JP6236706B2 - Manufacturing method of ceramic capacitor containing fine metal particles - Google Patents

Description

  The present invention relates to a method for manufacturing a ceramic capacitor in which fine metal particles are dispersed in a dielectric layer.

  With the downsizing and high functionality of electronic devices, development of compact and high capacity capacitors such as multilayer ceramic capacitors is underway. Ceramic capacitors are excellent in output density because no chemical reaction is involved in the energy accumulation process. On the other hand, if the energy density that can be stored is small and a large-capacity ceramic capacitor is developed, it can be applied not only to electronic parts but also to energy storage devices.

  Since the energy stored in the capacitor is determined by the capacitance and voltage, the energy that can be stored in the capacitor increases when a capacitor having a larger capacity is manufactured. In general, the capacitance C of a capacitor is expressed by the following Equation 1.

Here, ε _r is the dielectric constant of the dielectric, ε ₀ is the dielectric constant in vacuum, A is the electrode area, and d is the distance between the electrodes. Therefore, in order to greatly improve the capacitance, it is necessary to increase the relative dielectric constant of the material, increase the electrode area, and decrease the distance between the electrodes.

  For example, in a multilayer ceramic capacitor, an internal electrode called an interdigitated electrode is inserted into a dielectric layer to increase the net electrode area and decrease the net interelectrode distance to exceed several hundred nF. A large capacitance is realized.

  As a material for realizing a large capacity, a conductor / insulator composite material is a promising candidate because of its excellent dielectric properties. Specifically, a composite material group of a combination of metal / dielectric, metal / polymer, semiconductor / dielectric, carbon / dielectric, carbon / polymer, etc. has been studied and its dielectric properties have been reported.

Various microstructures have been devised for conductor / insulator composite capacitors. For example, as shown in the multilayer ceramic capacitor shown in FIG. 1, a structure in which sheet-like metal layers and insulator layers are alternately stacked, The surface layer type structure in which the surface layer of the semiconductor ceramic shown in FIG. 2 is insulated, the grain boundary layer type structure in which the insulating layer is formed at the crystal grain boundary of the semiconductor ceramic particles as seen in the grain boundary capacitor shown in FIG. Examples include a structure in which conductor particles found in many composite materials shown in FIG. 4 are dispersed in an insulator layer.

  In a metal / dielectric composite capacitor, a structure in which sheets made of a paste containing metal foil or fine metal particles shown in FIG. 5 and dielectric layers are alternately laminated, a dielectric on the surface of the metal foil or metal plate shown in FIG. A structure in which a body layer is formed and a structure in which fine metal particles shown in FIG. 7 are dispersed in a dielectric layer have been reported.

  In any of the composite capacitors enumerated so far, conductors or conductors and electrodes are present with a very thin insulator layer interposed therebetween, so that a minute capacitor is formed inside the structure. As described above, the conductor in the structure acts as an internal electrode, the net electrode area is increased, and the net distance between the internal electrodes is decreased, so that the capacitance indicated by the composite capacitor is increased.

  Based on the above, in order to realize a large capacity using a composite capacitor, a structure in which fine metal particles as shown in FIG. 7 are dispersed in a dielectric layer at a high concentration is suitable.

  The characteristics of a composite capacitor having a structure in which conductor particles are dispersed in a dielectric layer as shown in FIG. 4 or 7 will be described below. These composite materials are insulators when the concentration of the conductor is low, but when the concentration of the conductor is increased, the metal-insulator transition occurs when the concentration exceeds the certain concentration. This density is called the percolation threshold. As the metal concentration in the material increases, the capacitance tends to increase. In particular, a significant increase in capacitance is observed at a concentration near the percolation threshold.

  This phenomenon is understood by the percolation theory as follows. In the vicinity of the percolation threshold, conductor clusters existing in the composite capacitor are close to each other, and when an electric field is applied thereto, charges are accumulated across a very thin insulator layer. At this time, minute capacitors are formed everywhere in the composite capacitor, and these capacitors are three-dimensionally connected, so that the capacitance increases.

