Particle group, composition, molded body, and method for producing particle group

Abstract

To provide particles with high thermal expansion control properties.SOLUTION: A particle group is a group of particles containing multiple crystals and satisfies requirement 1 and at least one of requirements 2 and 3. Requirement 1: At one or more temperatures T1 at -200 to 1200°C, |dA(T) / dT| is equal to or higher than 10 ppm / °C [A is (lattice constant of a-axis (short axis) of crystal) / (lattice constant of c-axis (long axis) of crystal), and each lattice constant is obtained from X-ray diffraction measurements of the particle group]. Requirement 2: SBET / SPSD is 4.0 to 20.0 [SBET is a BET specific surface area of the particle group, SPSD is a specific surface area of a virtual particle group, the virtual particle group has a size distribution of particles based on the volume of the particle group obtained by laser diffraction scattering method and a true density of the particle group, and each virtual particle has a spherical shape]. Requirement 3: Porosity is 2.0 to 20.0% [Porosity (%)=(1-apparent density of particle group / true density of particle group)×100].SELECTED DRAWING: Figure 1

Description

Technical Field

[0001] The present invention relates to a particle group, a composition, a molded body, and a method for producing the particle group.

Background Art

[0002] Conventionally, in order to reduce the coefficient of thermal expansion of a solid material, it has been known to add a filler having a small value of the coefficient of thermal expansion to the solid material.

[0003] For example, Patent Document 1 discloses tungsten zirconium phosphate as a filler exhibiting a negative coefficient of thermal expansion.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] However, in conventional materials, the coefficient of thermal expansion is not necessarily sufficiently reduced.

[0006] The present invention has been made in view of the above circumstances, and an object thereof is to provide a particle group capable of exhibiting excellent control characteristics of the coefficient of thermal expansion, and a composition, a molded body, and a production method using the same.

Means for Solving the Problems

[0007] As a result of various studies, the present inventors have arrived at the present invention. That is, the present invention provides the following inventions.

[0008] One aspect of the present invention is a particle group, wherein each particle contains a plurality of crystals, satisfies the following requirement 1, and satisfies at least one of the following requirements 2 and 3. Requirement 1: |dA(T) / dT| is 10 ppm / °C or more at at least one temperature T1 between -200°C and 1200°C. A is (the lattice constant of the a-axis (short axis) of the crystal) / (the lattice constant of the c-axis (long axis) of the crystal), and each of the lattice constants is obtained from the X-ray diffraction measurement of the particle group. Requirement 2: S BET / S PSD is between 4.0 and 20.0. S BET is the specific surface area of the particle group obtained by the BET method. S PSD is the specific surface area of the virtual particle group. The virtual particle group has the same particle size distribution based on volume as that of the particle group obtained by the laser diffraction scattering method and the same true density as that of the particle group, and the shape of each virtual particle is a true sphere. Requirement 3: The porosity defined by the following formula is between 2.0 and 20.0%. Porosity (%) = (1 - apparent density of the particle group / true density of the particle group) × 100

[0009] The particle group can satisfy all of the above Requirements 1 to 3.

[0010] In the particle group, the particle size D50 at which the cumulative frequency is 50% in the cumulative particle size distribution curve based on volume of the particle group obtained by the laser diffraction scattering method can be between 1 and 100 μm.

[0011] The crystal can be a metal oxide.

[0012] The metal oxide can be a metal oxide containing a metal having d electrons.

[0013] The metal oxide can be a metal oxide containing titanium.

[0014] The metal oxide containing titanium can be TiO x (x = 1.30 to 1.66).

[0015] The composition according to one aspect of the present invention contains any of the above particle groups.

[0016] The above composition can have a powder form.

[0017] The above composition can further contain a matrix material.

[0018] The above composition can further contain an uncured curable resin.

[0019] The molded body according to one aspect of the present invention is a molded body of the composition having the above particle group or powder form.

[0020] The method according to one aspect of the present invention is a method for producing any of the above particle groups, including step 1 of firing a raw material to obtain an intermediate, step 2 of pulverizing the intermediate to obtain a precursor, and step 3 of firing the precursor, wherein the firing temperatures in step 1 and step 3 are 1000 to 1300 °C.

[0021] The method can include a step of granulating the precursor by spray drying between step 2 and step 3 to obtain a granular precursor.

Advantages of the Invention

[0022] According to the present invention, it is possible to provide a particle group capable of exhibiting excellent control characteristics of the coefficient of thermal expansion, and various compositions and molded bodies using the same. Further, according to the present invention, it is possible to provide a method for producing a particle group capable of exhibiting excellent control characteristics of the coefficient of thermal expansion.

Brief Description of the Drawings

[0023]

Figure 1

Modes for Carrying Out the Invention

[0024] Hereinafter, preferred embodiments of the present invention will be described in detail. However, the present invention is not limited to the following embodiments.

[0025] <Particle group P> The particle group P includes a plurality of particles. Each particle includes a plurality of crystals, and each particle can be an aggregate of a plurality of crystals. Each particle may be a secondary particle having one crystal as a primary particle, or a secondary particle having an aggregate of a plurality of crystals as a primary particle.

[0026] The particle group P satisfies the following requirement 1, and further satisfies at least one of the following requirements 2 and 3. It is preferable that the particle group P satisfies all of the following requirements 1 to 3. Requirement 1: |dA(T) / dT| is 10 ppm / °C or more at at least one temperature T1 in the range of -200°C to 1200°C. A is (the lattice constant of the a-axis (short axis) of the crystal) / (the lattice constant of the c-axis (long axis) of the crystal), and each lattice constant is obtained from the X-ray diffraction measurement of the particle group P.

[0027] Requirement 2: S BET / S PSD is 4.0 to 20.0. S BET is the specific surface area of the particle group P obtained by the BET method. S PSD is the specific surface area of the virtual particle group V. The virtual particle group V has the same particle size distribution based on volume of the particle group P obtained by the laser diffraction scattering method and the same true density as the particle group, and the shape of each virtual particle is a true sphere.

[0028] Requirement 3: The porosity defined by the following formula is 2.0 to 20.0%. Porosity (%) = (1 - apparent density of particle group P / true density of particle group P) × 100

[0029] (Requirement 1) Requirement 1 will be described in detail. The lattice constant in the definition of A is specified by powder X-ray diffraction measurement of the particle group P. Analytical methods include the Rietveld method and analysis by fitting using the least squares method.

[0030] In this specification, in the crystal structure in the particle group P specified by powder X-ray diffraction measurement, the axis corresponding to the smallest lattice constant is defined as the a-axis, and the axis corresponding to the largest lattice constant is defined as the c-axis. The length of the a-axis and the length of the c-axis of the crystal lattice are defined as the a-axis length and the c-axis length, respectively.

