Composite oxide particles

Abstract

Provided are spherical composite oxide particles having high crystallinity, white color, and low coefficient of thermal expansion. The composite oxide particles according to the present invention are polycrystalline, the main crystal phase contains cordierite and / or hexagonal cordierite, and the coefficient of thermal expansion of the composite oxide particles according to the TMA method is 1.5 ppm or less.

Description

TECHNICAL FIELD

[0001] The present application relates to a composite oxide particle. BACKGROUND

[0002] In recent years, various studies have been made on materials for next-generation semiconductor packages. For example, Patent Literature 1 describes a crystallized glass containing at least one crystal of cordierite and indialite, which is a polymorph thereof. As for the crystallized glass described in Patent Literature 1, it is described, for example, that a member of a high-frequency electronic device as a substrate for high frequencies is useful.

[0003] The softening point of a composite oxide containing a cordierite component is low around 900°C. Therefore, when the indialite phase, which is a polymorph of cordierite, starts to be generated, the particles adhere to each other to become massive, and the particle (spherical) structure cannot be maintained. Therefore, the crystallized glass described in Patent Literature 1 cannot be used in a powder and spherical shape as an inorganic filler.

[0004] PRIOR ART DOCUMENTS

[0005] PATENT LITERATURE

[0006] Patent Literature 1: International Publication No. 2022 / 059724 SUMMARY

[0007] PROBLEMS TO BE SOLVED BY THE INVENTION

[0008] The present application relates to a composite oxide particle.

[0009] MEANS FOR SOLVING THE PROBLEMS

[0010] The present inventors have conducted intensive studies in order to solve the above problems, and as a result, have found a solution means including the following configuration, thereby completing the present application.

[0011] (1) A composite oxide particle which is polycrystalline and whose main crystal phase contains at least one of cordierite and indialite, the composite oxide particle having a thermal expansion rate of 1.5 ppm or less based on the TMA method.

[0012] (2) The composite oxide particle according to the above (1), having a particle diameter of 0.1 μm or more and 500.0 μm or less.

[0013] (3) The composite oxide particle according to the above (1) or (2), wherein the crystallinity calculated from the following formula (I) is 40 or more, as measured by the X-ray diffraction method in a range of diffraction angle 2θ of 15 to 40°.

[0014] Crystallinity = Crystalline peak area / (Crystalline peak area + Amorphous peak area) (I)

[0015] (4) The composite oxide particles according to any one of (1) to (3) above, wherein, in a particle size distribution based on a laser diffraction method, a difference D90-D10 between a particle diameter D90 as a cumulative 90% diameter and a particle diameter D10 as a cumulative 10% diameter is 1000.0 μm or less.

[0016] (5) The composite oxide particles according to any one of (1) to (4) above, wherein a true circularity is 0.70 or more.

[0017] (6) The composite oxide particles according to any one of (1) to (5) above, wherein a half-value width of a main peak of a crystal having a diffraction angle 2θ within a range of 27.5 to 29.5° is 0.20° or less, as measured by an X-ray diffraction method.

[0018] (7) The composite oxide particles according to any one of (1) to (6) above, wherein the nanoparticles are contained at a proportion of 0.1 mass% or more and 30 mass% or less.

[0019] (8) The composite oxide particles according to any one of (1) to (7) above, wherein, in an L*a*b* color space, L* is 91.00 or more and 100.00 or less, a* is -10.00 or more and 3.00 or less, and b* is -10.00 or more and 5.00 or less.

[0020] (9) A method for producing composite oxide particles, comprising: a step of mixing cordierite particles and nanoparticles to obtain mixed particles; and a step of heating the mixed particles.

[0021] (10) The method for producing according to (9) above, wherein the heating step is performed at 1000°C or more and 1400°C or less.