  Non-Patent Document 1 describes an example of a ceramic capacitor having a structure in which fine metal particles are dispersed in a dielectric layer at a high concentration. In Non-Patent Document 1, a nickel / barium titanate composite material is obtained by mixing nickel particles and barium titanate and sintering them at 1300 ° C. in an argon atmosphere.

  In Non-Patent Document 2, electrolysis is performed using a titanium foil as an anode under hydrothermal conditions to generate barium titanate on the surface of the titanium foil, and a titanium / barium titanate composite is produced at a low temperature of 100 ° C. ing.

C. Pecharroman, et al., Adv. Mater., 13 (2001) 1541-1544. R. Bacsa, et al., J. Mater. Res., 7 (1992) 423-428.

  However, the nickel / barium titanate composite ceramic capacitor described in Non-Patent Document 1 requires heat treatment at a high temperature, and flows a reducing gas such as argon during the heat treatment in order to suppress oxidation of fine metal particles. Since the metal is not oxidized by heat treatment at a high temperature, there is a problem that the types of metal that can be used are significantly limited.

  Regarding Non-Patent Document 2, although it is a mild solution process, a special apparatus system is required to apply voltage under hydrothermal conditions, and the structure of the metal layer is limited to a two-dimensional structure such as a foil or a plate. In addition, in such a structure, there is a problem in that the capacitance is limited because the electrode area of the internal electrode is reduced.

  The method for producing a ceramic capacitor containing fine metal particles according to the present invention mixes fine particles containing metal and a first dielectric precursor, or contains fine particles containing metal and a first dielectric precursor and the first dielectric precursor. 2, a step of molding the mixed mixture into a pellet, a solvothermal treatment of the molded pellet, and the precursor of the first dielectric is used as the first dielectric. And a step of changing.

  According to the present invention, a ceramic capacitor having a structure in which fine metal particles are dispersed at a high concentration in a dielectric layer can be produced at a low temperature, and since there is no need for a heat treatment at a high temperature, there are few restrictions on the metal that can be used, In addition, since it is not necessary to use a reducing gas, the manufacturing apparatus can be simplified in structure and the cost can be reduced.