[0031] A(T) is a parameter indicating the magnitude of the anisotropy of the crystal axis length and is a function of the temperature T (unit: °C). The larger the value of A(T), the larger the a-axis length relative to the c-axis length, and the smaller the value of A, the smaller the a-axis length relative to the c-axis length.

[0032] Here, |dA(T) / dT| represents the absolute value of dA(T) / dT, and dA(T) / dT represents the derivative of A(T) with respect to T (temperature). Here, in this specification, |dA(T) / dT| is defined by the following formula (1). |dA(T) / dT| = |A(T + 50) - A(T)| / 50 …(1)

[0033] As described above, for the crystal in the particle group P according to this embodiment, it is necessary that |dA(T) / dT| satisfies 10 ppm / °C or more at at least one temperature T1 in the range of -200°C to 1200°C. However, |dA(T) / dT| is defined within the range where the crystal exists in a solid state. Therefore, the highest temperature of T in formula (1) is up to a temperature 50°C lower than the melting point of the crystal (particle). That is, when the limitation of "at least one temperature T1 in the range of -200°C to 1200°C" is given, the temperature range of T in formula (1) is -200 to 1150°C.

[0034] It is preferable that |dA(T) / dT| is 20 ppm / °C or more, more preferably 30 ppm / °C or more, at at least one temperature T1 in the range of -200°C to 1200°C. The upper limit of |dA(T) / dT| is preferably 1000 ppm / °C or less, more preferably 500 ppm / °C or less.

[0035] The fact that the value of |dA(T) / dT| is 10 ppm / °C or more at at least one temperature T1 means that the change in the anisotropy of the crystal structure due to temperature change is large.

[0036] At at least one temperature T1, dA(T) / dT may be positive or negative, but it is preferably negative.

[0037] Depending on the type of crystal, there are substances whose crystal structure changes due to structural phase transition in a certain temperature range. In this specification, in the crystal structure at a certain temperature, the axis corresponding to the smallest lattice constant is defined as the a-axis, and the axis corresponding to the largest lattice constant is defined as the c-axis. In any of the triclinic system, monoclinic system, orthorhombic system, tetragonal system, hexagonal system, and rhombohedral system, the a-axis and c-axis are defined as above.

[0038] When the crystal satisfies Requirement 1, it is easy to lower the coefficient of thermal linear expansion in the composition containing the particle group P and the molded body.

[0039] (Requirement 2) Next, Requirement 2 will be described. S BET / S PSD represents the degree of complexity of the shape of each particle of the particle group P and takes a value of 1 or more. S BET is the specific surface area of the particle group P obtained by the BET method. In this specification, the specific surface area is the value obtained by dividing the surface area of the sample by the mass of the sample.

[0040] The measurement method of the BET specific surface area is shown below. As a pretreatment, the particle group P is dried at 200 °C for 30 minutes in a nitrogen atmosphere. The BET flow method is used for the measurement of the specific surface area. As the adsorption gas, a mixed gas of nitrogen gas and helium gas is used. The ratio of nitrogen gas in the mixed gas is 30% by volume, and the ratio of helium gas in the mixed gas is 70% by volume. As the measuring device, for example, a BET specific surface area measuring device Macsorb HM-1201 (manufactured by Mountech Co., Ltd.) can be used.

[0041] S PSD is the specific surface area of the virtual particle group V. The virtual particle group V has the same particle size distribution based on volume of the particle group P obtained by the laser diffraction scattering method and the same true density as that of the particle group, and the shape of each virtual particle is a true sphere.

[0042] The method for measuring the particle size distribution curve of the volume-based cumulative particle group P by the laser diffraction scattering method is shown below.

[0043] As a pretreatment, 99 parts by weight of water is added to 1 part by weight of the particle group P for dilution, and ultrasonic treatment is performed using an ultrasonic cleaner. The ultrasonic treatment time is 10 minutes. As the ultrasonic cleaner, NS200-6U manufactured by Nippon Seiki Co., Ltd. can be used. The frequency of the ultrasonic wave can be about 28 kHz.

[0044] The particle size distribution of the volume-based particle group P is measured by the laser diffraction scattering method. For example, a laser diffraction type particle size distribution measuring device Mastersizer2000 manufactured by Malvern Instruments Ltd. can be used.

[0045] When the crystal is Ti2O3, it can be measured with the refractive index of Ti2O3 being 2.40.

[0046] S BET / S PSD The closer S BET / S PSD is to 1, the closer the shape of the particles in the particle group P is to a true sphere, and the larger S BET / S PSD is, the more complex the shape of the particles in the particle group P is considered to be.

[0047] As described above, in the particle group P according to the present embodiment, S BET / S PSD needs to be 4.0 or more and 20.0 or less. S BET / S PSD is preferably 4.3 or more, and more preferably 4.5 or more. S BET / S PSD may be 5.0 or more, 6.0 or more, 7.0 or more, 8.0 or more, 9.0 or more, or 10.0 or more. S BET / S PSD is preferably 16.0 or less, and more preferably 15.0 or less. S BET / S PSD may be 14.0 or less, 13.0 or less, or 12.0 or less.

[0048] When the particle group P satisfies the requirement 2, in the composition containing the particle group P and the molded body, it is easy to lower the coefficient of thermal expansion.

[0049] (Requirement 3) Next, the requirement 3 will be described. The requirement 3 stipulates that the porosity defined by the following formula is 2.0 to 20.0%. Porosity (%) = (1 - apparent density of particle group P / true density of particle group P) × 100

[0050] The apparent density of the particle group P is a value obtained by dividing the mass of the particle group P by the sum of the volume of the solid constituting the particle group P and the volume of the closed pores in the solid constituting the particle group P. In other words, the apparent density of the particle group P means the density with the total volume of the volume occupied by the solid and the volume of the closed pores as the volume for density calculation. The apparent density becomes smaller as the volume of the closed pores is larger, and is equal to the true density when there are no closed pores.

[0051] The true density of particle group P is the mass of particle group P divided by the volume of the solid that constitutes particle group P. In other words, the true density of particle group P means the density calculated using only the volume occupied by the solid part as the volume for density calculation. The true density is a value inherent to the substance and does not depend on the shape of the particles.

[0052] The closed pores in particle group P are the spaces existing inside the solid that constitutes particle group P. This space is usually a space that is not filled with other materials in the composition added with particle group P and the molded body etc. to be described later, and can contribute to the reduction of the coefficient of thermal expansion. The closed pores may be the spaces formed within the crystal or the spaces formed between the crystals. For example, when the particles are polycrystalline particles in which a large number of crystals are randomly arranged within the particles, the particles can have closed pores between the crystals.