[0022] Effects of the Invention

[0023] The composite oxide particles according to the present invention are spherical and have high crystallinity, are white, and have a low thermal expansion rate. Therefore, the composite oxide particles according to the present invention can be used, for example, to efficiently prevent warping of semiconductor packaging substrates and the like caused by heat, by being dispersed in the substrates. In addition, the composite oxide particles according to the present invention are white, and thus do not color even when used in semiconductor packaging substrates and the like. As a result, defects, contamination, and the like generated in semiconductor packaging substrates and the like are easily recognized optically. DETAILED DESCRIPTION

[0024] The composite oxide particles according to the present application are polycrystalline, and the main crystal phase contains at least one of cordierite and hexacordierite. That is, the composite oxide particles according to the present application contain a plurality of fine single crystals (grains) of at least one of cordierite and hexacordierite.

[0025] Cordierite and hexacordierite are compounds having a composition of 2MgO-2Al203-5Si02, and have different crystal structures. Whether the main crystal phase contains mainly cordierite or hexacordierite is presumed to depend on, for example, the heating temperature (firing temperature) at the time of producing the composite oxide particles according to the present application. Specifically, if heating is performed at 1000°C or higher and 1200°C or lower, there is a tendency to obtain composite oxide particles in which the hexacordierite phase is the main crystal phase. On the other hand, if heating is performed at 1200°C or higher and 1400°C or lower, there is a tendency to obtain composite oxide particles in which the cordierite phase is the main crystal phase.

[0026] The thermal expansion rate based on the TMA method of the composite oxide particles according to the present application is 1.5 ppm or less. By making the thermal expansion rate 1.5 ppm or less, it is possible to efficiently prevent warping of a substrate caused by heat when the composite oxide particles according to the present application are used, for example, by being dispersed in a semiconductor packaging substrate. The thermal expansion rate based on the TMA method of the composite oxide particles according to the present application is preferably less than 0.0 ppm.

[0027] The so-called TMA method (Thermomechanical Analysis) is a method in which the thermal expansion amount of a measurement sample is measured based on the difference in the thermal expansion amount between a standard sample and the measurement sample when they are heated at a certain rate. As the standard sample, quartz glass, alumina, or the like can be used.

[0028] As long as at least one of cordierite and hexacordierite constitutes the main crystal phase, the composite oxide particles according to the present application can contain other crystal phases, and can contain an amorphous phase. The other crystal phases and the amorphous phase are sometimes left as impurities (for example, unavoidable impurities) at the grain boundaries of the main crystal phase, and are sometimes intentionally added within a range that does not hinder the effects of the present application. There is no limitation on the other crystal phases and the amorphous phase, and for example, the following can be mentioned: a protoenstatite phase, a forsterite phase, a mullite phase, a cristobalite phase, and the like.

[0029] The composite oxide particles according to the present application can further contain nanoparticles. Nanoparticles are fine particles having a particle diameter of 1.0 nm or more and 600.0 nm or less, and preferably 50.0 nm or more and 500.0 nm or less. Nanoparticles are used in the production of the composite oxide particles according to the present application, and do not adversely affect the effects of the present application. Therefore, the presence of nanoparticles in the composite oxide particles according to the present application is not problematic. By the addition of nanoparticles, for example, the surface properties such as wettability can be adjusted to facilitate the addition to a resin substrate or the like.

[0030] The nanoparticles are not particularly limited, and examples thereof include nanosized silica particles, nanosized titanium dioxide particles, nanosized magnesium oxide particles, nanosized aluminum oxide particles, and the like. Nanosized silica particles are preferred. Nanosized particles of magnesium oxide and aluminum oxide, which are components of cordierite, are also preferred. The composite oxide particles according to the present application contain nanoparticles at a proportion of 0.1% by mass or more and 30% by mass or less, for example, relative to the total of nanosized silica particles (nanoparticles) and the composite oxide particles.

[0031] The composite oxide particles according to the present application are not particularly limited in size as long as they are spherical. For example, the composite oxide particles according to the present application preferably have an average particle diameter (D50) of 0.1 μm or more and 500.0 μm or less in terms of a volume average particle diameter cumulative 50% diameter (D50). In the case where the composite oxide particles according to the present application have an average particle diameter (D50) of 0.1 μm or more and 500.0 μm or less, the film thickness upon kneading with a resin can be reduced to 1 mm or less. The composite oxide particles according to the present application more preferably have a particle diameter of 1.0 μm or more and 250.0 μm or less.

