Ceramic composite, light-emitting device, and method for manufacturing ceramic composite

Abstract

To provide a ceramic composite, a light emitting device, and a method for manufacturing the ceramic composite capable of suppressing variations in the color tone of light emission.SOLUTION: A ceramic composite includes: a first crystal phase including an activation element and a first rare earth aluminate phosphor containing a first rare earth element different from the activation element; and a second crystalline phase including aluminum oxide, wherein the content of the first crystal phase is in a range of 5 volume% or more and 40 volume% or less with respect to the total volume, the content of the second crystalline phase is 57 volume% or more and 95 volume% or less, an average value of a second crystal diameter of the second crystalline phase measured under specific measurement conditions is 12 μm or less, and a QD value is 0.5 or less, which is represented by QD=(D75-D25) / (D75+D25) in a case where values of the second crystal diameter, when integrated values of the second crystal diameter in its grain size distribution curve from the small diameter side are 25% and 75%, are represented as D25 and D75, respectively.SELECTED DRAWING: Figure 6A

Description

Technical Field

[0001] The present invention relates to a ceramic composite, a light-emitting device, and a method for manufacturing a ceramic composite.

Background Art

[0002] A light-emitting device including a light-emitting diode (LED) or a laser diode (LD) and a wavelength conversion member including a phosphor that converts the wavelength of light emitted from the light-emitting element of the LED or LD is known. Such a light-emitting device is used, for example, as a light source for in-vehicle use, general lighting, a backlight for a liquid crystal display device, a projector, and the like.

[0003] For example, Patent Document 1 discloses a ceramic composite including a yttrium aluminum garnet phosphor activated with Ce, an inorganic material made of aluminum oxide present between the phosphor particles, and additive particles having a particle size smaller than that of the phosphor particles adhered so as to cover at least a part of the surface of the phosphor particles.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] A ceramic composite including a phosphor and a translucent inorganic material is required to suppress variations in the color tone of light emitted from the ceramic composite. Therefore, an aspect of the present invention aims to provide a ceramic composite capable of suppressing variations in the color tone of light emission, a light-emitting device using the ceramic composite, and a method for manufacturing the ceramic composite.

Means for Solving the Problems

[0006] The first aspect of the present invention includes a first crystal phase containing an activating element and a first rare earth aluminate phosphor containing a first rare earth element different from the activating element, and a second crystal phase containing aluminum oxide. With respect to the total amount, the content of the first crystal phase is in the range of 5% to 40% by volume, the content of the second crystal phase is in the range of 57% to 95% by volume, the average value of the second crystal diameter of the second crystal phase measured under the following measurement conditions is 12 μm or less, and the values of the second crystal diameter when the integrated values from the small-diameter side of the particle size distribution curve of the second crystal diameter are 25% and 75% are D 25 and D 75 When denoted as, QD = (D 75 - D 25 ) / (D 75 + D 25 ) is a ceramic composite in which the QD value represented by is 0.5 or less. Measurement conditions In an SEM image taken using a scanning electron microscope on the cross-section of the ceramic composite, the maximum width in the cross-section of the crystal phase separated by grain boundaries and the minimum width passing through the center point of the maximum width are measured, and the average of the maximum width and the minimum width is taken as the crystal diameter, and the arithmetic average value of the crystal diameters in a specific size range in the SEM image at the same magnification is taken as the average value of the crystal diameters.

[0007] The second aspect of the present invention is a light-emitting device including a wavelength conversion member containing a ceramic composite and an excitation light source.

[0008] A third aspect of the present invention includes preparing a raw material mixture containing first rare earth aluminate phosphor particles containing an activator element and a first rare earth element different from the activator element, and aluminum oxide particles; shaping the raw material mixture to prepare a molded body; and firing the molded body at a temperature range of 1550° C. to 1800° C. to obtain a sintered body, wherein the raw material mixture has a content of the first rare earth aluminate phosphor particles in the range of 5 mass % to 40 mass % and a content of the aluminum oxide particles in the range of 57 mass % to 95 mass % with respect to the total amount of the raw material mixture, the sintered body includes a first crystal phase containing the first rare earth aluminate phosphor particles and a second crystal phase containing the aluminum oxide particles, the average value of second crystal diameters of the second crystal phase contained in the sintered body measured under the measurement conditions is 12 μm or less, and the integrated values ​​from the small diameter side of a particle size distribution curve of the second crystal diameters are 25% and 75%. Said second The value of the crystal diameter is D 25 and D. 75 When written as QD=(D 75 -D 25 ) / (D 75 +D 25 ) is 0.5 or less. Effect of the Invention

[0009] Advantageous Effects of Invention According to one aspect of the present invention, it is possible to provide a ceramic composite capable of suppressing variation in the color tone of emitted light, a light emitting device using the ceramic composite, and a method for manufacturing the ceramic composite. [Brief description of the drawings]

[0010]

Figure 1

Figure 2A

Figure 2B

Figure 2C

Figure 3

Figure 4

Figure 5A

Figure 5B

Figure 6A

Figure 6B

Figure 7A

Figure 7B

Figure 8A

Figure 8B

DETAILED DESCRIPTION OF THE INVENTION

[0011] Hereinafter, a ceramic composite, a light-emitting device, and a method for manufacturing a ceramic composite will be described based on embodiments. However, the embodiments shown below are examples for embodying the technical idea of the present invention, and the present invention is not limited to the following ceramic composite, light-emitting device, and method for manufacturing a ceramic composite. The relationship between color names and chromaticity coordinates and the relationship between the wavelength range of light and the color names of monochromatic light follow JIS Z8110. In this specification, ceramics refer to any inorganic non-metallic material at a temperature of 1000°C or lower.

[0012] Ceramic composite The ceramic composite includes a first crystal phase containing a first rare earth aluminate phosphor containing an activating element and a first rare earth element different from the activating element, and a second crystal phase containing aluminum oxide, wherein the content of the first crystal phase is in the range of 5% to 40% by volume, and the content of the second crystal phase is in the range of 57% to 95% by volume with respect to the total amount, and the average value of the second crystal diameter of the second crystal phase measured under the following measurement conditions is 12 μm or less, and when the integrated values from the small diameter side of the particle size distribution curve of the second crystal diameter are 25% and 75%, the values of the second crystal diameter are D 25 and D 75 When expressed as, QD = (D 75 - D 25 ) / (D 75 + D 25 ) and the QD value represented by it is 0.5 or less. The particle size distribution curve of the second crystal diameter refers to the distribution curve of the crystal diameter measured under the following measurement conditions, assuming that one second crystal phase separated by grain boundaries is one particle. Measurement conditions In the SEM image taken using a scanning electron microscope on the cross section of the ceramic composite, measure the maximum width of the cross section of the crystal phase separated by grain boundaries and the minimum width passing through the center point of the maximum width, and take the average of the maximum width and the minimum width as the crystal diameter, and take the arithmetic average value of the crystal diameters in a specific size range in the SEM image at the same magnification as the average value of the crystal diameters.

[0013] First crystal phase The content of the first crystal phase containing the first rare earth aluminate phosphor in the ceramic composite is in the range of 5% to 40% by volume, preferably in the range of 6% to 38% by volume, and more preferably in the range of 7% to 35% by volume. The ceramic composite can convert the incident light into a different wavelength by the first rare earth aluminate phosphor in the first crystal phase containing the first rare earth aluminate phosphor and then emit the light. If the content of the first crystal phase containing the first rare earth aluminate phosphor in the ceramic composite is within the range of 5% to 40% by volume, the light incident on the first crystal phase containing the first rare earth aluminate phosphor can be efficiently wavelength-converted, and the light can be efficiently scattered by the second crystal phase serving as the matrix, so that the light with suppressed color tone variation can be emitted from the ceramic composite.

[0014] The content (% by volume) of the first crystal phase and the content (% by volume) of the second crystal phase in the ceramic composite can be calculated from the average values of the volume ratios of the first crystal phase and the second crystal phase in several cross-sections of the ceramic composite. The SEM images of any several cross-sections of the ceramic composite are taken by a scanning electron microscope (SEM), and the volume ratios of the first crystal phase and the second crystal phase are calculated from the SEM images.

[0015] The content (% by volume) of the first crystal phase and the content (% by volume) of the second crystal phase in the ceramic composite can be calculated from the mass ratio content, true density of the first rare earth aluminate phosphor particles, and true density of the aluminum oxide particles in the raw material mixture forming the ceramic composite.

[0016] Content (% by volume) of the first crystal phase The content of the first crystal phase in the ceramic composite can be calculated based on the following formula (1). The mass ratio (% by mass) of the first rare earth aluminate phosphor particles in the following formula (1) is the mass ratio of the first rare earth aluminate phosphor particles in the raw material mixture.

[0017]

Number

[0018] The first crystal diameter of the first crystal phase contained in the ceramic composite may be in the range of 5 μm or more and 40 μm or less, may also be in the range of 8 μm or more and 35 μm or less, and may also be in the range of 10 μm or more and 30 μm or less. If the first crystal diameter of the first crystal phase containing the first rare earth aluminate phosphor is in the range of 5 μm or more and 40 μm or less, the first rare earth aluminate phosphor contained in the first crystal phase can efficiently absorb the light incident on the ceramic composite and convert it into wavelength-converted light, and the mixed-color light of the light transmitted through the ceramic composite can be emitted from the ceramic composite. The first crystal phase containing the first rare earth aluminate phosphor can absorb the light emitted from the excitation light source and convert its wavelength, and emit high-brightness light from the ceramic composite. The first crystal diameter of the first crystal phase may also be in the range of 8 μm or more and 35 μm or less, and may also be in the range of 10 μm or more and 30 μm or less.

