JP4400718B2 - Method for producing single crystal ceramic particles - Google Patents

Description

  The present invention relates to a method for producing single crystal ceramic particles.

Conventionally, ceramic particles such as dielectric particles and magnetic ferrite particles have been used in many fields. For example, as dielectric particles, barium titanate, titanium oxide, and the like are excellent in dielectric properties, piezoelectricity, and pyroelectricity, and are used as materials for ceramic capacitors, filters, sensors, and the like.
When ceramic particles are used as a material for a ceramic capacitor, a material having a high dielectric constant and low loss is desired. When used as a magnetic ferrite material, it is desirable that the loss is small and the permeability is flat and extends to a high frequency range. These characteristics depend on the physical properties such as the shape, particle size, purity and reactivity of the ceramic particles. For example, if the ceramic particles are polycrystalline or amorphous particles, local abnormal grain growth or nonuniform composition tends to occur, leading to deterioration of magnetic characteristics and electrical characteristics. Therefore, the ceramic particles are preferably single-phase and single-crystal without crystal grain boundaries and impurities. In order to obtain more excellent characteristics, the ceramic particles are preferably a compound of two or more metals and oxygen.

  However, it is difficult to produce ceramic particles having excellent characteristics. For example, in the solid-phase reaction method, the mixed particles of metal oxide corresponding to the composition of the final product are fired in air or in an inert gas, thereby forming a metal oxide that is a compound of two or more metals and oxygen. Although a dielectric can be obtained, it is difficult to obtain single-phase particles. Further, in a liquid phase method such as a coprecipitation method, a precursor (primary particle) of a metal oxide such as a hydrate is produced from an aqueous solution of a metal salt or an organic solvent solution, and this precursor is used in the air or an inert gas. Baking in to obtain ceramic particles. However, it is difficult to obtain dielectric particles with excellent crystallinity, and since the bond of the metal oxide precursor is strong and finally obtained as a large lump, it is necessary to obtain dielectric particles after firing. Must be crushed. In the particles thus obtained, the shape of each particle is indefinite, the particle size distribution is wide, and there is a high possibility that impurities will be mixed.

  Thus, hydrothermal synthesis methods and gas phase reaction methods with improved particle shape and particle size distribution have been proposed, but it is difficult to produce them industrially efficiently in terms of productivity and cost. . Japanese Patent Application Laid-Open No. 7-33579 (Patent Document 1) discloses a method in which fine particles of oxide are formed by hydrolysis, coprecipitation method or the like in which a raw material is dissolved in a solution, and the fine particles are heat-treated to be crystallized and particles. A method of promoting single crystal growth and further dissolving and removing glass contained in the obtained product to obtain single crystal particles having a uniform particle size is disclosed. However, this method has complicated processes and is difficult to industrially mass-produce.

  JP-A-9-26396 (Patent Document 2) discloses a method of obtaining barium titanate in a single crystal by sintering barium titanate having an average particle size of 10 μm or less at a temperature lower than 1618 ° C. and 1200 ° C. or higher. It is disclosed. In this method, a single crystal barium titanate is formed at a temperature lower than the melting point of barium titanate to cause abnormal grain growth with a temperature gradient during sintering. However, in this method, the particle diameter of the obtained barium titanate is as large as about 500 μm, and fine particles are not obtained. Moreover, since the single crystal is obtained in a state of being contained in the polycrystal, a step of breaking the grain boundary portion by immersing the polycrystal in concentrated hydrochloric acid is required to take out the single crystal.

By the way, the ceramic particles may be used as a simple substance, but may be used as a composite material combined with a resin material. Ceramic particles used as a composite material are required to have dispersibility and filling properties with respect to a resin material. One factor for ensuring the dispersibility and filling properties of the resin material is the particle size of the particles.
However, the ceramic particles obtained by the above-described coprecipitation method have a too small particle size and cannot secure dispersibility and filling properties for the resin material. Further, since the ceramic particles obtained by the above-described solid phase reaction method are obtained by pulverization, the form of the particles becomes indefinite, and it is impossible to ensure dispersibility and filling properties for the resin material. Moreover, since the single crystal barium titanate described in Patent Document 2 has a large particle size, it is difficult to obtain high filling properties.

  In order to obtain spherical single crystal ceramic particles having excellent characteristics, the present inventors supplied a powder comprising a ceramic component together with a carrier gas to the heat treatment region, and the powder supply step was supplied to the heat treatment region. Proposed first a manufacturing method comprising a heat treatment step for heating the powder above the melting point of the powder, and a cooling step for obtaining single crystal ceramic particles by cooling the product obtained in the heat treatment step. (Japanese Patent Application No. 2002-160798).

JP-A-7-33579 JP-A-9-26396

The method proposed in Japanese Patent Application No. 2002-160798 is a suitable method for easily obtaining spherical single crystal ceramic particles excellent in dispersibility and filling properties in a resin material. However, according to the study by the present inventors, it was confirmed that the spherical particles obtained by the method may contain amorphous particles.
An object of the present invention is to provide a suitable method for easily obtaining spherical single crystal particles excellent in dispersibility and filling properties in a resin material while suppressing the generation of particles in an amorphous state. To do.