[0032] The particle diameter is measured, for example, as follows. First, the composite oxide particles are dispersed in an aqueous sodium hexametaphosphate solution. Next, a laser diffraction particle size distribution measuring device is used to measure the particle size distribution by laser diffraction. As the laser diffraction particle size distribution measuring device, for example, "Microtrac: MT-3300EXII" manufactured by Nikkiso Co., Ltd. or the like can be used.

[0033] According to the use, it is desirable that the composite oxide particles according to the present application have a small variation in particle diameter. For example, in the case of the composite oxide particles according to the present application, the difference D90-D10 between the particle diameter D90 as the cumulative 90% diameter and the particle diameter D10 as the cumulative 10% diameter in the particle size distribution based on the laser diffraction method is preferably 1000.0 μm or less. In the case where D90-D10 is 1000.0 μm or less, the composite oxide particles according to the present application are easily filled in a resin. D90-D10 is more preferably 800.0 μm or less. D10 and D90 are calculated from the cumulative frequency distribution curve based on the volume basis.

[0034] The composite oxide particles according to the present application are not limited in shape as long as they are spherical. According to the use, it is desirable that the composite oxide particles according to the present application are close to a perfect sphere. For example, the composite oxide particles according to the present application preferably have a sphericity of 0.70 or more. In the case where the sphericity is 0.70 or more, the composite oxide particles according to the present application are easily increased in filling amount when made into a resin composite by being mixed in a resin. The composite oxide particles according to the present application more preferably have a sphericity of 0.80, and further preferably have a sphericity of 0.85 or more.

[0035] The sphericity is measured, for example, by a device based on the principle of dynamic image analysis in compliance with ISO 13322-2. As such a device, for example, "CAMSIZER X2" manufactured by Verder Scientific, Inc., and the like can be given. The sphericity is specifically measured as follows. First, a prescribed amount of the composite oxide particles is weighed. Next, the composite oxide particles are sequentially fed into the device while dispersing the agglomerated particles with dry air at 50 kPa, and the particles passing in front of a camera are measured. The measurement is performed in a dry manner. The measurement is repeated three times, and the sphericity is analyzed based on the cumulative average of the measurement results.

[0036] The particle diameter is set as the equivalent circle particle diameter. The equivalent circle particle diameter means the particle diameter of a perfect circle which becomes the same area as the projected particle image. The basis of the particle diameter is set as the volume. The sphericity is analyzed in compliance with ISO 9276-6. The sphericity is calculated by 4πA / P 2 A represents the measured value of the area of the projected particle image, and P represents the measured value of the outer circumference of the projected particle image.

[0037] Although the particles have a three-dimensional shape, the particles passing in front of the camera are measured in a planar manner. Therefore, in the present specification, the "sphericity" is adopted, and the closer the sphericity to 1.00, the more the particles are close to a perfect sphere.

[0038] As to whether or not the compound oxide particles have crystallinity or amorphousness, for example, it is possible to determine using an X-ray diffraction spectrum. In the case of having amorphousness, a halo peak is observed in the X-ray diffraction spectrum. If the compound oxide particles according to the present application have crystallinity, it is also possible to include an amorphous phase. The crystallinity degree as a scale of crystallinity is not limited for the compound oxide particles according to the present application. The compound oxide particles according to the present application preferably have a crystallinity degree of 40 or more. In the case of having a crystallinity degree of 40 or more, the compound oxide particles according to the present application have an advantage of being less affected by an amorphous portion. The compound oxide particles according to the present application more preferably have a crystallinity degree of 80 or more, and further preferably 90 or more.

[0039] The crystallinity degree is determined using an X-ray diffraction method for the compound oxide particles according to the present application, the diffraction angle 2Θ is in the range of 15 to 40°, and is calculated from the following formula (I).

[0040] Crystallinity degree = crystalline peak area / (crystalline peak area + amorphous peak area) (I)

[0041] For the compound oxide particles according to the present application, the half-value width of the main peak of the crystal having a diffraction angle 2Θ in the range of 27.5 to 29.5°, which is determined using an X-ray diffraction method, is preferably 0.20° or less. In the case of having a half-value width of 0.20° or less, it can be said that the compound oxide particles according to the present application have high crystallinity of the crystal surface representing the main peak of the compound oxide. The compound oxide particles according to the present application more preferably have a half-value width of 0.18° or less.