[0019] Second crystal phase Aluminum oxide contained in the second crystal phase of the ceramic composite melts due to the heat during the formation of the ceramic composite, and the aluminum oxide particles contained in the raw material mixture are combined with each other to form a second crystal phase containing aluminum oxide. The second crystal phase containing aluminum oxide contained in the ceramic composite transmits the light that excites the first rare earth aluminate phosphor. When the second crystal diameter of the second crystal phase increases, the color difference between the light transmitted through the second crystal phase and the light wavelength-converted by the first rare earth aluminate phosphor contained in the first crystal phase increases, and the variation in the color tone of the light emitted from the ceramic composite increases. When the average particle diameter of the second crystal diameter of the second crystal phase is 12 μm or less and the QD value is 0.5 or less, the second crystal diameter of the second crystal phase is relatively small, the particle size distribution when the second crystal phase is assumed to be particles becomes narrow, and the sizes of the second crystal phases are uniform. Therefore, the light incident on the ceramic composite is scattered at the grain boundaries of the second crystal phase, and the variation in the color tone of the light emitted from the ceramic composite can be suppressed.

[0020] The average value of the second crystal diameter of the second crystal phase measured under the above measurement conditions is 12 μm or less, may be 11.95 μm or less, may be 11.94 μm or less, and may also be 11.93 μm or less. The second crystal diameter of the second crystal phase containing aluminum oxide may vary depending on the production conditions and the like, even when aluminum oxide of the same size is used as the raw material. The second crystal diameter of the second crystal phase may be 3 μm or more, may be 4 μm or more, and may be 5 μm or more.

[0021] When the second crystal phase has an average value of the second crystal diameter of 12 μm or less and a narrow particle size distribution and uniform size, it is easier to scatter the light incident on the ceramic composite evenly, and it is easier to suppress the variation in color tone. When the integrated values from the small-diameter side of the particle size distribution curve of the second crystal diameter are 25% and 75%, the values of the second crystal diameter are D 25 and D 75 When denoted as, QD = (D 75 - D 25 ) / (D 75 + D 25 ), the QD value represented thereby is 0.5 or less, preferably 0.495 or less, more preferably 0.492 or less, and still more preferably 0.490 or less. The smaller the QD value, the narrower the particle size distribution and the more uniform the crystal diameter. The QD value of the second crystal diameter of the second crystal phase may be 0.400 or more, may be 0.420 or more, and may be 0.450 or more.

[0022] The content of the second crystal phase containing aluminum oxide in the ceramic composite is in the range of 57% to 95% by volume, preferably in the range of 57% to 94.99% by volume, more preferably in the range of 58% to 94% by volume, and still more preferably in the range of 60% to 90% by volume. When the ceramic composite contains a third crystal phase containing the second rare earth aluminate described below, the content of the second crystal phase is preferably in the range of 57% to 94.9% by volume. The ceramic composite contains a second crystal phase containing more than 50% by volume of aluminum oxide, and the second crystal phase constitutes the matrix of the ceramic composite. When light is incident on the ceramic composite, the light incident by the first crystal phase containing the first rare earth aluminate phosphor is wavelength-converted, and the incident light is scattered by the second crystal phase. The size of the second crystal phase containing aluminum oxide that constitutes the matrix of the ceramic composite affects the color tone of the light emitted from the ceramic composite.

[0023] Content of the second crystal phase (volume%) The content of the second crystal phase in the ceramic composite can be calculated based on the following formula (2).

[0024]

Number

[0025] The first rare earth aluminate phosphor The first rare earth aluminate phosphor contained in the first crystal phase is at least one first rare earth element Ln selected from the group consisting of Y, Lu, Gd, and Tb 1 and the activating element Ce, Al, and may optionally contain Ga, and the first rare earth element Ln 1The total molar ratio with respect to the above Ce is 3, the molar ratio of the above Ce is the product of a variable a that exceeds 0 and is within the range of 0.22 or less and 3, the total molar ratio of the above Al and the above Ga is within the range of 4.5 or more and 5.5 or less, the molar ratio of the above Al is the product of a variable c that exceeds 0 and is within the range of 1.1 or less and 5, and the molar ratio of Ga, which may be included as necessary, is the product of a variable b that is within the range of 0 or more and 0.4 or less and 5. Having the composition of the first rare earth aluminate is preferable in order to obtain emission of a desired color tone. The first rare earth element Ln contained in the first rare earth aluminate phosphor particles 1 may contain two or more elements selected from the group consisting of Y, Lu, Gd, and Tb. The first rare earth element Ln 1 may be at least one selected from the group consisting of Y, Lu, and Gd. The first rare earth element Ln 1 may be Y and Gd, or may be Y and Lu. In the first rare earth aluminate phosphor, two or more first rare earth elements Ln 1 are included. When the first rare earth element Ln 1 is Y and Gd, in the composition of the first rare earth aluminate phosphor, the molar ratio of Y and Gd (Y:Gd) is preferably in the range of 99.5:0.5 to 70:30, may be within the range of 99:1 to 80:20, and may also be within the range of 99:1 to 90:10.

[0026] In the composition of the first rare earth aluminate phosphor particles, the molar ratio of Ce is represented by the product of 3 and the variable a. In the composition of the first rare earth aluminate phosphor particles, when the molar ratio of Ce exceeds 0 and is 0.66 Belowis preferably in the range of 0.001 or more and 0.60 or less, may be in the range of 0.003 or more and 0.450 or less, may be in the range of 0.006 or more and 0.300 or less, may be in the range of 0.012 or more and 0.270 or less, may be in the range of 0.015 or more and 0.240 or less. In the composition of the first rare earth aluminate phosphor particles, the variable a is in the range of more than 0 and 0.22 or less (0 < a ≤ 0.22), may be in the range of 0.0003 or more and 0.20 or less (0.0003 ≤ a ≤ 0.20), may be in the range of 0.001 or more and 0.150 or less (0.001 ≤ a ≤ 0.150), may be in the range of 0.002 or more and 0.100 or less (0.002 ≤ a ≤ 0.100), may be in the range of 0.004 or more and a≦0. 0.090 or less (0.004 ≤ a ≤ 0.090), may be in the range of 0.005 or more and 0.080 or less (0.005 ≤ a ≤ 0.080).

[0027] In the composition of the first rare earth aluminate phosphor particles, the molar ratio of Al is represented by the product of 5 and the variable c. In the composition of the first rare earth aluminate phosphor particles, the molar ratio of Al is in the range of more than 0 and 5.5 or less, may be in the range of 0.54 or more and 5.0 or less, may be in the range of 0.63 or more and 5.0 or less. In the composition of the first rare earth aluminate Phosphor phosphor particles, the variable c is in the range of more than 0 and 1.1 or less (0 < c ≤ 1.1), may be in the range of 0.6 or more and 1.0 or less (0.6 ≤ c ≤ 1.0), may be in the range of 0.7 or more and 1.0 or less (0.7 ≤ c ≤ 1.0).

[0028] In the composition of the first rare earth aluminate phosphor particles, Ga may not be contained. In the composition of the first rare earth aluminate phosphor particles, the molar ratio of Ga is represented by the product of 5 and the variable b. In the composition of the first rare earth aluminate phosphor particles, the molar ratio of Ga is in the range of 0 or more and 2.0 or less, may be in the range of 0.1 or more and 1.5 or less, may be in the range of 0.2 or more and 1.2 or less. In the composition of the first rare earth aluminate phosphor particles, the variable b is in the range of 0 or more and 0.4 or less (0 ≤ b ≤ 0.4), may be in the range of 0.02 or more and 0.3 or less (0.02 ≤ b ≤ 0.3), may be in the range of 0.04 or more 0.24It may also be within the following range (0.04 ≦ b ≦ 0.24).

[0029] In the composition of the first rare earth aluminate phosphor particles, the total molar ratio of Al and Ga is in the range of 4.5 or more and 5.5 or less, and may be 5. In the composition of the first rare earth aluminate phosphor particles, the sum of the variable b and the variable c is in the range of 0.9 or more and 1.1 or less (0.9 ≦ b + c ≦ 1.1), and may be 1 (b + c = 1).

[0030] The first rare earth aluminate phosphor preferably has a composition represented by the following formula (I). (Ln 1 1-a Ce a )3(Al c Ga b )5O 12 (I) (In the formula (I), Ln 1 is at least one selected from the group consisting of Y, Gd, Lu, and Tb, and a, b, and c satisfy 0 < a ≦ 0.22, 0 ≦ b ≦ 0.4, 0 < c ≦ 1.1, and 0.9 ≦ b + c ≦ 1.1.)

[0031] The third crystal phase The ceramic composite may include a third crystal phase including a second rare earth aluminate containing a second rare earth element. When second rare earth oxide particles containing a second rare earth element are included in the raw material mixture, the second rare earth oxide particles gather around the aluminum oxide particles when the molded body is fired, and the second rare earth oxide particles react with the aluminum oxide particles to form a third crystal phase containing the second rare earth aluminate. By the reaction of the second rare earth oxide particles with the aluminum oxide particles, the crystal growth of the aluminum oxide is suppressed, the second crystal diameter of the second crystal phase containing the aluminum oxide becomes smaller, the particle size distribution when the second crystal phase is assumed to be particles becomes narrower, and a second crystal phase with uniform size is formed. When the second rare earth oxide particles react with the first rare earth aluminate phosphor particles, the second rare earth oxide particles and the first rare earth aluminate phosphor particles become integrated without forming a grain boundary to form a first crystal phase containing the first rare earth aluminate phosphor. When the first rare earth aluminate phosphor particles, the aluminum oxide particles, and the second rare earth oxide particles are included in the raw material mixture, the resulting ceramic composite forms a first crystal phase containing the first rare earth aluminate phosphor, a second crystal phase containing the aluminum oxide, and a third crystal phase containing the second rare earth aluminate.

