Ceramic composite and method for manufacturing the ceramic composite

Abstract

[Problem] To provide: a ceramic composite that can have a reduced size or thickness, and can efficiently dissipate heat; and a production method for the ceramic composite. [Solution] This ceramic composite is produced by: a step for preparing a melt comprising at least aluminum oxide and yttrium oxide; a step for bringing either sapphire crystal or ruby crystal into contact with the melt to melt a crystal portion thereof which is in contact with the melt, and to, as a result of the melting, integrate an Al2O3 phase of the crystal and an Al2O3 phase of the aluminum oxide together without a junction interface thereof; and a step for cooling the melt. The produced ceramic composite has at least two oxide phases, i.e., a Y3Al5O12 phase and an Al2O3 phase, as a lamellar structure, wherein an Al2O3 phase, and an Al2O3 phase of either the sapphire crystal or the ruby crystal, are integrated together without a junction interface thereof.

Description

Technical Field

[0001] The present invention relates to a ceramic composite and a method for manufacturing the ceramic composite.

Background Art

[0002] Currently, lighting devices that use a light-emitting diode (LED) or semiconductor laser that emits blue light as a light source, and wavelength-convert part of the blue light to yellow light using a wavelength conversion member, and irradiate white light by mixing the blue light and the yellow light, are widespread. In such lighting devices, a phosphor material of the YAG (Y3Al5O 12 ) system is used, and a resin or glass containing phosphor powder has been proposed.

[0003] Also, Patent Documents 1 and 2 propose a ceramic composite having a lamellar structure in which the Y3Al5O 12 phase and the Al2O3 phase are continuously intertwined three-dimensionally as a eutectic. In such a ceramic composite described in Patent Documents 1 and 2, the Y3Al5O 12 phase wavelength-converts blue light to yellow light, and blue light and yellow light are scattered at the interface between the Y3Al5O 12 phase and the Al2O3 phase, and white color can be obtained by mixing colors.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Patent Document 2

Summary of the Invention

Problems to be Solved by the Invention

[0005] The YAG of the ceramic composite has a thermal conductivity that is only about one-fourth that of, for example, sapphire, and tends to generate heat more easily than the crystal materials (such as the sapphire crystal) conventionally used in lighting devices such as LEDs. Therefore, when the ceramic composite is thickened, the amount of heat generated increases and the heat dissipation deteriorates. Thus, miniaturization or thinning is required for the ceramic composite used in lighting devices and the like.

[0006] On the other hand, lighting devices require various shapes depending on their applications. In order to ensure the freedom of shape design, miniaturization or thinning is required for the ceramic composite incorporated in the lighting device.

[0007] However, with the miniaturization or thinning of the ceramic composite, the transmission of blue light concentrates on specific parts of the ceramic composite. Furthermore, depending on the application of the lighting device, a large amount of light is required. Therefore, with the miniaturization or thinning of the ceramic composite, heat is more likely to be generated from the ceramic composite, and the heat-generating part concentrates on specific parts of the ceramic composite, which causes failures and malfunctions in the lighting device.

[0008] The present invention has been made in view of the above problems, and an object thereof is to provide a ceramic composite that can be miniaturized or thinned and can dissipate heat efficiently, and a method for manufacturing the same.

Means for Solving the Problems

[0009] The above problems are achieved by the following present invention. That is, the ceramic composite of the present invention has at least two oxide phases, namely a Y3Al5O 12 phase and an Al2O3 phase, in a lamellar structure, and the Al2O3 phase of the ceramic composite and the Al2O3 phase of either a sapphire crystal or a ruby crystal are integrated without a bonding interface therebetween.

[0010] Furthermore, the ceramic composite of the present invention is provided with at least two crystals, and the Al2O3 phase of the crystal and the Al2O3 phase of the ceramic composite are sandwiched between the two crystals and integrated without a bonding interface therebetween.

[0011] Furthermore, the ceramic composite of the present invention is characterized in that the gap between the crystals sandwiching the ceramic composite is 0.01 mm or more and 1 mm or less.

[0012] Also, the ceramic composite of the present invention is characterized in that a stop hole or a through hole is formed in the crystal, the ceramic composite is inserted into the stop hole or the through hole, and the Al2O3 phase of the crystal and the Al2O3 phase of the ceramic composite are integrated without a joining interface therebetween.

[0013] Furthermore, the ceramic composite of the present invention is characterized in that the diameter of the stop hole or the through hole is 0.1 mm or more and 3 mm or less.

[0014] Also, the method for manufacturing the ceramic composite of the present invention includes a step of preparing a melt composed of at least aluminum oxide and yttrium oxide, a step of bringing either a sapphire crystal or a ruby crystal into contact with the melt to melt the crystal portion in contact with the melt, and integrating the Al2O3 phase of the crystal and the Al2O3 phase of aluminum oxide without a joining interface therebetween by melting, and a step of cooling the melt.

[0015] Furthermore, the method for manufacturing the ceramic composite of the present invention further includes a step of preparing at least two crystals and stacking them on each other, a step of charging a raw material containing at least aluminum oxide and yttrium oxide into a crucible, a step of heating the crucible to melt the raw material in the crucible to prepare a melt, a step of bringing the crystals into contact with the melt, allowing the melt to penetrate into the gap between the stacked crystals by capillary action, sandwiching the melt with the crystals and bringing the crystals into contact with the melt, melting the crystal portion in contact with the melt, and integrating the Al2O3 phase of the crystal and the Al2O3 phase of aluminum oxide without a joining interface therebetween by melting, and a step of taking out the crystals from the melt and cooling the melt integrated with the crystals.

[0016] Furthermore, the method for manufacturing the ceramic composite of the present invention is characterized in that the gap between the crystals is 0.01 mm or more and 1 mm or less.

[0017] Furthermore, the method for manufacturing the ceramic composite of the present invention is characterized in that the longitudinal direction of the gaps between the crystals is made orthogonal to the plane direction of the liquid surface of the melt.

[0018] Also, the method for manufacturing the ceramic composite of the present invention further includes a step of forming a stop hole or a through hole in the crystal, and allowing the melt to penetrate into the stop hole or the through hole by capillary action, melting the crystal portion in the stop hole or the through hole in contact with the melt, and integrating the Al2O3 phase of the crystal and the Al2O3 phase of aluminum oxide without a bonding interface by melting.

[0019] Furthermore, the method for manufacturing the ceramic composite of the present invention is characterized in that the diameter of the stop hole or the through hole is 0.1 mm or more and 3 mm or less.

Advantages of the Invention

[0020] According to the ceramic composite and the method for manufacturing the ceramic composite according to the present invention, miniaturization or thinning can be achieved, a ceramic composite capable of efficiently dissipating heat can be realized, and such a ceramic composite can be manufactured.

Brief Description of the Drawings

[0021]

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MODE FOR CARRYING OUT THE INVENTION

[0022] The first feature of the present embodiment is that it has at least two oxide phases of Y3Al5O 12 phase and Al2O3 phase in a lamellar structure, and the Al2O3 phase of the Al2O3 phase of either the sapphire crystal or the ruby crystal is integrated without a joining interface with each other as a ceramic composite.

[0023] The second feature of the present embodiment is a method for manufacturing a ceramic composite having a step of preparing a melt composed of at least aluminum oxide and yttrium oxide, bringing either a sapphire crystal or a ruby crystal into contact with the melt, melting the crystal portion brought into contact with the melt, and integrating the Al2O3 phase of the crystal and the Al2O3 phase of aluminum oxide without a joining interface by melting, and a step of cooling the melt. Only the crystal portion brought into contact with the melt is melted, and the other crystal portions are not melted.