These are sectional drawings of the multilayer ceramic capacitor by a prior art. These are sectional drawings of the ceramic capacitor by the semiconductor ceramic which insulated the surface by the prior art. These are sectional drawings of the grain boundary capacitor by a prior art. These are sectional drawings of the capacitor | condenser by which the conductor particle by the prior art was disperse | distributed to the insulator layer. These are sectional drawings of the multilayer ceramic capacitor using the sheet | seat which produced the internal electrode by the prior art from the paste containing metal foil or a fine metal particle. These are sectional drawings of the ceramic capacitor which formed the dielectric material layer in the metal foil or metal plate surface by a prior art. FIG. 3 is a cross-sectional view of a capacitor in which fine metal particles according to the prior art are dispersed in a dielectric layer. These are the figures for demonstrating embodiment of the manufacturing method of the fine metal particle containing ceramic capacitor by this invention, and are schematic diagrams at the time of using a fine metal particle. These are the figures for demonstrating embodiment of the manufacturing method of the fine metal particle containing ceramic capacitor by this invention, and are schematic diagrams at the time of using a core-shell particle. These are the schematic diagrams of the manufacturing method of the fine metal particle containing ceramic capacitor by Example 1 of this invention. These are figures which show the manufacture flow of the manufacturing method of the fine metal particle containing ceramic capacitor by Example 1 of this invention. These are the SEM images of the composite structure of the metal and dielectric material manufactured by the manufacturing method of the fine metal particle containing ceramic capacitor by Example 1 of this invention. These are figures which show the XRD measurement result of the composite structure of the metal and dielectric material manufactured with the manufacturing method of the fine metal particle containing ceramic capacitor by Example 1 of this invention. These are figures which show the reaction scheme of the manufacturing method of the fine metal particle containing ceramic capacitor by Example 1 of this invention. These are figures which show the dielectric property of the capacitor manufactured by the manufacturing method of the fine metal particle containing ceramic capacitor by Example 1 of this invention, (a) shows frequency dependence, (b) shows titanium mixing ratio dependence. FIG. These are figures which show the core-shell particle | grains used for the manufacturing method of the fine metal particle containing ceramic capacitor by Example 2 of this invention. These are figures which show the XRD measurement result of the core-shell particle | grains used for the manufacturing method of the fine metal particle containing ceramic capacitor by Example 2 of this invention. These are the surface SEM images of the core-shell particles used for the manufacturing method of the fine metal particle containing ceramic capacitor by Example 2 of this invention. These are schematic diagrams of a method for producing a ceramic capacitor containing fine metal particles according to Example 2 of the present invention. These are figures which show the manufacture flow of the manufacturing method of the fine metal particle containing ceramic capacitor by Example 2 of this invention. These are the SEM images of the composite structure of the metal and dielectric material manufactured by the manufacturing method of the fine metal particle containing ceramic capacitor by Example 2 of this invention. These are figures which show the XRD measurement result of the composite structure of the metal and dielectric material manufactured with the manufacturing method of the fine metal particle containing ceramic capacitor by Example 2 of this invention. Is a composite structure of metal and dielectric produced by the method for producing a ceramic capacitor containing fine metal particles according to Example 2 of the present invention, titanium oxide contained in the mixed powder pellets and barium hydroxide contained in the reaction solution. It is a figure which shows the relationship between molar ratio and relative mass. These are figures which show the reaction scheme of the manufacturing method of the fine metal particle containing ceramic capacitor by Example 2 of this invention. These are figures which show the frequency dependence of the dielectric property of the capacitor manufactured with the manufacturing method of the fine metal particle containing ceramic capacitor by Example 2 of this invention. These are figures which show the frequency dependence of the impedance of the capacitor manufactured with the manufacturing method of the fine metal particle containing ceramic capacitor by Example 2 of this invention. FIG. 5 is a graph showing the relationship between the dielectric properties of a capacitor produced by the method for producing a ceramic capacitor containing fine metal particles according to Example 2 of the present invention and the core-shell particle mixing ratio. These are schematic diagrams of a method for producing a ceramic capacitor containing fine metal particles according to Example 3 of the present invention. These are figures which show the manufacture flow of the manufacturing method of the fine metal particle containing ceramic capacitor by Example 3 of this invention. These are the SEM images of the composite structure of the metal and dielectric material manufactured by the manufacturing method of the fine metal particle containing ceramic capacitor by Example 3 of this invention. These are figures which show the XRD measurement result of the composite structure of the metal and dielectric material which were manufactured with the manufacturing method of the fine metal particle containing ceramic capacitor by Example 3 of this invention. These are figures which show the reaction scheme of the manufacturing method of the fine metal particle containing ceramic capacitor by Example 3 of this invention. These are figures which show the frequency dependence of the dielectric property of the capacitor manufactured by the manufacturing method of the fine metal particle containing ceramic capacitor by Example 3 of this invention. These are figures which show the frequency dependence of the impedance of the capacitor manufactured by the manufacturing method of the fine metal particle containing ceramic capacitor by Example 3 of this invention. FIG. 5 is a graph showing the relationship between the dielectric properties of a capacitor produced by the method for producing a ceramic capacitor containing fine metal particles according to Example 3 of the present invention and the core-shell particle mixing ratio. These are schematic views of a method for producing a ceramic capacitor containing fine metal particles according to Example 4 of the present invention. These are figures which show the manufacture flow of the manufacturing method of the fine metal particle containing ceramic capacitor by Example 4 of this invention. These are figures which show the XRD measurement result of the composite structure of the metal and dielectric material manufactured by the manufacturing method of the fine metal particle containing ceramic capacitor by Example 4 of this invention. These are figures which show the reaction scheme of the manufacturing method of the fine metal particle containing ceramic capacitor by Example 4 of this invention. FIG. 5 is a graph showing the relationship between the dielectric characteristics of a capacitor manufactured by the method for manufacturing a ceramic capacitor containing fine metal particles according to Example 4 of the present invention and the nickel particle mixing ratio.

  Hereinafter, embodiments of the present invention will be described in detail.

The method for producing a ceramic capacitor containing fine metal particles according to the present invention comprises mixing metal particles or composite particles containing metal with a dielectric precursor or a mixture of a dielectric and a dielectric precursor, and mixing the mixture into a pellet form. For hydrothermal treatment or solvothermal treatment
Therefore, it includes performing a dielectric formation reaction inside the pellet.