[0042] The compound oxide particles according to the present application have a color with white. Therefore, even if the compound oxide particles according to the present application are dispersed in a substrate such as a semiconductor package substrate, the substrate is not colored, and it is easy to optically find defects, contamination, and the like of the substrate. Further, since the compound oxide particles according to the present application have a color with white, it is also preferable from the viewpoint of being used as a mixed filler at the time of producing a composite. Specifically, for the compound oxide particles according to the present application, it is preferable that L* in the L*a*b* color space be 91.00 or more and 100.00 or less (more preferably 92.50 or more and 100.00 or less), a* be -10.00 or more and 3.00 or less (more preferably -5.00 or more and less than 1.50, and further preferably -2.00 or more and less than 1.00), and b* be -10.00 or more and 5.00 or less (more preferably -5.00 or more and 3.50 or less, and further preferably -1.50 or more and less than 3.00). In the case of L*, a*, and b* being in such a range, the compound oxide particles according to the present application can be determined to have a stronger white color.

[0043] The method of manufacturing the composite oxide particle according to the present application is not limited, and for example, includes: a step of mixing cordierite particles and nano particles to obtain mixed particles; and a step of heating the mixed particles.

[0044] In the step of mixing cordierite particles and nano particles to obtain mixed particles, the cordierite particles and the nano particles as raw materials are mixed. The cordierite particles can be used directly, or a substance that has been flame fused and solidified into particles can be used. Specifically, a substance that has been flame fused at 1200°C or higher and 1500°C or lower, caused to fall, and solidified into particles by cooling during the falling can be used.

[0045] As the nano particles, nano silica and the like can be given, as described above. Details of the nano particles are omitted as described above. The mixing ratio of the cordierite particles to the nano particles in the mixed particles including the cordierite particles and the nano particles is not limited. For example, it is preferable that the nano particles be included at a ratio of 0.1 mass% or more and 30 mass% or less. By using the nano particles at such a ratio, the spherical shape can be maintained.

[0046] In the step of heating the mixed particles, the obtained mixed particles are heated. The heating temperature is not limited, and it is preferable that the temperature be 1000°C or higher and 1400°C or lower. By heating at such a temperature, the composite oxide particles that are polycrystalline and in which the main crystal phase includes at least one of cordierite and hexagonal cordierite can be manufactured more efficiently, and amorphous substances are less likely to be obtained.

[0047] In order to efficiently obtain the composite oxide particles in which the main crystal phase includes hexagonal cordierite, it is preferable that the heating be performed at 1000°C or higher and 1200°C or lower. On the other hand, in order to obtain the composite oxide particles in which the main crystal phase includes cordierite, it is preferable that the heating be performed at 1200°C or higher and 1400°C or lower.

[0048] The heating can be performed in an atmosphere of air or in an atmosphere of an inactive gas. The inactive gas is not limited, and for example, nitrogen, argon, and the like can be given. The heating time is not limited, and for example, is 1 hour or more and 24 hours or less.

[0049] By such a procedure, the composite oxide particles according to the present application are obtained. Immediately after heating, the composite oxide particles are sometimes solidified in the shape of, for example, a container. Even in the case of such solidification, it is possible to easily break it with a hand, a wooden mallet, and the like after cooling, and obtain loose composite oxide particles. The obtained composite oxide particles are spherical and have crystallinity, are white, and the main crystal phase contains at least one of cordierite and hexagonal cordierite. By having such a configuration, the composite oxide particles according to the present application have a thermal expansion rate of 1.5 ppm or less, preferably less than 0.0 ppm, based on the TMA method.

[0050] Examples

[0051] Hereinafter, the present application will be specifically described by citing examples and comparative examples. However, the present application is not limited to these examples.

[0052] (Preparation Example)

[0053] First, the amorphous cordierite particles (manufactured by Marusu Glaze Co., Ltd., model number: SS400) were subjected to flame fusion at 1500°C, and the flame fusion product was allowed to fall. The falling product was solidified into a granular shape by cooling during the falling, and the raw material particles were prepared.