[0032] The content of the third crystal phase in the ceramic composite may be in the range of 0% by volume or more and 3% by volume or less with respect to the total amount of the ceramic composite. When the ceramic composite contains the third crystal phase, the content of the third crystal phase is preferably in the range of 0.01% by volume or more and 3% by volume or less, may be in the range of 0.05% by volume or more and 2.5% by volume or less, and may also be in the range of 0.1% by volume or more and 2% by volume or less with respect to the total amount of the ceramic composite. When the ceramic composite contains the third crystal phase, the content of the first crystal phase is preferably in the range of 5% by volume or more and 40% by volume or less, the content of the second crystal phase is preferably in the range of 57% by volume or more and 94.99% by volume or less, and the content of the third crystal phase is preferably in the range of 0.01% by volume or more and 3% by volume or less. When the ceramic composite contains the third crystal phase, the content of the first crystal phase is preferably in the range of 5% by volume or more and 40% by volume or less, the content of the second crystal phase is preferably in the range of 57.5% by volume or more and 94.95% by volume or less, and the content of the third crystal phase is preferably in the range of 0.05% by volume or more and 2.5% by volume or less. Yes. The When the lamix composite contains the third crystal phase, the content of the first crystal phase is preferably in the range of 5% by volume or more and 40% by volume or less, the content of the second crystal phase is preferably in the range of 58% by volume or more and 94.9% by volume or less, and the content of the third crystal phase is preferably in the range of 0.1% by volume or more and 2.0% by volume or less.

[0033] Content of the third crystal phase (% by volume) The content of the third crystal phase in the ceramic composite can be calculated based on the following formula (3).

[0034]

Equation

[0035] The content of the mass ratio of the third crystal phase in the ceramic composite (% by mass) can be calculated from the content of the mass ratio of the second rare earth oxide particles (% by mass) and the true density in the raw material mixture based on the following formulas (4) and (5).

[0036]

Equation

[0037]

Number

[0038] The third crystal diameter of the third crystal phase The third crystal diameter of the third crystal phase contained in the ceramic composite is preferably in the range of 0.5 μm or more and 5 μm or less, may be in the range of 0.6 μm or more and 4 μm or less, or may be in the range of 0.7 μm or more and 3 μm or less in order to suppress the crystal growth of the second crystal phase containing aluminum oxide and form a second crystal phase capable of evenly scattering the incident light. The third crystal diameter of the third crystal phase can be measured under the above measurement conditions.

[0039] The second rare earth aluminate contained in the third crystal phase may contain at least one second rare earth element selected from the group consisting of Y, La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The second rare earth aluminate may contain at least one second rare earth element Ln 2 selected from the group consisting of Y, Gd, Tb, and Lu. The second rare earth aluminate may contain at least one second rare earth element Ln 2 and Al, and may have a composition of a second rare earth aluminate in which the molar ratio of the second rare earth element Ln 2 is 3 and the molar ratio of Al is 5. The second rare earth aluminate having this composition suppresses the crystal growth of aluminum oxide particles, reduces the average value of the second crystal diameter of the second crystal phase, reduces the QD value, has a narrow particle size distribution, and easily forms a second crystal phase with uniform crystal diameters.

[0040] Since the third crystal phase is a crystal phase containing a second rare earth aluminate formed by the reaction of aluminum oxide and second rare earth oxide particles, the third crystal phase substantially does not contain elements that can serve as activators. The fact that the third crystal phase substantially does not contain elements that can serve as activators means that the content of elements that can serve as activators contained in the third crystal phase is 200 mass ppm or less. When the activating element of the first rare earth aluminate phosphor contained in the first crystal phase is cerium (Ce), the content of cerium (Ce) in the third crystal phase is 200 mass ppm or less. The content of elements that can serve as activators in the third crystal phase containing the second rare earth aluminate can be measured by energy dispersive X-ray spectrometry (EDX) of the cross section of the third crystal phase containing the second rare earth aluminate of the ceramic composite for elements that can serve as activators in the third crystal phase, for example, the content of cerium. The content of elements that can serve as activators contained in the third crystal phase containing the second rare earth aluminate in the ceramic composite is 200 mass ppm or less, may be 150 mass ppm or less, may be 100 mass ppm or less, may be below the measurement limit by EDX, may be 0 mass ppm, may be 0.1 mass ppm or more, or may be 1 mass ppm or more.

[0041] The second rare earth aluminate preferably has a composition represented by the following formula (II). The second rare earth aluminate contained in the third crystal phase is produced by the reaction of aluminum oxide particles and second rare earth oxide particles, and the second rare earth element Ln contained in the oxide particles 2 When at least one selected from the group consisting of Y, Gd, Tb, and Lu, a third crystal phase containing a second rare earth aluminate having a composition represented by the following formula (II) is formed. Ln 2 3Al5O 12 (II) (In the above formula (II), Ln 2 is at least one element selected from the group consisting of Y, Gd, Tb, and Lu.)

[0042] Relative density The relative density of the ceramic composite is preferably 98% or more. If the relative density of the ceramic composite is 98% or more, the crystal diameter is relatively small, and the second crystal phase, which is the matrix with uniform size, can evenly scatter the light incident on the ceramic composite, efficiently absorb it by the rare earth aluminate phosphor contained in the first crystal phase, convert the wavelength, and emit it, thereby suppressing the variation in color tone. The relative density of the ceramic composite may be 99% or more, 99.5% or more, 99.9% or more, or 100%.

[0043] The relative density of the ceramic composite can be calculated from the apparent density and the true density of the ceramic composite by the following formula (6).

[0044]

Number

[0045] The apparent density of the ceramic composite is the value obtained by dividing the mass of the ceramic composite by the volume of the ceramic composite, and can be calculated by the following formula (7).

[0046]

Number

[0047] When the ceramic composite contains the first crystal phase and the second crystal phase and does not contain the third crystal phase, the true density of the ceramic composite can be calculated by the following formula (8).

[0048]

Number

[0049] When the ceramic composite includes a first crystal phase, a second crystal phase, and a third crystal phase, the true density of the ceramic composite can be calculated by the following formula (9). The content (mass %) of the third crystal phase in the ceramic composite can be calculated based on the aforementioned formulas (4) and (5).

[0050]

Number

[0051] In addition, for the sintered body, the first sintered body, and the second sintered body obtained by the manufacturing method of the ceramic composite, the relative density, the apparent density, and the true density can be calculated by replacing the ceramic composite in the aforementioned formulas (6) to (9) with the sintered body, the first sintered body, or the second sintered body.

[0052] Manufacturing Method of Ceramic Composite The manufacturing method of the ceramic composite is Activating element and preparing a raw material mixture including first rare earth aluminate phosphor particles containing a first rare earth element different from the activating element and aluminum oxide particles; shaping the raw material mixture to prepare a shaped body; and firing the shaped body in a temperature range of 1550 °C or higher and 1800 °C or lower to obtain a sintered body, wherein the content of the first rare earth aluminate phosphor particles in the raw material mixture is in the range of 5 mass % or more and 40 mass % or less with respect to the total amount, the content of the aluminum oxide particles is in the range of 57 mass % or more and 95 mass % or less, the sintered body includes a first crystal phase containing the first rare earth aluminate phosphor particles and a second crystal phase containing the aluminum oxide particles, the average value of the second crystal diameter of the second crystal phase contained in the sintered body measured under the measurement conditions is 12 μm or less, and when the integrated values from the small-diameter side of the particle size distribution curve of the second crystal diameter are 25% and 75%, Said second junction the crystal diameter values are denoted as D 25 and D 75 and the QD value represented by QD = (D 75 − D 25 ) / (D 75 + D 25 ) is 0.5 or less.

[0053] FIG. 1 is a flowchart showing a first aspect of a method for manufacturing a ceramic composite. With reference to the drawings, the steps of the method for manufacturing a ceramic composite will be described. As shown in FIG. 1, the method for manufacturing a ceramic composite includes a step S101 of preparing a raw material mixture including first rare earth aluminate phosphor particles, aluminum oxide particles, and, if necessary, second rare earth oxide particles containing a second rare earth element, a step S102 of preparing a formed body obtained by shaping the raw material mixture, and a step S103 of firing the formed body in a temperature range of 1550° C. or higher and 1800° C. or lower to obtain a sintered body.

[0054] First rare earth aluminate phosphor particles As the first rare earth aluminate phosphor particles, first rare earth aluminate phosphors having the same composition as the aforementioned first rare earth aluminate phosphor can be used. The first rare earth aluminate phosphor particles contain at least one first rare earth element Ln selected from the group consisting of Y, Lu, Gd, and Tb 1 and the activating element Ce, Al, and may optionally contain Ga. It is preferable that the total molar ratio of the first rare earth element Ln 1 and the Ce is 3, the molar ratio of the Ce is the product of the variable a within the range of more than 0 and 0.22 or less and 3, the total molar ratio of the Al and the Ga is within the range of 4.5 or more and 5.5 or less, the molar ratio of the Al is the product of the variable c within the range of more than 0 and 1.1 or less and 5, and the molar ratio of the Ga, which may optionally be contained, is the product of the variable b within the range of 0 or more and 0.4 or less and 5. It is preferable that the first rare earth aluminate phosphor particles have the composition represented by the formula (I) in order to obtain light emission of a desired color tone.

[0055] The first rare earth aluminate phosphor particles preferably have an average particle size measured by the Fisher Sub-Sieve Sizer (hereinafter also referred to as "FSSS") method in the range of 4 μm or more and 40 μm or less, more preferably in the range of 5 μm or more and 35 μm or less, and even more preferably in the range of 8 μm or more and 30 μm or less. The FSSS method is a type of air permeability method that measures the specific surface area using the flow resistance of air and mainly determines the particle size of primary particles. The average particle size measured by the FSSS method is the Fisher Sub-Sieve Sizer’s Number. If the average particle size of the first rare earth aluminate phosphor particles measured by the FSSS method is in the range of 4 μm or more and 40 μm or less, a ceramic composite containing a first crystal phase having a first crystal diameter in the range of 5 μm or more and 40 μm or less can be produced.