A schematic diagram in the case of using metal particles is shown in FIG. As shown in the left diagram of FIG. 8, the fine metal particles are dispersed in the dielectric by solvothermal treatment or hydrothermal treatment in which the fine metal particles and the dielectric precursor are mixed and heat-treated in a pressure-resistant container. Create the structure.

FIG. 9 shows a case where composite particles containing a metal are used. As shown in the left figure of FIG. 9, instead of the fine metal particles in FIG. 8, composite particles having a metal as a core and a dielectric covering the surface of the core as a shell are used. The composite particles are mixed with a dielectric precursor, and a structure in which fine metal particles are dispersed in the dielectric is produced by solvothermal treatment or hydrothermal treatment in which heat treatment is performed in a pressure-resistant container.

8 and 9, a dielectric precursor is used, but a mixture of a first dielectric precursor and a second dielectric may be used. Here, the first dielectric and the second dielectric may be the same or different.

Fine metal particles or metal used as a core must not be dissolved in a solvent during hydrothermal treatment or solvothermal treatment. For example, particles such as titanium, nickel, tin, silver, palladium, platinum, silver, and gold are used. be able to.

  Moreover, there is no restriction | limiting in particular regarding the kind of dielectric material, For example, barium titanate, strontium titanate, potassium niobate, a barium zirconate etc. can be used. With respect to the dielectric precursor, for example, titanium oxide is used in the case of a barium titanate precursor. The precursor is not limited to an oxide, but may be a hydroxide. It may not be a crystalline compound.

Hereinafter, Example 1 of the present invention will be described in detail with reference to the drawings.

<Production of titanium / barium titanate composite capacitor using titanium particles>
FIG. 10 is a schematic diagram of a method for producing a ceramic capacitor containing fine metal particles according to the present embodiment, and FIG. 11 is a production flow. Titanium particles (particle size: 45 μm) are mixed with rutile-type titanium oxide particles having a particle size of about 50-100 nm and barium titanate particles having a particle size of 100 nm so that the content of titanium particles is 20-80% by mass. Prepare mixed powder. Here, the mixing ratio of the titanium oxide particles and barium titanate is set to 1: 1 as a molar ratio. At this time, since the specific gravity of each particle is greatly different, for example, a solvent such as acetone is added to the raw material powder, stirred while applying ultrasonic treatment, and the solvent is evaporated to mix the metal particles and the precursor particles well. It is desirable to do so.

  100 mg of this mixed powder is put into a die (die) and formed into a pellet shape having a diameter of 10 mm by uniaxial pressing of 5 tons.

Each of these pellets is transferred to a fluororesin container, and 50 mL of 50 mM barium hydroxide octahydrate aqueous solution and 7.5 mL are added. The fluororesin container is sealed in an autoclave container and kept at 160 ° C. for 24 hours, whereby titanium oxide and barium hydroxide are reacted to generate barium titanate. In this case, the reaction formula is expressed as follows.
TiO2 + Ba (OH) 2 → BaTiO3 + H2O

The obtained sample pellet is washed with water and methanol and dried at 80 ° C.

  A metal capacitor containing fine metal particles can be obtained by forming gold electrodes on both surfaces of the composite structure of metal and dielectric by sputtering and then cutting the gold electrodes.

  The BT conversion rate, open porosity, and relative density of the obtained composite structure of metal and dielectric were as shown in Table 1 at the level where the mixing ratio of titanium particles was changed.

  From the SEM observation results shown in FIG. 12, it was found that the obtained composite structure of metal and dielectric was a porous body and comprised of barium titanate nanoparticles and micro-sized titanium metal particles. It was also confirmed that the barium titanate particles contained in the pellets were grown by hydrothermal treatment and the particle size was increased.

  From the result of the XRD measurement shown in FIG. 13, it was found that the obtained composite structure of metal and dielectric had no residual titanium oxide as a raw material and was a mixed phase of titanium metal and barium titanate. Thus, the growth of the barium titanate added to the raw material powder in advance, or the growth of barium titanate generated from the reaction of titanium oxide and barium hydroxide, creates bonds between the particles, and the dielectric particles become A strongly connected structure can be manufactured. It can be said that the reaction scheme is illustrated again as shown in FIG.