[0054] (Example 1)

[0055] The raw material particles obtained in the preparation example were put into a mortar at a proportion of 95% by mass, and nano-silica was put into the mortar at a proportion of 5% by mass, and mixed for 10 minutes. As the nano-silica, SO-E1 manufactured by Admatechs Co., Ltd. was used.

[0056] Next, the raw material particles were put into an alumina crucible, and subjected to firing at 1200°C for 10 hours, and the spherical composite oxide particles were obtained. The obtained spherical composite oxide particles were subjected to XRD measurement. In the obtained spectrum, there was no broad halo peak, and it was confirmed that the obtained spherical composite oxide particles had high crystallinity. Furthermore, from the firing temperature and the XRD spectrum, it was confirmed that the obtained spherical composite oxide particles contained at least one of a hexagonal cordierite phase and a cordierite phase.

[0057] (Example 2)

[0058] Using the same procedure as in Example 1 except that the calcination was performed at 1400°C for 10 hours, spherical composite oxide particles were obtained. The obtained spherical composite oxide particles were subjected to XRD measurement, and as a result, a spectrum in which a broad halo peak was not present was obtained. From this spectrum, it was confirmed that the obtained spherical composite oxide particles had high crystallinity. Furthermore, from the calcination temperature and the XRD spectrum, it was confirmed that the obtained spherical composite oxide particles contained at least one of a hexagonal cordierite phase and a cordierite phase.

[0059] (Example 3)

[0060] Using the same procedure as in Example 2 except that the raw material particles obtained in the preparation example were used at a proportion of 70% by mass and the nanosilica was used at a proportion of 30% by mass, spherical composite oxide particles were obtained. The obtained spherical composite oxide particles were subjected to XRD measurement, and as a result, a spectrum in which a broad halo peak was not present was obtained. From this spectrum, it was confirmed that the obtained spherical composite oxide particles had high crystallinity. Furthermore, from the calcination temperature and the XRD spectrum, it was confirmed that the obtained spherical composite oxide particles contained at least one of a hexagonal cordierite phase and a cordierite phase.

[0061] (Example 4)

[0062] Using the same procedure as in Example 1 except that the raw material particles obtained in the preparation example were used at a proportion of 99% by mass and the nanosilica was used at a proportion of 1% by mass, spherical composite oxide particles were obtained. The obtained spherical composite oxide particles were subjected to XRD measurement, and as a result, a spectrum in which a broad halo peak was not present was obtained. From this spectrum, it was confirmed that the obtained spherical composite oxide particles had high crystallinity. Furthermore, from the calcination temperature and the XRD spectrum, it was confirmed that the obtained spherical composite oxide particles contained at least one of a hexagonal cordierite phase and a cordierite phase.

[0063] (Comparative Example 1)

[0064] With respect to the raw material particles obtained in the preparation example, the raw material particles were put in an alumina crucible and subjected to calcination at 850°C for 10 hours, and spherical composite oxide particles were obtained. The obtained spherical composite oxide particles were subjected to XRD measurement. In the obtained spectrum, a broad halo peak was present, and it was confirmed that the obtained spherical composite oxide particles contained an amorphous phase and a crystalline phase.

[0065] (Comparative Example 2)

[0066] In addition to firing at 1400°C for 10 hours, the same procedure as in Comparative Example 1 was used to attempt to obtain composite oxide particles having a spherical shape. However, a blocky composite oxide was obtained, and no spherical particles were obtained.

[0067] The particle diameter, specific surface area, true circularity, thermal expansion rate, crystallinity, and color were verified for the composite oxide particles having a spherical shape obtained in Examples 1 to 4 and Comparative Example 1.

[0068] <Particle diameter>

[0069] The obtained composite oxide particles having a spherical shape were dispersed in an aqueous sodium hexametaphosphate solution. Subsequently, using a laser diffraction particle size distribution measuring device (Microtrac: MT-3300EXII, manufactured by Nikkiso Co., Ltd.), the particle size distribution was measured using a laser diffraction method. From the cumulative frequency distribution curve on a volume basis, D10, D50, and D90 were calculated. The value of D50, and the difference between D90 and D10 (D90-D10) are shown in Table 1.

