 30 is sufficiently formed where the concentration of the first transition element gradually changes due to the diffusion of the first transition element. As a result, thermal distortion due to a rapid heat gradient is suppressed when the optical element 1 is used. Therefore, it is possible to suppress the deterioration of the optical properties of the composite optical ceramic element (optical element 1). Furthermore, this manufacturing method does not require precision machining of the ceramic shape or precision polishing of the joint surface as in conventional methods, thus reducing costs. Note that "diffusion" here refers to the diffusion caused by the mixing of powders when they come into contact with each other, rather than the diffusion of atoms due to heat.

[0048] Furthermore, the method described in Patent Document 1 requires at least two pressure molding processes: one to form a compacted body and another to integrate the compacted body and the powder. Additionally, when the compacted body and the powder are pressure molded together, the density difference between them becomes large, making it difficult to manufacture large components. In contrast, the manufacturing method according to this embodiment requires only one pressure molding process because the powders, in contact with each other, are pressure molded together. Moreover, because the powders are molded together, the density difference between them is relatively small, facilitating the manufacture of large components.

[0049] Furthermore, in the manufacturing method according to this embodiment, the first powder P1 and the second powder P2 include ceramic raw material powder. The first powder P1 and / or the second powder P2 may be obtained by crushing pre-formed ceramics into powder, but as in this embodiment, they may also include ceramic raw material powder. In this case, compared to the case in which crushed ceramic powder is used, the shrinkage rate during sintering is improved and the adhesion of the joint portion is increased, thereby suppressing bonding defects (such as the occurrence of voids). Therefore, it is possible to reliably suppress the deterioration of optical properties due to the occurrence of bonding defects.

[0050] In the manufacturing method according to this embodiment, in steps S2 to S5, the first region R1 and the second region R2 are separated by an inner container Q2, and the first powder P1 and the second powder P2 are placed in the first region R1 and the second region R2, respectively. Then, the inner container Q2 is removed to form a contact state. In this way, an optical element 1 having a complex-shaped joint portion CP according to the shape of the inner container Q2 can be easily manufactured.

[0051] The manufacturing method according to this embodiment includes a step S8 after step S7, in which the end faces of the composite PB are polished to form the optical surfaces, namely the first end face 1a and the second end face 1b. Therefore, an optical element 1 having optical surfaces can be manufactured.

[0052] In the manufacturing method according to this embodiment, in steps S2 to S5, the second powder P2 is placed in the second region R2, which is formed in a cylindrical shape surrounding the first region R1, thereby forming a contact state and creating a cylindrical contact region Pa between the first powder P1 and the second powder P2. Therefore, a buffer region 30 can be formed corresponding to the direction from the inside to the outside of the cylindrical contact region Pa.

[0053] The embodiments described above are examples of methods for manufacturing composite optical ceramic elements. Therefore, the method for manufacturing composite optical ceramic elements according to this disclosure can be modified as needed. Modifications will be described next. [First variation]

[0054] Figure 12 is a plan view showing an optical element according to the first modified example. Figure 13 is a diagram showing the concentration of transition elements in the optical element shown in Figure 12. Figure 13(a) is a conceptual diagram showing an enlarged view of the concentration distribution of transition elements in region CR of Figure 12, and Figure 13(b) is a graph showing the concentration distribution of transition elements. As shown in Figures 12 and 13, the optical element (composite optical ceramic element) 1A according to the first modified example differs from the optical element 1 according to the above embodiment in that the second ceramic portion 20 does not contain a second transition element. In this way, even if the second ceramic portion 20 does not contain a transition element, by using the manufacturing method according to the above embodiment, a buffer region 30 can be formed in the optical element 1A in which the concentration of the first transition element gradually decreases in the direction from the first ceramic portion 10 toward the second ceramic portion 20. [Second variation]

[0055] Figure 14 shows an optical element according to a second modified example. Figure 14(a) is a plan view and Figure 14(b) is a perspective view. As shown in Figure 14, the optical element (composite optical ceramic element) 1B according to the second modified example differs from the optical element 1 according to the above embodiment in that the first ceramic part 10 is formed in a prismatic (square prismatic) shape and the second ceramic part 20 is formed in a rectangular cylindrical shape. In this case, by preparing a rectangular cylindrical outer container Q1 and a rectangular cylindrical inner container Q2 in step S2, it is possible to achieve these shapes while also forming the joint part CP and buffer area 30 in a rectangular cylindrical shape. Even in this case, the same effects as in the above embodiment are achieved.

