JP2005162587A - Barium titanate and electronic part using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide barium titanate which has small particle diameters, contains little unnecessary impurities and has excellent electrical properties, and which can form a thin dielectric ceramic film necessary for a small size capacitor enabling miniaturization of electronic equipment. <P>SOLUTION: The barium titanate is a single crystal in the form of particles, in which particles without a void having a diameter of 1 nm or more are contained in an amount of ≥20% by number of the total particles. It is possible to miniaturize the electronic equipment by using slurry, films, dielectric materials, and piezoelectric materials using the barium titanate. <P>COPYRIGHT: (C)2005,JPO&NCIPI

Description

  The present invention relates to barium titanate used for dielectric materials, multilayer ceramic capacitors, piezoelectric materials, and the like, and a method for producing the same, and more particularly to barium titanate having no defects inside and a method for producing the same.

  Barium titanate is widely used as a functional material such as a dielectric material, a multilayer ceramic capacitor, and a piezoelectric material. Since electronic components are becoming smaller and lighter, development of a method for obtaining barium titanate having excellent electrical characteristics such as a smaller particle size and a high dielectric constant is desired.

  Defect-free barium titanate obtained by the solid phase method is known to have a high dielectric constant, but the particle size cannot be sufficiently reduced, and wet synthetic barium titanate with a small particle size is And having a defect, the dielectric constant could not be sufficiently increased.

  As a method for producing barium titanate particles such as barium titanate, a solid phase produced by using oxides or carbonates as raw materials, mixing them with a ball mill or the like, and then reacting them at a high temperature of about 800 ° C. or higher. First, oxalate method in which oxalic acid complex salt is first prepared and pyrolyzed to obtain barium titanate particles, alkoxide method in which metal alkoxide is used as raw material, and precursor is obtained by hydrolyzing them, and raw material is used as water solvent Among them, there is a hydrothermal synthesis method in which a precursor is obtained by reacting at high temperature and pressure. Also, a method of reacting a hydrolysis product of a titanium compound with a water-soluble barium salt in a strong alkaline aqueous solution (for example, Patent Document 1), a method of reacting a titanium oxide sol and a barium compound in an alkaline aqueous solution (for example, Patent Document) 2) There is a method of reacting a titanium oxide sol and a barium compound in a closed container (for example, Patent Document 3). In addition, there is a method of reducing the hydroxyl groups in the lattice to 0.1 wt% by using a raw material having a hydroxyl group content of 1 wt% or less in the crystal lattice and adjusting the firing conditions (for example, Patent Document 4).

  However, although the solid phase method can produce barium titanate particles having low production costs and no defects, the generated barium titanate particles have a large particle size and are not suitable for functional materials such as dielectric materials and piezoelectric materials.

  Although the oxalate method produces smaller particles than the solid phase method, the carbonate group derived from oxalic acid remains. In addition, there is a residual hydroxyl group due to water taken inside. It is known that hydroxyl groups can be removed by heat treatment, but at this time, pores are generated inside the particles (for example, Non-Patent Document 1). Therefore, barium titanate having excellent electrical characteristics cannot be obtained.

  In the alkoxide method and the hydrothermal synthesis method, barium titanate having a fine particle size is obtained, but there are many residual hydroxyl groups due to water taken into the interior. The hydroxyl group can be removed by heat treatment, but at this time, voids are generated inside the particles. Therefore, barium titanate having excellent electrical characteristics cannot be obtained. In the alkoxide method, carbonate groups remain.

  Since the hydrothermal synthesis method is performed under high-temperature and high-pressure conditions, there is a problem that dedicated equipment is required and the cost is increased.

  The methods of Patent Documents 1, 2, and 3 require a water washing step. In the process, dissolution of barium and incorporation of the resulting hydroxyl group occur. The hydroxyl group can be removed by heat treatment, but at this time, voids are generated inside the particles. Therefore, barium titanate having excellent electrical characteristics cannot be obtained. The method of Patent Document 3 has a problem in that a dedicated facility is required and the cost is increased because the pulverized media is heated and reacted in an airtight container while stirring.

The method of Patent Document 4 proposes a method for reducing the hydroxyl group in the lattice by paying attention to the hydroxyl group in the lattice, but the method is to reduce the hydroxyl group in the lattice that originally exists, and the hydroxyl group is reduced only to about 0.1 wt%. This is insufficient from the standpoint of improving the dielectric constant.
Japanese Patent No. 1841875 International Publication WO00 / 35811 JP-A-7-291607 Japanese Patent Laid-Open No. 11-273986 Proceedings of the 15th Autumn Symposium of the Ceramic Society of Japan, 149 pages

  The present invention is capable of forming a thin-film dielectric ceramic or dielectric film necessary for a small capacitor capable of downsizing an electronic device, has a small particle size, has few unnecessary impurities, and has excellent electrical characteristics. It is to provide barium titanate and an electronic component using the same.