  The frequency dependence of the dielectric characteristics of the obtained capacitor was measured at room temperature using an LCR meter. FIG. 15 (a) and FIG. 15 (b) show the frequency dependence and titanium mixing ratio dependence of the dielectric properties of the obtained sample. In a sample prepared from a mixed powder containing 80% by mass of titanium particles, an electrical path is formed by connecting metal particles, and percolation occurs. When the mixing ratio of titanium particles is 20% by mass to 40% by mass, the relative dielectric constant decreases. However, when the mixing ratio is 60% by mass close to the metal concentration at which metal-insulator transition occurs (so-called percolation threshold), the relative dielectric constant increases significantly. Is seen.

  According to the percolation theory, the increase in the relative permittivity at the metal concentration in the vicinity of the percolation threshold is that the metal clusters formed in the composite material approach each other, and a very small capacitor having a very thin dielectric layer is three-dimensionally. It is understood that the apparent relative permittivity increases when connected. Regarding the impedance, a significant decrease is observed when the mixing ratio of the titanium particles where percolation occurs is 80% by mass.

  Hereinafter, Example 2 of the present invention will be described in detail with reference to the drawings. In this embodiment, instead of using fine metal particles, composite particles having a metal as shown in FIG. 16 and a dielectric covering the surface of the core as a shell are used.

<Method of creating core-shell particles>
Put 1g of titanium particles (particle size ~ 45μm) in a fluororesin container,
Thereto, 7.5 mL of 50 mM barium hydroxide octahydrate solution is added. The fluororesin container is sealed in an autoclave container and kept at 230 ° C. for 12 hours to react the titanium metal and barium hydroxide to obtain core-shell particles in which the titanium metal surface is covered with fine particles of barium titanate. be able to.

  From the results of the XRD measurement shown in FIG. 17, it can be seen that the particles are a mixed phase of titanium and barium titanate. This is because, under hydrothermal conditions, titanium metal reacted with the barium hydroxide solution to produce barium titanate.

  From the result of SEM observation shown in FIG. 18, it can be confirmed that the surface of titanium metal is densely covered with barium titanate particles having a particle size of several hundred nm.

  In addition, the production | generation of the core-shell particle which has the same form was confirmed also in 130 degreeC and the hydrothermal conditions for 12 hours.

<Production of titanium / barium titanate composite capacitor using core-shell particles>
FIG. 19 shows a schematic diagram of a method for producing a ceramic capacitor containing fine metal particles according to the present example, and FIG. 20 shows a production flow. The above-mentioned titanium / barium titanate core-shell particles are mixed with rutile-type titanium oxide particles having a particle size of about 50 to 100 nm to prepare a mixed powder so that the content of the core-shell particles is 20 to 80% by mass. At this time, since the specific gravity of each particle is greatly different, for example, a solvent such as acetone is added to the raw material powder, stirred while applying ultrasonic treatment, and the solvent is evaporated to mix the metal particles and the precursor particles well. It is desirable to do so.

  100 mg of this mixed powder is put into a die and formed into a pellet having a diameter of 10 mm by uniaxial pressing of 5 tons.

Each of these pellets is transferred to a fluororesin container, and 50 mL of 50 mM barium hydroxide octahydrate aqueous solution and 7.5 mL are added. This fluororesin container is sealed in an autoclave container and kept at 160 ° C. for 24 hours, whereby titanium oxide and barium hydroxide are reacted to generate barium titanate. In this case, the reaction formula is expressed as follows.
TiO2 + Ba (OH) 2 → BaTiO3 + H2O

  The obtained pellets are washed with water and methanol and dried at 80 ° C.

  A metal capacitor containing fine metal particles can be obtained by forming gold electrodes on both surfaces of the composite structure of metal and dielectric by sputtering and then cutting the gold electrodes.

  The mass change rate, theoretical mass change rate, relative mass, and open porosity of the obtained composite structure of metal and dielectric were as shown in Table 2 at a level where the mixing ratio of titanium particles was changed.

  From the SEM observation results shown in FIG. 21, it was found that the obtained composite structure of metal and dielectric was a porous body and contained barium titanate nanoparticles and micro-sized titanium metal particles.