[0024] The third feature of this embodiment is that there are at least two crystals, and the Al2O3 phase of the crystal and the Al2O3 phase of the ceramic composite are integrated without an interface between them, being sandwiched by the two crystals, resulting in a ceramic composite.

[0025] The fourth feature of this embodiment is that at least two crystals are prepared, and there are steps of overlapping them with each other, putting a raw material containing at least aluminum oxide and yttrium oxide into a crucible, heating the crucible to melt the raw material in the crucible to prepare a melt, bringing the crystals into contact with the melt, allowing the melt to penetrate into the gaps between the overlapped crystals by capillary action, sandwiching the melt with the crystals and bringing the crystals into contact with the melt, melting the crystal parts in contact with the melt, and integrating the Al2O3 phase of the crystal and the Al2O3 phase of aluminum oxide without an interface between them by melting, and further having steps of taking out the crystals from the melt and cooling the melt integrated with the crystals, which is a method for manufacturing a ceramic composite.

[0026] The fifth feature of this embodiment is that a stop hole or a through hole is formed in the crystal, and a ceramic composite is inserted into the stop hole or the through hole, and the Al2O3 phase of the crystal and the Al2O3 phase of the ceramic composite are integrated without an interface between them, resulting in a ceramic composite.

[0027] The sixth feature of this embodiment is that there are steps of forming a stop hole or a through hole in the crystal, allowing the melt to penetrate into the stop hole or the through hole by capillary action, melting the crystal parts in the stop hole or the through hole in contact with the melt, and integrating the Al2O3 phase of the crystal and the Al2O3 phase of aluminum oxide without an interface between them by melting, which is a method for manufacturing a ceramic composite.

[0028] According to these configurations and manufacturing methods, the Al2O3 phases of either sapphire crystal or ruby crystal and the Al2O3 phases of the ceramic composite are directly integrated by melting without a bonding interface between them. Therefore, even if heat is generated from the ceramic composite, the heat is quickly conducted to the crystal, making it possible to realize a ceramic composite that can efficiently dissipate heat.

[0029] Furthermore, since the Al2O3 phases are integrated without a bonding interface between them, the Al2O3 phases are firmly bonded to prevent separation, and high impact resistance can be imparted to the ceramic bonded body, improving reliability.

[0030] Furthermore, by allowing the melt to penetrate into the crystal due to capillary action, it becomes possible to quickly manufacture a ceramic composite integrated with the Al2O3 phase of the crystal, improving mass productivity.

[0031] The seventh feature of this embodiment is that the ceramic composite is such that the gap between the crystals sandwiching the ceramic composite is 0.01 mm or more and 1 mm or less.

[0032] The eighth feature of this embodiment is that the manufacturing method of the ceramic composite is such that the gap between the crystals is 0.01 mm or more and 1 mm or less.

[0033] The ninth feature of this embodiment is that the ceramic composite is such that the diameter of the stop hole or through hole is 0.1 mm or more and 3 mm or less.

[0034] The tenth feature of this embodiment is that the manufacturing method of the ceramic composite is such that the diameter of the stop hole or through hole is 0.1 mm or more and 3 mm or less.

[0035] According to these configurations and manufacturing methods, in addition to the above effects, miniaturization or thinning of the ceramic composite can be achieved. Further, as the ceramic composite is miniaturized or thinned, heat is generated from the ceramic composite. Even if the heat generation part is concentrated on a specific part of the miniaturized or thinned ceramic composite, since the Al2O3 phases are directly integrated without a bonding interface by melting, heat is rapidly dissipated.

[0036] Furthermore, due to capillary action, the melt can uniformly penetrate into the gaps between the crystals, the stop holes, or the through holes. Therefore, unevenness in the thickness of the ceramic composite is prevented, and it is possible to obtain uniform white light over the entire in-plane area.

[0037] The eleventh feature of the present embodiment is that the manufacturing method of the ceramic composite is such that the longitudinal direction of the gaps between the crystals is orthogonal to the plane direction of the liquid surface of the melt.

[0038] According to this manufacturing method, in addition to the above effects, it is possible to perform capillary action most rapidly.

[0039] Hereinafter, with reference to FIGS. 1 to 10, a ceramic composite and its manufacturing method according to the first embodiment of the present invention will be described.

[0040] As shown in FIGS. 1 to 5, the ceramic composite 2 according to the present invention has at least two oxide phases of a Y3Al5O 12 phase and an Al2O3 phase in a lamellar structure, and the Al2O3 phase of the ceramic composite 2 and the Al2O3 phase of either the sapphire crystal or the ruby crystal 6 or 9 are integrated without a bonding interface therebetween.

[0041] FIG. 10 is a micrograph showing a cross section of the ceramic composite 2. As shown in FIG. 10, the ceramic composite 2 of the present embodiment has at least two oxide phases, namely, a YAG (Y3Al5O 12 ) phase as the first phase and an Al2O3 phase as the second phase, present as a eutectic, and is a solidified body having a lamellar structure in which the first phase and the second phase are continuously and three-dimensionally intertwined with each other.

[0042] The structure of the lamella in which the two oxide phases of the first phase and the second phase are continuously and three-dimensionally intertwined with each other means that there is no boundary phase such as amorphous between the oxide phases, and the oxide phases are in direct contact with each other. In FIG. 10, the region shown in dark color (black part) is the Y3Al5O 12 phase, and the region shown in light color (white part) is the Al2O3 phase. There are few cases where the first phase and the second phase are separated independently in an island shape, and they have regions continuous in the three-dimensional direction (three-dimensional direction). Further, when the ceramic composite 2, which is the obtained solidified body, was confirmed with the naked eye of the manufacturer, it exhibited a yellow color.

[0043] Also, the composition ratio of the Y3Al5O 12 phase contained in the ceramic composite 2 is 19.72 ± 2.00 mol% near the eutectic composition. When the composition ratio of the Y3Al5O 12 phase is outside this range, it is difficult to uniformly form a lamellar structure by eutectic with the Al2O3 phase.

[0044] Also, it is more desirable to contain Ce in the Y3Al5O 12 phase. The reason is that when Y in the Y3Al5O 12 phase is partially replaced by Ce, the Y3Al5O 12 phase functions as a phosphor material, absorbs blue light which is primary light, emits yellow light as secondary light, and white light can be obtained.

[0045] Y3Al5O 12 The content of Ce in the phase is preferably in the range of 0.01 mol% or more and 5.0 mol% or less. When Y in the Y3Al5O 12 phase is partially replaced by Ce, the Y3Al5O 12 phase functions as a phosphor material, absorbs blue light which is primary light, and emits yellow light as secondary light. In the Y3Al5O 12 phase, the absorption wavelength and emission wavelength change depending on the Ce concentration. However, in the ceramic composite of the present embodiment, as will be described later, even if the content of Ce is relatively large, a uniform and fine lamellar structure can be formed.

[0046] Here, the phase activated with Ce is shown as Y3Al5O 12 phase, but a part of Y may be replaced with Lu. The replacement amount of Lu is preferably set to 1.0 mol% or more and 10.0 mol% or less in terms of the fact that the Y3Al5O 12 phase absorbs blue light which is primary light and emits yellow light which is secondary light. Further, when a part of Y is replaced with Lu, the Y3Al5O 12 phase may be activated within the range of 0.01 mol% or more and 5.0 mol% or less with Ce.

[0047] Also, Cr may be added to the ceramic composite. The addition amount can be arbitrarily selected. For example, when it is desired to emit red fluorescent light from the ceramic composite, 0.01 mol% or more and 0.5 mol% or less is desirable.