[0056] Aluminum oxide particles The aluminum oxide particles preferably have a purity of aluminum oxide of 99.0 mass% or more, more preferably 99.5 mass% or more. When the purity of aluminum oxide in the aluminum oxide particles is 99.0 mass% or more, there are few impurities, and a ceramic composite capable of emitting high-brightness light can be produced. The purity of aluminum oxide in the aluminum oxide particles can be referred to the value of the purity of aluminum oxide described in the catalog. When the purity of aluminum oxide in the aluminum oxide particles is unknown, after measuring the mass of the aluminum oxide particles, the aluminum oxide particles are fired in an air atmosphere at 800 °C for 1 hour to remove organic substances and moisture attached or adsorbed to the aluminum oxide particles, the mass of the fired aluminum oxide particles is measured, and the purity of the aluminum oxide particles can be measured by dividing the mass of the fired aluminum oxide particles by the mass of the aluminum oxide particles before firing.

[0057] The average particle size measured by the FSSS method of the aluminum oxide particles may be in the range of 0.1 μm or more and 1.5 μm or less, or may be in the range of 0.2 μm or more and 1.0 μm or less. The second crystal phase containing aluminum oxide tends to have the second crystal diameter of the second crystal phase changed depending on the conditions for producing the ceramic composite, compared to the size of the aluminum oxide particles as the raw material. The particle size of the aluminum oxide particles may be referred to the value described in the catalog.

[0058] Second rare earth oxide particles In the step of preparing the raw material mixture, the raw material mixture may contain second Rare earth oxide material particles containing a second rare earth element. When the second rare earth oxide particles are contained in the raw material mixture, when the molded body described later is fired, the second rare earth oxide particles and the aluminum oxide particles are likely to react, and it is likely to suppress the crystal growth of the aluminum oxide particles. When the crystal growth of the aluminum oxide particles is suppressed, the second crystal diameter is small, the particle size distribution when the second crystal phase is assumed to be particles becomes narrow, and a ceramic composite containing the second crystal phase containing aluminum oxide with uniform crystal diameters can be obtained.

[0059] The second rare earth element contained in the second rare earth oxide particles is preferably an element different from the activating element contained in the first rare earth aluminate phosphor particles. The second rare earth element contained in the second rare earth oxide particles includes at least one selected from the group consisting of Sc, Y, La, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, and Lu. The second rare earth element contained in the second rare earth oxide particles is preferably at least one selected from the group consisting of Y, La, Nd, Pm, Gd, Tb, Dy, Ho, Er, Yb, and Lu, and more preferably at least one selected from the group consisting of Y, La, Nd, Gd, Tb, Yb, and Lu. The second rare earth oxide particles more preferably contain at least one second rare earth element Ln 2 selected from the group consisting of Y, Gd, Tb, and Lu. Specifically, the second rare earth oxide particles are, for example, Y2O3, La2O3, Pr7O 11It is preferably at least one selected from the group consisting of Nd2O3, Gd2O3, Tb4O7, Yb2O3, and Lu2O3. The second rare earth oxide particles are more preferably at least one selected from the group consisting of Y2O3, La2O3, Nd2O3, Gd2O3, Tb4O7, Yb2O3, and Lu2O3, and even more preferably at least one selected from the group consisting of Y2O3, Gd2O3, Tb4O7, and Lu2O3. The second rare earth oxide particles may be used alone or in combination of two or more. The second rare earth oxide particles may not contain aluminum. The oxide particles not containing aluminum refer to oxide particles having an aluminum content of less than 1% by mass.

[0060] The average particle size of the second rare earth oxide particles measured by the FSSS method is preferably in the range of 0.05 μm or more and less than 5 μm, and more preferably in the range of 0.1 μm or more and 4 μm or less. When the average particle size of the second rare earth oxide particles is in the range of 0.05 μm or more and less than 5 μm, when the molded body described below is fired, the second rare earth oxide particles and the aluminum oxide particles are likely to react, and the crystal growth of the aluminum oxide particles is likely to be suppressed.

[0061] raw material mixture In the raw material mixture, the content of the first rare earth aluminate phosphor particles is in the range of 5% by mass or more and 40% by mass or less, and the content of the aluminum oxide particles is in the range of 57% by mass or more and 95% by mass or less with respect to the total amount. The first rare earth aluminate phosphor Of particles When the content and the content of the aluminum oxide particles are within the above ranges, respectively, a ceramic composite capable of obtaining light emission of a desired color tone can be produced by irradiating excitation light.

[0062] The total amount of the raw material mixture may be the total amount of the first rare earth aluminate phosphor particles and the aluminum oxide particles. When the raw material mixture contains the first rare earth aluminate phosphor particles and the aluminum oxide particles and does not contain the second rare earth oxide particles, the content of the aluminum oxide particles with respect to the total amount may be the remainder obtained by subtracting the content of the first rare earth aluminate phosphor particles from the total amount. The raw material mixture may have a content of the first rare earth aluminate phosphor particles in the range of 5% by mass or more and 40% by mass or less, and a content of the aluminum oxide particles in the range of 60% by mass or more and 95% by mass or less with respect to the total amount. The content of the first rare earth aluminate phosphor particles in the raw material mixture may be in the range of 6% by mass or more and 38% by mass or less, or in the range of 7% by mass or more and 35% by mass or less with respect to the total amount. The content of the aluminum oxide particles in the raw material mixture may be in the range of 62% by mass or more and 94% by mass or less, or in the range of 65% by mass or more and 93% by mass or less with respect to the total amount.

[0063] When the raw material mixture contains the first rare earth aluminate phosphor particles, the aluminum oxide particles, and the second rare earth oxide particles, the content of the first rare earth aluminate phosphor particles is preferably in the range of 5% by mass or more and 40% by mass or less, the content of the aluminum oxide particles is in the range of 57% by mass or more and 94.99% by mass or less, and the content of the second rare earth oxide particles is in the range of 0.01% by mass or more and 3% by mass or less with respect to the total amount. When the second rare earth oxide particles are contained in the raw material mixture within the above range, when the molded body described below is fired, the second rare earth oxide particles and the aluminum oxide particles react to suppress the crystal growth of the aluminum oxide particles. When the crystal growth of the aluminum oxide particles is suppressed, a ceramic composite containing a second crystal phase containing aluminum oxide with a small crystal diameter, a narrow particle size distribution of the crystal diameter, and a uniform crystal diameter can be obtained. The obtained ceramic composite has a small second crystal diameter of the second crystal phase serving as a base material, a narrow particle size distribution of the second crystal diameter, and a uniform second crystal diameter. Therefore, when the light incident on the ceramic composite is wavelength-converted by the first rare earth aluminate phosphor contained in the first crystal phase SecondVariations in the color tone of light scattered by the crystalline phase and emitted from the ceramic composite can be suppressed.

[0064] When the raw material mixture contains first rare earth aluminate phosphor particles, aluminum oxide particles, and second rare earth oxide particles, the total amount of the raw material mixture may be the total amount of the first rare earth aluminate phosphor particles, aluminum oxide particles, and second rare earth oxide particles. The content of the aluminum oxide particles in the raw material mixture may be the remainder obtained by subtracting the total amount of the first rare earth aluminate phosphor particles and the second rare earth oxide particles from the total amount. The raw material mixture may have a content of the first rare earth aluminate phosphor particles in the range of 6% by mass or more and 38% by mass or less, a content of the second rare earth oxide particles in the range of 0.05% by mass or more and 2.5% by mass or less, and a content of aluminum oxide in the range of 59.5% by mass or more and 93.95% by mass or less, based on the total amount. The raw material mixture may have a content of the first rare earth aluminate phosphor particles in the range of 7% by mass or more and 35% by mass or less, a content of the second rare earth oxide particles in the range of 0.1% by mass or more and 2% by mass or less, and a content of aluminum oxide in the range of 63% by mass or more and 92.9% by mass or less, based on the total amount.

[0065] FIG. 2A is a flowchart showing a second aspect of the method for manufacturing a ceramic composite, FIG. 2B is a flowchart showing a third aspect of the method for manufacturing a ceramic composite, and FIG. 2C is a flowchart showing a fourth aspect of the method for manufacturing a ceramic composite. As shown in FIG. 2A, the method for manufacturing a ceramic composite may include a raw material mixing step S101a and a sieving step S101b of the raw material mixture in the step S101 of preparing the raw material mixture. As shown in FIG. 2B, the method for manufacturing a ceramic composite may include a wet mixing step S101c of the raw material in the step S101 of preparing the raw material mixture. As shown in FIG. 2C, the method for manufacturing a ceramic composite may include a wet mixing step S101c of the raw material, a step S101d of drying the obtained slurry after the wet mixing step S101c, and a sieving step S101e of the obtained dried product in the step S101 of preparing the raw material mixture.

[0066] Step of preparing a raw material mixture Mixing of raw materials In the step of preparing the raw material mixture, raw materials of the first rare earth aluminate phosphor particles, aluminum oxide particles, and, if necessary, the second rare earth oxide particles are mixed wet or dry using a mixer. As the mixer, a ball mill, a vibration mill, a roll mill, a jet mill, etc., which are industrially commonly used, can be used.

[0067] Sieving of the raw material mixture In the step of preparing the raw material mixture, it is preferable to include sieving the raw material mixture with a sieve having an opening of 160 μm or less and preparing the raw material mixture that has passed through the sieve. The sieve used for sieving preferably has an opening of 160 μm or less, and the opening of the sieve may be 150 μm, 140 μm, 130 μm, 125 μm, or 110 μm. In order to perform sieving in a short time, a sieve having an opening of 100 μm or more may be used. As the sieve, a sieve having an opening of 160 μm, a wire diameter of 71 μm, and nylon #110 mesh may be used. For example, N-No.110S (manufactured by NBC Mesh Tech Co., Ltd.) can be used as this sieve. By sieving the raw material mixture with a sieve having an opening of 160 μm or less and preparing the raw material mixture that has passed through the sieve, aggregation of aluminum oxide contained in the raw material mixture can be suppressed, and when firing the molded body described later, crystal growth of the aluminum oxide particles can be suppressed. When the crystal growth of the aluminum oxide particles is suppressed, the second crystal diameter is small, the particle size distribution when assuming the second crystal phase as particles becomes narrow, and a ceramic composite containing the second crystal phase containing aluminum oxide with a uniform crystal diameter can be obtained. The sieving of the raw material mixture is preferably performed at least once, and may be performed two or more times.