The feature of the method proposed in the above-mentioned Japanese Patent Application No. 2002-160798 is that the starting material powder is given thermal energy higher than the melting point in the heating region, and the crystallinity is once broken. Therefore, even if the raw material powder is an irregularly shaped lump of crushed particles or granules of fine particles agglomerated, a single (spherical) droplet is produced by melting it, and the surface tension It is explained that single-crystal ceramic particles recrystallized into a true sphere can be obtained by making the sphere into a sphere by being carried to the cooling region while keeping the sphere.
In Japanese Patent Application No. 2002-160798, if the heating temperature is lower than the melting point, for example, if it is an irregularly shaped lump of pulverized powder, it remains indefinite, and if it is a granulated form of fine particles, it passes through the heating region. Later, it is explained that ceramic particles in which hollow holes and particles are aggregated are formed.
However, according to studies by the present inventors, it was confirmed that single crystal particles can be obtained even when the heating temperature is lower than the melting point, depending on the properties of the starting raw material powder.
In the present invention, the raw material powder is supplied to the heat treatment region together with the carrier gas, and the raw material powder supplied to the heat treatment region is lower than the melting point of the ceramic to be finally produced and has a temperature of the melting point of −200 ° C. or higher. The heat treatment is performed, the product obtained by this heat treatment is cooled, the ceramic is any one of barium titanate, magnesium titanate and Ni-Cu-Zn ferrite, and the raw material powder is 700 to 1000 Single crystal ceramic particles characterized in that they are pulverized powders after being calcined by a solid phase reaction method in a temperature range of 0 ° C. and are in a highly active state because they have not completely advanced the sintering reaction It is a manufacturing method.

In the method for producing single crystal ceramic particles of the present invention, it is desirable to heat-treat the raw material powder while floating and cool the product.
In the method for producing single crystal ceramic particles of the present invention, the raw material powder can be composed of granules, or can be composed of particles that exist alone rather than as aggregates such as granules. When the raw material powder is a granule, the primary particles constituting the granule are solid-phase diffused by heat treatment in a floating state. Further, when the raw material powder is composed of single particles, the single particles are in contact with each other in a floating state, and the single particles are solid-phase diffused by heat treatment in the contacted state. Moreover, one single crystal particle is comprised from several particle | grains by this solid phase diffusion.

  According to the present invention, single crystal ceramic particles can be produced even at a heating temperature lower than the melting point. Moreover, amorphous spherical particles are not produced during this production process.

Embodiments of the present invention will be described below.
An example of the outline of the manufacturing process of single crystal ceramic particles according to the present invention will be described with reference to FIG. As shown in FIG. 1, the manufacturing method of this invention grind | pulverizes a raw material and obtains a primary particle. Next, granules are formed from the primary particles, and the granules are supplied to the heat treatment region. The product produced by heating to a predetermined temperature in the heat treatment region is cooled, and then the process proceeds to post-treatment. In addition, although the example which heat-processes the powder which consists of a granule here is shown, this invention is not limited to this.

  First, in the primary particle forming step, primary particles are formed from a raw material made of a ceramic component. In the primary particle forming step, the raw material composed of the ceramic component is pulverized and preferably adjusted so that the average particle size is 1 μm or less. This particle size not only affects the particle size of the finally obtained single crystal ceramic particles, but also makes the quality of the single crystal ceramic particles excellent by using primary particles of such particle size. be able to. Although the grinding method is not particularly limited, for example, a ball mill or the like can be used.

The ceramics component according to the present invention, there are dielectrics material, and a magnetic material, in particular, barium titanate, is selected from any one of magnesium titanate and Ni-Cu-Zn ferrite.

  As the primary particles constituting these ceramic components, commercially available ceramic fine particles, for example, metal oxide particles (particles obtained by a wet precipitation method, a spray pyrolysis method, a spray method, etc.) prepared from a metal salt are used. In addition, primary particles can be obtained by firing a composition or material for forming a ceramic component. Among these, by using the starting material in solution, the particle size distribution of the particles can be made sharper than the particles obtained through the pulverization step. For example, barium carbonate and titanium oxide are mixed to obtain granules, and the granules pulverized to an appropriate size are fired and reacted to obtain barium titanate as a ceramic component (primary particles). Can do.

As the primary particles, pulverized powder that has been calcined by a solid phase reaction method and then pulverized is used. However, the activity needs to be high. This is because solid phase diffusion is performed at a temperature lower than the melting point to obtain a single crystal. Here, high activity means a state in which the sintering reaction is not completely advanced in the case of pulverized powder that has been calcined and then pulverized. For example, when calcining two or more kinds of starting material particles, it is desirable to finish calcining at the lowest possible temperature within the temperature range in which a single phase appears. As this calcining temperature, 700-1000 degreeC is chosen for this invention.

  Next, a slurry for obtaining granules is prepared. The slurry can be obtained by adding an appropriate amount of primary particles to the solvent and then mixing using a mixer such as a ball mill. Water or ethanol can be used as the solvent, but it is recommended to add a dispersant in order to improve the dispersibility of the primary particles. The amount of the dispersant added is related to the particle size of the primary particles, but is about 1% with respect to the weight of the primary particles. A binder for mechanically binding the primary particles, for example, PVA (polyvinyl alcohol) can also be added. The obtained slurry is sprayed by a spray dryer to form droplets.

  Here, the spray nozzle as a spray dryer is for spraying the slurry and the compressed gas, and a two-fluid nozzle or a four-fluid nozzle can be used. Slurry discharged from the spray nozzle together with compressed gas (eg, air, nitrogen gas, etc.) is atomized to form a spray. The particle size of the droplets during spraying can be controlled by the ratio of slurry and compressed gas, and can also be controlled by the slurry concentration. By controlling the particle size of the droplets, the particle size of the finally obtained single crystal ceramic particles can be controlled. The spraying process using the spray nozzle is performed in a predetermined chamber. In addition, you may obtain a granule by the spray-drying method which served as drying under heating. When the spray drying method is used, huge particles such as pulverized powder are hardly mixed, so that the reliability of the quality of the finally obtained product can be ensured.