  As a result of intensive studies on the above-mentioned problems, the present inventors have reacted titanium oxide sol and barium compound in an alkaline solution in which a basic compound is present, and after the reaction, removed the basic compound as a gas and calcined. Thus, it was found that fine barium titanate having no defects that could not be obtained by the conventional production method was obtained, and the invention was completed.

That is, the present invention comprises the inventions of the following items.
(1) Barium titanate, which is a single crystal and contains 20% or more of the entire particles, in which particles having no pores of 1 nm or more are present in the grains.
(2) The barium titanate according to (1), wherein particles having no pores of 1 nm or more in the grains are 50% or more of the whole particles.
(3) The barium titanate according to (1), wherein particles having no pores of 1 nm or more in the grains are 80% or more of the whole particles.
(4) The barium titanate according to any one of (1) to (3), wherein the BET specific surface area is 0.1 m ² / g or more.
(5) The barium titanate according to any one of (1) to (4), wherein no steep peak is detected in the vicinity of 3500 cm ⁻¹ by infrared spectroscopy after heat treatment at 700 ° C.
(6) From Sn, Zr, Ca, Sr, Pb, Ho, Nd, Y, La, Ce, Mg, Bi, Ni, Al, Si, Zn, B, Nb, W, Mn, Fe, Cu, and Dy The barium titanate according to any one of (1) to (5), comprising at least one element selected from the group consisting of less than 5 mol% (including 0 mol%) with respect to BaTiO ₃ .
(7) The barium titanate according to any one of (1) to (6), wherein the barium titanate is powder.
(8) The barium titanate according to any one of (1) to (7), which is obtained by wet synthesis of barium titanate.
(9) A slurry containing barium titanate according to any one of (1) to (8).
(10) A paste containing barium titanate according to any one of (1) to (8).
(11) A dielectric material containing barium titanate according to any one of (1) to (8).
(12) A dielectric ceramic including the barium titanate according to any one of (1) to (8).
(13) A piezoelectric material containing barium titanate according to any one of (1) to (8).
(14) A piezoelectric ceramic containing the barium titanate according to any one of (1) to (8).
(15) A dielectric film containing the barium titanate according to any one of (1) to (8).
(16) A capacitor comprising the dielectric material according to (11).
(17) A capacitor comprising the piezoelectric material according to (13).
(18) A capacitor comprising the dielectric film according to (15).
(19) An in-substrate capacitor comprising the dielectric film according to (15).
(20) A printed wiring board comprising the dielectric film according to (15).
(21) An electronic device including the capacitor according to any one of (16) to (19).

The barium titanate obtained by the present invention was a single crystal without any hydroxyl group or defects due to elimination of the hydroxyl group in the grains. The material had a small particle size, a high dielectric constant, and excellent electrical characteristics.
By using dielectric materials such as dielectric ceramics obtained from this, small electronic parts such as multilayer ceramic capacitors and piezoelectric materials can be obtained. Furthermore, by using these for electronic devices, electronic devices can be reduced in size and weight. It became.
Moreover, the dielectric film which has the outstanding dielectric characteristic will be obtained if the slurry containing the barium titanate of this invention or the barium titanate of this invention is used.
Since the dielectric film has excellent dielectric characteristics, it can exhibit excellent characteristics even when it is thinned, so that it 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 titanate of the present invention, a general formula ABO perovskite-type compound represented by _3, the A Ba is, the B Ti refers to a BaTiO ₃ accounted together.
However, Sn, Zr, Ca, Sr, Pb, Ho, Nd, Y, La, Ce, Mg, Bi, Ni, Al, Si, Zn, B, Nb, W, Mn, Fe, Cu, and Dy It may contain at least one element selected from less than 5 mol% with respect to BaTiO ₃ .

  In addition, the barium titanate of the present invention is characterized in that there are no hydroxyl groups or defects due to elimination of hydroxyl groups in the grains.

  Furthermore, the barium titanate of the present invention is also characterized by being a single crystal.

Hydroxyl groups present in barium titanate are detected as a peak near 3500 cm ⁻¹ by infrared spectroscopy, but hydroxyl groups present on the surface are also detected in addition to the hydroxyl groups in the grains. However, it was found that the hydroxyl groups present on the surface were desorbed at a temperature lower than 700 ° C. Therefore, after heat treatment at 700 ° C. in advance, by performing infrared spectroscopic analysis, it is possible to detect the hydroxyl groups inside the particles that lower the dielectric constant.

  Moreover, the defect accompanying the desorption of a hydroxyl group means a void (void) having a diameter of 1 nm or more detected by, for example, TEM (transmission electron microscope) observation (preferably by observing particles as a thin film). This is the same as the void represented by symbol 22 in FIG. FIG. 1 shows a TEM photograph of the barium titanate powder prepared in the comparative example (actually taken at 150,000 times, but reduced in the attached drawing), but pores appearing as bubbles inside the particles (Void) can be recognized, and this is a defect accompanying the elimination of a hydroxyl group.