[0053] FIG. 1 is a schematic cross-sectional view of an example of the particles of particle group P according to the present embodiment. The particle 4 is an aggregate having a plurality of crystals 2, and the particle 4 has closed pores 6 disposed between the crystals 2.

[0054] The porosity defined by the above formula means the ratio of the total volume of the closed pores existing in particle group P to the apparent volume of particle group P. Note that the apparent volume of particle group P is the sum of the volume of the solid that constitutes particle group P and the volume of the closed pores within the solid that constitutes particle group P.

[0055] As described above, in the particles according to the present embodiment, the above porosity needs to be 2.0% or more and 20% or less. This porosity is preferably 2.3% or more, and more preferably 2.5% or more. The porosity may be 2.7% or more, 2.8 or more, 2.9 or more, 3.0% or more, 3.2 or more, 3.5% or more, 3.7 or more, or 4.0 or more. The porosity is preferably 16% or less, and more preferably 14% or less. The porosity may be 13.0% or less, 12.0% or less, 11.0% or less, 10.0% or less, 9.0% or less, 8.0% or less, 7.0% or less, 6.0% or less, or 5.0% or less.

[0056] When the particles satisfy Requirement 3, it is easy to lower the coefficient of thermal expansion in a composition containing the particle group P and the like, and in a molded article.

[0057] In this specification, in the cumulative particle size distribution curve of the particle group P based on volume, the cumulative frequency is calculated from the smaller diameter side, and the diameter of the particle at which the cumulative frequency becomes 50% is defined as D50.

[0058] From the viewpoint of ensuring the fluidity of the liquid composition added with the particle group P, D50 is preferably 1 μm or more, more preferably 3 μm or more, still more preferably 5 μm or more, and extremely preferably 7 μm or more. From the viewpoint of ensuring the ease of intrusion of the liquid composition added with the particle group P into a narrow gap, D50 is preferably 100 μm or less, more preferably 80 μm or less, and still more preferably 60 μm or less. D50 may be 50 μm or less, 40 μm or less, 30 μm or less, 25 μm or less, 20 μm or less, or 15 μm or less.

[0059] The crystal is preferably an oxide. In particular, the crystal is more preferably a metal oxide. The metal oxide may contain a plurality of metals.

[0060] The metal oxide is not particularly limited, but is preferably a metal oxide containing a metal having d electrons, and more preferably a metal oxide containing a metal having only 3d electrons among the d electrons.

[0061] Examples of the metal oxide containing a metal having d electrons include, but are not particularly limited to, metal oxides containing Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu, Y, Zr, Nb, and Mo.

[0062] Examples of the metal oxide containing a metal having only 3d electrons among the d electrons include metal oxides containing Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu. Among them, from the viewpoint of resources, a metal oxide containing titanium is preferable.

[0063] More specifically, the metal oxide containing titanium is preferably represented by the compositional formula TiO x (x = 1.30 to 1.66), and more preferably represented by the compositional formula TiO x (x = 1.40 to 1.60). In TiO x , a part of the Ti atoms may be substituted with other elements.

[0064] Note that the metal oxide containing titanium may be an oxide containing metal atoms other than titanium such as LaTiO3 in addition to TiO x .

[0065] As the crystal structure of the above crystal, it preferably has a perovskite structure or a corundum structure, and more preferably has a corundum structure.

[0066] The crystal system is not particularly limited, but it is preferably a rhombohedral crystal system. As the space group, it is preferably attributed to R-3c.

[0067] <Method for Producing Particle Group P> Subsequently, an example of the method for producing the above particle group P will be described. The method for producing particle group P according to the present embodiment includes Step 1 of firing a raw material to obtain an intermediate, Step 2 of pulverizing the intermediate to obtain a precursor, and Step 3 of firing the precursor, and the firing temperatures in Step 1 and Step 3 are 1000°C or higher and 1300°C or lower.

[0068] Step 1 The raw material refers to a material that can be converted into the above crystal through subsequent steps. The type of the raw material is not particularly limited and may be a single substance or a mixture. For example, when the crystal of the particle group P to be produced is a metal oxide containing titanium, the raw material can be a mixture of metallic titanium and titanium oxide.

[0069] The firing of the raw materials is preferably carried out in an electric furnace. Examples of the structure of the electric furnace include box type, crucible type, tubular type, continuous type, furnace bottom lifting type, rotary kiln, trolley type, etc. Examples of the box type electric furnace include FD-40×40×60-1Z4-18TMP (manufactured by Nemus Co., Ltd.). Examples of the tubular type electric furnace include PCR (manufactured by Motoyama Co., Ltd.) and DSPSH28 (manufactured by Motoyama Co., Ltd.). In Step 1, all of the raw materials may be converted into the above crystals, or only a part of the raw materials may be converted into the above crystals. In other words, the obtained intermediate may contain the crystals in the above particle group P, and may or may not contain unreacted raw materials.

[0070] Step 2 The method for pulverizing the intermediate obtained in Step 1 is not particularly limited. For example, there are a method of putting the pulverized material into a mortar and pulverizing it using a pestle, and a method of pulverizing it using a ball mill or a bead mill. The pulverization may be dry pulverization or wet pulverization. By appropriately changing the pulverization conditions, such as the strength of the applied force and the time for pulverization, the average particle diameter of the particle group of the obtained precursor can be adjusted.

[0071] Between Step 2 and Step 3, a step of granulating the pulverized precursor by a spray drying method to obtain a granular precursor may be further included.

[0072] Step 3 The firing of the precursor can be carried out in the same manner as the firing in Step 1.

[0073] As described above, the firing temperatures in Step 1 and Step 3 are 1000°C or higher and 1300°C or lower. From the viewpoint of enhancing the crystallinity in the particle group P, the firing temperature may be, for example, 1025°C or higher, 1040°C or higher, or 1050°C or higher. From the viewpoint of preventing an increase in the crystal grain size and each particle size of the particle group, the firing temperature may be, for example, 1275°C or lower, 1260°C or lower, or 1250°C or lower. The firing temperature in Step 1 and the firing temperature in Step 3 may be the same or different.

[0074] When the firing temperature is within the above range, S of the particle group BET / S PSD and the above porosity tend to be easily controlled. As a result, it is easy to produce a particle group that can exhibit excellent thermal expansion control characteristics.