[0048] Further, the ceramic composite 2 contains MgO in the range of 10 ppm or more and 500 ppm or less. By containing MgO within this range, the conversion efficiency from blue light to white light can be increased, and the emission intensity of white light can be increased.

[0049] Also, in the ceramic composite 2 of the present embodiment, in the lamellar structure of the Y3Al5O 12 phase and the Al2O3 phase, the average value of the lamellar spacing in the Y3Al5O 12 phase is 0.5 μm or more and 20 μm or less. Here, the lamellar spacing of the Y3Al5O 12 phase refers to the width of the Y3Al5O 12 phase sandwiched between the Al2O3 phases, and indicates the width across the longitudinal direction of the continuous Y3Al5O 12 phase. When the lamellar spacing is less than 0.5 μm, the size of the Y3Al5O 12 phase becomes several times the wavelength of blue light, making it difficult to uniformly wavelength-convert blue light to yellow light. Also, when the lamellar spacing is larger than 20 μm, the density of the lamellar structure becomes insufficient, and the number of times the blue light enters the interface between the Y3Al5O 12 phase and the Al2O3 phase during transmission through the ceramic composite 2 decreases, and the light is not sufficiently scattered, resulting in a decrease in the efficiency of wavelength conversion and color mixing.

[0050] The ceramic composite 2 is manufactured using a crucible 5 (see FIG. 9) described later. Therefore, molybdenum (Mo) or tungsten (W), which is the material of the crucible 5, dissolves slightly into a raw material melt 17 obtained by melting the raw materials of the ceramic composite 2 in the crucible 5 (hereinafter simply referred to as "melt" as necessary) and is incorporated into the ceramic composite 2. Therefore, in addition to the above Y3Al5O 12 phase, Al2O3 phase, MgO, Ce, and Lu and Cr, a trace amount of Mo or W is contained.

[0051] The amount of Mo or W contained in the ceramic composite 2 is preferably in the range of 1.0 mol·ppm or more and 30000 mol·ppm or less, and more preferably in the range of 100 mol·ppm or more and 3000 mol·ppm or less. In the production of the ceramic composite 2 using the Edge-defined Film-fed Growth (EFG) method, it is impossible to completely prevent the material of the crucible 5 from dissolving into the melt 17, and it is very difficult to make the content of Mo or W less than 1.0 mol·ppm. Further, when the content of Mo or W exceeds 30000 mol·ppm and becomes large, the crystallinity of the Y3Al5O 12 phase and Al2O3 phase deteriorates and the wavelength conversion efficiency deteriorates, which is not preferable. When the content of Mo or W is set to 100 mol·ppm or more and 3000 mol·ppm or less, these problems are solved, and at the same time, the primary light and the secondary light are scattered uniformly, making it possible to increase the emission amount of white light. Therefore, it is most desirable. Therefore, by setting the content of Mo or W contained in the ceramic composite 2 to at least 1.0 mol·ppm or more and 30000 mol·ppm or less, a fine lamellar structure can be formed to perform uniform light scattering, and the uniformity of the emission intensity and the conversion efficiency can be improved.

[0052] When a material other than Mo or W is used for the crucible 5, since the melting point is low, the amount of the material of the crucible 5 dissolved into the melt 17 increases, and the content of the elements derived from the crucible 5 contained in the ceramic composite 2 increases, which is not preferable. Further, using a material with a high melting point other than Mo or W as the material constituting the crucible 5 has problems such as reactivity with the melt 17 of the raw material and formability of the crucible 5, which is not preferable. Therefore, when manufacturing the ceramic composite 2 to Y3Al5O 12 In order to refine the lamellar structure of the Y3Al5O 12 phase and the Al2O3 phase, it is important that Mo or W is contained in the ceramic composite 2 within the above range.

[0053] As described above, in the ceramic composite 2 of the present embodiment, at least two oxide phases of the Y3Al5O 12 phase and the Al2O3 phase are in a lamellar structure, and the average value of the inter-lamellar spacing in the Y3Al5O 12 phase is 0.5 μm or more and 20 μm or less, and MgO is contained in an amount of 10 ppm or more and 500 ppm or less. Further, since Mo or W is contained, it is possible to uniformly scatter the primary light and the secondary light and improve the wavelength conversion efficiency.

[0054] In the ceramic composite 2 of the present embodiment, as described above, the Ce content is adjusted in the range of 0.01 mol% or more and 5.0 mol% or less. Therefore, the interfaces of the Y3Al5O 12 phase and the Al2O3 phase are included in the lamellar structure at a density of 30 pieces / mm or more and 800 pieces / mm or less. When the number of interfaces is less than 30 pieces / mm, the density of the lamellar structure is insufficient, and the number of times of incidence on the interfaces of the Y3Al5O 12 phase and the Al2O3 phase decreases while blue light passes through the ceramic composite 2, and the light is not sufficiently scattered, resulting in a decrease in the efficiency of wavelength conversion and color mixing. When the number of interfaces exceeds 800 pieces / mm, the size of the Y3Al5O 12 phase becomes small and becomes about several times the wavelength of blue light, so there is a possibility that it becomes difficult to uniformly wavelength-convert blue light into yellow light.

[0055] As crystals integrated with such a ceramic composite 2, two crystals (crystals 6, 6) are provided as shown in FIGS. 1 to 4, or a pipe-shaped crystal 9 shown in FIG. 5 is provided. In the crystal 9 of FIG. 5, a stop hole or a through hole is formed. In FIG. 5, an embodiment having a penetrated hole 9a is illustrated.

[0056] In the embodiment in which two flat plate-shaped crystals 6 shown in FIGS. 1 to 4 are provided, the surfaces of the crystals 6 facing each other are joined by direct contact without an adhesive or a bonding material or the like in between.

[0057] The melt 17 penetrates into the minute gaps of the joint surfaces of the joined crystals 6 facing each other by the capillary phenomenon described later and is sandwiched by the two crystals (6, 6). Therefore, the Al2O3 phase of the ceramic composite 2 is integrated with the Al2O3 phase of the crystal 6 without a joint interface on both of its surfaces. The gap between the crystals (6, 6) sandwiching the ceramic composite is set to be 0.01 mm or more and 1 mm or less.

[0058] When the gap between the crystals (6, 6) is less than 0.01 mm, the ceramic composite 2 formed in the gap is excessively thinned, so the influence of the thickness due to manufacturing errors and the influence of thickness unevenness in the plane become large, and it becomes difficult to obtain uniform white light over the entire plane. On the other hand, since the thermal conductivity of the Y3Al5O 12 phase contained in the ceramic composite 2 is only about one-fourth of that of the Al2O3 phase, when the gap between the crystals (6, 6) becomes large, the ceramic composite 2 formed in the gap also becomes thick and the heat dissipation deteriorates, and a temperature difference is likely to occur between the surface and the inside. Therefore, when the gap between the crystals (6, 6) is larger than 3 mm, a temperature difference between the outside and the inside is likely to occur, and there is a possibility that the uniformity of the lamellar spacing is impaired, which is not preferable. The desirable gap for preventing the temperature difference between the surface and the inside is 1 mm or less.