  The barium titanate of the present invention has a high dielectric constant because there are no hydroxyl groups or defects due to elimination of hydroxyl groups in the grains.

  Further, the barium titanate particles have a high dielectric constant if they are single crystals, but it can be confirmed from the lattice image analysis by TEM that they are single crystals.

  Since the barium titanate of the present invention is a single crystal, the dielectric constant is increased.

  Thus, the barium titanate of the present invention has a small particle size, a high dielectric constant, and excellent electrical characteristics. By using a dielectric material such as a dielectric ceramic obtained from the particles, a small electronic component such as a multilayer ceramic capacitor can be obtained. Further, by using these in an electronic device, the electronic device can be reduced in size and weight. Become.

Generally, in order to reduce the size of electronic equipment, if the BET specific surface area is smaller than 0.1 m ² / g, the particle size is too large to be effective, and if the BET specific surface area is 0.1 m ² / g or more, it is effective. Preferably it is 1 m < ² > / g or more, More preferably, it is 5 m < ² > / g or more.

  The method for producing barium titanate of the present invention is not particularly limited, but it is preferable to employ a wet method. In this case, it is preferable to use a titanium oxide sol as a raw material.

  The titanium oxide sol used in the present invention is not particularly limited, but a titanium oxide sol containing a brookite crystal is preferable. As long as it contains brookite-type crystals, it may contain brookite-type titanium oxide alone, or rutile-type or anatase-type titanium oxide. When the rutile type or anatase type titanium oxide is included, the ratio of the brookite type titanium oxide in the titanium oxide is not particularly limited, but is usually 1 to 100% by mass, preferably 10 to 100% by mass, more preferably Is 50-100 mass%, More preferably, it is 70-100 mass%. In order to make the titanium oxide particles excellent in dispersibility in a solvent, it is preferable that the particles are crystalline rather than indeterminate because they are easily formed into single particles. It is because it is excellent. The reason for this is not clear, but it is considered that the blue kite type has a higher zeta potential than the rutile type and the anatase type.

  As a method for producing titanium oxide particles containing brookite-type crystals, there is a production method for obtaining titanium oxide particles containing brookite-type crystals by heat-treating anatase-type titanium oxide particles. In addition, it can be produced in a liquid phase by obtaining a titanium oxide sol in which titanium oxide particles are dispersed by neutralizing or hydrolyzing a solution of titanium compounds such as titanium tetrachloride, titanium trichloride, titanium alkoxide, and titanium sulfate. There are methods.

  As a method for producing barium titanate particles using titanium oxide particles containing brookite crystals, the titanium salt is hydrolyzed in an acidic solution because the particles have a small particle size and excellent dispersibility. Thus, a method of obtaining a titanium oxide sol is preferable. That is, titanium tetrachloride is added to hot water of 75 to 100 ° C., and titanium tetrachloride is hydrolyzed at a temperature of 75 ° C. or higher and lower than the boiling point of the solution while controlling the chlorine ion concentration to obtain blue as titanium oxide sol. A method of obtaining titanium oxide particles containing kite-type crystals (Japanese Patent Laid-Open No. 11-043327), or adding titanium tetrachloride to hot water at 75 to 100 ° C., and the presence of either or both of nitrate ions and phosphate ions Below, titanium tetrachloride is hydrolyzed while controlling the total concentration of chlorine ions, nitrate ions and phosphate ions at a temperature of 75 ° C. or higher and lower than the boiling point of the solution to obtain a blue kite type crystal as a titanium oxide sol. A method of obtaining titanium oxide particles contained therein (International Publication WO99 / 58451) is preferred.

  The size of the titanium oxide particles containing the brookite crystal thus obtained has a primary particle size of usually 5 to 50 nm. When the particle diameter exceeds 50 nm, the particle diameter of the barium titanate particles produced using this as a raw material becomes large, which makes it unsuitable for functional materials such as dielectric materials and piezoelectric materials. When the particle diameter is less than 5 nm, it is difficult to handle in the step of producing titanium oxide particles.

  In the production method of the present invention, when a titanium oxide sol obtained by hydrolyzing a titanium salt in an acidic solution is used, the crystal form of the titanium oxide particles in the obtained sol is not limited, and the blue kite type is used. It is not limited.

  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 oxidized with excellent dispersibility. 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 particles, it is possible to reduce the mixing of anions into the particles when the barium titanate particles are produced.

  On the other hand, when the hydrolysis is carried out in a neutral or alkaline solution, the reaction rate increases and many nuclei are generated in the initial stage. Therefore, it becomes a titanium oxide sol having a small particle size but poor dispersibility, and the particles are aggregated in a bowl shape. When barium titanate particles are produced using such a titanium oxide sol as a raw material, even if the obtained particles have a small particle size, the dispersibility is poor. In addition, anions are likely to be mixed inside the titanium oxide particles, and it becomes difficult to remove these anions in the 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 the titanium salt of a raw material 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 is obtained. When the concentration is less than 0.01 mol / L, the resulting titanium oxide is obtained. This is because the concentration decreases and the productivity deteriorates.