  When a spray nozzle is used in this way, granules having a small particle size suitable for use in the present invention can be obtained, and for example, fine granules of about 1 to 10 μm can be obtained. This particle size determines the particle size of the finally obtained single crystal ceramic particles. As described above, the particle diameter can be controlled by the ratio of the slurry and the compressed gas, can also be controlled by the slurry concentration, and small droplets can be produced by colliding the slurry.

  The above raw material powder is supplied to the heat treatment region together with the carrier gas. As a specific configuration for carrying out the powder supply process, FIG. 1 shows a mode in which carrier gas and granules are separately prepared and the granules are supplied to the heat treatment region together with the carrier gas via the nozzle N. . Various gases can be used as the carrier gas, and for example, gases such as oxygen, nitrogen, argon, ammonia and air can be used.

The method of supplying the powder composed of the ceramic component to the heat treatment region is not limited to the method described in FIG. For example, it is possible to employ a system in which a compressed gas containing a carrier gas is sprayed on a powder made of a ceramic component and supplied to the heat treatment region. It is also possible to feed particles obtained from the output side to the heat treatment region by supply using a disperser, supply using the output of a classifier or pulverizer, that is, classification or pulverization.
In the present embodiment, the spray of the powder composed of the ceramic component may be in a dry state or a wet state containing moisture or the like.

  Next, the supplied raw material powder, specifically, the granule is heated to a predetermined temperature to obtain single crystal ceramic particles. In the present invention, the heating temperature at this time is less than the melting point. Since the activity of the particles constituting the raw material powder is high, the particles undergo solid phase diffusion at temperatures below the melting point to produce single crystal particles. With the improvement of crystallinity due to the single crystallization, the dielectric characteristics can be improved for dielectric ceramics, and the magnetic characteristics can be improved for magnetic materials. At this time, when heat energy is applied, the surface energy is small and a stable sphere is formed. Further, since solidification is not performed from a molten state, the generated particles can be prevented from becoming amorphous.

  The heat treatment is realized in a heating furnace. As the heating method, known methods such as heating by electricity, heating by gas combustion heat, and high-frequency heating can be adopted. In particular, the electric tubular furnace is easier to control the atmosphere in the furnace than the method using combustion gas. The powder made of the ceramic component is single-crystallized and spheroidized in a state of floating in the heating furnace together with a carrier gas that generates an air flow in the furnace. The flow rate of the powder composed of the ceramic component is appropriately determined according to the particle size of the ceramic particles to be produced, the collection efficiency, and the heating temperature, but is generally in the range of 0.05 to 10 m / s, particularly 0.5 to It is desirable to select in the range of 5 m / s. The flow rate of the powder can be changed by controlling the flow rate of the carrier gas.

Heating conditions, particularly temperature and time, are appropriately determined depending on the ceramic composition. As the heating conditions, the atmosphere in the heating furnace may be an oxidizing atmosphere, a reducing atmosphere or an inert atmosphere depending on the type of single crystal ceramic particles that are the final product of interest, such as a dielectric material or a magnetic material. Selected. The carrier gas can be selected according to the selected atmosphere, or the necessary gas is supplied into the heating furnace.
The heating temperature is set to be lower than the melting point of the ceramic to be finally produced. Since the raw material powder having high activity is used, the present invention is characterized in that a single crystal can be obtained even at a heating temperature lower than the melting point. If the temperature of the heat treatment is too low, solid phase diffusion is not performed, and therefore, the melting point is −200 ° C. or higher, preferably the melting point −100 ° C. or higher. However, this temperature should be appropriately set depending on the composition of the raw material powder to be treated.
Although the present invention uses a solid phase diffusion reaction, the longer the heating time, the more advantageous it is for the solid phase diffusion reaction to proceed. Although it is influenced by the size of the raw material powder, a heating time of about 0.1 to 10 seconds may be employed if the particle size is intended by the present invention.

The particle size of the particles to be finally produced can be controlled by the size of the raw material powder and the heat treatment temperature. For example, when the raw material powder is barium titanate having an average particle diameter of 0.3 μm (melting point = 1610 ° C.), for example, if it is desired to produce particles having a diameter of 1 μm, heat treatment can be performed at a temperature of 1420 ° C. or higher. It is preferable to produce at a temperature of 1500 ° C. or higher. For example, when an alumina core tube having a length of 2 m and an inner diameter of 80 mm is heated and powder is dispersedly supplied and cooled to obtain single crystal particles of barium titanate, the average particle size to be obtained is 0.2 μm. If the heating temperature is 1420 ° C. or higher and lower than the melting point, 0.2 to 1 μm, 1500 ° C. or higher and lower than the melting point, and 1 μm or higher, the heating temperature is 1600 ° C. or higher and lower than the melting point. Is possible.
In addition, since the heating temperature is less than the melting point, there are particles having low sphericity, but compared to the method of cooling and producing after giving a temperature to completely melt, the particles obtained are amorphous. Avoid mixing particles. However, when a synthetic powder obtained by a solution method or the like is used as a starting material, since it contains a large amount of Iglos component, many pores are generated inside the powder. In order to remove the Igros component, it is effective to perform a de-culturing process that is heated to around 700 ° C. By using the raw material that has been subjected to this process, single crystal particles having no pores can be produced.
When single crystal particles are produced using raw materials obtained by the solution method, single crystal particles with a clean surface are produced compared to the case of using pulverized powder obtained from a calcined body by a solid phase reaction method. Tend to be. It is presumed that this is due to the high activity of the raw material obtained by the solution method.

