JP5089870B2 - Barium calcium titanate, method for producing the same, and capacitor - Google Patents

Description

  The present invention relates to barium calcium titanate particles used for electronic materials such as dielectric materials, piezoelectric materials, pyroelectric materials, multilayer ceramic capacitors, and thin film materials, and a method for producing the same.

Specifically, the specific surface area D is 1 to 100 m ² / g, the c-axis length and the a-axis length obtained from the a-axis length (unit: nm) and c-axis length (unit: nm) of the crystal lattice calculated by the Rietveld method. The general formula (Ba _(1-X) Ca _X ) _Y TiO ₃ (0 <X <0.2, 0.98 ≦ Y ≦ 1.02) where D and y satisfy a certain relationship when the ratio of Y is y ) And barium calcium titanate particles containing 3 mol% or less of an orthorhombic perovskite compound and a method for producing the same.

  Since barium titanate has a perovskite structure in which barium is occupied at the A site and Ti is occupied at the B site, and titanium is slightly shifted from the center, the barium titanate exhibits ferroelectricity. Therefore, in order to exhibit excellent electrical characteristics such as dielectric properties, piezoelectricity, pyroelectricity, etc., it is widely used as various electronic materials.

  In addition, barium calcium titanate is widely used as a barium titanate-based electronic material in which a part of barium is replaced with calcium. Among them, ceramic capacitor materials with improved temperature dependence and reliability of the dielectric properties of barium titanate It is attracting attention as.

  Utilizing the high dielectric properties of these materials, various capacitor materials including multilayer ceramic capacitors, dielectric filters, dielectric antennas, dielectric resonators, dielectric duplexers, capacitors, phase shifters, and piezoelectricity Such laminated piezoelectric actuators are exemplified as applications. In addition, as a method of using barium titanate as an electronic material, a barium titanate powder is mixed with a solvent to form a slurry or paste, followed by molding / sintering, sheeting, etc. There is a way to do it.

  Recently, it is hoped to develop barium calcium titanate with a small particle size, narrow particle size distribution, excellent dispersibility, high crystallinity, and high purity corresponding to miniaturization, weight reduction, and high performance of electronic components. It is rare.

For example, in order to reduce the size, weight, and capacity of a multilayer ceramic capacitor, it is necessary to reduce the particle size of barium calcium titanate, decrease the stacking interval, and increase the number of stacks.
However, in general, when the particle size of barium calcium titanate becomes small, the c / a ratio becomes small and approaches a cubic crystal. However, when the c / a ratio becomes low, the ferroelectricity decreases, so that it was used as a dielectric material. The capacitance at the time becomes small. Therefore, barium calcium titanate showing a high c / a ratio even when the particles are small is desired. Moreover, in order to show a high c / a ratio, it is necessary to be a high crystal.
In addition, when the barium calcium titanate powder is mixed with a solvent to form a slurry or paste, if the powder is agglomerated, there is a problem that the sintered density is lowered and the electrical characteristics such as withstand voltage and migration are lowered. is there. Furthermore, impurities contained in barium calcium titanate also adversely affect the electrical characteristics.
Therefore, in order to cope with the reduction in size, weight, and performance of electronic components, it is necessary to develop barium calcium titanate having a small particle size, a narrow particle size distribution, excellent dispersibility, and high purity.

As a conventional method for producing barium titanate, the following method is used.
As a method for producing high-purity and high-crystal barium titanate particles, there is a flux method.
However, this method not only has a very high production cost, but can only be pulverized into particles, resulting in particles having a wide particle size distribution and poor dispersibility. Therefore, it is not suitable for an electronic material using particles as a material.

  As a method for producing barium titanate for electronic materials, a solid phase method in which oxides or carbonates are used as raw materials, and these powders are mixed by a ball mill or the like and then reacted at a high temperature of about 800 ° C. or higher. First, an oxalate method in which a oxalic acid complex salt is prepared and thermally decomposed to obtain titanium-containing complex oxide particles, a hydrothermal synthesis method in which a precursor is obtained by reacting the raw material at a high temperature and high pressure in an aqueous solvent, a metal alcoside In general, an alkoxide method, in which a precursor is obtained by hydrolyzing them as a raw material, is known.

  Further, as a method for producing barium titanate, a method in which a hydrolysis product of a titanium compound and water-soluble barium are reacted in a strong alkali (Patent Document 1), and a method in which a titanium oxide sol and a barium compound are reacted in a strong alkali aqueous solution. (Patent Literature 2, Patent Literature 3) and the like are generally known, and improvements in these synthesis methods are actively performed.

  However, although the above solid-phase method is low in production cost, there is a problem that the barium titanate particles to be produced have a large particle size. If pulverization is performed, the particle size becomes small, but the particle size distribution becomes wide and the molding density may not be improved. Further, the crystal structure is distorted by pulverization, and there is a drawback that a barium titanate powder suitable for miniaturization and high performance cannot be obtained.

  In addition, although the above-described oxalate method yields smaller particles than the solid phase method, carbonate groups derived from oxalic acid remain as impurities. In addition, there are many residual hydroxyl groups due to the water taken into the interior, and the electrical characteristics deteriorate. Thus, the oxalate method has a problem that a barium titanate powder having excellent electrical characteristics cannot be obtained.

  The hydrothermal synthesis method described above can produce fine barium titanate, but there are many defects due to residual hydroxyl groups due to the water taken inside, and it is difficult to obtain barium titanate particles with excellent electrical characteristics. . Moreover, since it carries out on high temperature / high pressure conditions, a dedicated installation is needed and there exists a problem that cost becomes high.

In the above alkoxide method, finer barium titanate can be obtained than in the hydrothermal synthesis method, but there are many defects due to the remaining hydroxyl groups due to the water taken into the interior, and titanium-containing composite oxidation with excellent electrical properties. It is difficult to get things.
Japanese Patent Publication No. 3-39014 International Publication No. 00/35811 Pamphlet International Publication No. 03/004416 Pamphlet JP 2002-60219 A JP 2003-48774 A

  In the method described in Patent Document 1 or Patent Document 2, potassium hydroxide or sodium hydroxide is used as an alkali. To obtain high-purity barium titanate particles, these alkali components are removed after the reaction. A process is required. Actually, since barium dissolution and hydroxyl group incorporation occur simultaneously in the removal step, barium titanate having high crystallinity may be difficult to obtain.

  On the other hand, in order to produce barium calcium titanate, a method of producing calcium by adding calcium to the raw material in each of the above methods can be considered. However, since barium and calcium have greatly different atomic radii, it is difficult to produce barium titanate in which barium and calcium are uniformly dissolved. As a result, orthorhombic perovskite compounds such as calcium titanate remain as raw materials and by-products, making it difficult to produce barium calcium titanate that can reduce the size, weight, and performance of electronic components. ing. In addition, in order to uniformly dissolve barium and calcium, it is necessary to perform a heat treatment at a high temperature, so that there is a problem that it is easy to grow grains and it is difficult to produce fine barium calcium titanate.

  Patent Document 3, Patent Document 4 and Patent Document 5 disclose methods for producing barium calcium titanate.

In the methods described in Patent Document 3 and Patent Document 4, fine barium calcium titanate can be obtained, but since a barium compound and a calcium compound are simultaneously added, an orthorhombic perovskite compound is used as a by-product in a competitive reaction. Are mixed.
The method described in Patent Document 4 is a very complicated process and requires expensive titanium alkoxide.
Furthermore, in the method described in Patent Document 5, fine heat treatment of calcium carbonate, titanium oxide, and barium titanate at 1000 ° C. or higher cannot provide fine barium calcium titanate of 0.2 μm or less.

  An object of the present invention is to provide a barium calcium titanate having a small particle size, a narrow particle size distribution, excellent dispersibility, high crystallinity and excellent electrical characteristics, and a method for producing the same.