  The barium compound used in the production method of the present invention is preferably water-soluble, and is usually a hydroxide, nitrate, acetate, chloride or the like. Moreover, these may be used individually by 1 type and may mix and use 2 or more types of compounds by arbitrary ratios. Specifically, for example, barium hydroxide, barium chloride, barium nitrate, barium acetate and the like are used.

  The barium titanate of the present invention is a method of reacting titanium oxide particles containing brookite crystals with a barium compound, or a method of reacting a titanium oxide sol obtained by hydrolyzing a titanium salt in an acidic solution with a barium compound. Can be manufactured.

  The reaction is preferably carried out in an alkaline solution in which a basic compound is present. The pH of the solution is preferably 11 or more, more preferably 13 or more, and particularly preferably 14 or more. By setting the pH to 14 or more, barium titanate particles having a smaller particle diameter can be produced. For example, it is desirable that the reaction solution is kept alkaline with a pH of 11 or more by adding an organic base compound. When the pH is lower than 11, the reaction rate between the titanium oxide sol and the barium compound is lowered, so that it is difficult to obtain barium titanate having a high dielectric constant.

  The basic compound to be added is not particularly limited, but is preferably a substance that becomes a gas by evaporation, sublimation, and / or thermal decomposition at a temperature equal to or lower than the firing temperature of barium titanate and under atmospheric pressure or reduced pressure. , TMAH (tetramethylammonium hydroxide), choline and the like can be preferably used. When an alkali metal hydroxide such as lithium hydroxide, sodium hydroxide, or potassium hydroxide is added, the alkali metal remains in the obtained barium titanate particles, and is molded, sintered, dielectric material, piezoelectric When a functional material such as a material is used, its characteristics may be inferior, so it is preferable to add the basic compound such as tetramethylammonium hydroxide.

Furthermore, by controlling the concentration of carbonate groups (including CO ₂ , H ₂ CO ₃ , HCO ₃ ⁻ , and CO ₃ ²⁻ as carbonic acid species) in the reaction solution, barium titanate with a large dielectric constant can be stabilized. Can be manufactured.

The concentration of carbonic acid groups in the reaction solution (CO ₂ equivalent value, hereinafter the same unless otherwise specified) is preferably 500 ppm by mass or less, more preferably 1 to 200 ppm by mass, and particularly preferably. 1-100 mass ppm. If the carbonate group concentration is outside this range, barium titanate having a large dielectric constant may not be obtained.

  In the reaction solution, the concentration of titanium oxide particles or titanium oxide sol is 0.1 to 5 mol / L, and the concentration of the metal salt containing barium is 0.1 to 5 mol / L in terms of metal oxide. It is preferable to prepare so that it becomes.

Furthermore, it consists of Sn, Zr, Ca, Sr, Pb, Ho, Nd, Y, La, Ce, Mg, Bi, Ni, Al, Si, Zn, B, Nb, W, Mn, Fe, Cu, and Dy. the compound of at least one element selected from the group, these elements titanate in barium after the reaction, may be added so as to be contained less than 5 mol% relative to BaTiO _3. Moreover, these elements may be unevenly distributed on the particle surface. For example, when a capacitor is manufactured, these elements may be adjusted in kind and addition amount so that characteristics such as temperature characteristics are desired.

  The alkaline solution prepared in this manner is usually heated and maintained at 40 ° C. to the boiling point temperature of the solution, preferably 80 ° C. to the boiling point temperature of the solution, under a normal pressure while stirring. The reaction time is usually 1 hour or longer, preferably 4 hours or longer.

  In general, impurity ions are removed from the slurry after the reaction by a method using electrodialysis, ion exchange, water washing, acid washing, osmosis membrane, etc. Since the barium contained in the ion is also ionized and partially dissolved, the controllability to a desired composition ratio is poor, and defects occur in the crystal, resulting in a low dielectric constant. As a process for removing impurities such as basic compounds, it is desirable not to use such a method but to use the method described later.

  The particle | grains of this invention can be obtained by baking the slurry after completion | finish of reaction. In the baking, the crystallinity of the barium titanate particles is improved, and anions such as chlorine ions, sulfate ions and phosphate ions remaining as impurities, and basic compounds such as tetramethylammonium hydroxide are evaporated, It can be removed as a gas by sublimation and / or thermal decomposition, and is usually performed at 300 to 1200 ° C. There is no restriction | limiting in particular in a baking atmosphere, Usually, it carries out in air | atmosphere. It is desirable to further improve the crystallinity by repeating the step of firing, grinding or mixing and then firing again.

  Prior to firing, solid-liquid separation may be performed as necessary for handling. Solid-liquid separation includes, for example, steps such as sedimentation, concentration, filtration, and / or drying. In the sedimentation, concentration, and filtration steps, a flocculant or a dispersant may be used to change the sedimentation rate or change the filtration rate. The drying step is a step of evaporating or sublimating the liquid component, and for example, methods such as reduced pressure drying, hot air drying, freeze drying and the like are used.