[0070] <Specific surface area>

[0071] The specific surface area of the obtained composite oxide particles having a spherical shape was measured in accordance with the gas adsorption-based powder (solid) specific surface area measurement method (JIS Z8830:2013). Specifically, 1 g of the composite oxide particles having a spherical shape was placed in a sample tube using nitrogen as the adsorption gas, and the adsorption-desorption isotherm was obtained. The specific surface area (m 2 / g) was calculated by the multipoint plotting method. The results are shown in Table 1.

[0072] <True circularity>

[0073] The true circularity of the obtained composite oxide particles having a spherical shape was measured by a device based on the principle of dynamic image analysis in accordance with ISO 13322-2 (CAMSIZER X2, manufactured by Verder Scientific). Specifically, 3 g of the composite oxide particles having a spherical shape was weighed. Subsequently, the composite oxide particles were sequentially fed into the device while dispersing the agglomerated particles using dry air at 50 kPa, and the particles passing in front of the camera were measured. The measurement was performed in a dry state. This measurement was repeated three times, and the true circularity was analyzed based on the cumulative average of the measurement results. The true circularity was calculated by 4πA / P 2 . A represents the measured value of the area of the projected particle image, and P represents the measured value of the outer perimeter of the projected particle image. The results are shown in Table 1.

[0074] <Thermal expansion rate>

[0075] Using the respective raw materials (raw material particles and, as necessary, nanometer-sized silica) of the obtained composite oxide particles having a spherical shape, sintered bodies (20 mm x 4 mm x 4 mm) of a cubic shape were obtained by firing at the same temperature as in Examples 1 to 4, Comparative Example 1, and Comparative Example 2. The linear expansion rate of the obtained sintered body (sample) was measured using a TD5020SE (manufactured by NETZSCH). Specifically, the linear expansion rate of the obtained sample was measured in the range of 30 to 300°C under the atmosphere in accordance with the thermal mechanical analysis method (JIS R1618). As a standard sample, sapphire was used. The linear expansion rate was taken as the thermal expansion rate. The results are shown in Table 1.

[0076] <crystallinity>

[0077] The crystallinity of the obtained composite oxide particles having a spherical shape was measured by X-ray diffraction. Specifically, the diffraction spectrum was obtained by measurement using a powder X-ray diffraction device X'Pert PRO MPD (manufactured by Spectris). As to the measurement conditions, the X-ray source was set to Cu Kα, the X-ray output power was set to 45 kV and 40 mA, and the scanning speed was set to 0.2 deg / s. If a clear and sharp peak was shown, it was determined to be crystalline, and if a broad halo peak was shown, it was determined to be amorphous. The degree of crystallinity was calculated from the results of the built-in software HighScore Plus by the above-described formula (I) (degree of crystallinity = crystalline peak area / (crystalline peak area + amorphous peak area) ). The results are shown in Table 1.

[0078] <color>

[0079] The color of the obtained composite oxide particles having a spherical shape was determined based on the L*a*b* color space. Specifically, the obtained composite oxide particles having a spherical shape were loaded on a 1.5 cm x 1.5 cm square glass plate without gaps, and a glass cover glass was loaded thereon to fix the sample to obtain a sample sheet. With respect to the obtained sample sheet, after black correction and white correction were performed using a spectrophotometer CM-3700A (manufactured by Konica Minolta), diffuse illumination 8° direction light reception was performed in accordance with JIS Z8722 Condition c, SCI reflection measurement was performed, and the lightness L* and the chromaticity a* and b* were obtained. L* = 0.00 indicates black, L* = 100.00 indicates white, 0.00 ≤ L* ≤ 100.00, -100.00 ≤ a* ≤ 100.00, and -100.00 ≤ b* ≤ 100.00. In the case where L* > 91.00, a* < 3.00, and b* < 5.00 were satisfied, it was determined to be white. The results are shown in Table 1.

[0080] [table 1]

[0081]

[0082] Note 1 A: a case where the particles are broken and become loose.

[0083] B: a case where, although solidified, the particles become loose when broken by hand.