In order to achieve the above object, the present invention provides the following means. That is,
[1] An orthorhombic perovskite represented by a composition formula of (Ba _1-X Ca _X ) _Y TiO ₃ (where 0 <X <0.2 and 0.98 ≦ Y ≦ 1.02). Barium calcium titanate having a compound content of 3 mol% or less (including 0 mol%) and a specific surface area D of 1 m ² / g or more and 100 m ² / g or less.
[2] When the ratio (c / a) between the a-axis length and the c-axis length of the crystal lattice calculated by the Rietveld method is y, the relationship between the y and the specific surface area D is expressed by the following formula (1). Or barium calcium titanate as described in [1] characterized by satisfy | filling following formula (2).
y ≧ 1.075−8.8 × 10 ⁻⁶ × D ³ (when 1 ≦ D ≦ 9.7) (1)
y ≧ 1.003 (when 9.7 <D ≦ 100) (2)
[3] The barium calcium titanate according to [1] or [2], wherein the barium calcium titanate contains 80% or more of single crystal particles.
[4] The barium calcium titanate according to any one of [1] to [3], wherein 80% or more of particles having no pores of 1 nm or more are contained in the particles.
[ 5 ] The barium calcium titanate according to any one of [1] to [ 4 ], wherein the specific surface area D is a powder having a specific surface area D of 5 m ² / g or more and 100 m ² / g or less.
[ 6 ] The barium calcium titanate according to any one of [1] to [ 5 ], wherein X in the composition formula is 0.05 ≦ X <0.2.
[ 7 ] A step of synthesizing barium titanate by adding barium hydroxide and titanium oxide to an alkaline solution containing a basic compound and having a pH of 10 or more and reacting them, and then adding calcium hydroxide. And a step of synthesizing barium calcium titanate by reacting, and then a step of vaporizing and removing the basic compound.
[ 8 ] The molar ratio of barium hydroxide to calcium hydroxide is in the range of 1: 0 to 0.8: 0.2, and the amount of titanium oxide is 0 with respect to the total molar amount of barium hydroxide and calcium hydroxide. The barium calcium titanate according to [ 7 ], wherein the barium calcium titanate is produced by reacting these barium hydroxide, calcium hydroxide and titanium oxide in an alkaline solution in an amount of .98 to 1.02. Manufacturing method.
[ 9 ] In the step of synthesizing the barium titanate, the reaction is performed until the remaining amount of barium ions in the alkaline solution becomes 1/100 or less of the input amount, and in the step of synthesizing the barium calcium titanate, The method for producing barium calcium titanate according to [ 7 ] or [ 8 ], wherein the reaction is performed until the remaining amount of calcium ions is 1/100 or less of the input amount.
[ 10 ] The method for producing barium calcium titanate according to any one of [ 7 ] to [ 9 ], wherein a heat treatment is performed in the range of 350 ° C. to 1200 ° C. after the step of removing the basic compound. .
[ 11 ] In the process from synthesis of barium titanate to synthesis of nbarium calcium titanate, the concentration of carbonate groups in the reaction solution is controlled in the range of 0 ppm to 500 ppm in terms of CO ₂ [ 7 ] Thru | or the manufacturing method of the barium calcium titanate in any one of [ 10 ].
[12] The method for producing barium calcium titanate according to any one of claims 7 to 11 wherein the titanium oxide is characterized in that containing brookite crystals.
[ 13 ] The method for producing barium calcium titanate according to any one of [ 7 ] to [ 12 ], wherein the titanium oxide is a titanium oxide sol obtained by hydrolyzing a titanium compound in an acidic solution.
[ 14 ] The above-mentioned [ 7 ] to [ 13 ], wherein the basic compound is a substance that is vaporized by at least one of evaporation, sublimation, and thermal decomposition under atmospheric pressure or reduced pressure. The manufacturing method of the barium calcium titanate in any one.
[ 15 ] The method for producing barium calcium titanate according to any one of [ 7 ] to [ 14 ], wherein the basic compound is an organic basic compound.
[ 16 ] The method for producing barium calcium titanate according to any one of [ 7 ] to [ 15 ], wherein the basic compound is tetramethylammonium hydroxide.
[ 17 ] A dielectric material comprising the barium calcium titanate according to any one of [1] to [ 6 ].
[ 18 ] A paste comprising the barium calcium titanate according to any one of [1] to [ 6 ].
[ 19 ] A slurry comprising the barium calcium titanate according to any one of [1] to [ 6 ].
[ 20 ] A thin film-like formed product comprising the barium calcium titanate according to any one of [1] to [ 6 ].
[ 21 ] A dielectric ceramic produced using the barium calcium titanate according to any one of [1] to [ 6 ].
[ 22 ] A pyroelectric ceramic produced using the barium calcium titanate according to any one of [1] to [ 6 ].
[ 23 ] A piezoelectric ceramic produced using the barium calcium titanate according to any one of [1] to [ 6 ].
[ 24 ] A capacitor comprising the dielectric ceramic according to [ 21 ].
[ 25 ] An electronic device comprising at least one selected from the group consisting of the thin film-like product according to any one of [ 20 ] to [ 24 ], porcelain, and a capacitor.
[ 26 ] A sensor comprising one or more of the thin film-like formed product or porcelain according to any one of [20] to [ 23 ].
[ 27 ] A dielectric film comprising the barium calcium titanate according to any one of [1] to [ 6 ].
[ 28 ] A capacitor manufactured using the dielectric film according to [ 27 ].

  The barium calcium titanate in a preferred embodiment of the present invention is provided with a fine particle, excellent dispersibility, few impurities, high crystallinity, solid solution barium calcium titanate powder in an arbitrary ratio, and a method for producing the same. It has a special effect.

  Such barium calcium titanate powders and slurries and pastes containing the powders can exhibit excellent electrical characteristics, and are excellent in performance, such as dielectric materials such as porcelain, thin films, dielectric films, piezoelectric materials, Electrical materials etc. are obtained. Furthermore, by using these for electronic devices, the electronic devices can be reduced in size and weight. Since the dielectric film has excellent dielectric characteristics, it can exhibit excellent characteristics even when it is thinned, and thus can be applied to an in-substrate capacitor. If the capacitor is used in electronic devices such as mobile phones and digital cameras, it is extremely effective in reducing the size, weight and performance of the device.

The present invention will be described in detail below.
The barium calcium titanate in a preferred embodiment of the present invention is represented by the general formula (Ba _(1-X) Ca _X ) _Y TiO ₃ (0 <X <0.2, 0.98 ≦ Y ≦ 1.02). This is a solid solution type perovskite compound. Here, “solid solution” is not mere “mixing” but a state in which atoms are dissolved in a certain ratio. The crystal structure of barium calcium titanate in a preferred embodiment of the present invention can be known by X-ray diffraction measurement, and the ratio of barium to calcium in barium calcium titanate is determined from the peak position of the X-ray diffraction diagram. Can do.

  The ratio (solid solution ratio) X of barium and calcium in the powder is preferably 0 to 0.2, more preferably 0 to 0.1. For example, the solid solution ratio X is preferably adjusted so as to reach desired electrical characteristics. For example, the dielectric constant at room temperature is about 1600 for barium titanate (X = 0) and about 900 for calcium barium titanate with X = 0.15. The barium calcium titanate of the present invention can control the X and Y values with an accuracy of 1/100 or less, preferably 1/1000. Thus, barium calcium titanate in which the dielectric constant at room temperature is adjusted to a desired value can be obtained by adjusting the solid solution ratio of barium and calcium.

  The ratio (Y) of the total number of moles of barium and calcium to the number of moles of titanium is preferably 0.98 to 1.02, preferably 0.99 to 1.01, and more preferably 0.0. It is 995 to 1.005, and is adjusted so as to reach a desired electric characteristic. The ratio Y is preferably as close to 1 as there is no defect and the crystallinity becomes high.

  In order to improve the electrical characteristics of barium calcium titanate in a preferred embodiment of the present invention, there is no problem even if another compound is added and used.

For miniaturization of electronic devices in general, a specific surface area of 1 m 2 ^{/ g} smaller than the particle size is not too large effective, on the specific surface area tends to aggregate exceeds 100 m 2 / ^g, the powder Handling becomes difficult. In a preferred embodiment of the present invention, the barium calcium titanate has a specific surface area of 1 to 100 m ² / g, preferably 5 to 70 m ² / g, more preferably 5 to 50 m ² / g. In the present invention, it is desirable to adopt the specific surface area value obtained by the BET method.