  Furthermore, baking may be performed after removing a basic compound or the like as a gas in advance in the temperature range of room temperature to baking temperature under atmospheric pressure or reduced pressure.

The barium titanate produced in this way is excellent in electrical characteristics in which there are no hydroxyl groups or defects due to elimination of hydroxyl groups in the grains. As described above, the hydroxyl group is detected as a peak around 3500 cm ⁻¹ by infrared spectroscopy, but the hydroxyl group inside the particle that lowers the dielectric constant is detected by performing infrared spectroscopy after heat treatment at 700 ° C. in advance. I can do it. Defects associated with hydroxyl desorption are detected as voids having a diameter of 1 nm or more by TEM observation.

  In conventional well-known barium titanate, when thinly observed and carefully observed, almost all particles have vacancies, but about 100 or less particles may have no vacancies. . However, several hundreds of barium titanates in the examples of the present invention were examined, but no defects (vacancies) associated with the elimination of hydroxyl groups were observed. That is, in the barium titanate powder of the present invention, the number of particles that do not contain defects (vacancies) associated with desorption of hydroxyl groups is 20% or more, preferably 50% or more, more preferably 80% or more, and still more preferably It can be 90% or more, particularly preferably 98% or more, and can be substantially all.

In addition, the barium titanate particles have a high dielectric constant if they are single crystals, but the fact that the barium titanate particles of the present invention are single crystals can be confirmed from the analysis of lattice images by TEM.
A film having a high dielectric constant can be obtained by dispersing the filler containing barium titanate of the present invention in at least one selected from the group consisting of a thermosetting resin and a thermoplastic resin.

When a filler other than barium titanate is included, it is possible to use one or more selected 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 barium titanate of the present invention in at least one of a thermosetting resin and / or a thermoplastic resin, the filler is dispersed in advance in a solvent or a mixture of the resin composition and the solvent. It is desirable to obtain a slurry.
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 add 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 barium titanate 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 and the like 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 titanate particles are coated. However, if the amount is too large, it may remain unreacted and may have an adverse effect. The effect may be reduced. Therefore, it is preferable to select a blending amount capable of uniformly dispersing the filler depending on the particle diameter and specific surface area of the filler containing barium titanate and the type of coupling agent. A blending amount of about 05 to 20% by mass 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 titanate, it is desirable to include a heat treatment step after making 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.

When the barium titanate of the present invention or the slurry containing the barium titanate of the present invention is used, a dielectric film having excellent dielectric properties can be obtained.
Since the dielectric film has excellent dielectric characteristics, it can exhibit excellent characteristics even when it is thinned, so that it can be applied to an in-substrate capacitor. If the in-substrate capacitor using the dielectric film of the present invention is employed in an electronic device such as a mobile phone or a digital camera, it is effective in reducing the size, weight and performance of the device.

  EXAMPLES Hereinafter, the present invention will be specifically described with reference to examples and comparative examples, but the present invention is not limited only to these examples.

(Dielectric constant measurement method)
The dielectric constant of the obtained barium titanate was measured as follows.
Barium titanate and MgO (high-purity magnesium oxide 500-04R manufactured by Kyowa Chemical Industry Co., Ltd.), Ho ₂ O ₃ (fine powdered holmium oxide manufactured by Japan Yttrium Co., Ltd.), BaSiO ₃ (manufactured by Soekawa Riken Co., Ltd.) The mixture was mixed so that the molar ratio was 100: 0.5: 0.75: 1.0. After 0.3 g of the mixed powder was uniaxially molded with a 13 mmφ mold, it was calcined at 1300 ° C. for 2 hours in a nitrogen atmosphere. After accurately 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 capacitance of the capacitor was measured with a LF impedance analyzer 4192A manufactured by HEWLETT PACKARD, and the dielectric constant was calculated from the capacitance when the measurement frequency was 1 kHz and the measurement temperature was changed from −55 ° C. to 125 ° C. and the size of the sintered body. Calculated.

Example 1:
Titanium tetrachloride (manufactured by Sumitomo Titanium Co., Ltd .: purity 99.9%) An aqueous solution with a concentration of 0.25 mol / L was introduced into a reactor equipped with a reflux condenser to suppress the escape of chlorine ions and keep it acidic. Heated to near boiling point. The titanium tetrachloride was hydrolyzed by holding at that temperature for 60 minutes to obtain a titanium oxide sol. Part of the obtained titanium oxide sol was dried at 110 ° C., and the crystal form was examined with an X-ray diffractometer (RAD-B rotor flex) manufactured by Rigaku Corporation. As a result, oxidation of blue kite type 80% and anatase type 20% was performed. It was found to be titanium.