[0068] Wet mixing In the step of preparing the raw material mixture, it is preferable to include adding a solvent to the raw materials of the first rare earth aluminate phosphor particles, aluminum oxide particles, and, if necessary, the second rare earth oxide particles and performing wet mixing. Examples of the solvent used for wet mixing include deionized water, ethanol, and the like. By wet mixing the first rare earth aluminate phosphor particles, aluminum oxide particles, and, if necessary, the second rare earth oxide particles, the aluminum oxide particles are dispersed in the solvent, aggregation of the aluminum oxide particles is suppressed, and when the molded body described later is fired, crystal growth of the aluminum oxide particles can be suppressed. When the crystal growth of the aluminum oxide particles is suppressed, the second crystal diameter is small, the particle size distribution when the second crystal phase is assumed to be particles is narrow, and a ceramic composite containing the second crystal phase containing aluminum oxide with a uniform crystal diameter can be obtained. The wet mixing time varies depending on the solid dispersion medium and solvent used, but in order to improve productivity, it is preferably 30 minutes or more, more preferably 60 minutes or more, still more preferably 90 minutes or more, and preferably within 420 minutes.

[0069] Drying and sieving of the dried product In the step of preparing the raw material mixture, it is preferable to include drying the slurry obtained by wet mixing, sieving the obtained dried product with a sieve having an opening of 160 μm or less, and preparing the raw material mixture that has passed through the sieve. As the sieve used for sieving the dried product, the same sieve as the sieve used for sieving the raw material mixture can be used. Sieving of the dried product is preferably performed at least once, and may be performed two or more times. The drying time of the slurry may be 15 hours or more, may be 20 hours or more, or may be within 30 hours. The drying temperature may be a temperature at which the solvent volatilizes, for example, within the range of 80°C or higher and 105°C or lower, or within the range of 90°C or higher and 100°C or lower.

[0070] Step of preparing a molded body The step of preparing the formed body prepares the formed body by molding the raw material mixture. As a method for forming the formed body, a known method such as a press molding method can be adopted. As a method of press molding, for example, die press molding, cold isostatic pressing (CIP) defined in JIS Z2500:2000, No. 2109, etc. can be mentioned. In addition, the raw material mixture may be molded by uniaxially compressing to obtain a formed body. As a method of molding the raw material mixture to obtain a formed body, two methods may be adopted to adjust the shape of the formed body. For example, after die press molding, CIP may be performed, or after uniaxially compressing by the roller bench method, CIP may be performed. CIP preferably presses the formed body by a cold isostatic pressing method using water as a medium.

[0071] The pressure during die press molding or the pressure when molding by uniaxial compression is preferably 5 MPa or more and 50 MPa or less, more preferably 5 MPa or more and 30 MPa or less. If the pressure during die press molding or the pressure when molding by uniaxial compression is within the above range, the formed body can be adjusted to a desired shape.

[0072] The pressure in CIP is preferably 50 MPa or more and 200 MPa or less, more preferably 50 MPa or more and 180 MPa or less. When the pressure in CIP is within the range of 50 MPa or more and 200 MPa or less, a formed body capable of obtaining a ceramic composite having a relative density of 95% or more by firing at 1550 °C or more and 1800 °C or less described later can be formed.

[0073] Step of obtaining a sintered body (primary firing step) The step of obtaining the sintered body involves firing the green compact within a temperature range of 1550°C or higher and 1800°C or lower to obtain the sintered body. The green compact may be first fired within a temperature range of 1550°C or higher and 1800°C or lower to obtain a first sintered body. The firing temperature is preferably within a range of 1600°C or higher and 1750°C or lower, and more preferably within a temperature range of 1650°C or higher and 1700°C or lower. If the temperature at which the green compact is fired is within the temperature range of 1550°C or higher and 1800°C or lower, without dissolving the first rare earth aluminate phosphor, a first crystal phase containing the first rare earth aluminate phosphor, a second crystal phase containing aluminum oxide, and, if necessary, a third crystal phase containing a second rare earth aluminate are included. A sintered body can be obtained.

[0074] The firing of the green compact can be carried out under an oxygen-containing atmosphere. The oxygen content in the atmosphere is preferably 5% by volume or more, more preferably 10% by volume or more, and even more preferably 15% by volume or more. The green compact may be fired under an atmosphere of air (oxygen content of 20% by volume or more). The firing atmosphere may be at atmospheric pressure (0.101 MPa).

[0075] The method for manufacturing a ceramic composite includes, in the step of obtaining a sintered body, first firing a green compact within a temperature range of 1550°C or higher and 1800°C or lower to obtain a first sintered body, and second firing the first sintered body within a temperature range of 1500°C or higher and 1800°C or lower by hot isostatic pressing (HIP) to obtain a second sintered body. It is preferable to obtain a ceramic composite in which the second crystal diameter of the second crystal phase contained in the second sintered body measured under the said measurement conditions is 12 μm or less.

[0076] Figure 3 is a flowchart showing a fifth aspect of the method for manufacturing a ceramic composite. As shown in Figure 3, the method for manufacturing a ceramic composite may include, in the step of obtaining a sintered body, a step S103a of first firing a green compact to obtain a first sintered body, and a step S103b of second firing the first sintered body by HIP to obtain a second sintered body.

[0077] Second firing process The secondary firing process is a process of obtaining a second sintered body by subjecting the first sintered body to secondary firing within a temperature range of 1500°C or higher and 1800°C or lower by hot isostatic pressing (HIP). In the secondary firing process, it is preferable to perform secondary firing within a temperature range of 1500°C or higher and 1800°C or lower by hot isostatic pressing (HIP) as defined in JIS Z2500:2000, No. 2112. By performing the secondary firing process, a ceramic composite with a higher relative density can be obtained. The temperature of the secondary firing is more preferably within a range of 1550°C or higher and 1800°C or lower, still more preferably within a range of 1600°C or higher and 1750°C or lower, and particularly preferably within a range of 1650°C or higher and 1700°C or lower. The secondary firing can be performed in an argon or nitrogen atmosphere.

[0078] For the secondary firing performed by HIP, the pressure is preferably within a range of 50 MPa or higher and 300 MPa or lower, and more preferably within a range of 80 MPa or higher and 200 MPa or lower. When the pressure in HIP is within a range of 50 MPa or higher and 300 MPa or lower, the entire second sintered body can be made uniformly denser without damaging the crystal structure of the first crystal phase containing the first rare earth aluminate phosphor.

[0079] The secondary firing performed by HIP is, for example, within 0.5 hours or more and 20 hours or less, and is preferably performed within 1 hour or more and 10 hours or less in order to make the entire second sintered body uniformly denser.

[0080] The method for manufacturing a ceramic composite may include at least one of an annealing process, a processing process, and a surface treatment process after the process of obtaining a sintered body, may include two or more processes, or may include three processes. FIG. 4 is a flowchart showing a sixth aspect of the method for manufacturing a ceramic composite. As shown in FIG. 4, the method for manufacturing a ceramic composite may optionally include an annealing process S104 after the process S103 of obtaining a sintered body. Further, the method for manufacturing a ceramic composite may include a processing process S105 of cutting the obtained sintered body, the first sintered body, or the second sintered body into a desired size or thickness after the process S103 of obtaining a sintered body, and may optionally include a surface treatment process S106.

[0081] Annealing treatment The obtained sintered body, the first sintered body, or the second sintered body may be annealed in a reducing atmosphere. By annealing the obtained sintered body in a reducing atmosphere, the oxidized activating element contained in the first crystal phase containing the first rare earth aluminate phosphor can be reduced, and a decrease in wavelength conversion efficiency and a decrease in luminance due to oxidation of the activating element serving as a light emission center can be suppressed. The reducing atmosphere may be an atmosphere containing at least one noble gas selected from the group consisting of helium, neon, and argon or nitrogen gas and hydrogen gas or carbon monoxide gas, and it is more preferable that the atmosphere contains at least argon or nitrogen gas and hydrogen gas or carbon monoxide gas. The annealing treatment may be performed on the sintered body or the first sintered body, may be performed on the second sintered body, or may be performed on either the first sintered body or the second sintered body.

[0082] The temperature of the annealing treatment is lower than the firing temperature and preferably within the range of 1000°C or higher and 1500°C or lower. The temperature of the annealing treatment is more preferably within the range of 1000°C or higher and 1400°C or lower, and even more preferably within the range of 1100°C or higher and 1350°C or lower. If the temperature of the annealing treatment is lower than the firing temperature, the primary firing temperature or the secondary firing temperature and within the range of 1000°C or higher and 1500°C or lower, the oxidized activating element contained in the first crystal phase containing the first rare earth aluminate phosphor in the ceramic composite can be reduced, and a decrease in the efficiency of wavelength conversion and a decrease in luminance can be suppressed.

[0083] Processing step The obtained sintered body may be processed by cutting it to a desired size or thickness. As the cutting method, known methods can be used. For example, there is a method of cutting using at least one method selected from blade dicing, laser dicing, and wire saw. Among these, a wire saw is preferable in terms of being able to further reduce the unevenness of the cut surface.