In the case of producing single crystal particles using a pulverized powder obtained from a calcined body by a solid phase reaction method as a starting material, it is desirable to carry out a calcining temperature for producing a single phase at about 700 to 1000 ° C. If it is temperature at which a phase is obtained, it is more preferable to set it as a low temperature around 700 ° C. If thermal energy at a temperature higher than 1000 ° C. is applied, the activity of the particles decreases, atomic diffusion at a lower temperature becomes worse, and single crystal particles cannot be easily produced. When producing single crystal particles using pulverized powder by a solid phase reaction method as a starting material, the shape may be distorted even if single crystal particles are obtained.
As in the present embodiment, when the raw material powder in the solid phase is supplied to the heating furnace in a dry state, compared with the spray pyrolysis method in which the raw material powder in the solid phase is dispersed and supplied in the liquid Since the heat loss due to the presence of the liquid is eliminated, single crystal particles can be produced with less energy. In this case, for example, the produced granule can be directly supplied to the heating furnace of the heat treatment step together with the carrier gas without being once held and stored.

The product obtained by the heat treatment is cooled. Specifically, a cooling zone is provided in the heating furnace, or the product is cooled by being discharged into the atmosphere together with the carrier gas from the heating furnace. Although this cooling may be allowed to cool, it can also be forcibly cooled using a cooling medium. Through this cooling step, desired single crystal ceramic particles are obtained. By cooling the product relatively rapidly, the shape of the product sphere is maintained. Moreover, since the heated powder is cooled as it is in the cooling step, the obtained single crystal ceramic particles can be obtained with a particle size as small as about 0.1 to 10 μm. More preferably, about 0.5-5 μm can be obtained. The cooling rate can be 1 to 100 ° C./sec in the range from the heating temperature to −50 ° C., and 100 to 800 ° C./sec in the temperature range below it.
After the cooling step, for example, particles are collected by a cyclone or a bag filter, while the carrier gas is exhausted after an appropriate exhaust gas treatment is performed.

  The ceramic particles obtained as described above are single crystals and can be spherical. Here, the “spherical shape” includes a perfect spherical shape having a smooth surface and a polyhedron very close to a true sphere. Specifically, polyhedral particles having isotropic symmetry surrounded by a stable crystal plane as represented by the Wulff model and having a sphericity close to 1 are also included. Here, “sphericity” is Wadell's practical sphericity, that is, the ratio of the diameter of the smallest circle circumscribing the projected image of a particle having a circle diameter equal to the projected area of the particle. In the present embodiment, the sphericity is preferably 0.9 to 1, and more preferably 0.95 to 1. When the sphericity is 0.9 or more, when the single crystal ceramic particles are used as a composite material in which the single crystal ceramic particles are dispersed in the resin material, the single crystal ceramic particles are easily dispersed uniformly in the resin material and further pressed. It is difficult to generate cracks due to non-uniformity.

As described above, the single crystal ceramic particles obtained in the present embodiment have no crystal grain boundaries and impurities, are single phase and single crystal. Therefore, when used as a dielectric material or a magnetic material, the single crystal ceramic particles exhibit excellent characteristics that can contribute to improvement of magnetic or dielectric characteristics.
In addition, when the single crystal ceramic particles are formed by the method described in this embodiment, since no acid or organic solvent used in the conventional method is used, no harmful gas is generated, and relatively inexpensive equipment is used. Can be manufactured. Furthermore, in this invention, the raw material powder supplied to a heat processing area | region is not restricted to a granule, The particle | grains which exist independently are included, and the shape is not limited.

Furthermore, in the present embodiment, single crystal ceramic particles having a small particle size and a spherical shape can be obtained. Such single crystal ceramic particles have low cohesiveness and excellent dispersibility and filling properties. Therefore, the obtained single crystal ceramic particles can be mixed with a resin to form a composite material. At this time, it is preferable to contain single crystal ceramic particles in the range of 30 to 98 wt% in the composite material. As this resin, for example, both thermoplastic resin and thermosetting resin can be used. Specifically, epoxy resin, phenol resin, polyolefin resin, polyimide resin, polyester resin, polyphenylene oxide resin, melamine resin. , Cyanate ester resins, diallyl phthalate resins, polyvinyl benzyl ether compound resins, liquid crystal polymers, fluorine resins, polyvinyl butyral resins, polyvinyl alcohol resins, ethyl cellulose resins, nitrocellulose resins, resins containing at least one of acrylic resins, etc. Can be mentioned.
The above concept can also be applied when the single crystal ceramic particles are made of a magnetic material. That is, it is possible to obtain a composite magnetic material in which single crystal ceramic particles made of a magnetic material having a relatively high melting point are dispersed and held in a magnetic material having a relatively low melting point.