The relationship between the length of the c-axis length and the length of the a-axis length with respect to the Ca substitution amount is described in J. Am. Amer. Ceram. Soc. , 38, 142 (1955). As the Ca substitution amount increases, the c-axis length and a-axis length decrease. The barium calcium titanate in a preferred embodiment of the present invention has a specific surface area determined by the BET method as D (unit: m ² / g), and the ratio of the c-axis length to the a-axis length determined by the Rietveld method (c / When a) is y, the following general formula (1) or (2) is satisfied, and the particles are fine and have a high c / a ratio.

y ≧ 1.075−8.8 × 10 ⁻⁶ × D ³ (where 1 <D ≦ 9.7) (1)
y ≧ 1.003 (when 9.7 <D ≦ 100) (2)

In the preferred embodiment of the present invention, barium calcium titanate may contain an orthorhombic perovskite compound as a by-product in an amount of 3 mol% or less. An orthorhombic perovskite compound is detected as an X-ray diffraction peak when its abundance is greater than 3 mol%. Moreover, when the abundance is 3 mol% or less, it can be determined as a difference between the solid solution ratio of barium calcium titanate and the average Ca mixing amount of all powders. The solid solution ratio of barium calcium titanate can be determined by measuring the peak position of X-ray diffraction and the phase transition point of orthorhombic and tetragonal crystal diameters among the three sequential phase transition points. The average Ca mixing amount of all the powders can be obtained by the fluorescent X-ray method for a sample prepared by using the glass bead method for all the powders. In addition, orthorhombic perovskite compounds have different shapes and can be detected by observation with a scanning electron microscope.
Furthermore, the barium calcium titanate in a preferred embodiment of the present invention may contain calcium hydroxide, barium hydroxide and titanium oxide as raw materials in less than about 1 mole per 1000 minutes.

In addition, barium calcium titanate in a preferred embodiment of the present invention is characterized in that 80% or more is a single crystal. Preferably 90% or more is a single crystal, more preferably 100%. It can be known that it is a single crystal by TEM (transmission electron microscope) observation (preferably observing barium calcium titanate particles as a thin film).
Further, in the barium calcium titanate according to a preferred embodiment of the present invention, particles having no pores of 1 nm or more in the particles are 80% or more, preferably 90% or more, more preferably 100% of the whole particles. It is desirable that a hydroxyl group or a defect caused by desorption of a hydroxyl group does not exist in the particle, or even if it exists, its size is less than 1 nm.

Hydroxyl groups present in barium calcium titanate are detected as a peak around 3500 cm ⁻¹ by infrared spectroscopy, but hydroxyl groups present on the surface are also detected in addition to the hydroxyl groups in the particles. However, since the hydroxyl groups present on the surface are desorbed at a temperature lower than 700 ° C., the hydroxyl groups in the particles can be detected by performing infrared spectroscopic analysis after heat treatment at 700 ° C. in advance.
In the barium calcium titanate according to a preferred embodiment of the present invention, the powder having no pores of 1 nm or more in the grains accounts for 80% or more of the whole powder, and the hydroxyl group or the hydroxyl group is eliminated in the particle. Since there are almost no defects to be generated, the dielectric constant becomes high.

  The barium calcium titanate according to a preferred embodiment of the present invention has a volume-based average particle diameter determined by image analysis method of D1, and a particle diameter of 5% integrated from the smaller particle diameter is D2 and 95%. When the particle diameter is D3 and the maximum particle diameter is D4, D2 / D1 is preferably 0.5 to 1. D3 / D1 is preferably 1 to 1.8, and preferably D4 / D1 is 1 to 2. The barium calcium titanate in a preferred embodiment of the present invention has a narrow particle size distribution due to the small number of orthorhombic perovskite compounds having a large particle size.

The closer each value of D2 / D1 and D3 / D1 is to 1, the smaller the particle size distribution of the primary particles, which is preferable.
In a preferred embodiment of the present invention, D2 / D1 is 0.5 or more and 1 or less, preferably 0.6 or more and 1 or less.
In the preferred embodiment of the present invention, D3 / D1 is 1 or more and 1.8 or less, preferably 1 or more and 1.7 or less.
Furthermore, D4 / D1 in a preferred embodiment of the present invention is 1 or more and 2 or less, preferably 1 or more and 1.9 or less.

  Such a barium calcium titanate has a small particle size, a high dielectric constant, and excellent electrical characteristics. By using a dielectric material such as a dielectric ceramic obtained therefrom, a compact ceramic capacitor or the like can be obtained. Electronic components can be obtained, and further, by using these electronic components, it is possible to reduce the size and weight of the electronic device.

Next, the manufacturing method of the barium calcium titanate of this invention is demonstrated.
In the method for producing barium calcium titanate of the present invention, the molar ratio of barium hydroxide to calcium hydroxide is in an arbitrary range of 1: 0 to 0.8: 0.2, and the total of barium hydroxide and calcium hydroxide is The amount of titanium oxide with respect to the number of moles is preferably 0.98 to 1.02 times, and these are preferably reacted in an alkaline solution having a basic compound and having a pH of 10 or more. At this time, first, barium hydroxide and titanium oxide are reacted in the alkaline solution to synthesize barium titanate. Then, calcium hydroxide is added and further reacted to produce barium calcium titanate.

  In the present invention, it is preferable that barium hydroxide and titanium oxide are reacted first to produce barium titanate, and then this barium titanate is reacted with calcium hydroxide to obtain barium calcium titanate. When all of barium hydroxide, calcium hydroxide and titanium oxide are added and reacted at the same time, the reaction of barium hydroxide and titanium oxide and the reaction of titanium oxide and barium titanate cause a competition reaction, and orthorhombic perovskite. A compound tends to be formed, and only 5 mol% of calcium can be dissolved in a solid solution at the maximum. According to the preferred method of the present invention, since calcium is reacted after producing barium titanate having high crystallinity first, barium calcium titanate having an orthorhombic perovskite compound of 3 mol% or less can be produced, preferably 2 mol % Or less, more preferably 1 mol% or less, and particularly preferably 0 mol%. Further, according to a preferred embodiment of the present invention, barium calcium titanate having high crystallinity in which about 20% of barium is substituted with calcium can be produced.

More specifically, in a preferred embodiment of the present invention, a mixture of barium hydroxide, calcium hydroxide, and titanium oxide sol in an arbitrary ratio at a predetermined ratio, and titanium in arbitrary ratios X and Y Manufacture barium calcium acid. For example, by adding barium hydroxide: calcium hydroxide: titanium oxide = 99 mol: 1 mol: 100 mol, Ba _0.99 Ca _0.01 TiO ₃ powder can be produced, and barium hydroxide: calcium hydroxide: oxidation By adding titanium = 90 mol: 10 mol: 100 mol, Ba _0.9 Ca _0.1 TiO ₃ powder can be produced.
More preferably, by adding barium hydroxide: calcium hydroxide: titanium oxide = 99.0 mol: 1.0 mol: 100.0 mol, Ba _0.990 Ca _0.010 TiO _3.000 powder can be produced. Ba _0.900 Ca _0.100 TiO _3.000 powder can be produced by charging barium hydroxide: calcium hydroxide: titanium oxide = 90.0 mol: 10.0 mol: 100.0 mol.

  In the method for producing barium calcium titanate in a preferred embodiment of the present invention, it is preferable to use an alkaline solution in which a basic compound is present. The reason is not clear, but it seems that the higher the alkalinity, the easier the barium and calcium ions react with titanium oxide. The pH of the solution is 10 or more, preferably 13 or more, particularly preferably 14 or more. The upper limit of the amount of basic compound used is the saturated solubility of the basic compound in water.

Further, in a preferred embodiment of the present invention, in an alkaline solution having a basic compound and having a pH of 10 or more, until the remaining amount of barium ions is 1/100 or less, preferably 1/1000 or less. It reacts with titanium oxide to synthesize barium titanate. Moreover, after adding calcium hydroxide, it is made to react until the residual amount of calcium ions becomes 1/100 or less of the input, preferably 1/1000 or less, to produce barium calcium titanate. Thereby, the barium calcium titanate whose content of raw material calcium hydroxide, barium hydroxide, and titanium oxide is less than 1/100 mol, and preferably less than 1/1000 mol, can be produced. In other words, it is possible to produce barium calcium titanate in which the values of X and Y are controlled to 1/100 order, preferably 1/1000 order.
The amount of barium ions and calcium after the reaction can be determined by removing the solid content of the reaction solution and then quantifying the amount of each ion in the reaction solution by ICP emission method or atomic absorption method.

  In the present invention, as described above, the reaction is carried out until the total concentration of each ion in the solution after the reaction becomes 1/100 or less, preferably 1/1000 or less of the input amount. The reaction is preferably carried out to 1/2000 or less, more preferably 1/5000 or less, particularly preferably 1 / 10,000 or less. This increases the reaction rate to barium calcium titanate, reduces raw materials such as unreacted hydroxide and titanium oxide, increases the purity, and improves the crystallinity. The reduction rate of the total concentration after the reaction can be obtained from the following formula (3).