[0059] When it is desired to form the gap between the (6,6) crystals in the vicinity of 1 mm, which is relatively large within the range of 0.01 mm to 1 mm, allowing the melt 17 to penetrate into the direct bonding surface between the crystals 6 by capillary action to form the gap is not preferable because the gap of the direct bonding surface expands as the melt 17 penetrates. Consequently, there is a risk that the bonding state cannot be maintained and peeling may occur. Therefore, as shown in FIG. 4, it is preferable to separately provide a slit with a width W on the bonding surface by means of a step 6c, and allow the melt 17 to penetrate into the slit to form the ceramic composite 2. The width W is set as the desired width of the ceramic composite 2 to be formed and is less than the width of the crystal 6. Note that the thickness of the slit formed by the step 6c is such that the melt 17 that has penetrated into the slit is held within the slit by its surface tension and does not drip or flow out of the slit. The upper limit of the thickness of the slit may be set to 1 mm, which is the upper limit value of the gap between the (6,6) crystals.

[0060] The size of the crystal 6 in the planar direction is not particularly limited, but from the viewpoint of preventing deterioration of workability, a rectangular shape with a width of 0.5 mm or more and 300 mm or less and a length of 10 mm or more and 1000 mm or less is desirable.

[0061] On the other hand, as shown in FIG. 5, in an embodiment in which a pipe-shaped crystal 9 having a stop hole or a through hole formed therein is provided, the ceramic composite 2 is inserted into the stop hole or the through hole, and the Al2O3 phase of the crystal 9 and the Al2O3 phase of the ceramic composite 2 are integrated in a state where there is no bonding interface between them. Further, by setting the diameter of the stop hole or the through hole to 0.1 mm or more and 3 mm or less, it becomes possible to allow the melt 17 to penetrate into the stop hole or the through hole by capillary action.

[0062] If the diameter of the stop hole or the through hole is less than 0.1 mm, the portion of the ceramic composite 2 becomes too small in diameter, making it difficult to obtain uniform white light. On the other hand, if it exceeds 3 mm, the ceramic composite 2 becomes too thick, deteriorating the heat dissipation performance and possibly impairing the uniformity of the lamellar spacing, which is not preferable.

[0063] FIG. 5 shows an embodiment having a through hole 9a, which may also be a blind hole. The diameter dimension of the crystal 9 is not particularly limited as long as a blind hole or a through hole (hole 9a in FIG. 5) having a diameter of 0.1 mm or more and 3 mm or less can be formed.

[0064] The crystal 6 or 9 is composed of either a sapphire crystal or a ruby crystal. Examples of the crystal 6 or 9 include single crystals, polycrystals, and crystals having an intermediate structure between them. However, single crystals are most preferable particularly for lighting device applications because they have high thermal conductivity and high transparency.

[0065] As described above, according to the ceramic composite 2 according to the first embodiment of the present invention, the Al2O3 phase of the crystal 6 or 9, which is either a sapphire crystal or a ruby crystal, and the Al2O3 phases of the ceramic composite 2 are directly integrated without a bonding interface between them by melting described later. Therefore, even if heat is generated from the ceramic composite 2, the heat is quickly conducted to the crystal 6 or 9, so that a ceramic composite 2 capable of efficiently dissipating heat can be realized.

[0066] Furthermore, since the Al2O3 phases are integrated without a bonding interface between them, the Al2O3 phases are firmly bonded to prevent separation, and the ceramic bonded body 2 can also be provided with high impact resistance and its reliability is improved.

[0067] Also, the ceramic composite 2 is thinned by being sandwiched between the gaps (0.01 mm or more and 1 mm or less) between two crystals (6, 6), or is miniaturized (reduced in diameter) by being inserted into the blind hole or through hole (diameter 0.1 mm or more and 3 mm or less) of the crystal 9. Therefore, miniaturization or thinning of the ceramic composite 2 can be achieved.

[0068] Furthermore, with the miniaturization or thinning of the ceramic composite 2, even if heat is generated from the ceramic composite 2 and the heat-generating part is concentrated on a specific part of the miniaturized or thinned ceramic composite 2, since the crystal (6 or 9) and the Al2O3 phases of the ceramic composite 2 are directly integrated without a bonding interface by melting, heat is dissipated rapidly.

[0069] Accordingly, even if the ceramic composite 2 is used in a lighting device, it is possible to prevent failures and malfunctions of the lighting device.

[0070] Furthermore, with reference to FIGS. 6 to 9, a method for manufacturing the ceramic composite 2 according to the first embodiment of the present invention will be described. As shown in FIG. 9, the manufacturing apparatus 1 for the ceramic composite 2 includes a crucible 5 as a container 3 for manufacturing the ceramic composite 2 and a lifting container 4.

[0071] The container 3 includes a crucible 5, a crucible driving unit 18, a heater 7, an electrode 8, and a heat insulating material 10. The crucible 5 is made of molybdenum (Mo) or tungsten (W) and melts the raw material of the ceramic composite 2. The crucible driving unit 18 rotates the crucible 5 about its vertical axis. The heater 7 heats the crucible 5. Also, the electrode 8 energizes the heater 7. The heat insulating material 10 surrounds the crucible 5 and the heater 7.

[0072] Furthermore, the container 3 includes an atmospheric gas inlet 11 and an exhaust port 12 for the atmospheric gas. The atmospheric gas inlet 11 is an inlet for introducing, for example, argon gas as the atmospheric gas into the container 3 to prevent oxidation and consumption of the crucible 5 and the heater 7. On the other hand, the exhaust port 12 is provided for exhausting the atmospheric gas in the container 3.

[0073] The lifting container 4 includes a shaft 13, a shaft drive unit 14, a gate valve 15, and an inlet / outlet 16 of the ceramic composite 2. The shaft 13 holds the separately produced crystal 6. The shaft drive unit 14 raises and lowers the shaft 13 toward the crucible 5 and rotates the shaft 13 about its lifting direction as an axis. The gate valve 15 separates the container 3 and the lifting container 4. The inlet / outlet 16 is for taking in and out the ceramic composite according to the present invention.

[0074] Next, the manufacturing process of the ceramic composite 2 using the manufacturing apparatus 1 will be described. As the first step, a predetermined amount of granulated raw material powder (for example, a powder containing 64.71 wt% of aluminum oxide, 35.02 wt% of yttrium oxide, 0.003 wt% of magnesium oxide, and 0.27 wt% of cerium oxide), which is the raw material of the ceramic composite 2, is put into the crucible 5 and filled. The raw material powder may contain compounds and elements other than those described above according to the purity or composition of the ceramic composite 2 to be manufactured, but at least aluminum oxide and yttrium oxide shall be included.

[0075] Subsequently, in order not to oxidize and consume the crucible 5 and the heater 7, the inside of the container 3 is replaced with argon gas to make the oxygen concentration below a predetermined value.

[0076] As the next step, the crucible 5 is heated by the heater 7 to a predetermined temperature to melt the raw material powder. The heating temperature of the crucible 5 is set to be above the melting point of the ceramic composite 2 and below the melting point of aluminum oxide, sapphire crystal, or ruby crystal. Since the melting point of the ceramic composite 2 is about 1820°C to 1870°C, for example, the heating temperature of the crucible 5 is set to be about 50°C higher than the melting point of the ceramic composite 2. Also, the melting point of aluminum oxide, sapphire crystal, or ruby crystal is about 2050°C to 2072°C. When the crucible 5 is heated to such a temperature, the raw material powder melts after heating for a while, and a melt 17 of the raw material (see FIG. 6) is prepared. The temperature of the melt 17 is set to be above the melting point of the ceramic composite 2 and below the melting point of aluminum oxide, sapphire crystal, or ruby crystal.

[0077] As the next step, the shaft 13 is lowered to immerse and bring the crystal into contact with the melt 17. The crystal to be immersed in the melt 17 is either the two crystals (6, 6) directly joined to each other as described above, or the pipe-shaped crystal 9 shown in Fig. 5. In the crystal 9 of Fig. 5, a stop hole or a through hole is formed in advance by drilling or the like. In Figs. 6 to 9, as an example of the manufacturing method according to the present invention, the immersion state of the crystal (6, 6) directly joined by the step of preliminarily overlapping the flat plate-shaped crystals 6 shown in Figs. 1 to 4 is shown.