[0075] <Composition containing particle group P> <First composition (powder composition for filler)> One embodiment of the present invention is a powder composition containing the above particle group P and other powders. Such a powder composition can be suitably used as a filler for controlling the thermal expansion coefficient of a solid composition described later. There is no limitation on the content of the particle group P in the powder composition, and a function of controlling the amount of thermal expansion can be exhibited according to the content. From the viewpoint of efficiently controlling the amount of thermal expansion, the content of the above particle group P may be 75% by mass or more, 85% by mass or more, or 95% by mass or more.

[0076] Examples of other powders in the powder composition include calcium carbonate, talc, mica, silica, clay, wollastonite, potassium titanate, zonotrite, gypsum fiber, aluminum borate, aramid fiber, carbon fiber, glass fiber, glass flake, polyoxybenzoyl whisker, glass balloon, carbon black, graphite, alumina, aluminum nitride, boron nitride, beryllium oxide, ferrite, iron oxide, barium titanate, lead zirconate titanate, zeolite, iron powder, aluminum powder, barium sulfate, zinc borate, red phosphorus, magnesium oxide, hydrotalcite, antimony oxide, aluminum hydroxide, magnesium hydroxide, zinc carbonate, TiO2, and TiO.

[0077] The D50 of the powder composition can be set in the same manner as the D50 of the above particles.

[0078] The method for producing the powder composition is not particularly limited. For example, the above particle group P and other powders may be mixed, and if necessary, the particle size distribution may be adjusted by crushing, sieving, pulverization, etc.

[0079] <Second Composition (Solid Composition)> The solid composition according to this embodiment contains a matrix material and the above-described particle group P.

[0080] [Matrix Material] The matrix material is not particularly limited, and examples thereof include resins, alkali metal silicates, ceramics, metals, and the like. The matrix material only needs to be able to hold the above-described particle group P in a solid state at room temperature (20°C).

[0081] Examples of the resin are a thermoplastic resin and a cured product of a heat- or active energy ray-curable resin.

[0082] Examples of the thermoplastic resin are polyolefins (such as polyethylene and polypropylene), ABS resin, polyamides (such as nylon 6 and nylon 6,6), polyamideimide, polyesters (such as polyethylene terephthalate and polyethylene naphthalate), liquid crystal polymers, polyphenylene ether, polyacetal, polycarbonate, polyphenylene sulfide, polyimide, polyetherimide, polyethersulfone, polyketone, polystyrene, and polyetheretherketone.

[0083] Examples of the thermosetting resin are epoxy resin, oxetane resin, unsaturated polyester resin, alkyd resin, phenol resin (such as novolak resin and resol resin), acrylic resin, urethane resin, silicone resin, polyimide resin, and melamine resin. Examples of the active energy ray-curable resin are an ultraviolet-curable resin and an electron beam-curable resin, and for example, they can be urethane acrylate resin, epoxy acrylate resin, acrylic acrylate resin, polyester acrylate resin, and phenol methacrylate resin. Other examples of the resin are adhesives such as silicone-based, urethane-based, rubber-based, and acrylic-based adhesives.

[0084] The matrix material may contain one kind of the above resin or may contain two or more kinds.

[0085] From the viewpoint of improving heat resistance, the matrix material is preferably an epoxy resin, a polyethersulfone, a liquid crystal polymer, a polyimide, a polyamideimide, or a silicone.

[0086] Examples of the alkali metal silicate include lithium silicate, sodium silicate, and potassium silicate. The first material may contain one kind of alkali metal silicate or two or more kinds thereof. These materials are preferable because of their high heat resistance.

[0087] The ceramics are not particularly limited, and examples thereof include oxide-based ceramics such as alumina, silica (including silicon oxide and silica glass), titania, zirconia, magnesia, ceria, yttria, zinc oxide, and iron oxide; nitride-based ceramics such as silicon nitride, titanium nitride, and boron nitride; and ceramics such as silicon carbide, calcium carbonate, aluminum sulfate, barium sulfate, aluminum hydroxide, potassium titanate, talc, kaolin clay, kaolinite, halloysite, pyrophyllite, montmorillonite, sericite, mica, amesite, bentonite, asbestos, zeolite, calcium silicate, magnesium silicate, diatomaceous earth, and silica sand. The first material may contain one kind of ceramics or two or more kinds thereof. Ceramics are preferable because they can improve heat resistance. A sintered body can be produced by, for example, spark plasma sintering.

[0088] The metal is not particularly limited, and examples thereof include simple metals such as aluminum, tantalum, niobium, titanium, molybdenum, iron, nickel, cobalt, chromium, copper, silver, gold, platinum, lead, tin, and tungsten; alloys such as stainless steel (SUS); and mixtures thereof. The first material may contain one kind of metal or two or more kinds thereof. Such metals are preferable because they can improve heat resistance.

[0089] [Other components] The solid composition may contain a matrix material and other components other than the above particle group P. Examples of such components include catalysts. The catalyst is not particularly limited, and examples thereof include acidic compounds, alkaline compounds, and organometallic compounds. As the acidic compound, acids such as hydrochloric acid, sulfuric acid, nitric acid, phosphoric acid, formic acid, acetic acid, and oxalic acid can be used. As the alkaline compound, ammonium hydroxide, tetramethylammonium hydroxide, tetraethylammonium hydroxide, etc. can be used. Examples of the organometallic compound include those containing aluminum, zirconium, tin, titanium, or zinc. Further, it may contain other powders other than the particle group P exemplified in the first composition (powder composition).

[0090] The content of the above particle group P in the solid composition is not particularly limited, and a function of controlling thermal expansion can be exhibited according to the content. The content of the above particle group P in the solid composition can be, for example, 1% by weight or more, and may be 3% by weight or more, 5% by weight or more, 10% by weight or more, 20% by weight or more, 40% by weight or more, or 70% by weight or more. When the content of the above particle group P increases, the effect of reducing the coefficient of thermal linear expansion is likely to be exhibited. The content of the above particle group P in the solid composition can be, for example, 99% by weight or less. The content of the above particle group P in the solid composition may be 95% by weight or less, or 90% by weight or less.

[0091] The content of the matrix material in the solid composition can be, for example, 1% by weight or more. The content of the matrix material in the solid composition may be 5% by weight or more, or 10% by weight or more. The content of the matrix material in the solid composition can be, for example, 99% by weight or less. The content of the matrix material in the solid composition may be 97% by weight or less, 95% by weight or less, 90% by weight or less, 80% by weight or less, 60% by weight or less, or 30% by weight or less.

[0092] Since the solid composition according to this embodiment contains the above particle group P, the coefficient of thermal expansion of the solid composition can be made lower than in the case where the particle group P is not added. Therefore, according to this solid composition, a member with extremely little dimensional change when the temperature changes can be obtained. For this reason, it can be suitably used for optical members and members for semiconductor manufacturing apparatuses that are particularly sensitive to dimensional changes due to temperature.