  From the result of the XRD measurement shown in FIG. 22, the obtained composite structure of metal and dielectric material shows that the raw material titanium oxide remains, and is a mixed phase of titanium metal, barium titanate, and titanium oxide. I understood that. The sample produced from the raw material powder containing more titanium oxide has a larger amount of remaining titanium oxide. This is because the amount of barium hydroxide in the reaction solution is constant. For example, looking at the relationship between the molar ratio of titanium oxide contained in the mixed powder pellets shown in FIG. 23 and the relative mass of barium hydroxide contained in the reaction solution, the higher the molar ratio of barium hydroxide to titanium oxide, It shows a tendency that the formation reaction of barium acid is further accelerated. Therefore, in this manufacturing process, the ratio of the amount of the dielectric precursor contained in the pellet to the amount of the metal ion contained in the reaction solution is one of the important factors.

  A structure in which barium titanate is generated from the reaction of titanium oxide previously added to the raw material powder and barium hydroxide and grows to form bonds between the particles, and the dielectric particles are firmly connected to each other. Can be produced. The reaction scheme is shown again in FIG.

  The frequency dependence of the dielectric characteristics of the obtained capacitor was measured at room temperature using an LCR meter. The dielectric characteristics of the obtained titanium / barium titanate composite capacitor shown in FIG. 25 largely depend on the frequency, particularly in the low frequency region. The relative permittivity and dielectric loss of the obtained composite capacitor tend to decrease as the frequency increases.

  The impedance of the obtained composite capacitor shown in FIG. 26 decreases exponentially with increasing frequency.

  As shown in FIG. 27, the relative permittivity of the obtained titanium / barium titanate composite capacitor tends to increase as the mixing ratio of titanium / barium titanate core-shell particles increases. In particular, in a sample having a mixing ratio of core-shell particles of 80% by mass, the relative dielectric constant is about 750 to 950, and the value of dielectric loss is 10% or less. The reason why the relative permittivity increases as the mixing ratio of the core-shell particles increases is due to the percolation effect described above.

Hereinafter, Example 3 of the present invention will be described in detail with reference to the drawings. Also in this example, the core-shell particles used in Example 2 are used.
<Production of titanium / barium titanate composite capacitor using core-shell particles>
FIG. 28 is a schematic diagram of a method for producing a fine metal particle-containing ceramic capacitor according to this example, and FIG. 29 is a production flow. Titanium / barium titanate core-shell particles are mixed with rutile-type titanium oxide particles having a particle size of about 50 to 100 nm and barium titanate particles having a particle size of 100 nm so that the content of the core-shell particles is 20 to 80% by mass. Prepare mixed powder. At this time, since the specific gravity of each particle is greatly different, for example, a solvent such as acetone is added to the raw material powder, stirred while applying ultrasonic treatment, and the solvent is evaporated to mix the metal particles and the precursor particles well. It is desirable to do so.

  100 mg of this mixed powder is put into a die (die) and formed into a pellet shape having a diameter of 10 mm by uniaxial pressing of 5 tons.

Each of these pellets was transferred to a fluororesin container, and a 50 mM barium hydroxide octahydrate aqueous solution and 7.5 mL were added. This fluororesin container is sealed in an autoclave container and kept at 160 ° C. for 24 hours, whereby titanium oxide and barium hydroxide are reacted to generate barium titanate. In this case, the reaction formula is expressed as follows.
TiO2 + Ba (OH) 2 → BaTiO3 + H2O

  The obtained sample pellet is washed with water and methanol and dried at 80 ° C.

  A ceramic electrode containing fine metal particles can be obtained by forming gold electrodes on both surfaces of the sample by sputtering and then cutting the gold electrodes.

  The BT conversion rate, open porosity, and relative density of the obtained composite structure of metal and dielectric were as shown in Table 3 at the level where the mixing ratio of titanium particles was changed.

  From the SEM observation results shown in FIG. 30, it was found that the obtained composite structure of metal and dielectric was a porous body and comprised of barium titanate nanoparticles and micro-sized titanium metal particles. It was also confirmed that the barium titanate particles contained in the sample pellets were grown by hydrothermal treatment and the particle size was increased. At this time, the particle size of the barium titanate particles constituting the shell layer is also increasing.