Moreover, it is most industrial to carry out the above synthesis reaction by heating and stirring. Particularly when mechanically stirred, the raw materials are mixed and suitable. Moreover, since the reaction solution is alkaline, it tends to absorb CO ₂ in the air. Therefore, it is preferable to carry out the reaction while sealing or blowing an inert gas so that the reaction solution does not come into contact with air. When CO ₂ is absorbed by the reaction solution, it is contained as a carbonate group in the reaction solution. (As species _carbonate, CO _{2, H} 2 CO 3, HCO ₃ ^-, and _CO containing ^{3 2-)} The carbonate group, form a stable barium and calcium carbonate react with barium hydroxide or calcium hydroxide To do. Barium carbonate and calcium carbonate tend to remain as impurities in the barium calcium titanate without reacting with titanium oxide. Therefore, it is preferable to control the concentration of carbonic acid groups in the reaction solution (CO ₂ equivalent value, hereinafter the same unless otherwise noted). By controlling the concentration of the carbonate group, highly pure barium calcium titanate can be stably produced.

Preferred terms of CO ₂ concentration in the reaction solution is 0 to 500 mass ppm, preferably from 0 to 200 mass ppm, more preferably from 0 to 100 mass ppm. In order to reduce the concentration of carbonate groups in the reaction solution, it is preferable to decarboxylate the water before dissolving the basic compound by heat treatment immediately before production.

In order to increase the crystallinity of barium calcium titanate, it is desirable to increase the reaction temperature as much as possible. In order to increase the reaction temperature, a hydrothermal reaction from 100 ° C. to the critical temperature of the solution is possible. However, for this purpose, a safety-conscious facility such as an autoclave is required.
Therefore, it is preferable to boil at 95 ° C. or higher and maintain the temperature.

  The reaction time of barium hydroxide and titanium oxide is usually 2 hours or longer, preferably 3 hours or longer, more preferably 4 hours or longer. The reaction time after the addition of calcium hydroxide is usually 2 hours or longer, preferably 4 hours or longer, more preferably 6 hours or longer.

  Impurities that adversely affect the electrical properties of barium calcium titanate include components such as trace amounts of metal ions and anions. In order to remove these impurities, there are various methods such as treatment of the slurry after completion of the reaction with electrodialysis, ion exchange, water washing, pickling, osmosis membrane and the like. However, in these methods, barium contained in barium calcium titanate simultaneously with impurity ions may be ionized at the same time and partially dissolved in the slurry, so that barium and calcium are dissolved in a desired ratio. Not only is this difficult, but there is a case where defects occur in the crystal and the crystallinity may be lowered. Further, since the reaction solution is alkaline, carbon dioxide in the air is likely to be mixed during these treatments. Therefore, the carbonate contained in barium calcium titanate may increase.

  In view of the above, it is preferable to select a raw material with few impurities and to prevent impurities from being mixed in the synthesis reaction and firing. In addition, after completion of the synthesis reaction, it is preferable to remove impurities as a gas by evaporation, sublimation, and / or thermal decomposition in a temperature range from room temperature to a sinterable temperature under atmospheric pressure or reduced pressure. At this time, it is preferable that the basic compound contained in the alkaline solution is simultaneously decomposed and removed as a gas.

  Firing is generally performed to improve the crystallinity of the titanium-containing composite oxide. On the other hand, the impurities can be removed by evaporation, sublimation, and / or thermal decomposition as a gas. Impurities that can be removed by this method include organic amines having a low carbon number, organic bases such as ammonia salt hydroxides, and trace amounts of organic substances and carbonates as impurities contained in the raw material. Usually, the firing is performed at a firing possible temperature of 350 to 1200 ° C. There is no restriction | limiting in particular in a baking atmosphere, Usually, it carries out in air | atmosphere or pressure reduction.

  In addition, after completion | finish of a synthesis reaction, it is preferable to perform baking after performing solid-liquid separation of a slurry from a viewpoint of the reduction of the thermal energy in baking, and the improvement of crystallinity. Solid-liquid separation includes powder settling, concentration, filtration, and / or drying and crushing steps. Impurities that dissolve in the liquid can be removed by sedimentation, concentration, and filtration. In order to change the sedimentation rate or the filtration rate, a flocculant or a dispersant may be used. The flocculant or dispersant is preferably one that can be removed as a gas by evaporation, sublimation, and / or thermal decomposition.

  The drying step is a step of evaporating water, but depending on the type of basic compound or impurities, some or all of the impurities can be removed by evaporation, sublimation and / or thermal decomposition. For drying, methods such as reduced-pressure drying, hot-air drying, and freeze-drying are used. Drying is usually performed at room temperature to 350 ° C. for 1 to 24 hours. The drying atmosphere is not particularly limited, but is usually performed in the air, in an inert gas, or under reduced pressure. Then, you may crush by an appropriate method.

  The barium hydroxide and calcium hydroxide used in the present invention are not particularly limited as long as they are hydroxides, and may be anhydrous salts or hydrates. The barium calcium titanate of the present invention can also be produced using barium and calcium salts.

  The titanium oxide sol used in the present invention is not particularly limited, but a titanium oxide sol containing a brookite crystal is desirable. Alternatively, a titanium oxide sol obtained by hydrolyzing a titanium salt in an acidic solution is desirable.

  As long as it contains brookite-type crystals, it may contain brookite-type crystals of titanium oxide alone or rutile-type crystals or anatase-type crystals of titanium oxide. When the titanium oxide of rutile type crystal or anatase type crystal is included, the ratio of titanium oxide of brookite type crystal in titanium oxide is not particularly limited, but is usually 1 to 100% by mass, preferably 10 to 100% by mass. %, More preferably 50 to 100% by mass. In order to make the titanium oxide powder excellent in dispersibility in a solvent, it is preferable that it is crystalline rather than amorphous so that it can be easily made into single grains, and in particular, titanium oxide of brookite crystal is dispersed. It is because it is excellent in property. The reason for this is not clear, but it is considered that the zeta potential of brookite crystals at pH 2 is higher than that of rutile crystals and anatase crystals.

  The manufacturing method of titanium oxide powder containing brookite-type crystals includes a manufacturing method for obtaining titanium oxide powder containing brookite-type crystals by heat treatment of titanium oxide powder of anatase-type crystals, titanium tetrachloride, titanium trichloride, titanium There is a production method in a liquid phase obtained by neutralizing or hydrolyzing a solution of a titanium compound such as alkoxide and titanium sulfate to obtain a titanium oxide sol in which titanium oxide powder is dispersed.

  When using titanium oxide powder containing brookite crystals as a raw material for production, it is preferable to use a titanium oxide sol obtained by hydrolyzing a titanium salt in an acidic solution as the titanium oxide powder. Such a titanium oxide sol has a small powder particle size and excellent dispersibility. As a method for producing a titanium oxide sol, for example, titanium tetrachloride is added to hot water of 75 to 100 ° C., and the titanium tetrachloride is hydrolyzed while controlling the chlorine ion concentration at a temperature of 75 ° C. or higher and lower than the boiling point of the solution. Thus, a method of obtaining titanium oxide powder containing brookite crystals as a sol (Japanese Patent Laid-Open No. 11-43327) or adding titanium tetrachloride to hot water at 75 to 100 ° C. to form nitrate ions and phosphate ions In the presence of either or both, by hydrolyzing titanium tetrachloride at a temperature of 75 ° C. or higher and below the boiling point of the solution while controlling the total concentration of chlorine ions, nitrate ions and phosphate ions, A method of obtaining titanium oxide powder containing brookite-type crystals as a sol (WO99 / 58451 pamphlet) is preferred.

  As for the size of the titanium oxide powder containing the brookite-type crystal thus obtained, the primary powder diameter is usually 1 to 100 nm, preferably 3 to 50 nm, more preferably 5 to 20 nm. When the thickness exceeds 100 nm, the particle size of the titanium-containing composite oxide powder produced using this as a raw material becomes large, and may not be suitable for functional materials such as dielectric materials and piezoelectric materials. If it is less than 1 nm, handling in the step of producing the titanium oxide powder may be difficult.

  When a titanium oxide sol obtained by hydrolyzing a titanium salt in an acidic solution is used, the crystal form of titanium oxide is not limited and is not limited to a brookite crystal phase.

  Hydrolysis of titanium salts such as titanium tetrachloride and titanium sulfate in acidic solutions suppresses the reaction rate compared to neutral or alkaline solutions, so the particle size is reduced to a single particle and the dispersible oxidation A titanium sol is obtained. In addition, since anions such as chloride ions and sulfate ions are not easily taken into the produced titanium oxide powder, it is possible to reduce the inclusion of anions into the titanium-containing composite oxide powder. it can.