[0093] <Third Composition (Liquid Composition)> The liquid composition according to this embodiment contains the above particle group P and a liquid material. The liquid composition of this embodiment is a composition that has fluidity at 25°C. This liquid composition can be a raw material of the above solid composition. "Having fluidity at 25°C" means that after supplying the composition into a predetermined container and making the liquid surface horizontal, the container is tilted at 45 degrees, and after 1 hour, the liquid surface moves or deforms.

[0094] [Liquid Material] The liquid material is liquid and may be one in which the above particle group P can be dispersed. The liquid material can be a raw material of the matrix material.

[0095] For example, when the matrix material is an alkali metal silicate, the liquid material can include an alkali metal silicate and a solvent capable of dissolving or dispersing the alkali metal silicate. When the matrix material is a thermoplastic resin, the liquid material can include a thermoplastic resin and a solvent capable of dissolving or dispersing the thermoplastic resin. When the matrix material is a cured product of a heat- or active energy ray-curable resin, the liquid material is a heat- or active energy ray-curable resin before curing.

[0096] The heat-curable resin before curing has fluidity at room temperature and cures by a crosslinking reaction or the like when heated. The heat-curable resin before curing may contain one kind of resin or two or more kinds of resins.

[0097] Before curing, the active energy ray-curable resin has fluidity at room temperature and undergoes a crosslinking reaction or the like to cure upon irradiation with active energy rays such as light (e.g., UV) or electron beams. The active energy ray-curable resin before curing contains a curable monomer and / or a curable oligomer, and may further contain a solvent and / or a photoinitiator as necessary. Examples of the curable monomer and the curable oligomer are photo-curable monomers and photo-curable oligomers. Examples of the photo-curable monomer are monofunctional or polyfunctional acrylate monomers. Examples of the photo-curable oligomer are urethane acrylate, epoxy acrylate, acrylic acrylate, polyester acrylate, and phenol methacrylate.

[0098] Examples of the solvent include organic solvents such as alcohol solvents, ether solvents, ketone solvents, glycol solvents, hydrocarbon solvents, and aprotic polar solvents, and water. In the case of alkali metal silicate, the solvent is, for example, water.

[0099] [Other Components] The liquid composition of this embodiment may contain a liquid material and other components other than the above particle group P. For example, it can contain other powders other than the particle group P mentioned in the first composition (powder composition).

[0100] The content of the above particle group P in the liquid composition of this embodiment is not particularly limited and can be appropriately set from the viewpoint of controlling the thermal expansion coefficient in the solid composition after curing. Specifically, it can be made the same as the content of the above particle group P in the second composition (solid composition).

[0101] <Method for Producing Liquid Composition> The method for producing the liquid composition is not particularly limited. For example, the liquid composition can be obtained by stirring and mixing the above particle group P or powder composition with the liquid material. Examples of the stirring method include stirring and mixing with a mixer. Alternatively, the particle group P etc. can be dispersed in the liquid material by ultrasonic treatment.

[0102] Examples of the mixing method used in the mixing process include, for example, the ball mill method, the rotating and revolving mixer, the impeller swirling method, the blade swirling method, the swirling thin film method, the rotor / stator type mixer method, the colloid mill method, the high-pressure homogenizer method, and the ultrasonic dispersion method. In the mixing process, multiple mixing methods may be performed sequentially or multiple mixing methods may be performed simultaneously. In the mixing process, the composition can be homogenized and shear can be applied to enhance the fluidity and deformability of the composition.

[0103] <Method for manufacturing a solid composition> After shaping the above liquid composition into a desired shape, by converting the liquid material in the liquid composition into a matrix material, a solid composition in which the above particle group P or powder composition and the matrix material are combined can be manufactured.

[0104] For example, when the liquid material contains an alkali metal silicate and a solvent capable of dissolving or dispersing the alkali metal silicate, and when it contains a thermoplastic resin and a solvent capable of dissolving or dispersing the thermoplastic resin, after shaping the liquid composition into a desired shape, by removing the solvent from the liquid composition, a solid composition containing the above particle group or the like and the matrix material (alkali metal salt or thermoplastic resin) can be obtained.

[0105] As the method for removing the solvent, a method of evaporating the solvent by natural drying, vacuum drying, heating, etc. can be applied. From the viewpoint of suppressing the generation of coarse bubbles, when removing the solvent, it is preferable to remove the solvent while maintaining the temperature of the mixture below the boiling point of the solvent.

[0106] When the liquid material is a heat or active energy ray curable resin before curing, after shaping the liquid composition into a desired shape, the liquid composition may be cured by heat or active energy rays (such as UV).

[0107] Examples of the method for shaping the liquid composition into a predetermined shape include pouring it into a mold and applying it to the substrate surface to form a film shape.

[0108] Further, when the matrix material is ceramics or metal, the following can be done. A mixture of the raw material powder of the matrix material and the above particle group P etc. is prepared, and the mixture is heat-treated to sinter the raw material powder of the matrix material, whereby a solid composition containing the matrix material as a sintered body and the above particle group P etc. is obtained. If necessary, the pores of the solid composition can be adjusted by heat treatment such as annealing. As the sintering method, methods such as normal heating, hot pressing, and spark plasma sintering can be adopted.

[0109] Spark plasma sintering means passing a pulsed current through a mixture of the raw material powder of the matrix material and the above particle group P etc. while applying pressure to the mixture. Thereby, discharge occurs between the raw material powders of the matrix material, and the raw material powders of the matrix material can be heated and sintered.

[0110] In order to prevent the obtained compound from deteriorating when it comes into contact with air, the plasma sintering process is preferably carried out in an inert atmosphere such as argon, nitrogen, or vacuum.

[0111] The pressure applied in the plasma sintering process is preferably in the range exceeding 0 MPa and not exceeding 100 MPa. In order to obtain a high-density first material, the pressure applied in the plasma sintering process is preferably 10 MPa or more, and more preferably 30 MPa or more.

[0112] The heating temperature of the plasma sintering process is preferably sufficiently lower than the melting point of the target matrix material.

[0113] Furthermore, by heat-treating the obtained solid composition, adjustments such as the size and distribution of the pores can be made.

[0114] <Formed body of particle group P or powder composition> The formed body according to this embodiment is a formed body of the above particle group P or powder composition. The formed body in this embodiment may be a sintered body obtained by sintering the above particle group P or powder composition.

[0115] Generally, a molded body is obtained by sintering the above particle group P or powder composition. In this case, it is preferable to perform sintering within a temperature range in which the crystal structure in the particle group P is maintained.