[0078] Fig. 7 shows the state of the step in which the crystal (6, 6) is immersed in the melt 17 and a part of the melt 17 penetrates into the gap 6b between the joining surfaces of the crystals 6 by capillary action. In Figs. 6 to 8, the gap 6b is exaggerated for easy understanding. By the penetration, a part of the melt 17 is sandwiched by the crystal (6, 6), and the melt 17 and the crystal (6, 6) are brought into contact. It should be noted that the crystal 9 in Fig. 5 may be immersed in the melt 17, the melt 17 may be allowed to penetrate into the stop hole or the through hole by capillary action, and the melt 17 and the crystal 9 may be brought into contact.

[0079] The crystal portion in contact with the melt 17 is melted. The applicant has found that the Al2O3 phase of the crystal 6 gathers on the contact surface with the melt 17, so that only the contact surface is preferentially melted even below the melting point of the crystal 6. By the melting, the Al2O3 phase of the crystal (6, 6) and the Al2O3 phase of the aluminum oxide in the melt are integrated in a state where there is no joining interface with each other. In the case of Fig. 7, the Al2O3 phase of the aluminum oxide of the melt 17 is integrated with the surfaces of the two crystals (6, 6) forming the gap 6b, the other surface in contact with the melt 17, and the ends.

[0080] It should be noted that when the crystal 9 in Fig. 5 is immersed in the melt 17, the crystal portion in the stop hole or the through hole is melted by the temperature of the melt 17. By the melting, the Al2O3 phase of the crystal (6, 6) and the Al2O3 phase of the aluminum oxide in the melt are integrated in a state where there is no joining interface with each other. Further, when the crystal 9 is immersed in the melt 17, the end portion of the crystal 9 in contact with the melt 17 and the side surface of the crystal 9 are also integrated with the Al2O3 phase of the aluminum oxide of the melt 17.

[0081] Thereafter, the shaft 13 is raised to take out the crystal (6,6) or 9 from the melt 17, and the melt 17 integrated with the crystal (6,6) or 9 is cooled to form the ceramic composite 2 which is a solidified body. By forming the solidified ceramic composite 2, the Al2O3 phase of the crystal (6,6) or 9 and the Al2O3 phase of the ceramic composite 2 are integrated in a state where there is no joining interface with each other.

[0082] After immersing the crystal in the melt 17, as soon as the intrusion of the melt 17 into the gap 6b of the joining surface, the stop hole or the through hole is confirmed, the crystal is immediately taken out from the melt 17. Then, the melted portion of the crystal (6,6) or 9 is limited to only the contact portion with the melt 17, the heating of the entire crystal (6,6) or 9 is suppressed, and when the crystal (6,6) or 9 is a single crystal in particular, it becomes possible to maintain the crystal structure in a single-phase state, which is desirable.

[0083] Thereafter, the obtained ceramic composite 2 is allowed to cool, the gate valve 15 is opened, it is moved to the lifting container 4 side, and taken out from the entrance / exit 16.

[0084] After taking out from the entrance / exit 16, except for the ceramic composite 2 formed in the gap 6b or the stop hole or the through hole, the ceramic composite integrated on the surface of the crystal (6,6) or 9 is unnecessary, and it may be removed by polishing (see FIG. 8).

[0085] By controlling the temperature of the liquid surface of the melt 17 to be constant when contacting the crystal, the crystal formation conditions of the ceramic composite 2 in the capillary phenomenon can be kept equivalent in the width direction, and a uniform lamellar structure can be formed over the entire ceramic composite 2.

[0086] As described above, in the present invention, it has been found that capillary action occurs in the melt 17 of the ceramic composite 2. Therefore, by allowing the melt to penetrate into the crystal by capillary action, it becomes possible to manufacture the ceramic composite 2 that is quickly integrated with the Al2O3 phase of the crystal, and the mass productivity can be improved.

[0087] Furthermore, due to capillary action, the melt 17 can uniformly penetrate into the gaps 6b between the joint surfaces of the crystals (6,6), or into the stop holes or through holes of the crystal 9. Therefore, unevenness in the thickness of the ceramic composite 2 is prevented, and it becomes possible to obtain uniform white light over the entire in-plane area of the ceramic composite 2.

[0088] Furthermore, with respect to the plane direction of the liquid surface of the melt 17 (the horizontal direction in FIG. 7 or FIG. 8), the longitudinal direction of the gap 6b between the crystals (6,6) (the vertical direction in FIG. 7 or FIG. 8) is set as the orthogonal direction, and the crystals (6,6) are immersed in a direction perpendicular to the liquid surface of the melt 17. Alternatively, the longitudinal direction of the stop hole or the through hole is made orthogonal to the plane direction of the liquid surface of the melt 17, and the stop hole or the through hole is immersed in a direction perpendicular to the liquid surface of the melt 17. By such immersion, it becomes possible to perform capillary action most rapidly.

[0089] The crystal 6 or 9 may be produced using a known method. For sapphire crystals and ruby crystals, those grown by the EFG method, the Kyropoulos method, the Czochralski method, the Verneuil method, the vertical Bridgman method, etc. are used.

[0090] Next, with reference to FIGS. 11 to 25, a ceramic composite and a manufacturing method thereof according to the second embodiment of the present invention will be described. In addition, the same reference numerals are given to the portions overlapping with the first embodiment, and the overlapping explanations are omitted or simplified.

[0091] In the embodiment shown in FIGS. 11 to 13, two crystals (6,6) are provided, and a step 6c is provided only in the lower crystal 6. The ceramic composite 2 is disposed within the step 6c and sandwiched by the crystals (6,6) to integrate the Al2O3 phase of the crystals (6,6) and the Al2O3 phase of the ceramic composite 2.

[0092] In the embodiment shown in FIGS. 11 to 13, the planar shapes of the two crystals (6,6) are circular shapes having orifices with respect to each other, the diameter is from 1 inch (25.4 mm) to 8 inches (203.2 mm), and the thickness is formed to be 1 mm. Also, the height of the step 6c is 0.01 mm or more and less than the thickness of the crystal 6, and the width is less than the diameter of the crystal 6.

[0093] In the embodiments shown in FIGS. 14 to 16, three crystals 6 are provided, and only the middle crystal 6 with a relatively small diameter sandwiched between the upper and lower crystals (6, 6) is provided with a through hole 6a. The ceramic composite 2 is inserted or disposed between the inside of the through hole 6a and the upper and lower crystals (6, 6) sandwiching the middle crystal 6, and the Al2O3 phases of the three crystals 6 and the Al2O3 phase of the ceramic composite 2 are integrated.

[0094] The planar shapes of the three crystals 6 are circular shapes having orifices with respect to each other, and the thicknesses are each formed to be 1 mm. The diameters of the upper and lower crystals (6, 6) are from 1 inch (25.4 mm) to 8 inches (203.2 mm), and only the diameter of the middle crystal 6 is set to be less than the diameters of the upper and lower crystals (6, 6). Further, the diameter of each through hole 6a is set to be 0.1 mm or more and 3 mm or less. Also, each through hole 6a is formed in the middle crystal 6 in advance by drilling or the like.