  In the present invention, the above composite material can be applied to various electronic components. One example is shown in FIGS. 2 and 3. FIG. 2 is a perspective view showing a high-frequency module which is an example of an electronic component. In this high-frequency module, a diode 6, a transistor 7 and a chip resistor 8 are mounted on the surface of the composite dielectric layer 5. In the high frequency module, the ground electrode 1 is disposed on the back surface and inside of the composite dielectric layer 5. Furthermore, the high-frequency module has a through-hole conductor 2 and a capacitor forming electrode 3 disposed therein. The composite dielectric material described above is applied to the composite dielectric layer 5. FIG. 3 is a perspective view showing a chip coil which is an example of an electronic component. In this chip coil, a coil forming conductor 13 and a through-hole conductor 12 are disposed inside a composite magnetic layer 14. Furthermore, this chip coil has an external terminal electrode 11 formed on the side surface of the composite magnetic layer 14. The composite magnetic material described above is applied to the composite magnetic layer 14. In addition, the above is an illustration of an electronic component to the last, and it cannot be overemphasized that the composite magnetic material of this invention is applicable to other electronic components, such as a board | substrate.

Hereinafter, the present invention will be described based on more specific examples.
<First embodiment>
As a starting material, commercially available high-purity barium carbonate (manufactured by Nippon Chemical Industry Co., Ltd. F03: purity 99.9, average particle size 0.3 μm) and high-purity titanium oxide (Toho Titanium Co., Ltd. HT2301, average particle size) The diameter was 0.2 μm) so that the molar ratio was 1: 1, and pure water was added to obtain a slurry. This slurry was mixed in a ball mill for 12 hours. The mixed particles obtained by drying the slurry were calcined at 1000 ° C. for 2 hours and then pulverized for 5 hours and 24 hours using a ball mill. The particles obtained by the pulverization treatment for 5 hours have an average particle size of 0.6 μm (particle size distribution is 0.2 to 1.5 μm), and the particles obtained by the pulverization treatment for 24 hours have an average particle size of 0.3 μm ( The particle size distribution is 0.1 to 1 μm).

  The above particles and a surface treatment agent (TSL8113: GE Toshiba Silicone Co., Ltd., 2 wt%) were charged into a mixing / dispersing machine, mixed, and dispersed to subject the particles to surface treatment to obtain a raw material powder. The raw material powder was supplied to the heating furnace with a carrier gas (oxygen gas, flow rate of 4 l / min) while being dispersed by a disperser in the supply device using a supply device. As the heating furnace, an alumina furnace tube having an inner diameter of 55 mm was used, and the heating temperatures in the furnace were three types of 1400 ° C., 1500 ° C. and 1600 ° C. (only particles having an average particle size of 0.3 μm).

Particles obtained by heat-treating raw material powder having an average particle size of 0.3 μm at 1400 ° C. were observed by SEM (scanning electron microscope), and most of them formed polycrystalline aggregates without being single-crystallized. It was confirmed.
The upper limit of the particle size distribution of the heat-treated particles is 5 μm, whereas the particle size distribution of the raw material powder is 0.1 to 1 μm. This is because solid phase diffusion was performed to form one new particle.
When the raw material powder having an average particle size of 0.3 μm is heat-treated at 1500 ° C., the particle size distribution of the particles is 0.1 to 5 μm. Among these, spherical particles having a particle diameter of 0.1 to 1 μm were confirmed to be single crystals by SEM observation similar to the above. Further, the sphericity of the particles was 0.95.
When the raw material powder having an average particle size of 0.3 μm is heat-treated at 1600 ° C., the particle size distribution of the particles is 0.1 to 5 μm. Among these, the spherical particles having a particle diameter of 0.1 to 2 μm were confirmed to be single crystals by SEM observation similar to the above. Further, the sphericity of the particles was 0.98.

  Particles were obtained in the same manner as the heat treatment at 1500 ° C., except that the calcining temperature was 1200 ° C. The particle diameter is 0.1 to 5 μm. By SEM observation, it was confirmed that the particles of about 1 μm remained in the form of pulverized powder and formed into a polycrystalline aggregate without being largely crystallized. Thus, when the calcining temperature is as high as 1200 ° C. and the activity of the starting material is deteriorated, single crystal particles cannot be obtained at a heating temperature lower than the melting point.

  FIG. 4 is a graph showing analysis results of TG-DTA (differential heat / thermogravimetric measurement device) of the pulverized powder after calcining at 1000 ° C. and the pulverized powder calcined at 1200 ° C. As shown in FIG. 4, Tf1 <Tf2, Ts1 <Ts2, and the one calcined at 1000 ° C. starts reaction at a lower temperature than the one calcined at 1200 ° C. and has a higher activity. Recognize. Tf1 is the endothermic peak of the pulverized powder after calcining at 1000 ° C., and Tf2 is the endothermic peak of the pulverized powder after calcining at 1200 ° C. Ts1 is an exothermic peak of the pulverized powder after calcining at 1000 ° C., and Ts2 is an exothermic peak of the pulverized powder after calcining at 1200 ° C.

FIG. 5 shows an SEM image of particles obtained by heat treatment at 1500 ° C., and FIG. 6 shows an SEM image of particles obtained by heat treatment at 1600 ° C. FIG. 7 is a chart showing X-ray diffraction results of particles obtained by heat treatment at 1500 ° C. and 1600 ° C. Only the tetragonal BaTiO ₃ peak is observed. 8 shows a TEM (transmission electron microscope) image and an electron diffraction image of the particles obtained by heat treatment at 1500 ° C., and FIG. 9 shows a TEM (transmission type) of the particles obtained by heat treatment at 1600 ° C. An electron microscope image and an electron diffraction image are shown. 5 to 9, it was confirmed that spherical and single crystal particles made of BaTiO ₃ were produced. The melting point of BaTiO ₃ is 1610 ° C. as described above.