  On the other hand, when the hydrolysis is carried out in a neutral or alkaline solution, the reaction rate increases and many nucleation often occurs in the initial stage. Therefore, there is a case where the titanium oxide sol has a small particle size but poor dispersibility, and the powder aggregates in a bowl shape. When a titanium-containing composite oxide powder is produced using such a titanium oxide sol as a raw material, even if the obtained powder has a small particle size, the dispersibility may be poor. In addition, anions are likely to be mixed inside the titanium oxide powder, and it may be difficult to remove these anions in subsequent steps.

The method for obtaining a titanium oxide sol by hydrolyzing a titanium salt in an acidic solution is not particularly limited as long as the solution is kept acidic, but in a reactor equipped with a reflux condenser using titanium tetrachloride as a raw material. The method of suppressing the escape of chlorine generated at that time and keeping the solution acidic (JP-A-11-43327) is preferred.
Moreover, it is preferable that the density | concentration in the acidic solution of a titanium salt is 0.01-5 mol / L. This is because when the concentration exceeds 5 mol / L, the hydrolysis reaction rate increases, and a titanium oxide sol having a large particle size and poor dispersibility may be obtained. This is because the produced titanium oxide concentration decreases and the productivity may deteriorate.

  There are no particular restrictions on the method of charging the titanium oxide sol, but in order to obtain barium calcium titanate having excellent dispersibility by suppressing aggregation of the titanium oxide sol, barium having at least a saturated solubility in an alkaline solution in which a basic compound is present. It is better to add a little by little to the reaction solution which has been charged with calcium salt and heated and stirred. Examples of the method of adding the titanium oxide sol in small amounts include a method of dropping using a pump or the like and a method of injecting it into the liquid.

  The alkaline solution used as the reaction solution in the present invention contains a basic compound, and the pH of the alkaline solution is maintained at 10 or more by this basic compound. The basic compound is not particularly limited, but is preferably a substance that becomes a gas by evaporation, sublimation and / or thermal decomposition under atmospheric pressure or reduced pressure. For example, organic bases such as ammonia, organic amines having a high carbon solubility and a low carbon number, and ammonium salt hydroxides are preferred.

  Of these, hydroxides of ammonium salts are suitable without dissolving during the reaction because they act as strong bases with a high degree of detachment when dissolved in water. On the other hand, an organic amine having a high solubility in ammonia or water and having a low carbon number is weak as a base and may be difficult to use because of its low boiling point.

  Industrially known as the hydroxide of ammonium salt are choline, tetramethylammonium hydroxide (TMAH) and the like, which are available at low cost. In particular, tetramethylammonium hydroxide is suitable for use in the electronics industry, and is not only available with few impurities such as metal ions, but it can be thermally decomposed at 135 to 140 ° C. and removed as a gas.

The barium calcium titanate composite powder of the present invention can also be produced using an inexpensive inorganic compound such as lithium hydroxide, sodium hydroxide or potassium hydroxide.
There is no restriction | limiting in particular in these basic compounds, These may be used individually by 1 type, and even if it mixes and uses 2 or more types of compounds by arbitrary ratios, it is satisfactory.

The barium calcium titanate powder thus produced is made of barium and calcium having a small particle size, a narrow particle size distribution, excellent dispersibility, high crystallinity, excellent electrical characteristics, and particularly low impurities. It is made into a solid solution at an arbitrary ratio, and is formed into a dielectric ceramic, pyroelectric ceramic, piezoelectric ceramic, or thin film-like product.
These porcelain and thin film-like products are used for capacitor materials, sensors, and the like.

  In addition, barium calcium titanate powder is mixed with a single product or additives, other materials, etc., and slurried or pasted with one or more solvents consisting of water, existing inorganic binder, existing organic binder. It is also possible to use it.

  The electrical characteristics of the barium calcium titanate powder are obtained by adding various additives such as a sintering aid to the powder and forming into a disk shape, or by adding various additives to the slurry and paste containing the powder to form a thin film. The molded article can be evaluated using an impedance analyzer or the like after firing under suitable conditions.

  A film having a high dielectric constant can be obtained by dispersing a filler containing barium calcium titanate powder into at least one selected from the group consisting of a thermosetting resin and a thermoplastic resin.

  When a filler other than the barium calcium titanate powder is included, it is possible to select one or more types from the group consisting of alumina, titania, zirconia, tantalum oxide, and the like.

  Thermosetting resins and thermoplastic resins are not particularly limited, and commonly used resins can be used. Examples of thermosetting resins include epoxy resins, polyimide resins, polyamide resins, and bistriazine resins. Is preferred. As the thermoplastic resin, for example, polyolefin resin, styrene resin, polyamide and the like are suitable.

  In order to uniformly disperse the filler containing the barium calcium titanate powder into at least one of a thermosetting resin and a thermoplastic resin, the filler is dispersed in advance in a solvent or a mixture of the resin composition and the solvent to obtain a slurry. Is desirable.

  A method for obtaining a slurry by dispersing the filler in a solvent or a mixture of the resin composition and the solvent is not particularly limited, but it is preferable to include a wet crushing step.

  The solvent is not particularly limited, and any solvent that is usually used can be used. For example, methyl ethyl ketone, toluene, ethyl acetate, methanol, ethanol, N, N-dimethylformamide, N, N-dimethylacetamide, N-methylpyrrolidone and methyl cellosolve can be used alone or in admixture of two or more.

In order to obtain a slurry in which the filler is dispersed in a solvent or a mixture of the resin composition and the solvent, it is desirable to treat with a coupling agent. The coupling agent is not particularly limited, and examples thereof include silane coupling agents, titanate coupling agents, and aluminate coupling agents. Since the hydrophilic group of the coupling agent reacts with the active hydrogen on the surface of the filler containing the barium calcium titanate powder of the present invention and is coated on the surface, the dispersibility in the solvent is improved. The selection of the hydrophobic group of the coupling agent can increase the compatibility with the resin. For example, when an epoxy resin is used as the resin, a silane coupling agent having any one of monoamino, diamino, cationic styryl, epoxy, mercapto, anilino, ureido, etc. as one of functional groups, phosphite, amino, A titanate coupling agent having any one of diamino, epoxy, mercapto and the like as one of functional groups is suitable. When using a polyimide resin as the resin, a silane coupling agent having one of monoamino, diamino, anilino, etc. as one of the functional groups, or a titanate system having any of monoamino, diamino, etc. as one of the functional groups Coupling agents are preferred.
Among these, one can be used alone, or two or more can be mixed and used.

  The blending amount of the coupling material is not particularly limited as long as a part or all of the barium calcium titanate powder is coated, but if it is too much, it may remain unreacted and adversely affect it. The ring effect may be reduced. Therefore, it is preferable to select a blending amount capable of uniformly dispersing the filler depending on the particle size and specific surface area of the filler containing the barium calcium titanate powder and the type of the coupling agent. A blending amount of about 0.05 to 20% by mass of the material is desirable.

  In order to complete the reaction between the hydrophilic group of the coupling agent and the active hydrogen on the surface of the filler containing barium calcium titanate powder, it is desirable to include a heat treatment step after forming the slurry. Although there is no restriction | limiting in particular in heating temperature and time, It is preferable to heat-process at 100-150 degreeC for 1 hour to 3 hours. In addition, when the boiling point of the solvent is 100 ° C. or lower, the heating temperature is preferably lower than the boiling point of the solvent, and the heating time is increased accordingly.

FIG. 1 is a schematic cross-sectional view of a multilayer ceramic capacitor which is an example of a capacitor.
As shown in FIG. 1, the multilayer ceramic capacitor 1 includes a multilayer body 5 in which a dielectric layer 2 and internal electrodes 3 and 4 are sequentially stacked, and an external electrode 6 attached to a side surface of the multilayer body 5. 7. One end of each of the internal electrodes 3, 4 is exposed on the side surface of the laminate 5, and each one end is connected to the external electrodes 6, 7.
The dielectric layer 2 is formed by solidifying and molding barium calcium titanate powder with a binder or the like. The internal electrodes 3 and 4 are made of, for example, Ni, Pd, Ag, or the like. The external electrodes 6 and 7 are made of, for example, a sintered body made of Ag, Cu, Ni or the like and plated with Ni.
A capacitor 1 shown in FIG. 1 is used by being mounted on a circuit board 11 of a mobile phone 10, for example, as shown in FIG.