[0095] Furthermore, a method for manufacturing the ceramic composite 2 according to each of the embodiments shown in FIGS. 11 to 16 will be described. First, a method for manufacturing the ceramic composite 2 disposed on the crystal 6 in FIG. 11 or FIG. 14 will be described with reference to FIGS. 17 to 25. FIGS. 17 to 24 are diagrams for explaining a method for manufacturing a plurality of ceramic composites.

[0096] As shown in FIG. 17, a manufacturing apparatus 19 for a ceramic composite includes a container 20 for growing the ceramic composite 2 and a lifting container 4 for lifting the grown ceramic composite 2, and grows and grows the ceramic composite 2 by the EFG method.

[0097] The container 20 includes a crucible 5, a crucible driving unit 18, a heater 7, an electrode 8, a die 22, and a heat insulator 10. The crucible 5 is made of molybdenum or tungsten and melts the raw material. The crucible driving unit 18 rotates the crucible 5 about its vertical axis. The heater 7 heats the crucible 5. Also, the electrode 8 energizes the heater 7. The die 22 is installed in the crucible 5 and determines the liquid surface shape of the raw material melt (hereinafter, simply referred to as "melt" as necessary) 17 when pulling up the ceramic composite 2. The heat insulator 10 surrounds the crucible 5, the heater 7, and the die 22.

[0098] Furthermore, the container 20 includes an atmospheric gas inlet 11 and an exhaust port 12. The atmospheric gas inlet 11 is an inlet for introducing, for example, argon gas as the atmospheric gas into the container 20, and prevents oxidation and consumption of the crucible 5, the heater 7, and the die 22. On the other hand, the exhaust port 12 is provided for exhausting the inside of the container 20.

[0099] The pulling-up container 4 includes a shaft 13, a shaft driving unit 14, a gate valve 15, and a substrate entrance / exit 16, and pulls up a plurality of flat ceramic composites 2 grown from the seed crystal 23. The shaft 13 holds the seed crystal 23. The shaft driving unit 14 raises and lowers the shaft 13 toward the crucible 5 and rotates the shaft 13 about its raising and lowering direction. The gate valve 15 separates the container 20 and the pulling-up container 4. The substrate entrance / exit 16 is for inserting and removing the seed crystal 23.

[0100] The manufacturing apparatus 19 also has a control unit (not shown), and the control unit controls the rotation of the crucible driving unit 18 and the shaft driving unit 14.

[0101] Next, the die 22 will be described. The die 22 is made of molybdenum and has a number of partition plates 24 as shown in FIG. 18. In FIG. 18, as an example of the die, a case is shown where there are 30 partition plates 24 and 15 dies 22 are formed. The partition plates 24 have the same flat plate shape and are arranged parallel to each other so as to form minute gaps (slits) 25, thereby forming one die 22. The slit 25 is provided over substantially the entire width of the die 22. Further, since the plurality of dies 22 have the same shape and are arranged in parallel at a predetermined interval such that their longitudinal directions are parallel to each other, a plurality of slits 25 are provided. An inclined surface 29 is formed at the upper part of each partition plate 24, and by arranging the inclined surfaces 29 facing each other, an acute-angled opening 31 is formed. Also, the slit 25 has the role of raising the melt 17 from the lower end of each die 22 to the opening 31 by capillary action.

[0102] The raw material charged into the crucible 5 melts (raw material melt) based on the temperature rise of the crucible 5 and becomes the melt 17. A part of this melt 17 infiltrates into the slit 25 of the die 22, rises in the slit 25 based on capillary action as described above, and is exposed from the opening 31, and a raw material melt pool 30 is formed at the opening 31 (see FIG. 21(a)). In the EFG method, the ceramic composite 2 grows according to the shape of the melt surface formed in the raw material melt pool (hereinafter, referred to as "melt pool" as necessary) 30. In the die 22 shown in FIG. 18, since the shape of the melt surface is an elongated rectangle, a flat plate-shaped ceramic composite 2 is manufactured.

[0103] Next, the seed crystal 23 will be described. As shown in FIGS. 17, 20, and 21, in this embodiment, a substrate made of a flat plate-shaped ceramic composite is used as the seed crystal 23. Further, the seed crystal 23 is arranged such that the plane direction of the seed crystal 23 and the longitudinal direction of the die 22 are orthogonal to each other at an angle of 90°. Also, since the seed crystal 23 and the ceramic composite 2 are also orthogonal to each other at an angle of 90°, FIG. 17 shows the side surface of the ceramic composite 2.

[0104] If the contact area of the seed crystal 23 with a substrate holder (not shown) at the lower part of the shaft 13 is large, it will deform due to stress caused by the difference in thermal expansion coefficient and may be damaged in some cases. Conversely, the fixing of the seed crystal 23 may be loosened due to the difference in thermal expansion coefficient. Therefore, it is preferable that the contact area between the seed crystal 23 and the substrate holder is small. Also, the seed crystal 23 needs to have a substrate shape that can be securely fixed to the substrate holder.

[0105] FIG. 19 is a view showing an example of the substrate shape of the seed crystal 23. Among them, FIGS. 19(a) and (b) are those in which a notch 26 is provided at the upper part of the seed crystal 23. By using this notch 26, for example, a U-shaped substrate holder can be inserted from below the two notches 26, and it becomes possible to securely hold the seed crystal 23 while reducing the contact area.

[0106] Also, as shown in FIG. 19(c), a notch hole 27 may be provided inside the seed crystal 23. By using this notch hole 27, for example, locking claws can be inserted into the two notch holes 27, and it becomes possible to securely hold the seed crystal 23 while reducing the contact area between the substrate holder and the seed crystal 23.

[0107] Next, a method for manufacturing the ceramic composite 2 using the manufacturing apparatus 19 will be described. First, a predetermined amount of granulated raw material powder (as an example, a powder containing 64.71 wt% of aluminum oxide, 35.02 wt% of yttrium oxide, 0.003 wt% of magnesium oxide, and 0.27 wt% of cerium oxide), which is a raw material of the ceramic composite, is put into and filled in the crucible 5 in which the die 22 is housed. The raw material powder may contain compounds and elements other than the above according to the purity or composition of the ceramic composite to be manufactured.

[0108] Subsequently, in order not to oxidize and consume the crucible 5, the heater 7, or the die 22, the inside of the container 20 is replaced with argon gas to make the oxygen concentration below a predetermined value.

[0109] Next, heat with the heater 7 to set the crucible 5 to a predetermined temperature and melt the raw material powder. The heating temperature of the crucible 5 is set to be above the melting point of the ceramic composite 2 and below the melting point of aluminum oxide, sapphire crystal, or ruby crystal. Since the melting point of the ceramic composite 2 is about 1820°C to 1870°C, as an example, the heating temperature of the crucible 5 is set to be about 50°C higher than the melting point of the ceramic composite 2. After heating the crucible 5 for a while, the raw material powder melts to prepare a melt 17 of the raw material. The temperature of the melt 17 is set to be above the melting point of the ceramic composite 2 and below the melting point of aluminum oxide, sapphire crystal, or ruby crystal. Further, a part of the melt 17 rises through the slit 25 of the die 22 by capillary action and reaches the surface of the die 22, and a melt pool 30 is formed above the slit 25.

[0110] Next, as shown in FIGS. 20 and 21, lower the seed crystal 23 while holding it at an angle perpendicular to the longitudinal direction of the melt pool 30 above the slit 25, and bring the seed crystal 23 into contact with the melt surface of the melt pool 30. The seed crystal 23 is previously introduced into the lifting container 4 from the substrate entrance / exit 16. In FIG. 20, for the sake of easy viewing of the slit 25 and the opening 31, the illustration of the melt 17 and the melt pool 30 is omitted.