  From the result of XRD measurement shown in FIG. 31, it was found that the obtained composite structure of metal and dielectric had no residual titanium oxide as a raw material and was a mixed phase of titanium metal and barium titanate.

  Thus, the growth of the barium titanate added to the raw material powder in advance, or the growth of barium titanate generated from the reaction of titanium oxide and barium hydroxide, creates bonds between the particles, and the dielectric particles become A strongly connected structure can be manufactured. The reaction scheme is shown again in FIG.

  The frequency dependence of the dielectric characteristics of the obtained capacitor was measured at room temperature using an LCR meter. The dielectric characteristics of the obtained titanium / barium titanate composite capacitor shown in FIG. 33 largely depend on the frequency, particularly in the low frequency region. The relative permittivity and dielectric loss of the obtained composite capacitor tend to decrease as the frequency increases.

  The impedance of the obtained composite capacitor shown in FIG. 34 decreases exponentially with increasing frequency.

  As shown in FIG. 35, the relative permittivity of the obtained titanium / barium titanate composite capacitor tends to increase as the sample has a higher mixing ratio of titanium / barium titanate core-shell particles. In particular, in a sample having a mixing ratio of core-shell particles of 80% by mass, the relative dielectric constant is about 3000 to 4500, and the value of dielectric loss is 10% or less. The reason why the relative permittivity increases as the mixing ratio of the core-shell particles increases is due to the percolation effect described above.

Hereinafter, Example 4 of the present invention will be described in detail with reference to the drawings. In this embodiment, nickel is used as the metal particles.
<Preparation of nickel / barium titanate composite capacitor using nickel particles>
FIG. 36 shows a schematic diagram of a method for producing a ceramic capacitor containing fine metal particles according to the present example, and FIG. 37 shows a production flow. Nickel particles (particle size 2 to 3 μm) are mixed with rutile-type titanium oxide particles having a particle size of about 50 to 100 nm and barium titanate particles having a particle size of 300 nm, and the content of nickel particles is 20 to 50% by mass. Prepare the mixed powder as follows. Here, the mixing ratio of the titanium oxide particles and barium titanate is set to 1: 1 as a molar ratio. At this time, mixing is performed by a hand mill.

  100 mg of this mixed powder is put into a die and formed into a pellet having a diameter of 10 mm by uniaxial pressing of 5 tons.

Each of these pellets was transferred to a fluororesin container, and a 50 mM barium hydroxide octahydrate aqueous solution and 7.5 mL were added. The fluororesin container is sealed in an autoclave container and kept at 160 ° C. for 24 hours, whereby titanium oxide and barium hydroxide are reacted to generate barium titanate. In this case, the reaction formula is expressed as follows.
TiO2 + Ba (OH) 2 → BaTiO3 + H2O

  The obtained pellets are washed with water and methanol and dried at 80 ° C.

  A metal capacitor containing fine metal particles can be obtained by forming gold electrodes on both surfaces of the composite structure of metal and dielectric by sputtering and then cutting the gold electrodes.

  From the result of the XRD measurement shown in FIG. 38, it was found that the obtained composite structure of metal and dielectric had no residual titanium oxide as a raw material and was a mixed phase of nickel metal and barium titanate. The obtained sample is a porous body and is composed of nanoparticles of barium titanate and micro-sized nickel metal particles.

  Thus, the growth of the barium titanate added to the raw material powder in advance, or the growth of barium titanate generated from the reaction of titanium oxide and barium hydroxide, creates bonds between the particles, and the dielectric particles become A strongly connected structure can be manufactured. The reaction scheme is shown again in FIG.

  The frequency dependence of the dielectric characteristics of the obtained capacitor was measured at room temperature using an LCR meter. The dielectric characteristics of the obtained nickel / barium titanate composite capacitor depend largely on the frequency, particularly in the low frequency region. The relative permittivity and dielectric loss of the obtained composite capacitor tend to decrease as the frequency increases.