[0084] Surface treatment step Furthermore, a surface treatment step described below may be added. The surface treatment step is a step of surface-treating the surface of the obtained sintered body or the cut object obtained by cutting the second sintered body. By this surface treatment step, not only can the surface of the ceramic composite be made into an appropriate state for improving the light emission characteristics of the ceramic composite, but also, in combination with the above-described processing step or alone, the ceramic composite can be made into a desired shape, size, or thickness. The surface treatment step may be performed before the processing step of cutting the sintered body or the second sintered body to a desired size or thickness for processing, or may be performed after the processing step. Examples of the surface treatment method include at least one method selected from methods using sandblasting, mechanical grinding, dicing, and chemical etching.

[0085] The obtained ceramic composite may contain a third crystal phase containing a second rare earth aluminate in which the content of an element that can serve as an activator is 200 ppm by mass or less. The second rare earth oxide particles contained in the raw material mixture react with the aluminum oxide particles to suppress the crystal growth of the aluminum oxide particles and form a third crystal phase containing a second rare earth aluminate. Since the third crystal phase in the ceramic composite contains a second rare earth aluminate formed by reacting with the aluminum oxide particles by firing in a temperature range of 1550 °C or higher and 1800 °C or lower, the third crystal phase substantially does not contain an element that can serve as an activator, and the content of the element that can serve as an activator is 200 ppm by mass or less. When the activator element of the first rare earth aluminate phosphor is cerium (Ce), the content of cerium (Ce) in the third crystal phase containing the second rare earth aluminate is 200 ppm by mass or less. The content of an element that can serve as an activator in the third crystal phase containing the second rare earth aluminate can be measured by energy dispersive X-ray spectrometry (EDX) of a cross section of the third crystal phase containing the second rare earth aluminate of the ceramic composite for the content of an element that can serve as an activator in the third crystal phase, for example, cerium. The content of an element that can serve as an activator contained in the third crystal phase containing the second rare earth aluminate in the ceramic composite is 200 ppm by mass or less, may be 150 ppm by mass or less, may be 100 ppm by mass or less, may be below the measurement limit by EDX, may be 0 ppm by mass, may be 0.1 ppm by mass or more, or may be 1 ppm by mass or more.

[0086] The second rare earth aluminate contained in the third crystal phase may have a composition represented by the above formula (II).

[0087] Light-emitting device The above-described ceramic composite can be used as a member constituting a wavelength conversion member of a light-emitting device in combination with a light source. An example of a light-emitting device using the ceramic composite will be described.

[0088] The light-emitting device includes a wavelength conversion member containing a ceramic composite and an excitation light source. FIG. 5A shows an example of a light-emitting device and is a schematic plan view of the light-emitting device 100. FIG. 5B is a schematic cross-sectional view taken along line VB-VB' of the light-emitting device 100 shown in FIG. 5A. The light-emitting device 100 includes a light-emitting element 20 composed of an LED or an LD, and a wavelength conversion member 30 composed of a ceramic composite that emits light when excited by the light from the light-emitting element 20. The light-emitting element 20 is flip-chip mounted on the mounting substrate 10 via bumps which are conductive members 60. The light-emitting element 20 is an excitation light source of the light-emitting device 100, and the wavelength conversion member Of 20 is joined to the light-emitting surface. The light-emitting element 20 and the wavelength conversion member 30 may be joined via an adhesive layer 40. The side surfaces of the light-emitting element 20 and the wavelength conversion member 30 are covered by a covering member 50 that reflects light. The light-emitting element 20 can receive power supply from outside the light-emitting device 100 via wirings and conductive members 60 formed on the mounting substrate 10, and cause the light-emitting device 100 to emit light. The light-emitting device 100 may include a semiconductor element 70 such as a protection element for protecting the light-emitting element 20 from destruction due to application of an excessive voltage. The covering member 50 is provided, for example, so as to cover the semiconductor element 70. The covering member 50 may include a resin 51 and at least one additive 52 selected from the group consisting of a colorant, a phosphor, and a filler. Hereinafter, each member used in the light-emitting device will be described. For details, reference can also be made to the disclosure of, for example, Japanese Patent Application Laid-Open No. 2014-112635.

[0089] Light-emitting element As the light-emitting element, for example, an LED chip or an LD chip which is a semiconductor light-emitting element using a nitride-based semiconductor can be used.

[0090] The light-emitting element preferably has an emission peak wavelength in the range of 380 nm or more and 500 nm or less, more preferably in the range of 390 nm or more and 495 nm or less, still more preferably in the range of 400 nm or more and 490 nm or less, and particularly preferably in the range of 420 nm or more and 490 nm or less. The light-emitting element is provided with a p electrode and an n electrode. The p electrode and the n electrode of the light-emitting element may be formed on the same side surface of the light-emitting element, or may be provided on different side surfaces. The light-emitting element may be flip-chip mounted.

[0091] Wavelength conversion member As the wavelength conversion member, the above-described ceramic composite can be used. The thickness of the ceramic composite used as the wavelength conversion member may be in the range of 50 μm or more and 500 μm or less, may be in the range of 60 μm or more and 450 μm or less, or may be in the range of 70 μm or more and 400 μm or less. The size of the ceramic composite used as the wavelength conversion member may be any size that entirely covers the light extraction surface of the light-emitting element. An adhesive layer may be interposed between the light-emitting element and the wavelength conversion member, and the light-emitting element and the wavelength conversion member may be fixed with the adhesive layer. The wavelength conversion member may include the above-described ceramic composite and other members, for example, a light-transmitting member.

[0092] The mounting substrate of the light-emitting device is an insulating material and is preferably made of a material that is difficult to transmit light from the light-emitting element and external light. Examples of the material of the mounting substrate include ceramics such as aluminum oxide and aluminum nitride, and resins such as phenol resin, epoxy resin, polyimide resin, bismaleimide triazine resin (BT resin), and polyphthalamide (PPA) resin. Since ceramics have high heat resistance, they are preferable as the material of the mounting substrate. When an adhesive layer is interposed between the light-emitting element and the wavelength conversion member, the adhesive constituting the adhesive layer is preferably made of a material that can optically connect the light-emitting element and the wavelength conversion member. The material constituting the adhesive layer is preferably at least one resin selected from the group consisting of epoxy resin, silicone resin, phenol resin, and polyimide resin. The semiconductor elements provided as required in the light-emitting device include, for example, transistors for controlling the light-emitting elements, and protective elements for suppressing the destruction and performance degradation of the light-emitting elements due to excessive voltage application. Examples of the protective elements include Zener diodes and capacitors. As the material of the coating member, it is preferable to use an insulating material. More specifically, examples include phenolic resins, epoxy resins, bismaleimide triazine resins (BT resins), polyphthalamide (PPA) resins, and silicone resins. The coating member may contain at least one additive selected from the group consisting of a colorant, a phosphor, and a filler as required. As the conductive member, bumps can be used. As the material of the bumps, Au or its alloy can be used. As other conductive members, eutectic solder (Au-Sn), Pb-Sn, lead-free solder, etc. can be used.

[0093] Manufacturing method of the light-emitting device An example of the manufacturing method of the light-emitting device will be described. For details, reference can also be made to the disclosures of, for example, Japanese Patent Application Laid-Open No. 2014-112635 or Japanese Patent Application Laid-Open No. 2017-117912. The manufacturing method of the light-emitting device preferably includes a step of arranging the light-emitting elements, a step of arranging the semiconductor elements as required, a step of forming a wavelength conversion member including a ceramic composite, a step of bonding the light-emitting element and the wavelength conversion member, and a step of forming a coating member. In the step of arranging the light-emitting elements, the light-emitting elements are arranged and mounted on the mounting substrate. The light-emitting elements and the semiconductor elements are, for example, flip-chip mounted on the mounting substrate. In the step of bonding the light-emitting element and the wavelength conversion member, the wavelength conversion member is opposed to the light-emitting surface of the light-emitting element, and the wavelength conversion member is joined to the light-emitting element with an adhesive layer. In the step of forming the covering member, the side surfaces of the light-emitting element and the wavelength conversion member, excluding the light-emitting surface, are covered with the covering member composition, and the covering member is formed on the side surfaces of the light-emitting element and the wavelength conversion member excluding the light-emitting surface. This covering member is for reflecting the light emitted from the light-emitting element, covers the side surfaces without covering the light-emitting surface of the wavelength conversion member, and is formed so as to embed the semiconductor element. As described above, the light-emitting device shown in FIGS. 5A and 5B can be manufactured.

Example

[0094] Hereinafter, the present invention will be specifically described by way of examples. The present invention is not limited to these examples.

[0095] Example 1 Step of preparing the raw material mixture First rare earth aluminate phosphor particles Containing Ce as an activating element and containing Y and Gd as the first rare earth elements, (Y 0.806 Gd 0.16 Ce 0.034 )3Al5O 12 First rare earth aluminate phosphor particles having the composition of were prepared. The average particle size of the first rare earth aluminate phosphor particles by the FSSS method was 15 μm. Aluminum oxide particles As the aluminum oxide particles, aluminum oxide (Al2O3) particles having a purity of 99% by mass of aluminum oxide were prepared. The average particle size of the aluminum oxide particles by the FSSS method was 0.6 μm. Second rare earth oxide particles Containing Y as the second rare earth element, yttrium oxide (Y2O3) particles were prepared as the second rare earth oxide particles. The average particle size of the yttrium oxide particles by the FSSS method was 0.1 μm. Preparation of the raw material mixture The first rare earth aluminate phosphor particles were weighed out in an amount of 11 g, the aluminum oxide particles in an amount of 88.9 g, and the yttrium oxide particles in an amount of 0.1 g, and mixed in a dry ball mill, and the balls serving as the mixing medium were removed to prepare a raw material mixture. The content of each particle relative to 100 mass% of the raw material mixture consisting of the first rare earth aluminate phosphor particles, the aluminum oxide particles, and the yttrium oxide particles is shown in Table 1.