And barium hydroxide octahydrate (barytes Kogyo Co.) 126 g, tetramethylammonium 20 wt% aqueous solution of hydroxide (Seikemu Showa Co., Ltd.) in carbonate group concentration of 60 mass ppm (CO ₂ converted blowing carbon dioxide gas Thereafter, 456 g of the aqueous solution was added to adjust the pH to 14 and heated to 95 ° C. in a reactor equipped with a reflux condenser. 213 g of sol having a titanium oxide concentration of 15% by mass obtained by precipitation concentration of the sol was dropped into the reactor at a rate of 7 g / min.

  The liquid temperature was raised to 110 ° C., and the reaction was carried out while maintaining stirring for 4 hours. The resulting slurry was allowed to cool to 50 ° C. and then filtered. The filtration residue was dried at 300 ° C. for 5 hours to obtain fine particle powder. The ratio of the actual yield to the theoretical yield calculated from the amount of titanium oxide and barium hydroxide used in the reaction was 99.8%.

  When the obtained fine particle powder was observed by TEM, it was a single crystal. 5 g of the powder was put in a porcelain dish, heated at 20 ° C./min in an electric furnace, held at the temperature shown in Table 1 for 2 hours (fired), and then naturally cooled.

As a result of examining the X-ray diffraction of this powder with an X-ray diffractometer (RAD-B rotor flex) manufactured by Rigaku Corporation, it was found that the obtained powder was a perovskite-type BaTiO ₃ . The c / a ratio was determined from the X-ray diffraction intensity by Rietveld analysis. The specific surface area of the powder was determined by the BET method. The results thus obtained are shown in Table 1 and FIGS. 2, 3, 4, and 5.

Furthermore, the amount of carbonate groups contained in the sample fired at 950 ° C. was quantified using a BIORAD infrared spectroscopic analyzer (FTS6000). When all the carbonate groups were barium carbonate, the amount was equivalent to about 1% by mass. At the same time, a sharp absorption peak in the vicinity of 3500 cm ⁻¹ corresponding to the hydroxyl group in the lattice did not appear. The dielectric constant at 25 ° C. was 3200. The temperature characteristic at that time satisfied the X7R characteristic of the classification code of CLASSII (high dielectric constant system) of the EIA standard (American Electronic Machinery Industry Standard). The dielectric ceramic, dielectric film, capacitor, and piezoelectric material obtained from the barium titanate have excellent characteristics.

Example 2:
In the same manner as in Example 1, a perovskite-type BaTiO ₃ was obtained. However, it was crystallized by holding at 600 ° C. for 2 hours. When examined in the same manner as in Example 1, the specific surface area was 25 m ² / g and the c / a ratio was 1.0032. Infrared spectroscopic analysis was performed in the same manner as in Example 1 except that this sample was heat-treated at 700 ° C. As a result, a sharp absorption peak in the vicinity of 3500 cm ⁻¹ corresponding to the hydroxyl group in the lattice did not appear. The dielectric constant at 25 ° C. was 1100. The temperature characteristic at that time satisfied the X7R characteristic of the EIA standard. The dielectric ceramic, dielectric film, capacitor, and piezoelectric material obtained from the barium titanate have excellent characteristics.

Example 3:
In the same manner as in Example 1, a perovskite-type BaTiO ₃ was obtained. However, it was crystallized by holding at 950 ° C. for 2 hours. When examined in the same manner as in Example 1, the specific surface area was 4.1 m ² / g, and the c / a ratio was 1.0092. This sample was subjected to infrared spectroscopic analysis in the same manner as in Example 1. As a result, a sharp absorption peak in the vicinity of 3500 cm ⁻¹ corresponding to the hydroxyl group in the lattice did not appear. The dielectric constant at 25 ° C. was 3600. The temperature characteristic at that time satisfied the X7R characteristic of the EIA standard. The dielectric ceramic, dielectric film, capacitor, and piezoelectric material obtained from the barium titanate have excellent characteristics. TEM observation was performed at 250,000 times, but no defects due to the elimination of hydroxyl groups were observed.

Example 4:
In the same manner as in Example 1, a perovskite-type BaTiO ₃ was obtained. However, it was crystallized by holding at 1200 ° C. for 2 hours. When examined in the same manner as in Example 1, the specific surface area was 0.5 m ² / g and the c / a ratio was 1.0110. This sample was subjected to infrared spectroscopic analysis in the same manner as in Example 1. As a result, a sharp absorption peak in the vicinity of 3500 cm ⁻¹ corresponding to the hydroxyl group in the lattice did not appear. The dielectric constant at 25 ° C. was 4000. The temperature characteristic at that time satisfied the X7R characteristic of the EIA standard. The dielectric ceramic, dielectric film, capacitor, and piezoelectric material obtained from the barium titanate have excellent characteristics. TEM observation was performed at 250,000 times, but no defects due to the elimination of hydroxyl groups were observed.