[0116] Various known sintering methods can be applied to obtain a sintered body. As methods for obtaining a sintered body, methods such as normal heating, hot pressing, and spark plasma sintering can be adopted.

[0117] Note that the molded body according to this embodiment is not limited to a sintered body, and may be, for example, a compact obtained by pressure molding the above particle group P or powder composition.

[0118] According to the molded body of the above particle group P or powder composition according to this embodiment, a member with little thermal expansion can be provided, and the dimensional change of the member when the temperature changes can be made extremely small. Therefore, it can be suitably used for various members used in devices that are particularly sensitive to dimensional changes due to temperature. For this reason, it can be suitably used for optical members and members for semiconductor manufacturing devices that are particularly sensitive to dimensional changes due to temperature.

[0119] Subsequently, specific usage forms of the above solid composition and molded body will be described. Since the solid composition and molded body according to the above embodiment are excellent in electrical insulation, they can be a member for an electronic device, a mechanical member, a container, an optical member, or an adhesive.

[0120] [Member for Electronic Device] Examples of members for electronic devices are a sealing member, a conductive adhesive, a circuit board, a prepreg, and an insulating sheet.

[0121] Examples of the sealing member are a sealing member for a semiconductor element, an underfill member, and an interchip fill for 3D-LSI. Examples of semiconductor elements are power semiconductors such as power transistors and power ICs; light-emitting elements such as LED elements. According to the sealing member using the above solid composition and molded body, it is possible to suppress cracking due to the difference in the coefficient of thermal linear expansion.

[0122] Examples of the conductive adhesive include an anisotropic conductive film and an anisotropic conductive paste. By incorporating the particles of the present embodiment into the conductive adhesive, the thermal expansion of the adhesive member can be reduced, the problems of cracking and warping at the contact portion of different materials can be eliminated, and the electrical insulation can be enhanced.

[0123] The circuit board includes a metal layer and an electrical insulation layer provided on the metal layer. By using the solid composition and the molded body for the electrical insulation layer, the coefficient of thermal expansion can be reduced while maintaining the electrical insulation, the difference from the coefficient of thermal expansion of the metal layer can be decreased, and problems such as warping and cracking can be eliminated. Specific examples of the circuit board include a printed circuit board, a multilayer printed wiring board, a build-up board, a capacitor-embedded board, and the like.

[0124] The prepreg is a semi-cured product of an impregnated substrate containing a reinforcing substrate and a matrix material impregnated into the reinforcing substrate. By incorporating the particles of the present embodiment into the prepreg, it becomes possible for the cured prepreg to exhibit high dimensional stability even in an environment subjected to a thermal load.

[0125] Examples of the insulating sheet are resin sheets such as polyvinyl chloride. By incorporating the above particles into the insulating sheet, it becomes possible to improve the dimensional accuracy while maintaining the electrical insulation.

[0126] [Mechanical member] A mechanical member is a member that constitutes various mechanical devices. Examples of the mechanical device are machine tools such as cutting devices, process equipment, and semiconductor manufacturing devices. Examples of the mechanical member are a fixing mechanism, a moving mechanism, tools, and the like. According to the heat dissipation member using the solid composition and the molded body, dimensional deviation due to thermal expansion can be suppressed, and it becomes possible to improve the accuracy such as working accuracy and processing accuracy. It is also suitable for use at the joint portion between members of different materials.

[0127] Further, the mechanical member may be a rotating member. The rotating member refers to a member that exerts a mechanical action on other members while rotating, such as a gear. In the case of a rotating member, when the dimensions change due to thermal expansion, problems such as poor meshing and wear may occur, so the above solid composition and molded body are suitable for application.

[0128] Further, the mechanical member may be a substrate. In the case of a substrate, when the dimensions change due to thermal expansion, problems such as displacement may occur, so the above solid composition and molded body are suitable for application.

[0129] [Container] A container is a member for containing gases, liquids, solids, etc. For example, an example of a container is a mold for producing a molded body. For example, in the case of a mold, when the dimensions change due to thermal expansion, problems such as the dimensional accuracy of the molded body not being maintained may occur, so the above solid composition and molded body are suitable for application.

[0130] [Optical member] Examples of optical members are optical fibers, optical waveguides, lenses, mirrors, prisms, optical filters, diffraction gratings, fiber gratings, and wavelength conversion members. Examples of lenses are optical pickup lenses and camera lenses. Examples of optical waveguides are arrayed waveguides and planar optical circuits.

[0131] Optical members have the problem that their characteristics fluctuate when the lattice spacing, refractive index, optical path length, etc. change with a change in temperature. According to the optical member or the fixing member or supporting substrate of the optical member using the above solid composition and molded body, it becomes possible to reduce such fluctuations in the characteristics of the optical member based on temperature.

[0132] [Adhesive] Examples of the adhesive include thermosetting resins such as epoxy and silicone resin as the matrix material and the above-mentioned particles. The adhesive may be liquid or solid before curing. The cured product of this adhesive can have a low coefficient of thermal expansion, so it is possible to suppress cracking. In particular, it is suitable for application to heat-resistant adhesive members subjected to heat load and the like.

Examples

[0133] Hereinafter, the present invention will be described in more detail with reference to examples. 1. Crystal structure analysis of particle group As the analysis of the crystal structure, using a powder X-ray diffractometer SmartLab (manufactured by Rigaku Corporation), the particle group was subjected to powder X-ray diffraction measurement at different temperatures under the following conditions to obtain a powder X-ray diffraction pattern. For the compound constituting the crystal, based on the obtained powder X-ray diffraction pattern, using PDXL2 (manufactured by Rigaku Corporation) software, the lattice constants were refined by the least squares method to obtain two lattice constants, namely, the a-axis length and the c-axis length.

[0134] Measuring device: Powder X-ray diffractometer SmartLab (manufactured by Rigaku Corporation) X-ray generator: CuKα ray source, voltage 45 kV, current 200 mA Slit: Slit width 2 mm Scan step: 0.02 deg Scan range: 5 - 80 deg Scan speed: 10 deg / min X-ray detector: One-dimensional semiconductor detector Measurement atmosphere: Ar 100 mL / min Sample stage: Made of a dedicated glass substrate SiO2

[0135] 2. BET specific surface area (S BET ) measurement The BET specific surface area of the particles was measured by the following method. Pretreatment: The particle group was dried at 200 °C for 30 minutes in a nitrogen atmosphere. Measurement: Measured by the BET flow method. Measurement conditions: A mixed gas of nitrogen gas and helium gas was used. The ratio of nitrogen gas in the mixed gas was 30% by volume, and the ratio of helium gas in the mixed gas was 70% by volume. Measuring device: BET specific surface area measuring device Macsorb HM-1201 (manufactured by Mountech Co., Ltd.)