[0096] Preparation process for molded body The mixture of raw materials is filled into a mold and subjected to a pressure of 10 MPa (102 kgf / cm 2 A cylindrical molded body having a diameter of 100 mm and a thickness of 12 mm was formed at a pressure of 100 MPa. The obtained molded body was placed in a packaging container, vacuum-packed, and subjected to CIP at 176 MPa using a cold isostatic pressurizing device (manufactured by Kobe Steel, Ltd. (KOBELCO)) to obtain a molded body.

[0097] Process for obtaining sintered body First firing process The obtained molded body was subjected to primary firing at a temperature of 1650° C. in an air atmosphere (0.101 MPa, oxygen concentration 20% by volume) using a firing furnace (manufactured by Marusho Denki Co., Ltd.) to obtain a first sintered body. Secondary firing process The obtained first sintered body was subjected to secondary firing by HIP using a hot isostatic pressing (HIP) device (manufactured by Kobe Steel, Ltd. (KOBELCO)) in a nitrogen gas atmosphere (99.99% by volume or more) using nitrogen gas as a pressure medium at a temperature of 1650°C and a pressure of 195 MPa for 2 hours to obtain a second sintered body. This second sintered body was cut into a predetermined shape and size using a wire saw, and the surface of the cut surface was polished with a surface grinder to obtain a plate-shaped ceramic composite of Example 1 having a thickness of 180 μm. The ceramic composite of Example 1 contained Y3Al5O formed by the reaction of aluminum oxide particles and yttrium oxide particles. 12 The third crystal phase of the second rare earth aluminate represented by the following formula was formed. The second crystal phase in the cross section of the ceramic composite was analyzed by a wavelength dispersive X-ray analyzer (EPMA) (WDS) (JXA-8230, manufactured by JEOL Ltd.). Second junctionWhen the Ce content in the crystal phase was measured, the Ce content was 100 mass ppm or less.

[0098] Examples 2 to 3 Each ceramic composite of Examples 2 to 3 was obtained in the same manner as in Example 1, except that the contents of the aluminum oxide particles and yttrium oxide particles contained in the raw material mixture were changed as shown in Table 1.

[0099] Example 4 The first rare earth aluminate phosphor used in Example 1 Particles and the aluminum oxide particles used in Example 1 were used to weigh 11 g of the first rare earth aluminate phosphor Particles and 89 g of aluminum oxide particles, respectively, mixed in a dry ball mill, and after removing the balls as the mixing medium, sieved using a sieve with an opening of 160 μm, a wire diameter of 71 μm, and nylon #110 mesh (N-No.110S, manufactured by NBC Mesh Tech Co., Ltd.) to prepare a raw material mixture that passed through the mesh. The content of each particle with respect to 100% by mass of the raw material mixture composed of the total of the first rare earth aluminate phosphor particles and aluminum oxide particles is shown in Table 1. A ceramic composite of Example 4 was obtained in the same manner as in Example 1, except that the prepared raw material mixture was used.

[0100] Example 5 The first rare earth aluminate phosphor used in Example 1 Particles and the aluminum oxide particles used in Example 1 were used to weigh 11 g of the first rare earth aluminate phosphor Particles and 89 g of aluminum oxide particles, respectively, and the first rare earth aluminate phosphor Particles50 g of deionized water was added as a solvent to the total of the first rare earth aluminate phosphor particles and aluminum oxide particles, and mixed in a wet ball mill, and the balls as a mixing medium were removed to obtain a slurry. The obtained slurry was dried at 100°C for 24 hours to obtain a dried product. The obtained dried product was sieved using a nylon #110 mesh (N-No.110S, manufactured by NBC Meshtec Co., Ltd.) with an opening of 160 μm and a wire diameter of 71 μm as specified in, and a raw material mixture that passed through the mesh was prepared. The content of each particle relative to 100 mass% of the raw material mixture consisting of the total of the first rare earth aluminate phosphor particles and aluminum oxide particles is shown in Table 1. A ceramic composite of Example 5 was obtained in the same manner as in Example 1, except that the prepared raw material mixture was used.

[0101] Comparative Example 1 First rare earth aluminate phosphor used in Example 1 Particles The aluminum oxide particles used in Example 1 were used to produce a first rare earth aluminate phosphor. Particles A raw material mixture was obtained in the same manner as in Example 1, except that 11 g of the powder and 89 g of the aluminum oxide particles were weighed out. Using this raw material mixture, a ceramic composite of Comparative Example 1 was obtained in the same manner as in Example 1.

[0102] Measurement of the average particle size of raw materials The average particle size of each of the first rare earth aluminate phosphor particles, the aluminum oxide particles, and the yttrium oxide particles which are the second rare earth oxide particles was measured as follows. Each particle was measured using a Fisher Sub-Sieve Sizer Model 95 (manufactured by Fisher Scientific) at a temperature of 25°C and a relative humidity of 70% to determine the size of the particle. 3 Each particle of the sample Raw materials After weighing out each of them and packing them into a special tubular container, dry air was passed through them at a constant pressure, and the specific surface area was read from the pressure difference, and the particle size was calculated using the FSSS method. The results are as shown above.

[0103] Measurement of ceramic composites Content of the first and second crystal phases The content (volume %) of the first crystal phase and the content (volume %, mass %) of the second crystal phase were determined based on the above formulas (1) to (5).

[0104] Measurement of relative density The relative density of each ceramic composite of the examples and comparative examples was determined based on the above formulas (6) to (9). The true density of the first rare earth aluminate phosphor ((Y 0.806 Gd 0.16 Ce 0.034 )3Al5O 12 ) is 4.67 g / cm 3 , the true density of the aluminum oxide particles is 3.98 g / cm 3 , and the true density of the second rare earth aluminate (Y3Al5O 12 ) in the ceramic composite was calculated as 4.60 g / cm 3 .

[0105] SEM image - Secondary electron image Using a scanning electron microscope (SEM) (SU3500, manufactured by Hitachi High-Technologies Corporation), SEM images of secondary electron images of the cross-sections (polished surfaces) of each ceramic composite of the examples and comparative examples were obtained.

[0106] Measurement of crystal diameter From the SEM images of the polished surfaces of the cross-sections of the ceramic composites of the examples and comparative examples, the second crystal diameter of the second crystal phase containing aluminum oxide was measured under the following measurement conditions. Measurement conditions In the SEM image taken using a scanning electron microscope on the cross-section of the ceramic composite, the maximum width in the cross-section of the crystal phase separated by the grain boundary and the minimum width passing through the center point of the maximum width were measured, and the average of the maximum width and the minimum width was taken as the crystal diameter, and the arithmetic mean value of the crystal diameters in a specific size range in the SEM image at the same magnification was taken as the average value of the crystal diameters. The average value of the second crystal diameters of 20 randomly selected second crystal phases was calculated. Also, assuming 20 randomly selected second crystal phases as particles, a particle size distribution curve of the second crystal diameter was created, and the values of the second crystal diameter when the integrated values from the small-diameter side of the particle size distribution curve of the second crystal diameter are 25% and 75% are D25 and D 75 When expressed as QD = (D 75 - D 25 ) / (D 75 + D 25 ), the QD value represented by QD was calculated.

[0107] Fabrication of the light-emitting device Regarding each of the obtained ceramic composites of the examples and comparative examples, the light-emitting device 100 shown in FIGS. 5A and 5B was fabricated as follows. The light-emitting element 20 and the semiconductor element 70 were placed on the mounting substrate 10. Specifically, a light-emitting element 20 having a thickness of about 0.11 mm, a substantially square planar shape of about 1.0 mm square, and a main wavelength of 450 nm, which was formed by laminating a nitride semiconductor on a sapphire substrate, was arranged such that the sapphire substrate side, which is a semiconductor growth substrate, became the light-emitting surface. The light-emitting element 20 and the semiconductor element 70 were arranged in a row and flip-chip mounted on the conductive pattern formed on the mounting substrate 10 using a conductive member 60 made of Au. Next, a silicone resin was placed as the adhesive 40 on the upper surface of the light-emitting element 20, and the wavelength conversion member 30 formed in a plate shape from each of the ceramic composites of the examples and comparative examples was adhered to the upper surface of the sapphire substrate of the light-emitting element 20. Next, a covering member 50 was arranged around the light-emitting element 20, the wavelength conversion member 30, and the semiconductor element 70. The covering member 50 was arranged along the side surfaces of the light-emitting element 20 and the wavelength conversion member 30, and the semiconductor element 70 was completely buried in the covering member 50. The resin 51 contained in the covering member 50 used a dimethyl silicone resin, and titanium oxide particles having an average particle diameter of 0.28 μm were contained in the resin 51 at 60% by mass as the light-reflective material 52. Through such steps, the light-emitting device 100 shown in FIGS. 5A and 5B was fabricated. Regarding each of the light-emitting devices using the ceramic composites of the examples and comparative examples, evaluation was performed as follows. The results are shown in Table 1.

[0108] Chromaticity coordinates (x, y) and standard deviation Forty light-emitting devices using each of the ceramic composites of the examples and comparative examples were fabricated, and the chromaticity coordinates (x, y) in the chromaticity coordinate system of the CIE (International Commission on Illumination: Commission Internationale de l’Eclarirage) 1931 chromaticity diagram were determined using an imaging color luminance meter (ProMetric I8, manufactured by Radiant Vision Systems). The average values of the chromaticity coordinates (x, y) of the 40 light-emitting devices using each of the ceramic composites of the examples and comparative examples were taken as the chromaticity coordinates (x, y) of the ceramic composites of the examples and comparative examples. Also, the standard deviation (1σ) of the chromaticity coordinates (x, y) of the 40 light-emitting devices using each of the ceramic composites of the examples and comparative examples was determined as an index for evaluating the variation in color tone. The results are shown in Table 1.