[0056] In particular, as in this modified example, when the joint portion CP has a corner, stress tends to concentrate at the corner, and bonding defects (such as the generation of voids) are likely to occur at the interface of the corner between the first ceramic portion 10 and the second ceramic portion 20. According to the method of this disclosure, even in such cases, the deterioration of optical properties due to bonding defects can be effectively suppressed. [Third variation]

[0057] Figure 15 shows an optical element according to a third modified example. Figure 15(a) is a plan view, and Figure 15(b) is a perspective view. As shown in Figure 15, the optical element (composite optical ceramic element) 1C according to the third modified example differs from the optical element 1 according to the above embodiment in that a cylindrical (in this case, cylindrical) third ceramic part 40 is formed so as to surround the second ceramic part 20.

[0058] In manufacturing such an optical element 1C, as an example, first, in step S2, a cylindrical intermediate container is placed between the outer container Q1 and the inner container Q2 so as to surround the inner container Q2. This forms a third region between the outer container Q1 and the intermediate container, and the space between the intermediate container and the inner container Q2 is designated as the second region R2. Then, before step S5, the third powder for the third ceramic part 40 is placed in the third region between the outer container Q1 and the intermediate container. In addition, the second powder P2 is placed in the second region R2, and the first powder P1 is placed in the first region R1. The subsequent steps are then carried out. This results in obtaining the optical element 1C.

[0059] Therefore, in the optical element 1C, a bonding portion CP1 and a buffer region 30 are formed between the first ceramic portion 10 and the second ceramic portion 20, and a buffer region 50 is formed between the second ceramic portion 20 and the third ceramic portion 40. In the buffer region 50, the concentration of the second transition element gradually decreases in the direction from the second ceramic portion 20 toward the third ceramic portion 40 (here, from the radial center toward the outside), and if the third ceramic portion 40 contains a transition element, the concentration of that transition element gradually decreases in the direction from the third ceramic portion 40 toward the second ceramic portion 20 (here, from the radial outside toward the center). Thus, even in this case, the same effects as in the first embodiment are achieved.

[0060] In particular, when three or more ceramic parts are combined, as in this modified example, bonding defects (such as the formation of voids) are likely to occur due to differences in density and shrinkage rates between the different materials used for each ceramic part. According to the method of this disclosure, even in such cases, the deterioration of optical properties due to bonding defects can be effectively suppressed. Furthermore, even when three or more ceramic parts are combined, as in this modified example, the manufacturing process can be simplified because they can be molded in a single step. [Other embodiments]

[0061] In addition, as shown in Figure 16, by appropriately setting the shapes of the outer container Q1 and inner container Q2 prepared in step S2, the first ceramic part 10 and the second ceramic part 20 can be formed in any shape, and it is also possible to form other ceramic parts. In the optical element 1D shown in Figure 16(a), the first ceramic part 10 is formed in a polygonal columnar shape, and in the optical element 1E shown in Figure 16(b), multiple columnar (here cylindrical) first ceramic parts 10 are formed inside the second ceramic part 20. In the case of Figure 16(b), by preparing multiple inner containers Q2 in step S2 and then carrying out the same process thereafter, a cylindrical buffer region 30 (not shown) can be formed around each first ceramic part 10.