[0111] FIG. 20 is a diagram showing the positional relationship between the seed crystal 23 and the partition plate 24. As described above, by making the plane direction of the seed crystal 23 orthogonal to the longitudinal direction of the partition plate 24, it becomes possible to reduce the contact area between the seed crystal 23 and the melt 17. Therefore, the contact portion of the seed crystal 23 conforms to the melt 17, and crystal defects are less likely to occur in the ceramic composite 2 that grows and develops.

[0112] When bringing the seed crystal 23 into contact with the melt surface, the lower part of the seed crystal 23 may be brought into contact with the upper part of the partition plate 24 and melted. FIG. 21(b) is a diagram showing a state where a part of the seed crystal 23 is melted. By melting a part of the seed crystal 23 in this way, the temperature difference between the seed crystal 23 and the melt 17 can be quickly eliminated, and the generation of crystal defects in the ceramic composite 2 can be further reduced.

[0113] Subsequently, the substrate holder is pulled up at a predetermined rising speed to start pulling up the seed crystal 23. Specifically, the substrate holder is raised at a predetermined speed by the shaft 13.

[0114] In addition, in order to more easily align the seed crystal with the opening 31 of the die 22, unevenness may be provided on the lower side of the seed crystal 23. FIG. 22 is a diagram illustrating the shape of the lower side of the seed crystal 23. FIG. 22(a) shows the case where the lower side has a comb-tooth shape, and FIG. 22(b) shows the case where the lower side has a sawtooth shape.

[0115] The interval of this unevenness is adjusted according to the interval of the opening 31, and the convex portion is aligned with the center of the melt pool 30. By providing the convex portion, the convex portion can be used as the growth starting point of the ceramic composite 2, and the ceramic composite 2 can be more easily formed. Note that the shape of the unevenness is not limited to that shown in FIG. 22, and for example, a corrugated unevenness shape may be used.

[0116] The substrate holder is raised at a predetermined speed, and crystal growth (spreading) is performed so that the ceramic composite 2 expands in the longitudinal direction of the die 22 as shown in FIG. 23 with the seed crystal 23 as the center. When the ceramic composite 2 expands to the full width of the die 22 (full spread), a flat-plate-shaped ceramic composite 2 having a width approximately equal to the full width of the die 22 is grown (straight-bar process). FIG. 23 is a schematic diagram showing how the width of the ceramic composite 2 expands by the spreading process. By obtaining a wide ceramic composite 2, the yield of the ceramic composite product is improved.

[0117] After growing the ceramic composite 2 to the full width of the die 22 by the spreading process, a pulling-up process is performed in which a straight-bar portion 28 having a flat-plate shape and a constant width approximately equal to the full width of the die 22 is pulled up at a predetermined speed to a predetermined length (straight-bar length) as shown in FIG. 24, and a flat-plate-shaped ceramic composite 2 is obtained.

[0118] During the lifting process, temperature control is performed using a heater 7 or the like so that the interface temperature of the melt 17 in the melt reservoir 30 formed above the slit 25 becomes constant. The ceramic composite 2 grows as the melt 17 that has risen to the melt reservoir 30 contacts the seed crystal 23 and is cooled while being lifted. Therefore, by controlling the temperature of the melt reservoir 30 to be constant, the crystal growth conditions can be kept equivalent during the growth period of the ceramic composite 2, and a uniform lamellar structure can be formed throughout the ceramic composite 2.

[0119] The pulling speed of the seed crystal 23 in the pulling process is preferably in the range of 0.9 mm / hour or more and 400 mm / hour or less. More preferably, it is in the range of 50 mm / hour or more and 200 mm / hour or less. By setting the pulling speed of the seed crystal 23 to 50 mm / hour or more, it becomes possible to prevent the introduction of cracks into the ceramic composite 2. Further, by setting the pulling speed to 200 mm / hour or less, the growth state of the ceramic composite 2 can be further stabilized.

[0120] When the pulling speed is less than 0.9 mm / hour, the size variation of the lamellar structure becomes large with respect to the error of the pulling speed, so it becomes difficult to control the size of the lamellar structure. Therefore, it causes a decrease in the emission intensity of white light of the grown ceramic composite 2. Also, since the growth rate is slow, the productivity becomes low. When the pulling speed is greater than 400 mm / hour, it becomes difficult to control the temperature of the melt reservoir 30, so it also becomes difficult to control the size of the lamellar structure. Further, if the pulling speed is too large, the melt 17 in the melt reservoir 30 is likely to separate from the seed crystal 23 and the straight body portion 28 and the growth is interrupted, which is not preferable.

[0121] Thereafter, the obtained ceramic composite 2 is allowed to cool, the gate valve 15 is opened, it is moved to the side of the lifting container 4, and taken out from the substrate entrance / exit 16. The appearance of the obtained flat-plate-shaped ceramic composite 2 is shown in FIG. 24. The straight body length is not particularly limited, but 2 inches or more (50.8 mm or more) is preferable.

[0122] Also, as shown in FIG. 25, the entire width of the die 22 and the width of the seed crystal 23 may be made the same, and the ceramic composite 2 may be grown with the same width as the entire width of the seed crystal 23. In FIG. 25, for the sake of easy viewing of the slit 25, the illustration of the melt 17 and the melt reservoir 30 is omitted.

[0123] By using the manufacturing apparatus 19, the seed crystal 23, and the die 22 as described above, a plurality of ceramic composites 2 can be simultaneously manufactured from a common seed crystal 23.

[0124] The die 22 including the seed crystal 23 and the partition plate 24 needs to be precisely positioned. Therefore, as shown in FIG. 17, the manufacturing apparatus 19 is provided with a crucible drive unit 18 that rotates the crucible 5 on which the die 22 is installed, and a control unit (not shown) that controls the rotation. Also, with respect to the shaft 13, a shaft drive unit 14 that rotates the shaft 13 and a control unit (not shown) that controls the rotation are provided. That is, the positioning of the seed crystal 23 with respect to the die 22 is adjusted by rotating the shaft 13 or the crucible 5 by the control unit. In addition, precise positioning between the seed crystal 23 and the die 22 can also be performed by using a die 22 in which a part of the slope 29 of each partition plate 24 is cut out.

[0125] The ceramic composite 2 of the solidified body is prepared in advance as described above. Further, in the embodiments of FIGS. 11 to 13, the prepared ceramic composite 2 of the solidified body is placed on the step 6c. Next, only the ceramic composite 2 of the solidified body placed on the step 6c is melted, and a melt composed of at least aluminum oxide and yttrium oxide is prepared and spread in the step 6c, which is the gap between the crystals (6, 6).

[0126] The melting method for only the ceramic composite 2 is carried out by utilizing the difference between the melting point of the ceramic composite 2 and the melting point of the crystal 6. Specifically, the ceramic composite 2 and the crystals (6, 6) in the state of FIG. 12 are heated in a heating furnace or the like. The heating temperature at that time may be set to exceed the melting point of the ceramic composite 2 and be less than the melting point of aluminum oxide, sapphire crystal, or ruby crystal. As an example, the heating temperature is set to be about 50 °C higher than the melting point of the ceramic composite 2.

[0127] Only the upper and lower crystal (6, 6) portions in contact with the melt that has spread within the step 6c are melted. As described above, the applicant has found that by the Al2O3 phase of the crystal 6 gathering at the contact surface with the melt, only the contact surface is preferentially melted even at a temperature lower than the melting point of the crystal 6. By this melting, the Al2O3 phase of each crystal (6, 6) and the Al2O3 phase of the aluminum oxide in the melt are integrated in a state where there is no bonding interface between them.