  It was confirmed by SEM observation that the raw material powder having an average particle size of 0.6 μm was heat-treated at 1400 ° C. and 1500 ° C. and formed a polycrystalline aggregate without being single-crystallized. .

<First Reference Example>
Mixing and dispersing barium titanate (BT05 manufactured by Sakai Chemical Industry Co., Ltd., average particle size 0.5 μm) and surface treatment agent (TSL8113: GE Toshiba Silicone Co., Ltd., 2 wt%) produced by hydrothermal synthesis method The particles were subjected to surface treatment by being put into a machine and mixed and dispersed to obtain a raw material powder. The raw material powder was supplied to the heating furnace with a carrier gas (oxygen gas, flow rate of 4 l / min) while being dispersed by a disperser in the supply device using a supply device. As the heating furnace, an alumina furnace tube having an inner diameter of 55 mm was used, and the heating temperatures in the furnace were two types of 1500 and 1600 ° C.

The produced particles and the carrier gas were separated by passing the particles passing through the furnace and the carrier gas through a bag filter, and the produced particles were collected.
When the particle size of the particles collected in the heat treatment at 1500 ° C. and the heat treatment at 1600 ° C. was measured, both the heat treated at 1500 ° C. and 1600 ° C. had a particle size distribution of 0.5 to 5 μm. . By SEM observation, it was confirmed that most of the collected particles were single crystal particles. The single crystal particles are faceted, and those having a heat treatment of 1500 ° C. are spherical particles having a particle size of about 0.5 to 1 μm and those having a heat treatment of 1600 ° C. are about 0.5 to 2 μm. The sphericity of the particles was 0.95 and 0.97, respectively.
Among the collected particles, there are some polycrystalline particles having a particle size larger than that of the single crystal particles. The reason why such a large particle size is produced is considered to be that the raw material powder is carried to the heat treatment region by the carrier gas while the dispersion state of the raw material powder is insufficient. In addition, particles that appeared to be amorphous particles were not observed in the produced spherical single crystal particles. This is probably because the heating temperature for particle preparation is lower than the melting point, and the mechanism for forming single crystal particles is different from the method of preparing single crystal particles above the melting point.

The difference between the particles obtained by the heat treatment at 1500 ° C. and the particles obtained by the heat treatment at 1600 ° C. is that the single crystal particles obtained by the heat treatment at 1600 ° C. have a particle size of 1500 ° C. It is larger than the obtained single crystal particle. It is understood that the difference in particle size of the single crystal particles is due to the heating temperature. That is, even if the raw material powder is the same, the particle diameter of the single crystal particles obtained can be controlled by controlling the heating temperature.
As shown in FIG. 10, since the peak of tetragonal barium titanate was observed by X-ray diffraction for the particles obtained by the heat treatment at 1500 ° C., the TEM of particles having a particle size of 1 μm and a particle size of 2 μm ( Transmission electron microscope) observation was performed. From the electron beam transmission diffraction results, it was confirmed that these particles consisted of tetragonal barium titanate single crystals.

< Second Reference Example>
Barium titanate (BT01 manufactured by Sakai Chemical Industry Co., Ltd., average particle size 0.1 μm) and surface treatment agent (TSL8113: GE Toshiba Silicone Co., Ltd., 2 wt%) prepared by hydrothermal synthesis method are mixed and dispersed. The particles were subjected to surface treatment by being put into a machine and mixed and dispersed to obtain a raw material powder. The raw material powder was supplied to the heating furnace with a carrier gas (oxygen gas, flow rate of 4 l / min) while being dispersed by a disperser in the supply device using a supply device. The heating furnace was the same as in Example 1, and the heating temperature was set to 1420 ° C.

The repaired particles had a particle size distribution of 0.1 to 3 μm. By SEM observation, it was confirmed that the repaired particles were single crystal particles, and the particle size of the single crystal particles was 0.3 μm or less. Further, the sphericity of the particles was 0.97.
TEM observation was performed on the obtained single crystal particles having a particle size of 0.1 μm and a particle size of 0.3 μm. From the results of electron beam transmission diffraction, these particles were composed of tetragonal barium titanate single crystals. It was confirmed that

< Third reference example>
Mixing and dispersing barium titanate (BT03 manufactured by Sakai Chemical Industry Co., Ltd., average particle size 0.3 μm) and surface treatment agent (TSL8113: GE Toshiba Silicone Co., Ltd., 2 wt%) produced by hydrothermal synthesis method The particles were subjected to surface treatment by being put into a machine and mixed and dispersed to obtain a raw material powder. The raw material powder was supplied to the heating furnace with a carrier gas (oxygen gas, flow rate 4 l / min) while being dispersed with a disperser in the supply device using a supply device. The heating furnace was the same as in Example 1, and the heating temperature was set to two types of 1400 ° C. and 1420 ° C.
The particles heat-treated at 1420 ° C. had a particle size distribution of 0.1 to 3 μm. SEM observation confirmed that the particles having a particle size of 0.1 to 0.5 μm were single crystal particles. Further, the sphericity of the particles was 0.97.
On the other hand, some of the particles heat-treated at 1400 ° C. having a particle size of 0.1 to 0.5 μm were observed to be single crystals, but most were polycrystalline aggregates. .