Next, an example of a method for producing the above multilayer ceramic capacitor will be described.
First, a slurry is produced by mixing barium calcium titanate powder, a binder, a dispersant, and water. The slurry is preferably vacuum degassed in advance.
Next, the slurry is thinly applied to a substrate by a doctor blade method or the like, and then heated to evaporate water, thereby forming a dielectric layer mainly composed of barium calcium titanate powder.
Next, a metal paste such as Ni, Pd, or Ag is applied to the obtained dielectric layer, another dielectric layer is laminated, and a metal paste that serves as an internal electrode is further applied. By repeating this process, a laminate in which a dielectric layer and internal electrodes are sequentially laminated is obtained. Further, it is desirable to press the laminated body so that the dielectric layer and the internal electrode are in close contact.
Next, the laminate is cut into a capacitor size and then fired at 1000 ° C. to 1350 ° C. Next, an external electrode paste is applied to the side surface of the fired laminate, and this paste is fired at 600 to 850 ° C. Finally, Ni plating is applied to the surface of the external electrode.
In this way, a multilayer ceramic capacitor 1 as shown in FIG. 1 is obtained.

Since the multilayer ceramic capacitor 1 uses barium calcium titanate having a high dielectric constant, which is a preferred embodiment of the present invention, as a dielectric, the capacitance of the capacitor can be increased. In addition, since the capacitor 1 uses barium calcium titanate having a small particle diameter, which is a preferred embodiment of the present invention, as a dielectric, the dielectric layer can be thinned, and thus the capacitor itself can be reduced in size. . In addition, the capacitance of the capacitor can be further increased by reducing the thickness of the dielectric layer.
Such a small multilayer ceramic capacitor can be suitably used as a component of electronic devices, particularly portable devices such as mobile phones.

EXAMPLES Hereinafter, although an Example and a comparative example are given and this invention is demonstrated concretely, this invention is not limited only to these Examples.
(Dielectric constant measurement method)
The dielectric constant of the obtained barium calcium titanate was measured as follows.
Barium calcium titanate and MgO (high purity magnesium oxide 500-04R manufactured by Kyowa Chemical Industry Co., Ltd.), Y ₂ O ₃ (fine powder yttrium UU-HP manufactured by Shin-Etsu Chemical Co., Ltd.), SiO ₂ —BaO—Li ₂ O ₃ (glass additive for ceramics low temperature sintering manufactured by Asahi Techno Glass Co., Ltd.) was mixed at a molar ratio of 100: 2: 1.5: 2.
After 0.3 g of the mixed powder was uniaxially molded with a 13 mmφ mold, it was calcined at 1020 ° C. for 2 hours in a nitrogen atmosphere. Similarly, after 0.3 g of the mixed powder was uniaxially molded with a 13 mmφ mold, it was fired in a nitrogen atmosphere at the temperature shown in Table 1 for 2 hours.
After precisely measuring the size of the sintered body thus obtained, a silver electrode for baking was applied and baked at 800 ° C. for 10 minutes in an air atmosphere to form an electrode to obtain a single plate capacitor.
The area, thickness, and weight of the capacitor were measured to determine the sintered density.
The capacitance of the capacitor was measured with an LF impedance analyzer 4192A manufactured by HEWLETT PACKARD, and the dielectric constant was calculated from the capacitance at a measurement frequency of 1 kHz and a measurement temperature of −55 ° C. to 125 ° C. and the size of the sintered body.

Example 1
An aqueous solution containing titanium tetrachloride (Sumitomo Titanium Co., Ltd .: purity 99.9%) at a concentration of 0.25 mol / L was prepared. This aqueous solution was put into a reactor equipped with a reflux condenser, and heated to near the boiling point while suppressing escape of chlorine ions and keeping acidic. Further, titanium tetrachloride was hydrolyzed while maintaining the temperature for 60 minutes to obtain a titanium oxide sol. The obtained titanium oxide sol was dried at 110 ° C., and the crystal form was examined with an X-ray diffractometer (X-ray diffractometer RAD-B, Rotorflex, manufactured by Rigaku Corporation). I found out.

  Next, 450 g of a 20% by mass aqueous solution of tetramethylammonium hydroxide (manufactured by Seychem Showa Co., Ltd., carbonate group concentration of 60 ppm or less) and barium hydroxide octahydrate in a reactor equipped with a reflux condenser under a nitrogen stream. 119.89 g was added and the aqueous solution adjusted to pH 14 was boiled with stirring. Next, after removing the titanium oxide sol with an electrodialyzer until the chlorine ion was reduced to 500 ppm, 213.1 g of sol having a titanium oxide concentration of 15% by mass obtained by precipitation concentration was charged into the reactor at a rate of 7 g / min. It was dripped. Boiling was maintained for 4 hours with stirring. A part of the reaction solution was filtered, and barium in the filtrate was measured by an ICP emission method. As a result, barium ions were 2 ppm, and barium ions reacted to 1/1000 or less of the input amount.

  Next, 1.48 g of calcium hydroxide (manufactured by Wako Pure Chemical Industries, Ltd .: reagent grade) was added to the reaction solution, and boiling was maintained for 6 hours while stirring as it was. When calcium ions were extracted from a part of the reaction solution and measured for calcium by the ICP emission method, the calcium ions were 3 ppm, and the calcium ions were reacted up to 1/1000 of the input amount.

  Thereafter, the solid content obtained by filtering the reaction solution was dried at 300 ° C. for 5 hours to obtain a dry powder. The ratio of the actual yield to the theoretical yield calculated from the amount of titanium oxide, barium hydroxide and calcium hydroxide used in the reaction was 99.9%.

The dried powder was crushed in a mortar and the specific surface area of the powder was measured by the BET method. The specific surface area of the powder was 48 m ² / g.

This powder was evaluated by the aforementioned X-ray diffractometer. The X-ray diffraction spectrum at that time is shown in FIG. As shown in FIG. 3, the diffraction peak of the orthorhombic perovskite compound was not observed, and the content of the orthorhombic perovskite compound was 3 mol% or less.
Further, when Rietveld analysis was performed from the X-ray diffraction intensity, it was found that the obtained powder was Ba _0.950 Ca _0.050 TiO ₃ powder in which barium and calcium were dissolved. y obtained from the length of the a-axis length and the length of the c-axis length was 1.0045, which satisfied the formula (1).

Next, the powder shape was magnified and observed with a scanning electron microscope. The results are shown in FIG.
Furthermore, the obtained sample was observed with a transmission electron microscope (Hitachi, Ltd., H-9000UHR). Elemental analysis by EDX revealed that barium and calcium were uniformly dissolved in the powder as shown in FIG.

Further, the amount of carbonate group contained in the powder was quantified using an infrared spectroscopic analyzer (FTS6000 manufactured by BIORAD). Assuming that all the carbonate groups are barium carbonate and calcium carbonate, an amount of carbonate groups corresponding to about 1% by mass was detected. Note that a sharp absorption peak in the vicinity of 3500 cm ⁻¹ corresponding to a hydroxyl group in the crystal lattice did not appear.

(Example 2)
The powder obtained in Example 1 was put into an electric furnace (KDFP-90 manufactured by Denken Co., Ltd.) and fired. The firing conditions were such that the temperature was raised at 20 ° C. per minute, held at 950 ° C. for 2 hours, and then naturally cooled. Thus, the barium calcium titanate powder of Example 2 was obtained.

When the specific surface area of the barium calcium titanate powder of Example 2 was measured by the BET method, the specific surface area was 6.8 m ² / g.
Moreover, the X-ray-diffraction spectrum of the barium calcium titanate powder after heat processing is shown in FIG. As shown in FIG. 6, no peak of the orthorhombic perovskite compound was observed, and the content of the orthorhombic perovskite compound was 3 mol% or less. Y (c / a) was 1.0081, which satisfied the expression (1).

Next, with respect to the barium calcium titanate powder of Example 2, the phase transition point between the orthorhombic system and the tetragonal crystal diameter was measured using a differential scanning calorimeter (manufactured by Seiko Denshi Kogyo Co., Ltd.). The measurement was performed under the condition that the temperature was increased from −40 ° C. to 200 ° C. at a rate of 10 ° C./min, maintained at 200 ° C. for 10 minutes, and then decreased to −40 ° C. at a rate of 10 ° C./min. As a result, the phase transition point between the orthorhombic system and the tetragonal system was −16 ° C.
Moreover, about the barium calcium titanate powder of Example 2, it heated up from room temperature to 100 degreeC at the speed | rate of 10 degree-C / min using Booker AXS Co., Ltd. product: DSC320SA, and it was 10 minutes at 100 degreeC. Thereafter, the temperature was lowered to −100 ° C. at 10 ° C./min, and further raised to 150 ° C. at 10 ° C./min. Also in this case, the phase transition point between the orthorhombic system and the tetragonal crystal diameter was −16 ° C.