[0084] C: a case where, although solidified, the particles become loose when broken by a wooden hammer.

[0085] D: a case where, although solidified, the particles do not break even by a wooden hammer and cannot become loose.

[0086] As described above, the composite oxide particles obtained in Examples 1 to 4 (corresponding to the composite oxide particles according to the present application) contain at least one of a cordierite phase and a hexagonal cordierite phase. As shown in Table 1, the D50 of the composite oxide particles obtained in Examples 1 to 4 is each 0.1 μm or more and 500.0 μm or less, and the difference D90-D10 between the D90 and the D10 is each 1000.0 μm or less. The composite oxide particles obtained in Examples 1 to 4 are each white, spherical, have a true circularity of 0.7 or more, and have a thermal expansion rate (linear expansion rate) of 0.0 ppm or less, which is less than 1.5 ppm. The composite oxide particles obtained in Examples 1 to 4 are each crystalline, have a crystallinity of 40 or more in a range of diffraction angles 2θ of 15 to 40°, and have a half-value width of a main peak of a crystal in a range of diffraction angles 2θ of 27.5 to 29.5° of 0.20° or less.

[0087] Further, the composite oxide particles obtained in Examples 1 to 4 are each crystalline, have a crystallinity of 40 or more in a range of diffraction angles 2θ of 15 to 40°, and have a half-value width of a main peak of a crystal in a range of diffraction angles 2θ of 27.5 to 29.5° of 0.20° or less.

[0088] On the other hand, the composite oxide particles obtained in Comparative Example 1 are not white but pink, have a thermal expansion rate (linear expansion rate) of 4.0 ppm, which exceeds 1.5 ppm, and it is considered that there is an amorphous portion. In the case of the composite oxide particles obtained in Comparative Example 2, as also described in Table 1, the particles are in a block shape after firing and cannot be broken by a wooden hammer, but are crushed into a loose particle shape by a metal hammer. The composite oxide particles obtained in Comparative Example 2 are crystalline and white, but have a thermal expansion rate (linear expansion rate) of 1.7 ppm, which exceeds 1.5 ppm. Comparative Example 3 described in Table 1 relates to the raw material particles obtained in the preparation example, and the color is determined based on the L*a*b* color space.

Claims

1. A composite oxide particle which is polycrystalline and whose main crystal phase contains at least one of cordierite and hexacordierite, the composite oxide particle having a thermal expansion rate of 1.5 ppm or less based on a TMA method.

2. The composite oxide particle according to claim 1, having an average particle diameter (D50) of 0.1 μm or more and 500.0 μm or less.

3. The composite oxide particles according to claim 1, wherein a crystallinity of 40 or more calculated from the following formula (I) in a range of diffraction angles 2θ of 15 to 40° measured by an X-ray diffraction method, Crystallinity = Crystalline peak area / (Crystalline peak area + Amorphous peak area)... (I).

4. The composite oxide particles as claimed in claim 1, wherein, In a particle size distribution based on a laser diffraction method, a difference D90-D10 between a particle diameter D90 as a cumulative 90% diameter and a particle diameter D10 as a cumulative 10% diameter is 1000.0 μm or less.

5. The composite oxide particle according to claim 1, having a true circularity of 0.70 or more.

6. The composite oxide particles as claimed in claim 1, wherein, a half-value width of a main peak of a crystal measured by an X-ray diffraction method and having a diffraction angle 2θ in a range of 27.5 to 29.5° is 0.20° or less.

7. The composite oxide particles as claimed in claim 1, wherein, The nanoparticles are contained in a proportion of 0.1 mass% or more and 30 mass% or less.

8. The composite oxide particles as claimed in claim 1, wherein, In an L*a*b* color space, L* is 91.00 or more and 100.00 or less, a* is -10.00 or more and 3.00 or less, and b* is -10.00 or more and 5.00 or less.

9. A method for producing a composite oxide particle, comprising: a step of mixing a particulate cordierite with nanoparticles to obtain mixed particles; and a step of heating the mixed particles.

10. The production method as claimed in claim 9, wherein, The heating step is performed at 1000°C or more and 1400°C or less.

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