< Fourth Reference Example>
Using barium titanate produced by hydrothermal synthesis (BT01, Sakai Chemical Industry Co., Ltd., average particle size 0.1 μm) as a starting material, granules having an average particle size of 0.7 μm are prepared by the following method. did.
With respect to the powder made of barium titanate, the dispersant (A-30SL: Toagosei Co., Ltd.) is 10.0 wt% with respect to the total weight of the powder, and polyvinyl alcohol as a binder is based on the total weight of the powder. On the other hand, 0.5 wt% was added, and water was added so that the concentration of the powder became 50.0 wt%, and then stirred for 12 hours with a ball mill (using zirconia balls) to prepare a water-dispersed slurry.

Granules were prepared using the slurry obtained as described above as a raw material and using a spray dryer (Fujisaki Electric Co., Ltd .: MDL-050). Specifically, slurry is introduced into the spray dryer by a liquid feed pump. This slurry is sprayed into the spray dryer from the following four fluid nozzles at the following gas flow rate. The inside of the spray dryer is maintained at 200 ° C., and dried granules can be obtained.
Spray nozzle: 4-fluid nozzle (Fujisaki Electric Co., Ltd .: SF4003)
Gas (air) flow rate: 80 l / min
Liquid feed pump speed: 50 ml / min
Spray dryer internal temperature: 200 ° C

The granule obtained as described above was used as a raw material powder, and was supplied to a heating furnace with a carrier gas (oxygen gas, flow rate 4 l / min) while being dispersed with a disperser in the supply device. The heating furnace was the same as in Example 1, and the heating temperatures were two types of 1400 ° C and 1500 ° C.
It was confirmed by SEM observation that most of the particles heat-treated at 1400 ° C. were polycrystalline aggregates without being single-crystallized. The particles heat-treated at 1500 ° C. had a particle size distribution of 0.5 to 3 μm. Spherical particles having a particle size of 0.5 to 1.2 μm were confirmed to be single crystal particles by SEM observation similar to the above.

< Second embodiment>
As a starting material, commercially available high purity magnesium oxide (MH-V05P manufactured by Ube Materials Co., Ltd., average particle size 0.3 μm) and high purity titanium oxide (HT2301, manufactured by Toho Titanium Co., Ltd.), average particle size 0 . the 2.mu. m) and, so as to constitute a stoichiometric magnesium titanate, were weighed in one-to-one mol ratio. Further, manganese carbonate (C2-SP manufactured by Chuo Denki Kogyo Co., Ltd., average particle size: 0.5 μm) was weighed so as to be 0.5 mol% with respect to the magnesium titanate, and pure water was added in the same weight as the powder. Thus, a slurry having a solid content of 50 wt% was obtained. These starting materials are all prepared by a solid phase method. This slurry was mixed in a ball mill for 12 hours. The mixed particles obtained by drying the slurry were calcined at 1000 ° C. for 5 hours, and then pulverized again using a ball mill for 24 hours to produce particles having an average particle size of 0.4 μm (particle size distribution is 0.2 to 0.2). 1 μm).

  The above particles and a surface treatment agent (TSL8113: GE Toshiba Silicone Co., Ltd., 2 wt%) were charged into a mixing / dispersing machine, mixed and dispersed, whereby the particles were subjected to a surface treatment to obtain a raw material powder. The raw material powder was supplied to the heating furnace with a carrier gas (oxygen gas, flow rate 4 l / min) while being dispersed by a disperser in the supply device using a supply device. As the heating furnace, an alumina furnace core tube having an inner diameter of 55 mm was used, and the temperature in the furnace was set to two types of 1600 ° C. and 1640 ° C.

When the particles heat-treated at 1600 ° C. were observed with an SEM, the upper limit of the particle size distribution was 7 μm. Single crystal particles were observed in particles less than 1 μm. In addition, a polycrystal composed of a plurality of grains was observed in the particles of 1 μm or more.
Moreover, the particle | grains heat-processed at 1640 degreeC were observed with SEM. One example is shown in FIG. 11. Single crystal particles were observed in particles of 3 μm or less. The sphericity of this single crystal particle was 0.95. The single crystal particles are composed of magnesium titanate (melting point: 1650 ° C.) because magnesium oxide and titanium oxide are used as the raw material powder.

< Fifth Reference Example>
Magnesium titanate having a particle size of 100 nm or less was prepared by an alkoxide method, and a starting material having an average particle size of 0.3 μm (particle size distribution of 0.1 to 1 μm) was prepared by a firing and pulverization process. The starting material and the surface treatment agent (TSL8113: GE Toshiba Silicone Co., Ltd., 2 wt%) were charged into a mixing / dispersing machine, mixed, and dispersed, whereby the particles were surface treated to obtain a raw material powder. The raw material powder was supplied to the heating furnace with a carrier gas (oxygen gas, flow rate 4 l / min) while being dispersed by a disperser in the supply device using a supply device. As the heating furnace, an alumina furnace core tube having an inner diameter of 55 mm was used, and the temperature in the furnace was set to two types of 1600 ° C. and 1640 ° C.

When the particles heat-treated at 1600 ° C. were observed with an SEM, the upper limit of the particle size distribution was 8 μm. Single crystal particles were observed in particles less than 2 μm. In addition, a polycrystalline body composed of a plurality of grains was observed in the particles of 2 μm or more.
An SEM image of the particles heat-treated at 1640 ° C. is shown in FIG. FIG. 13 shows an X-ray diffraction chart performed on particles of 6 μm or less, and FIG. 14 shows a TEM (transmission electron microscope) image and an electron diffraction image. From the above results, it was confirmed that this particle was a single crystal composed of tetragonal magnesium titanate. Further, the sphericity of this single crystal particle was 0.97.