Next, the barium calcium titanate powder of Example 2 was enlarged and observed with a scanning electron microscope. A SEM photograph is shown in FIG.
The photograph shown in FIG. 7 was analyzed to determine the area of the barium calcium titanate powder, and the volume in spherical form was determined. Similarly, the volume of the barium calcium titanate powder was determined, and the particle size distribution was measured. The volume-based average particle size obtained by the image analysis method is D1, the particle size that becomes 5% integrated from the smallest particle size is D2, the particle size that becomes 95% is D3, and the maximum particle size is D4. Sometimes D2 / D1 was 0.6, D3 / D1 was 1.6, and D4 / D1 was 1.8.

Furthermore, the barium calcium titanate powder of Example 2 was observed with a transmission electron microscope.
Elemental analysis by EDX revealed that barium and calcium were uniformly dissolved in the powder as shown in FIG.
In addition, as shown in FIG. 9, the barium calcium titanate powder of Example 2 was observed with a transmission electron microscope at a magnification of 250,000 times, but no defects due to the elimination of hydroxyl groups were observed.
Furthermore, the barium calcium titanate powder of Example 2 was found to be a single crystal from an electron diffraction image.
The dielectric constant measurement results are shown in Table 1.

(Example 3)
The powder obtained in Example 1 was calcined in the same manner as in Example 2 except that the powder was held at 1000 ° C. for 2 hours to obtain barium calcium titanate in Example 3.

The specific surface area of the barium calcium titanate powder of Example 3 was 5.1 m ² / g. Y was 1.0093, which satisfied the expression (1). Furthermore, D2 / D1 obtained by the image analysis method was 0.6, D3 / D1 was 1.7, and D3 / D1 was 1.8.
The dielectric constant measurement results are shown in Table 1.

Example 4
The barium titanate of Example 4 was obtained in the same manner as in Example 1 except that the amount of barium hydroxide octahydrate input was 107.27 g and that of calcium hydroxide was 4.45 g. Calcium powder was produced.

The specific surface area of the obtained barium calcium titanate powder of Example 4 was 49 m ² / g. In the X-ray diffraction spectrum, no peak of the orthorhombic perovskite compound was observed, and the content of the orthorhombic perovskite compound was 3 mol% or less.
Furthermore, when Rietveld analysis was performed from the X-ray diffraction intensity, the obtained powder was Ba _0.850 Ca _0.150 TiO ₃ powder in which barium and calcium were dissolved, and y was 1.0048. (2) Formula was satisfied.
Furthermore, the powder of Example 4 was observed with a transmission electron microscope at a magnification of 250,000 times, but no defects due to the elimination of hydroxyl groups were observed.

(Example 5)
The powder obtained in Example 4 was calcined in the same manner as in Example 2 except that the powder was held at 1100 ° C. for 2 hours to obtain the barium calcium titanate powder of Example 5.

The specific surface area of the obtained powder of Example 5 was 5 m ² / g. In the X-ray diffraction spectrum, no peak of the orthorhombic perovskite compound was observed, and the content of the orthorhombic perovskite compound was 3 mol% or less. Furthermore, y was 1.0092, which satisfied the expression (1). Furthermore, D2 / D1 obtained by the image analysis method was 0.6, D3 / D1 was 1.8, and D4 / D1 was 1.9. Further, observation with a transmission electron microscope was carried out at 250,000 times, but no defects due to elimination of hydroxyl groups were observed.
The dielectric constant measurement results are shown in Table 1.

(Example 6)
The barium calcium titanate powder of Example 6 was produced by performing the same operation as in Example 1 except that the reaction temperature was changed to 110 ° C. using an autoclave reactor.

The non-surface area of the obtained barium calcium titanate powder of Example 6 was 43 m ² / g. In the X-ray diffraction spectrum, no peak of the orthorhombic perovskite compound was observed, and the content of the orthorhombic perovskite compound was 3 mol% or less.
Furthermore, when Rietveld analysis was performed from the X-ray diffraction intensity, the obtained powder was Ba _0.950 Ca _0.050 TiO ₃ powder in which barium and calcium were dissolved, and y was 1.0038. (2) Formula was satisfied.
Furthermore, the powder of Example 6 was observed with a transmission electron microscope at a magnification of 250,000 times, but no defects due to the elimination of hydroxyl groups were observed.

(Example 7)
The powder obtained in Example 6 was calcined in the same manner as in Example 2 except that the powder was held at 880 ° C. for 2 hours to obtain barium calcium titanate of Example 7.

The specific surface area of the obtained powder of Example 7 was 10 m ² / g. In the X-ray diffraction spectrum, no peak of the orthorhombic perovskite compound was observed, and the content of the orthorhombic perovskite compound was 3 mol% or less. Furthermore, y was 1.0067, which satisfied the expression (2). Furthermore, D2 / D1 obtained by the image analysis method was 0.8, D3 / D1 was 1.5, and D4 / D1 was 1.6. Further, observation with a transmission electron microscope was carried out at 250,000 times, but no defects due to elimination of hydroxyl groups were observed.
The dielectric constant measurement results are shown in Table 1.

(Comparative Example 1)
In a reactor equipped with a reflux condenser, 450 g of a 20% by mass aqueous solution of tetramethylammonium hydroxide (manufactured by Seychem Showa Co., Ltd., carbonate group concentration of 60 ppm or less) and 119 of barium hydroxide octahydrate under a nitrogen stream. .89 g and 1.48 g of calcium hydroxide octahydrate were added, and the aqueous solution adjusted to pH 14 was boiled with stirring. Next, a titanium oxide sol was prepared in the same manner as in Example 1, and after removing this sol with an electrodialyzer until the chlorine ion reached 500 ppm, 213 g of a sol having a titanium oxide concentration of 15% by mass obtained by precipitation concentration was obtained. To the reactor at a rate of 7 g / min. Boiling was maintained for 4 hours with stirring. A part of the reaction solution was filtered, and barium in the filtrate was measured by an ICP emission method. As a result, barium ions were 2 ppm, and barium ions reacted to 1/1000 or less of the input amount.
Thereafter, operations other than those described above were performed in the same manner as in Example 1 to produce the barium calcium titanate powder of Comparative Example 1.

The specific surface area of the obtained powder was 38 m ² / g. The X-ray diffraction spectrum diagrams are shown in FIGS. FIG. 11 is an enlarged view of FIG. In FIG. 11, the peak of the orthorhombic perovskite compound is indicated by a circle. Thus, the orthorhombic perovskite compound peak was observed in the barium calcium titanate of Comparative Example 1. As a result, it was found that the content of the orthorhombic perovskite compound was larger than 3 mol%.

(Comparative Example 2)
The powder obtained in Comparative Example 1 was calcined in the same manner as in Example 2 except that the powder was held at 1000 ° C. for 2 hours to obtain Barium calcium titanate in Comparative Example 2.

The specific surface area of the obtained powder was 5.1 m ² / g. The X-ray diffraction spectrum is shown in FIGS. FIG. 13 is an enlarged view of FIG. In FIG. 13, the peak of the orthorhombic perovskite compound is indicated by a circle. Thus, the rhombic perovskite compound peak was also observed in barium calcium titanate of Comparative Example 2. As a result, it was found that the content of the orthorhombic perovskite compound was larger than 3 mol%. Moreover, y was 1.0077 and did not satisfy the formula (1). The phase transition point between the orthorhombic and tetragonal crystal phase transition points was measured and found to be -15 ° C. Further, D2 / D1 obtained by the image analysis method was 0.4, D3 / D1 was 2.0, and D4 / D1 was 2.5.
The dielectric constant measurement results are shown in Table 1.

(Comparative Example 3)
The barium calcium titanate powder of Comparative Example 3 was prepared in the same manner as in Comparative Example 1, except that the amount of barium hydroxide octahydrate input was 107.27 g and that of calcium hydroxide was 4.45 g. Manufactured.