  As shown in FIG. 40, the relative permittivity of the obtained nickel / barium titanate composite capacitor tends to increase as the mixing ratio of nickel particles increases. In particular, in a sample having a mixing ratio of nickel particles of 50% by mass, the relative dielectric constant is on the order of 10 to the fourth power. The value of the dielectric loss tends to increase as the mixing ratio of nickel particles increases.

  The method for producing a ceramic capacitor containing fine metal particles according to the present invention can produce a ceramic capacitor having a structure in which fine metal particles are dispersed at a high concentration in a dielectric layer at a low temperature. Since the ceramic capacitor containing fine metal particles produced by the production method of the present invention is excellent in output density and energy density, it is highly likely to be used not only as an electronic component but also as an energy storage device. It can also be used for many purposes, such as the accumulation of renewable energy with unstable production, a power storage system for power failure countermeasures in an emergency, and an energy supply source for emergency countermeasures that can be carried.

Claims (15)

Mixing the metal-containing microparticles with the first dielectric precursor, or mixing the metal-containing microparticles with the first dielectric precursor and the second dielectric;
Molding the mixed mixture into pellets;
Performing hydrothermal treatment or solvothermal treatment on the molded pellets, and changing the first dielectric precursor to the first dielectric; and
A method for producing a ceramic capacitor containing fine metal particles.   2. The method for producing a ceramic capacitor containing fine metal particles according to claim 1, wherein the precursor of the first dielectric is a metal oxide or hydroxide.   3. The first dielectric body and the second dielectric body are each barium titanate, strontium titanate, potassium niobate, barium zirconate, or a mixture thereof. A method for producing a ceramic capacitor containing fine metal particles according to 1.   4. The fine metal particle according to claim 1, wherein the metal is a metal selected from nickel, titanium, tin, palladium, platinum, silver, and gold, or an alloy or a mixture of these metals. A method for producing a ceramic capacitor.   5. The method for producing a ceramic capacitor containing fine metal particles according to claim 1, wherein the fine particles containing metal are metal particles.   6. The method for producing a ceramic capacitor containing fine metal particles according to claim 5, wherein the metal particles are titanium or nickel.   5. The microparticle according to claim 1, wherein the metal-containing microparticle is a composite particle including a core that is a metal particle and a shell that is a dielectric covering the surface of the core. A manufacturing method of a ceramic capacitor containing metal particles.   8. The method for producing a ceramic capacitor containing fine metal particles according to claim 7, wherein the core is titanium and the shell is barium titanate.   9. The micrometal according to claim 1, wherein the hydrothermal treatment or solvothermal treatment is performed by adding a basic solution containing barium and performing a heat treatment at a temperature of 130 ° C. or more in a pressure-resistant container. A method for producing a particle-containing ceramic capacitor.   10. The method for producing a ceramic capacitor containing fine metal particles according to claim 9, wherein the basic solution containing barium is a barium hydroxide octahydrate aqueous solution.   10. The method for producing a ceramic capacitor containing fine metal particles according to claim 9, wherein the basic solution containing barium is a mixed solution of barium acetate as a barium source and sodium hydroxide as a pH control agent. The metal-containing microparticles in which the core is titanium and the shell is barium titanate are obtained by heat-treating a basic solution containing titanium particles and barium at a temperature of 130 ° C. or higher in a pressure-resistant vessel. 9. The method for producing a ceramic capacitor containing fine metal particles according to claim 8, wherein:   The metal-containing fine particles in which the core is titanium and the shell is barium titanate are obtained by heat-treating titanium particles and an aqueous solution of barium hydroxide octahydrate at 230 ° C. for 12 hours in a pressure-resistant vessel. 13. The method for producing a ceramic capacitor containing fine metal particles according to claim 12, wherein:   A mixture of the metal-containing microparticles and the first dielectric precursor or a mixture of the metal-containing microparticles, the first dielectric precursor and the second dielectric is acetone. 14. The method for producing a ceramic capacitor containing fine metal particles according to any one of claims 1 to 13, wherein stirring is performed while applying ultrasonic waves as a solvent.   The ceramic capacitor containing fine metal particles according to any one of claims 1 to 14, further comprising a step of washing the pellets subjected to hydrothermal treatment or solvothermal treatment with water and methanol and then drying the pellets. Manufacturing method.