< Third embodiment>
As a starting material, commercially available high-purity iron oxide (FRO-6, Sakai Chemical Industry Co., Ltd., average particle size 0.06 μm), high-purity nickel oxide (Morimura Corporation, average particle size 2 μm) and High purity zinc oxide (Honjo Chemical Co., Ltd., average particle size 0.4 μm), high purity copper oxide (Furukawa Machine Metal Co., Ltd., average particle size 0.8 μm) in a molar ratio of 50: 25: 15: 10 Then, pure water was added to obtain a slurry with a solid content of 50 wt%. This slurry was mixed in a ball mill for 12 hours. The mixed particles obtained by drying the slurry were calcined at 800 ° C. for 4 hours and then pulverized again using a ball mill for 24 hours to obtain particles having an average particle size of 0.5 μm (particle size distribution is 0.2 to 1.5 μm). ) Was produced.
A surface treatment agent (TSL8113: GE Toshiba Silicone Co., Ltd., 2 wt%) was added to a mixing / dispersing machine to mix and disperse the above particles, whereby the particles were surface-treated to obtain a raw material powder. The raw material powder was supplied to the heating furnace with a carrier gas (oxygen gas, flow rate 4 l / min) while being dispersed by a disperser in the supply device using a supply device. As the heating furnace, an alumina furnace core tube having an inner diameter of 55 mm was used, and the furnace temperature was set to two types of 1350 ° C. and 1550 ° C.

  When the particles heat-treated at 1350 ° C. were observed with an SEM, they remained almost unmelted. An SEM image of the particles heat-treated at 1550 ° C. is shown in FIG. 15, and spherical particles with facets were observed. FIG. 16 shows an X-ray diffraction chart performed on particles of 5 μm or less. From the above results, it was confirmed that the particles were single crystal particles made of Ni—Cu—Zn ferrite. Further, the sphericity of this single crystal particle was 0.94. Note that the melting point of Ni—Cu—Zn ferrite is about 1600 ° C.

It is a figure which shows the manufacturing process outline of the single-crystal ceramic particle in this Embodiment. It is a see-through | perspective perspective view which shows the high frequency module to which the single crystal ceramic particle obtained by this invention is applied. It is a see-through | perspective perspective view which shows the chip coil to which the single crystal ceramic particle obtained by this invention is applied. In 1st Example, it is a graph which shows the analysis result of TG-DTA of the ground powder after calcining at 1000 degreeC, and the ground powder calcined at 1200 degreeC. In 1st Example, it is a photograph which shows the SEM image of the particle | grains obtained by heat-processing at 1500 degreeC. In 1st Example, it is a photograph which shows the SEM image of the particle | grains obtained by heat-processing at 1600 degreeC. In 1st Example, it is a chart which shows the X-ray-diffraction result of the particle | grains obtained by heat-processing at 1500 degreeC and 1600 degreeC. In 1st Example, it is a photograph which shows the TEM image and electron diffraction image of the particle | grains obtained by heat-processing at 1500 degreeC. In 1st Example, it is a photograph which shows the TEM image and electron diffraction image of the particle | grains which were heat-processed at 1600 degreeC. It is a chart which shows the X-ray-diffraction result of the particle | grains obtained by heat-processing at 1500 degreeC in a 1st reference example. In 2nd Example, it is a photograph which shows the SEM image of the particle | grains obtained by heat-processing at 1640 degreeC. In a 5th reference example, it is a photograph which shows the SEM image of the particle | grains obtained by heat-processing at 1640 degreeC. In a 5th reference example, it is a chart which shows the X-ray diffraction result of the particle obtained by heat-processing at 1640 ° C. In a 5th reference example, it is a photograph which shows the TEM image and electron diffraction image of the particle | grains which were heat-processed at 1640 degreeC. In 3rd Example, it is a photograph which shows the SEM image of the particle | grains obtained by heat-processing at 1550 degreeC. In 3rd Example, it is a chart which shows the X-ray-diffraction result of the particle | grains obtained by heat-processing at 1550 degreeC.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Ground electrode, 2 ... Through-hole conductor, 3 ... Capacitor formation electrode, 5 ... Composite dielectric layer, 6 ... Diode, 7 ... Transistor, 8 ... Chip resistance, 11 ... External terminal electrode, 12 ... Through-hole conductor, 13 ... Coil-forming conductor, 14 ... Composite magnetic layer

Claims (5)

Supply raw material powder with carrier gas to heat treatment area,
The raw material powder supplied to the heat treatment region is subjected to heat treatment at a temperature lower than the melting point of the ceramic to be finally produced and the melting point of −200 ° C. or higher.
Cooling the product obtained by the heat treatment ,
The ceramic is any one of barium titanate, magnesium titanate and Ni-Cu-Zn ferrite,
The raw material powder is a pulverized powder pulverized after being calcined by a solid-phase reaction method in a temperature range of 700 to 1000 ° C., and is in a state of high activity because the sintering reaction is not completely advanced. A method for producing single crystal ceramic particles.   The method for producing single crystal ceramic particles according to claim 1, wherein the heat treatment is performed while the raw material powder is suspended, and the product is cooled.   The method for producing single crystal ceramic particles according to claim 1 or 2, wherein the raw material powder is composed of granules or particles existing alone.   4. The method for producing single crystal ceramic particles according to claim 3, wherein in the suspended state, primary particles constituting the granules are solid-phase diffused by the heat treatment. 5.   The single-crystal ceramic particles according to claim 3, wherein the single particles are in contact with each other in a floating state, and the single particles are solid-phase diffused by the heat treatment in the contact state. Method.

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