The specific surface area of the obtained powder was 38 m ² / g. In the X-ray diffraction spectrum, an orthorhombic perovskite compound peak was observed. As a result, it was found that the content of the orthorhombic perovskite compound was larger than 3 mol%.

(Comparative Example 4)
The barium calcium titanate powder of Comparative Example 4 was produced by firing the powder obtained in Comparative Example 3 in the same manner as in Example 2 except that the powder was held at 1020 ° C. for 2 hours.

The specific surface area of the obtained powder was 5.3 m ² / g. Further, in the X-ray diffraction spectrum, an orthorhombic perovskite compound peak was found, and it was found that the content of the orthorhombic perovskite compound was larger than 3 mol%. Moreover, y was 1.0081 and did not satisfy the expression (1). Further, D2 / D1 obtained by the image analysis method was 0.3, D3 / D1 was 2.2, and D4 / D1 was 2.8.
The dielectric constant measurement results are shown in Table 1.

As for the temperature characteristics, those satisfying the EIA standard X7R are indicated as “◯”, and those not satisfying as “X”.
* Indicates barium titanate and MgO (high-purity magnesium oxide 500-04R manufactured by Kyowa Chemical Industry Co., Ltd.), Y ₂ O ₃ (fine powder yttrium UU-HP manufactured by Shin-Etsu Chemical Co., Ltd.) SiO ₂ —BaO—Li ₂ O ₃ (glass additive for ceramic low-temperature sintering manufactured by Asahi Techno Glass Co., Ltd.) was adjusted to a molar ratio of 100: 0.5: 1.5: 2.
Table 1 shows the results of dielectric constant evaluation using a single plate capacitor.
The barium calcium titanate of the present invention of Examples 2, 3, 5, and 7 had a high sintered density, and the temperature characteristics at that time satisfied E7 standard X7R.
Since the sintered density of the barium calcium titanate of Comparative Examples 2 and 4 is low, the firing temperature cannot be increased. As a result, the dielectric constant satisfying X7R of the EIA standard was lowered.

It is a cross-sectional schematic diagram which shows an example of the multilayer ceramic capacitor which is a preferable embodiment of this invention. FIG. 2 is an exploded view illustrating an example of an internal structure of a mobile phone including the multilayer ceramic capacitor of FIG. 1. 1 is an example of an X-ray diffraction spectrum diagram of Ba _0.950 Ca _0.050 TiO ₃ powder of Example 1. FIG. 2 is an example of a scanning electron micrograph of Ba _0.950 Ca _0.050 TiO ₃ powder of Example 1. FIG. It is an example of elemental analysis diagram with a transmission electron micrograph and EDX of _Ba 0.950 _Ca 0.050 TiO ₃ powder of Example 1. 2 is an example of an X-ray diffraction spectrum diagram of Ba _0.950 Ca _0.050 TiO ₃ powder of Example 2. FIG. 2 is an example of a scanning electron micrograph of Ba _0.950 Ca _0.050 TiO ₃ powder of Example 2. FIG. It is an example of elemental analysis diagram with a transmission electron micrograph and EDX of _Ba 0.950 _Ca 0.050 TiO ₃ powder of Example 2. The _Ba 0.950 _Ca 0.050 TiO ₃ powder of Example 2 is an example of a transmission electron microscope photograph observed with 250,000-fold. 2 is an example of an X-ray diffraction spectrum diagram of Ba _0.950 Ca _0.050 TiO ₃ powder of Comparative Example 1. FIG. It is an example of the X-ray diffraction spectrum figure which expanded FIG. 4 is an example of an X-ray diffraction spectrum diagram of Ba _0.950 Ca _0.050 TiO ₃ powder of Comparative Example 2. FIG. It is an example of the X-ray diffraction spectrum figure which expanded FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Multilayer ceramic capacitor (capacitor), 2 ... Dielectric layer

Claims (28)

(Ba _1-X Ca _X ) _Y TiO ₃ (where 0 <X <0.2 and 0.98 ≦ Y ≦ 1.02), and containing an orthorhombic perovskite compound The barium calcium titanate having a rate of 3 mol% or less (including 0 mol%) and a specific surface area D of 1 m ² / g or more and 100 m ² / g or less. When the ratio (c / a) between the a-axis length and the c-axis length of the crystal lattice calculated by the Rietveld method is y, the relationship between the y and the specific surface area D is the following formula (1) or the following formula: The barium calcium titanate according to claim 1, wherein (2) is satisfied.
y ≧ 1.075−8.8 × 10 ⁻⁶ × D ³ (when 1 ≦ D ≦ 9.7) (1)
y ≧ 1.003 (when 9.7 <D ≦ 100) (2)   The barium calcium titanate according to claim 1 or 2, wherein the barium calcium titanate contains 80% or more of single crystal particles. The barium calcium titanate according to any one of claims 1 to 3, wherein 80% or more of particles having no pores of 1 nm or more are contained in the particles . Barium calcium titanate as claimed in any one of claims 1 to 4, wherein the specific surface area D is less powder 5 m 2 ^{/ g} or more 100 m 2 / ^g. The barium calcium titanate according to any one of claims 1 to 5 , wherein X in the composition formula satisfies 0.05 ≦ X <0.2. A step of synthesizing barium titanate by introducing barium hydroxide and titanium oxide and reacting them in an alkaline solution containing a basic compound and having a pH of 10 or more;
Next, a step of synthesizing barium calcium titanate by adding and reacting calcium hydroxide;
And a step of vaporizing and removing the basic compound. A method for producing barium calcium titanate, comprising: The molar ratio of barium hydroxide to calcium hydroxide is in the range of 1: 0 to 0.8: 0.2, and the amount of titanium oxide is 0.98 to the total molar amount of barium hydroxide and calcium hydroxide. The method for producing barium calcium titanate according to claim 7 , wherein the barium calcium titanate is produced by reacting barium hydroxide, calcium hydroxide and titanium oxide in an alkaline solution at 1.02 times. . In the barium titanate synthesis step, the reaction is performed until the remaining amount of barium ions in the alkaline solution is 1/100 or less of the input amount,
The barium calcium titanate according to claim 7 or 8 , wherein in the barium calcium titanate synthesis step, the reaction is performed until the remaining amount of calcium ions is 1/100 or less of the input amount. Production method. Method for producing a barium calcium titanate according to any one of claims 7 to 9 after the step of removing the basic compound, and performing a heat treatment in the range of 350 ° C. or higher 1200 ° C. or less. In the step of barium titanate synthesized until titanate emissions barium calcium synthesis, claims 7 to the concentration of carbonate groups in the reaction solution, and controlling the 500ppm following range of 0ppm in terms of CO ₂ 10. The method for producing barium calcium titanate according to any one of 10 above. Method for producing a barium calcium titanate according to any one of claims 7 to 11, wherein the titanium oxide are those containing brookite crystals. The titanium oxide, a manufacturing method of the barium calcium titanate according to any one of claims 7 to 12, characterized in that a titanium oxide sol obtained by hydrolyzing a titanium compound in an acidic solution. The basic compound, under an atmospheric pressure or a reduced pressure, evaporation, sublimation, any of claims 7 to 13, characterized in that a substance that vaporizes at least one or more means of pyrolysis 1 The manufacturing method of barium calcium titanate as described in an item. Wherein the basic compound, method for producing a barium calcium titanate according to any one of claims 7 to 14, characterized in that an organic base compound. Wherein the basic compound, method for producing a barium calcium titanate according to any one of claims 7 to 15, characterized in that tetramethyl ammonium hydroxide. A dielectric material comprising the barium calcium titanate according to any one of claims 1 to 6 . A paste comprising the barium calcium titanate according to any one of claims 1 to 6 . A slurry comprising the barium calcium titanate according to any one of claims 1 to 6 . A thin film-like formed product comprising the barium calcium titanate according to any one of claims 1 to 6 . A dielectric ceramic produced using the barium calcium titanate according to any one of claims 1 to 6 . A pyroelectric porcelain produced using the barium calcium titanate according to any one of claims 1 to 6 . A piezoelectric ceramic manufactured using the barium calcium titanate according to any one of claims 1 to 6 . A capacitor comprising the dielectric ceramic according to claim 21 . 25. An electronic device comprising at least one selected from the group consisting of a thin film-like product according to any one of claims 20 to 24 , a porcelain, and a capacitor. 24. A sensor comprising one or more of the thin film-like formation or porcelain according to any one of claims 20 to 23 . A dielectric film comprising the barium calcium titanate according to any one of claims 1 to 6 . A capacitor manufactured using the dielectric film according to claim 27 .

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