[0109]

Table 1

[0110] For the ceramic composites according to Examples 1 to 5, the average value of the second crystal diameter of the second crystal phase measured under the above measurement conditions was 12 μm or less, and the QD value was 0.5 or less. The average value of the second crystal diameter of the second crystal phase contained in the ceramic composites according to Examples 1 to 5 was Comparative Example 1 smaller than the average value of the second crystal diameter of the second crystal phase of the ceramic composite according to, the particle size distribution was narrow when the second crystal phase was assumed to be particles, and the sizes of the second crystal phases were uniform. The light-emitting devices using the ceramic composites according to Examples 1 to 5 had a standard deviation (xσ, yσ) of the chromaticity coordinates (x, y) of the emitted light that was Comparative Example 1 smaller than the standard deviation (xσ, yσ) of the chromaticity coordinates (x, y) of the light emitted from the light-emitting devices using the ceramic composite according to, and the variation in color tone was suppressed.

[0111] FIG. 6A is a SEM photograph of a secondary electron image of a cross section (polished surface) of the ceramic composite according to Example 3, and FIG. 6B is a diagram showing grain boundaries of the first crystal phase, the second crystal phase, and the third crystal phase of the SEM photograph of FIG. 6A by lines. The ceramic composite according to Example 3 includes a first crystal phase 1 containing a first rare earth aluminate phosphor, a second crystal phase 2 containing aluminum oxide, and a third crystal phase 3 containing a second rare earth aluminate formed by reacting aluminum oxide particles with a second rare earth oxide. It was confirmed that the average value of the second crystal diameter of the second crystal phase in the ceramic composite according to Example 3 was smaller than the average value of the second crystal diameter of the second crystal phase in the ceramic composite according to Comparative Example 1 described later.

[0112] FIG. 7A is a SEM photograph of a secondary electron image of a cross section (polished surface) of the ceramic composite according to Example 4, and FIG. 7B is a diagram showing grain boundaries of the first crystal phase and the second crystal phase of the SEM photograph of FIG. 7A by lines. The ceramic composite according to Example 4 includes a first crystal phase 1 containing a first rare earth aluminate phosphor and a second crystal phase 2 containing aluminum oxide. The ceramic composite according to Example 4 does not have a third crystal phase containing a second rare earth aluminate. Since the raw material mixture of the ceramic composite according to Example 4 is sieved with a sieve having an opening of 160 μm or less, the average value of the second crystal diameter of the second crystal phase in the ceramic composite according to Example 4 is smaller than the average value of the second crystal diameter of the second crystal phase in the ceramic composite according to Comparative Example 1 described later. It was confirmed that it was.

[0113] FIG. 8A is a SEM photograph of a secondary electron image of a cross-section (polished surface) of the ceramic composite according to Comparative Example 1, and FIG. 8B is a diagram showing the grain boundaries of the first crystal phase and the second crystal phase of the SEM photograph of FIG. 8A represented by lines. The ceramic composite according to Comparative Example 1 included a first crystal phase 1 containing a first rare earth aluminate phosphor and a second crystal phase 2 containing aluminum oxide. The average value of the second crystal diameter of the second crystal phase in the ceramic composite according to Comparative Example 1 was larger than the average value of the second crystal diameter of the second crystal phase of the ceramic composites according to Examples 3 and 4. The ceramic composite according to Comparative Example 1 used the same aluminum oxide particles as in Example 3, but since the second rare earth oxide was not contained in the raw material mixture, the crystal growth of the aluminum oxide particles was not suppressed. Further, the ceramic composite according to Comparative Example 1 used a raw material mixture containing the same composition and the same raw materials as in Example 4, but since the raw material mixture was not sieved, the crystal growth of the aluminum oxide particles was not suppressed.

Industrial Applicability

[0114] The ceramic composite obtained by the method for producing a ceramic composite according to one aspect of the present invention can be used as a wavelength conversion member for an in-vehicle light source, a lighting device for general lighting, a backlight for a liquid crystal display device, and a light source for a projector in combination with an excitation light source of an LED or an LD.

Explanation of Symbols

[0115] 1: First crystal phase, 2: Second crystal phase, 3: Third crystal phase, 10: Mounting substrate, 20: Light emitting element, 30: Wavelength conversion member, 40: Adhesive layer, 50: Coating member, 60: Conductive member, 70: Semiconductor element, 100: Light emitting device.

Claims

Claim 1: A ceramic composite comprising a first crystal phase containing a first rare earth aluminate phosphor having a composition represented by the following formula (I), a second crystal phase containing aluminum oxide, and a third crystal phase containing a second rare earth aluminate having a composition represented by the following formula (II), wherein the content of the first crystal phase is in the range of 5% by volume or more and 40% by volume or less, the content of the second crystal phase is in the range of 57% by volume or more and 94.99% by volume or less, and the content of the third crystal phase is in the range of 0.01% by volume or more and 3% by volume or less, based on the total amount; the average value of the second crystal diameter of the second crystal phase measured under the following measurement conditions is 12 μm or less, and when the values of the second crystal diameter at the integrated values of 25% and 75% from the small-diameter side of the particle size distribution curve of the second crystal diameter are denoted as D ２５ and D ７５ respectively, the QD value represented by QD = (D ７５ - D ２５ ) / (D ７５ + D ２５ ) is 0.5 or less. (Ln11-aCea)3(AlcGab)5O12 (I) (In the formula (I), Ln1 is at least one selected from the group consisting of Y, Gd, Lu, and Tb, and a, b, and c satisfy 0 < a ≤ 0.22, 0 ≤ b ≤ 0.4, 0 < c ≤ 1.1, and 0.9 ≤ b + c ≤ 1.1.) Ln23Al5O12 (II) (In the formula (II), Ln2 is at least one element selected from the group consisting of Y, Gd, Tb, and Lu.) Measurement conditions In an SEM image taken using a scanning electron microscope on a cross-section of the ceramic composite, measure the maximum width and the minimum width passing through the center point of the maximum width on the cross-section of the crystal phase separated by grain boundaries, and take the average of the maximum width and the minimum width as the crystal diameter, and take the arithmetic average value of the crystal diameters in a specific size range in the SEM image at the same magnification as the average value of the crystal diameters. Claim 2 A light-emitting device including a wavelength conversion member containing the ceramic composite according to claim 1 and an excitation light source.

3. The light-emitting device according to claim 2, further comprising a light-emitting element which is the excitation light source and to which the wavelength conversion member is bonded to a light-emitting surface, a mounting substrate on which the light-emitting element is disposed, and a covering member that covers side surfaces of the light-emitting element and the wavelength conversion member.

4. Preparing a raw material mixture including first rare earth aluminate phosphor particles having a composition represented by the following formula (I), aluminum oxide particles, and second rare earth oxide particles containing a second rare earth element; Molding the raw material mixture to form a molded body; Firing the molded body in a temperature range of 1550 °C or higher and 1800 °C or lower to obtain a sintered body, wherein the content of the first rare earth aluminate phosphor particles in the raw material mixture is in the range of 5% by mass or more and 40% by mass or less, the content of the aluminum oxide particles is in the range of 57% by mass or more and 94.99% by mass or less, and the content of the second rare earth oxide particles is in the range of 0.01% by mass or more and 3% by mass or less, based on the total amount; the sintered body includes a first crystal phase containing the first rare earth aluminate phosphor particles, a second crystal phase containing the aluminum oxide particles, and a third crystal phase containing a second rare earth aluminate having a composition represented by the following formula (II); the second rare earth oxide particles are at least one selected from the group consisting of Y2O3, Gd2O3, Tb4O7, and Lu2O3; the average value of the second crystal diameter of the second crystal phase contained in the sintered body measured under the following measurement conditions is 12 μm or less, and when the integrated values from the small-diameter side of the particle size distribution curve of the second crystal diameter are 25% and 75%, the values of the second crystal diameter are D ２５ and D ７５ and when expressed as QD = (D ７５ − D ２５ ) / (D ７５ + D ２５ ), the QD value is 0.5 or less. A method for manufacturing a ceramic composite. (Ln₁₁₋ₐCeₐ)₃(AlcGab)₅O₁₂ (I) (In the above formula (I), Ln₁ is at least one selected from the group consisting of Y, Gd, Lu, and Tb, and a, b, and c satisfy 0 < a ≤ 0.22, 0 ≤ b ≤ 0.4, 0 < c ≤ 1.1, and 0.9 ≤ b + c ≤ 1.1.) Ln₂₃Al₅O₁₂ (II) (In the above formula (II), Ln₂ is at least one element selected from the group consisting of Y, Gd, Tb, and Lu.) Measurement conditions In an SEM image taken using a scanning electron microscope on the cross-section of the ceramic composite, measure the maximum width of the cross-section of the crystal phase separated by grain boundaries and the minimum width passing through the center point of the maximum width, and take the average of the maximum width and the minimum width as the crystal diameter. Take the arithmetic average value of the crystal diameters in a specific size range in the SEM image at the same magnification as the average value of the crystal diameters.

5. In the step of preparing the raw material mixture, sieving the raw material mixture with a sieve having an aperture of 160 μm or less to prepare a raw material mixture that has passed through the sieve, the method for manufacturing a ceramic composite according to claim 4.

6. In the step of preparing the raw material mixture, wet-mixing the first rare earth aluminate phosphor particles, the aluminum oxide particles, and the second rare earth oxide particles, the method for manufacturing a ceramic composite according to claim 4 or 5.

7. In the step of preparing the raw material mixture, drying the slurry obtained by wet-mixing, sieving the obtained dried product with a sieve having an aperture of 160 μm or less to prepare a raw material mixture that has passed through the sieve, the method for manufacturing a ceramic composite according to claim 6.

8. In the step of obtaining the sintered body, subjecting the molded body to a primary firing in a temperature range of 1550 °C or higher and 1800 °C or lower to obtain a first sintered body, and The first sintered body is secondarily fired in a temperature range of 1500°C or higher and 1800°C or lower by hot isostatic pressing (HIP) to obtain a second sintered body, The method for manufacturing a ceramic composite according to any one of claims 4 to 7, wherein the second crystal diameter of the second crystal phase contained in the second sintered body measured under the measurement conditions is 12 µm or less.

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