Example 5:
Barium titanate was synthesized in the same manner as in Example 1 except that the amount of TMAH added was reduced to pH 11. The ratio of the actual yield to the theoretical yield was 98%. When observed by TEM, it was a single crystal. The sample crystallized by holding at 880 ° C. for 2 hours was examined in the same manner as in Example 1. As a result, the specific surface area was 7.3 m ² / g and the c / a ratio was 1.0090. This sample was subjected to infrared spectroscopic analysis in the same manner as in Example 1. As a result, a sharp absorption peak in the vicinity of 3500 cm ⁻¹ corresponding to the hydroxyl group in the lattice did not appear. The dielectric constant at 25 ° C. was 2600. The temperature characteristic at that time satisfied the X7R characteristic of the EIA standard. The dielectric ceramic, dielectric film, capacitor, and piezoelectric material obtained from the barium titanate have excellent characteristics.

Example 6:
Barium titanate was synthesized in the same manner as in Example 1 except that a choline aqueous solution having a carbonate group concentration of 75 mass ppm was used instead of the TMAH aqueous solution. The ratio of the actual yield to the theoretical yield was 99.9%. When observed by TEM, it was a single crystal. A sample crystallized by holding at 880 ° C. for 2 hours was examined in the same manner as in Example 1. As a result, the specific surface area was 7 m ² / g and the c / a ratio was 1.0091. This sample was subjected to infrared spectroscopic analysis in the same manner as in Example 1. As a result, a sharp absorption peak in the vicinity of 3500 cm ⁻¹ corresponding to the hydroxyl group in the lattice did not appear. The dielectric constant at 25 ° C. was 2700. The temperature characteristic at that time satisfied the X7R characteristic of the EIA standard. The dielectric ceramic, dielectric film, capacitor, and piezoelectric material obtained from the barium titanate have excellent characteristics.

Example 7:
Barium titanate was synthesized in the same manner as in Example 1 except that a commercially available anatase type titanium oxide sol (STS-02 manufactured by Ishihara Sangyo) was used instead of the blue kite type titanium oxide sol synthesized in Example 1. The ratio of the actual yield to the theoretical yield was 99.8%. When observed by TEM, it was a single crystal. The sample crystallized by holding at 880 ° C. for 2 hours was examined in the same manner as in Example 1. As a result, the specific surface area was 7.7 m ² / g and the c / a ratio was 1.0071. This sample was subjected to infrared spectroscopic analysis in the same manner as in Example 1. As a result, a sharp absorption peak in the vicinity of 3500 cm ⁻¹ corresponding to the hydroxyl group in the lattice did not appear. The dielectric constant at 25 ° C. was 2400. The temperature characteristic at that time satisfied the X7R characteristic of the EIA standard. The dielectric ceramic, dielectric film, capacitor, and piezoelectric material obtained from the barium titanate have excellent characteristics.

Example 8:
Barium titanate was synthesized in the same manner as in Example 1 except that TMAH having a carbonate group content of 110 mass ppm was used instead of TMAH having a carbonate group content of 60 mass ppm. The ratio of the actual yield to the theoretical yield was 99.8%. When observed by TEM, it was a single crystal. The sample crystallized by holding at 880 ° C. for 2 hours was examined in the same manner as in Example 1. As a result, the specific surface area was 7.3 m ² / g and the c / a ratio was 1.0090. This sample was subjected to infrared spectroscopic analysis in the same manner as in Example 1. As a result, a sharp absorption peak in the vicinity of 3500 cm ⁻¹ corresponding to the hydroxyl group in the lattice did not appear. The dielectric constant at 25 ° C. was 2700. The temperature characteristic at that time satisfied the X7R characteristic of the EIA standard. The dielectric ceramic, dielectric film, capacitor, and piezoelectric material obtained from the barium titanate have excellent characteristics.

Example 9:
Barium titanate was synthesized in the same manner as in Example 1 except that TMAH having a carbonate group content of 215 mass ppm was used instead of TMAH having a carbonate group content of 60 mass ppm. The ratio of the actual yield to the theoretical yield was 99.7%. When observed by TEM, it was a single crystal. The sample crystallized by holding at 880 ° C. for 2 hours was examined in the same manner as in Example 1. As a result, the specific surface area was 7.5 m ² / g and the c / a ratio was 1.0087. This sample was subjected to infrared spectroscopic analysis in the same manner as in Example 1. As a result, a sharp absorption peak in the vicinity of 3500 cm ⁻¹ corresponding to the hydroxyl group in the lattice did not appear. The dielectric constant at 25 ° C. was 2500. The temperature characteristic at that time satisfied the X7R characteristic of the EIA standard. The dielectric ceramic, dielectric film, capacitor, and piezoelectric material obtained from the barium titanate have excellent characteristics.

Example 10:
Barium titanate was synthesized in the same manner as in Example 1 except that TMAH having a carbonate group content of 490 mass ppm was used instead of TMAH having a carbonate group content of 60 mass ppm. The ratio of the actual yield to the theoretical yield was 99.4%. When observed by TEM, it was a single crystal. The sample crystallized by holding at 880 ° C. for 2 hours was examined in the same manner as in Example 1. As a result, the specific surface area was 8.1 m ² / g and the c / a ratio was 1.0061. This sample was subjected to infrared spectroscopic analysis in the same manner as in Example 1. As a result, a sharp absorption peak in the vicinity of 3500 cm ⁻¹ corresponding to the hydroxyl group in the lattice did not appear. The dielectric constant at 25 ° C. was 2000. The temperature characteristic at that time satisfied the X7R characteristic of the EIA standard. The dielectric ceramic, dielectric film, capacitor, and piezoelectric material obtained from the barium titanate have excellent characteristics.