[0128] Thereafter, by allowing the melt and the melted portions of the respective crystals (6, 6) to cool naturally, a solidified ceramic composite 2 is formed within the step 6c as shown in FIG. 13, and the Al2O3 phase of the upper and lower crystals (6, 6) and the Al2O3 phase of the ceramic composite 2 are integrated in a state where there is no bonding interface between them.

[0129] On the other hand, in the embodiments of FIGS. 14 to 16, the prepared solidified ceramic composite 2 is placed on the surface of the lower substrate 6, and then only the ceramic composite 2 is melted by the heating furnace or the like to prepare a melt composed of at least aluminum oxide and yttrium oxide. The heating temperature of the ceramic composite 2 is set to exceed the melting point of the ceramic composite 2 and be less than the melting point of aluminum oxide, sapphire crystal, or ruby crystal. As an example, the heating temperature is set to be about 50 °C higher than the melting point of the ceramic composite 2.

[0130] The melt spreads over the main surfaces of the middle and lower crystals 6, comes into contact with each main surface, and also penetrates into each through-hole 6a by capillary action, bringing the crystal portions within each through-hole 6a into contact with the melt. Further, the melt passes through each through-hole 6a and spreads over the other main surface of the middle crystal 6 and the main surface of the upper crystal 6, coming into contact with each main surface.

[0131] Only the main surfaces of each of the three crystals 6 in contact with the melt and the crystal 6 portions in the through-holes 6a are melted by the melt, and the Al2O3 phase of each crystal 6 and the Al2O3 phase of the aluminum oxide in the melt are integrated without a joining interface therebetween.

[0132] Thereafter, by allowing the melt and the melted portions of each crystal 6 to cool and cool naturally, a ceramic composite body 2 in a solid state is formed as shown in Fig. 16, with the upper and lower crystals (6, 6) sandwiching the middle crystal 6 and further covering the middle crystal 6. Therefore, the Al2O3 phases of the main surfaces of each of the three crystals 6 and the crystal 6 portions in the through-holes 6a and the Al2O3 phase of the ceramic composite body 2 are integrated without a joining interface therebetween. Also, the ceramic composite body 2 is sandwiched between the upper and lower crystals (6, 6).

[0133] Note that the gap between the upper and lower crystals (6, 6) in Fig. 16 is equal to the thickness (1 mm) of the middle crystal 6.

[0134] The shape of each crystal 6 in the planar direction from Fig. 11 to Fig. 16 may be rectangular. Also, the arrangement position of the ceramic composite body 2 shown in Figs. 14 and 15 may be changed to between the upper crystal 6 main surface and the middle crystal 6 main surface. Also, each through-hole 6a may be used as a blind hole.

Example

[0135] Examples 1 and 2 of the present invention will be described below, but the present invention is not limited only to the following examples. In Examples 1 and 2, sapphire single crystals were used for the crystals. The sapphire single crystals were directly joined using two flat plates each having a rectangular outer shape, an outer dimension of 44.5 mm × 100 mm, a diagonal length of 109 mm, and a thickness of 1 mm for each example. Further, only in Example 2, a slit composed of steps (6c in Figs. 3 and 4) was formed on the joining surface with W = 30 mm and a thickness of 0.01 mm.

[0136] The raw materials of the ceramic composite were prepared by melting a raw material powder containing 64.71 wt% aluminum oxide, 35.02 wt% yttrium oxide, 0.003 wt% magnesium oxide, and 0.27 wt% cerium oxide in the crucible to obtain a melt. Also, Ce was contained at 0.3 mol% in Example 1 and 0.1 mol% in Example 2.

[0137] A Mo crucible was used. Therefore, the melt contained Mo at 1.0 mol·ppm or more and 30000 mol·ppm or less.

[0138] After filling the crucible with the raw material powder, the crucible was heated to form a melt. After the formation of the melt, a directly bonded sapphire single crystal was immersed in the melt up to 30 mm in Example 1 and up to 50 mm in Example 2 out of the outer dimensions of 100 mm. The sapphire single crystals were immersed in the melt with the longitudinal direction of the gap between the sapphire single crystals orthogonal to the plane direction of the melt surface, and the melt was allowed to penetrate into the gap or slit of the bonding surface by capillary action.

[0139] The part of the sapphire single crystal in contact with the melt by immersion melted, and the Al2O3 phase of the sapphire single crystal and the Al2O3 phase of the aluminum oxide in the raw materials of the ceramic composite 2 were integrated by melting. Then, cooling and polishing were performed to form a ceramic composite composed of a solidified body. It was confirmed that in the ceramic composite of each example, the Al2O3 phases on both sides and the Al2O3 phase of the sapphire single crystal were integrated without a bonding interface between each other. Also, the obtained ceramic composite exhibited a yellow color.

[0140] Also, it was confirmed that the gap between the crystals was formed as thin as 0.01 mm in both examples. In Example 2, it was confirmed that the melt penetrated only within the range of the slit width W = 30 mm and a ceramic composite was formed.

[0141] When the ceramic composite was irradiated with blue light from the outside of the sapphire single crystal, it was confirmed that both examples were converted into white light.

Explanation of Reference Signs

[0142] 1. Manufacturing apparatus for 19 ceramic composites 2. Ceramic composites 3. 20 containers 4. Lifting container 5. Crucible 6. Crystal 6a. Hole 6b. Gap of joint surface between crystals 6c. Step 7. Heater 8. Electrode 9. Pipe-shaped crystal 9a. Hole 10. Heat insulator 11. Inlet for atmosphere gas 12. Exhaust port for atmosphere gas 13. Shaft 14. Shaft drive part 15. Gate valve 16. Inlet and outlet of ceramic composite 17. Melt 18. Crucible drive part 22. Die 23. Seed crystal 24. Partition plate 25. Slit 26. Notch part 27. Notch hole 28. Straight barrel part 29. Inclined surface 30. Melt reservoir 31. Opening W. Width of step 6c

Claims

1. The ceramic composite has at least Y ３ Al ５ O １２ phase and Al ２ O ３ phase, and has a lamellar structure of two oxide phases, and at least two crystals, either sapphire crystals or ruby crystals, are provided, and the ceramic composite is sandwiched by the two crystals, a ceramic composite in which the Al2O3 phase of the crystal and the Al2O3 phase of the ceramic composite are integrated without a bonding interface therebetween.

2. The ceramic composite according to claim 1, wherein the gap between the crystals sandwiching the ceramic composite is 0.01 mm or more and 1 mm or less.

3. Providing at least two crystals, either sapphire crystals or ruby crystals, and a step of overlapping them with each other, a step of introducing a raw material containing at least aluminum oxide and yttrium oxide into a crucible, a step of heating the crucible to melt the raw material in the crucible to prepare a melt composed of at least the aluminum oxide and the yttrium oxide, bringing the crystals into contact with the melt, allowing the melt to penetrate into the gap between the overlapped crystals by capillary action, sandwiching the melt with the crystals, bringing the crystal portions in contact with the melt into contact with the melt, melting the crystal portions in contact with the melt, and integrating the Al2O3 phase of the crystal and the Al2O3 phase of the aluminum oxide without a bonding interface therebetween by melting, a method for producing a ceramic composite, comprising a step of taking out the crystals from the melt and cooling the melt integrated with the crystals.

4. The method for producing a ceramic composite according to claim 3, wherein the gap between the crystals is 0.01 mm or more and 1 mm or less.

5. The method for producing a ceramic composite according to claim 3 or 4, wherein the longitudinal direction of the gap between the crystals is orthogonal to the plane direction of the liquid surface of the melt.

Images