[0062] In the above examples, the first powder P1 may not contain any transition elements other than the first transition element, or it may contain other transition elements (e.g., the second transition element) in addition to the first transition element. If the first powder P1 contains the second element, the concentration of the second transition element in the first powder P1 may differ from that of the second transition element in the second powder P2. Also, the second powder P2 may contain the same first transition element as the first powder P1. In this case, the concentration of the first transition element in the second powder P2 will differ from that of the first transition element in the first powder P1. For example, if the second powder P2 contains the first transition element, the concentration of the first transition element in the second powder P2 may be less than the concentration of the first transition element in the first powder P1.

[0063] Furthermore, the first powder P1 and / or the second powder P2 may contain, in addition to or instead of the ceramic raw material powder, powdered ceramics formed by crushing pre-formed ceramics.

[0064] Furthermore, the above example described a method for manufacturing an optical element 1 in which a second ceramic part 20 surrounds a first ceramic part 10. However, a similar manufacturing method can also be applied when manufacturing an optical element in which a flat plate-shaped first ceramic part 10 and a flat plate-shaped second ceramic part 20 are laminated together. That is, by laminating the second powder P2 for the second ceramic part 20 onto the first powder P1 for the first ceramic part 10 to form a contact state, and then sintering while maintaining that contact state, it is possible to form a buffer region 30 in the lamination direction and achieve a similar effect. [Explanation of symbols]

[0065] 1, 1A, 1B, 1C, 1D, 1E... Optical element (composite optical ceramic element), 1a... First end face (optical surface), 1b... Second end face (optical surface), 10... First ceramic part, 20... Second ceramic part, 30... Buffer region, CP... Joint portion, P1... First powder, P2... Second powder, R1... First region, R2... Second region, Q2... Inner container (partition member), PB... Composite.

Claims

1. A method for manufacturing a composite optical ceramic element, comprising a first ceramic portion and a second ceramic portion bonded to the first ceramic portion, A first step of preparing a first powder for the first ceramic portion containing a first transition element, and a second powder for the second ceramic portion having a lower concentration of the first transition element than the first powder, A second step is performed after the first step, in which the first powder is placed in the first region and the second powder is placed in the second region adjacent to the first region, and the first powder and the second powder are brought into contact at the boundary between the first region and the second region to form a contact state. A third step is to form a composite by sintering the first powder and the second powder while maintaining the contact state, thereby forming the first ceramic portion and the second ceramic portion from the first powder and the second powder, respectively, and forming a buffer region in the area where the first powder and the second powder are in contact, in which the concentration of the first transition element gradually decreases from the first region to the second region. A method for manufacturing a composite optical ceramic element comprising [a specific component].

2. The first powder and / or the second powder includes ceramic raw material powder. A method for manufacturing a composite optical ceramic element according to claim 1.

3. The second powder contains a second transition element different from the first transition element, If the first powder contains the second transition element, the concentration of the second transition element in the first powder is less than the concentration of the second transition element in the second powder. In the buffer region, the concentration of the second transition element gradually decreases from the second region toward the first region. A method for manufacturing a composite optical ceramic element according to claim 1 or 2.

4. In the second step, the first powder and the second powder are placed in the first and second regions, respectively, with the first region and the second region separated by a partition member, and then the contact state is formed by removing the partition member. A method for manufacturing a composite optical ceramic element according to any one of claims 1 to 3.

5. The method further comprises a fourth step of forming an optical surface by polishing at least one surface of the composite after the third step, A method for manufacturing a composite optical ceramic element according to any one of claims 1 to 4.

6. In the second step, the second powder is placed in the second region, which is formed in a cylindrical shape surrounding the first region, to form the contact state, thereby forming a cylindrical contact region between the first powder and the second powder. A method for manufacturing a composite optical ceramic element according to any one of claims 1 to 5.

7. The process includes a fifth step, which occurs after the second step and before the third step, in which the first powder and the second powder are compressed and molded while maintaining the contact state. A method for manufacturing a composite optical ceramic element according to any one of claims 1 to 6.

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