[0136] 3. Measurement of particle size distribution of particle group The particle size distribution of the particle group was measured by the following method. Pretreatment: 99 parts by weight of water was added to 1 part by weight of the particle group and diluted, and ultrasonic treatment was performed using an ultrasonic cleaner. The ultrasonic treatment time was 10 minutes, and NS200-6U manufactured by Nippon Seiki Co., Ltd. was used as the ultrasonic cleaner. The ultrasonic frequency was about 28 kHz. Measurement: The particle size distribution of the particle group based on volume was measured by the laser diffraction scattering method. Measurement conditions: The refractive index of Ti2O3 was set to 2.40. Measuring device: Laser diffraction particle size distribution measuring device Mastersizer 2000 (manufactured by Malvern Instruments Ltd.) Based on the obtained particle size distribution of the particle group and the assumption that the shape of each particle is spherical, S PSD was calculated. Also, D50 of the particle group was determined.

[0137] 4. Measurement of porosity of particle group The apparent density of the particle group was measured by a method conforming to JIS Z 8807 using a specific gravity bottle (manufactured by AS ONE Corporation) with a volume of 10 mL. Water was used as the liquid. When the material of the particle group is Ti2O3, the true density of Ti2O3 is 4.49 g / cm 3 was calculated. The porosity of the particle group was calculated from equation (2) using the apparent density and the true density of the particle group. Porosity (%) = (1 - apparent density of particle group / true density of particle group) × 100…(2)

[0138] 5. Evaluation of thermal expansion control characteristics (epoxy resin composite material) A composite material of a particle group and an epoxy resin was produced by the following method, and the heat expansion control characteristics were evaluated. 57.5 g of an epoxy resin (manufactured by Sumitomo Chemical Co., Ltd., ELM-100), 26.4 g of a curing agent (manufactured by Tokyo Chemical Industry Co., Ltd., Bis(4-aminophenyl) Sulfone), and 0.3 g of a curing accelerator (manufactured by Tokyo Chemical Industry Co., Ltd., Piperidinium Trifluoroborate) were mixed to obtain an uncured epoxy resin composition. A mixture was obtained by mixing 5.0 g of the particle group of the examples and comparative examples and 1.3 g of the uncured epoxy resin composition. The obtained mixture was put into a mold, cured at 180 °C for 5 minutes while applying pressure, then cooled to room temperature and removed from the mold, and further cured at 220 °C for 2 hours to obtain an epoxy resin composite material.

[0139] The coefficient of thermal expansion of the obtained epoxy resin composite material was measured using the following apparatus. Measuring device: Thermo plus EVO2 TMA series Thermo plus 8311 The measurement conditions were a temperature range of -10 °C to 160 °C, a temperature change rate of 10 °C / min, and a sampling interval of 2.7 seconds. Reference solid: silica

[0140] The typical size of the measurement sample of the solid composition was 15 mm × 4 mm × 4 mm. The sample length L(T) at temperature T was measured with the longest side of the measurement sample of the solid composition as the sample length L. The dimensional change rate ΔL(T) / L(30 °C) with respect to the sample length at 30 °C (L(30 °C)) was calculated by the following formula. ΔL(100 °C) / L(30 °C) = (L(100 °C) - L(30 °C)) / L(30 °C)

[0141] When the dimensional change rate at 100 °C, that is, ΔL(100 °C) / L(30 °C), was less than 0.1%, the heat expansion control characteristics were evaluated as good.

[0142] (Examples 1 to 2 and Comparative Examples 1 to 2) The particle groups of Examples 1 to 2 and Comparative Examples 1 to 2 were obtained by the following method.

[0143] <Example 1> <Step 1> Into a 1 L plastic polybottle (outer diameter 97.4 mm), 1000 g of 2 mm φ zirconia balls, 166.7 g of TiO2 (manufactured by Ishihara Sangyo Co., Ltd., CR-EL), and 33.3 g of Ti (manufactured by Kojundo Chemical Laboratory Co., Ltd., <38 μm) were put, the 1 L polybottle was placed on a ball mill stand, and ball mill mixing was carried out at a rotation speed of 60 rpm for 4 hours to prepare raw material mixed powder 1.

[0144] The raw material mixed powder 1 was filled into a firing container (manufactured by Nikkato Corporation, SSA-T Saya 90-degree angle), placed in an electric furnace (manufactured by Motoyama Corporation, PCR), the atmosphere in the electric furnace was replaced with Ar, and the raw material mixed powder was fired. The firing program was set to raise the temperature from 0 °C to 1100 °C in 11 hours, hold at 1100 °C for 1 hour, and lower the temperature from 1100 °C to 0 °C in 11 hours. Ar gas was flowed at 5 L / min during the operation of the firing program. After firing, intermediate powder 1 was obtained.

[0145] <Step 2> Intermediate powder 1 was pulverized using a batch-type ready mill (manufactured by Aimex Co., Ltd., RM B-08). Using a 800 cm 3 vessel, pulverization was carried out under the conditions of 1348 rpm and a peripheral speed of 5 m / s. ZrO2 beads with a particle diameter of 0.5 mm were used, and ethanol 113 g, ZrO2 675 g, and intermediate powder 1 80 g were mixed at a ratio and pulverized for 60 minutes. After pulverization, powder A1 was obtained.

[0146] 50 g of powder A1, 200 g of pure water, 10 g of a 10 wt% aqueous solution of polyvinyl alcohol (manufactured by Fujifilm Wako Pure Chemical Corporation, PVA-3500), and polyethylene glycol (manufactured by Fujifilm Wako Pure Chemical Corporation, PEG-400) were mixed to obtain slurry B1.

[0147] Slurry B1 was spray-dried using a small spray dryer (manufactured by Yamato Scientific Co., Ltd.). Under the conditions of a pressure of 1.0 MPa, an outlet temperature of 85 °C, and an aspirator display value of 40, the output of the liquid feed pump was appropriately adjusted so that the outlet temperature was constant, and spray drying was performed. After spray drying, precursor powder 1 was obtained.

[0148] <Step 3> Precursor powder 1 was filled into a firing container (manufactured by AS ONE Corporation, firing boat No. 5), placed in a tubular furnace (manufactured by Motoyama Co., Ltd., DSPSH28), and the atmosphere in the tubular furnace was replaced with Ar to fire the precursor powder. The firing program was set to increase the temperature from 0 °C to 1150 °C over 11.5 hours, hold at 1150 °C for 1 hour, and decrease the temperature from 1150 °C to 0 °C over 11.5 hours. During the operation of the firing program, Ar gas was flowed at 100 mL / min. After firing, the particle group of Example 1 was obtained.

[0149] <Example 2> <Step 1> Raw material mixed powder 1 was prepared by the method described in Example 1.

[0150] The raw material mixed powder 1 was filled into a firing container (manufactured by Nikkato Corporation, SSA-T sheath 150 square), placed in an electric furnace (manufactured by NEMUS Co., Ltd., FD-40×40×60-1Z4-18TMP), and the atmosphere in the electric furnace was replaced with Ar to fire the raw material mixed powder. The firing program was set to increase the temperature from 0 °C to 1150 °C over 11.5 hours, hold at 1150 °C for 1 hour, and decrease the temperature from 1150 °C to 0 °C over 11.5 hours. During the operation of the firing program, Ar gas was flowed at 2 L / min. After firing, intermediate powder 2 was obtained.

[0151] <Step 2> Intermediate powder 2 was pulverized using a batch-type ready mill (manufactured by AIMEX Co., Ltd., RM B-08). Pulverization was performed under the conditions of using a 800 cm 3 vessel at 1348 rpm and a peripheral speed of 5 m / s. ZrO2 beads with a particle diameter of 0.5 mm were used, and ethanol 113 g, ZrO2 675 g, and intermediate powder 2 80 g were mixed at a ratio and pulverized for 60 minutes. After pulverization, powder A2 was obtained.

[0152] 50 g of powder A, 200 g of pure water, 10 g of a 10 wt% aqueous solution of polyvinyl alcohol (manufactured by Fujifilm Wako Pure Chemical Corporation, PVA-3500), and polyethylene glycol (manufactured by Fujifilm Wako Pure Chemical Corporation, PEG-400) were mixed to obtain slurry B2.

[0153] Slurry B2 was spray-dried by the method described in Example 1 to obtain precursor powder 2.

[0154] <Step 3> Precursor powder 2 was filled into a firing container (manufactured by AS ONE Corporation, firing boat No. 5), placed in a tubular furnace (manufactured by Motoyama Corporation, DSPSH28), and the atmosphere in the tubular furnace was replaced with Ar to fire the precursor powder. The firing program was set to raise the temperature from 0 °C to 1220 °C over 12.2 hours, hold at 1220 °C for 5 hours, and lower the temperature from 1220 °C to 0 °C over 12.2 hours. During the operation of the firing program, Ar gas was flowed at 100 mL / min. After firing, the particle group of Example 2 was obtained.

[0155] <Comparative Example 1> A raw material mixed powder was obtained by the method described in Example 1. 1000 g of the raw material mixed powder was filled into a firing container (manufactured by Nikkato Corporation, SSA-T sleeve 150 square), placed in an electric furnace (manufactured by Nemus Corporation, FD-40×40×60-1Z4-18TMP), and the atmosphere in the electric furnace was replaced with Ar to fire the raw material mixed powder. The firing program was set to raise the temperature from 0 °C to 1500 °C over 15 hours, hold at 1500 °C for 3 hours, and lower the temperature from 1500 °C to 0 °C over 15 hours. During the operation of the firing program, Ar gas was flowed at 2 L / min. After firing, powder C was obtained.

[0156] Put 1000 g of 2 mm φ zirconia balls and 161 g of powder C into a 1 L plastic polybottle (outer diameter 97.4 mm), place the 1 L polybottle on a ball mill stand, and perform ball mill pulverization at a rotation speed of 60 rpm for 4 hours to pulverize the intermediate powder. After pulverization, powder D was obtained. The pulverized powder was sieved through a 45 μm mesh sieve, and the powder passing through the sieve was used as the powder of Comparative Example 1.

[0157] <Comparative Example 2> Ti2O3 (manufactured by High Purity Chemical Laboratory Co., Ltd., <45 μm) was used as the powder of Comparative Example 2.

[0158] The results of each measurement of Examples 1 to 2 and Comparative Examples 1 to 2 obtained are summarized in Table 1.

Table 1

[0159] According to the particle group according to the example, the dimensional change rate in the solid composition could be lowered. That is, the particle group according to the example was a particle group excellent in thermal expansion control characteristics.

Explanation of Signs

[0160] 2…Crystal, 4…Particle, 6…Closed pore.

Claims

1. A particle group, wherein each particle contains a plurality of crystals, satisfies the following Requirement 1, and satisfies at least one of the following Requirements 2 and 3. The particle group, wherein the crystal is a metal oxide containing titanium. Requirement 1: |dA(T) / dT| is 10 ppm / °C or more at at least one temperature T1 in the range of -200°C to 1200°C. A is (the lattice constant of the a-axis (short axis) of the crystal) / (the lattice constant of the c-axis (long axis) of the crystal), and each lattice constant is obtained from the X-ray diffraction measurement of the particle group. Requirement 2: S ＢＥＴ / S ＰＳＤ is 4.0 to 20.

0. S ＢＥＴ is the specific surface area of the particle group obtained by the BET method. S ＰＳＤ is the specific surface area of the virtual particle group. The virtual particle group has the same particle size distribution based on volume of the particle group obtained by the laser diffraction scattering method and the same true density as the particle group, and each of the virtual particles has a spherical shape. Requirement 3: The porosity defined by the following formula is 2.0 to 20.0%. Porosity (%) = (1 - the apparent density of the particle group / the true density of the particle group) × 100

2. The particle group according to Claim 1, which satisfies all of the above Requirements 1 to 3.

3. The particle group according to Claim 1 or 2, wherein the diameter D50 at which the cumulative frequency is 50% in the volume-based particle size distribution curve of the particle group obtained by the laser diffraction scattering method is 1 to 100 μm.

4. The metal oxide containing titanium is TiO ｘ The particle group according to any one of claims 1 to 3, wherein (x = 1.30 to 1.66).

5. A composition containing the particle group according to any one of Claims 1 to 4.

6. The composition according to Claim 5, which has a powder form.

7. The composition according to Claim 5, further containing a matrix material.

8. The composition according to Claim 5, further containing an uncured curable resin.

9. A molded body of the particle group according to any one of Claims 1 to 4 or the composition according to Claim 5 or 6.

10. A method for producing the particle group according to any one of Claims 1 to 4, including Step 1 of firing a raw material to obtain an intermediate, Step 2 of pulverizing the intermediate to obtain a precursor, and Step 3 of firing the precursor, wherein the firing temperatures in Step 1 and Step 3 are 1000 to 1300°C.

11. The method according to Claim 10, further including a step of granulating the precursor by a spray drying method to obtain a granular precursor between Step 2 and Step 3.

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