Example 11:
Barium titanate was synthesized in the same manner as in Example 1 except that a commercially available anatase type titanium oxide sol (ST-02, manufactured by Ishihara Sangyo) was used instead of the blue kite type titanium oxide sol synthesized in Example 1. The ratio of the actual yield to the theoretical yield was 99.8%. When observed by TEM, it was a single crystal. The sample crystallized by holding at 880 ° C. for 2 hours was examined in the same manner as in Example 1. As a result, the specific surface area was 7.7 m ² / g and the c / a ratio was 1.0066. This sample was subjected to infrared spectroscopic analysis in the same manner as in Example 1. As a result, a sharp absorption peak in the vicinity of 3500 cm ⁻¹ corresponding to the hydroxyl group in the lattice did not appear. The dielectric constant at 25 ° C. was 2200. The temperature characteristic at that time satisfied the X7R characteristic of the EIA standard. The dielectric ceramic, dielectric film, capacitor, and piezoelectric material obtained from the barium titanate have excellent characteristics.

Example 12:
In the same manner as in Example 1, a perovskite-type BaTiO ₃ fine particle powder was obtained. The powder was crystallized by holding at 300 ° C. for 2 hours. When examined in the same manner as in Example 1, the specific surface area was 45 m ² / g and the c / a ratio was 1.0000. This sample was subjected to infrared spectroscopic analysis in the same manner as in Example 1. As a result, a sharp absorption peak in the vicinity of 3500 cm ⁻¹ corresponding to the hydroxyl group in the lattice did not appear.

Comparative Example 1:
The aqueous oxalic acid solution was heated to 80 ° C. with stirring, and a mixed aqueous solution of BaCl ₂ and TiCl ₄ was added dropwise thereto to obtain titanyl barium oxalate. After washing with water to remove chlorine from the obtained sample, this was thermally decomposed at 950 ° C. to obtain BaTiO ₃ . When examined in the same manner as in Example 1, the specific surface area was 4 m ² / g and the c / a ratio was 1.0080. When the amount of carbonate groups contained in this sample was quantified with an infrared spectroscopic analyzer, it was found that 8% by mass was present when converted to barium carbonate. Since a large amount of carbonic acid groups that act as impurities were generated, the tetragonalization rate did not increase. At the same time, there was a steep absorption peak in the vicinity of 3500 cm ⁻¹ corresponding to the hydroxyl group in the lattice. The dielectric constant at 25 ° C. was 2000. The temperature characteristic at that time satisfied the X7R characteristic of the EIA standard.

Comparative Example 2:
After putting 667 g of the blue kite type titanium oxide sol synthesized in Example 1, 592 g of barium hydroxide octahydrate (Ba / Ti molar ratio 1.5) and 1 L of ion-exchanged water into a 3 L autoclave, Hydrothermal treatment was performed under saturated vapor pressure by holding for 1 hour. Excess barium contained in the obtained sample was washed with water and crystallized by maintaining at 800 ° C. for 2 hours. When examined in the same manner as in Example 1, the specific surface area was 6.9 m ² / g and the c / a ratio was 1.0033. When this sample was evaluated with an infrared spectroscopic analyzer, steep absorption of hydroxyl groups in the lattice was observed in the vicinity of 3500 cm ⁻¹ . In the hydrothermal synthesis method, it is estimated that the tetragonalization rate is lowered due to bringing a hydroxyl group into the lattice. The dielectric constant at 25 ° C. was 1200. The temperature characteristic at that time did not satisfy the X7R characteristic of the EIA standard. This is because MgO, Ho ₂ O ₃ , and BaSiO ₃ diffuse into the barium titanate due to low crystallinity.

Comparative Example 3:
Barium titanate was synthesized in the same manner as in Example 1 except that TMAH was not added. The pH at this time was 10.2. The ratio of the actual yield to the theoretical yield was 86%. It was found that the yield decreased with decreasing pH and was impractical.

Comparative Example 4:
Barium titanate was synthesized in the same manner as in Example 1 except that KOH was used instead of TMAH. The ratio of the actual yield to the theoretical yield was 99.9%. The filtered sample was washed with water to make the K concentration 100 ppm. A sample crystallized by holding this sample at 800 ° C. for 2 hours was examined in the same manner as in Example 1. As a result, the specific surface area was 9 m ² / g and the c / a ratio was 1.0030. When this sample was evaluated with an infrared spectroscopic analyzer, steep absorption of hydroxyl groups in the lattice was observed in the vicinity of 3500 cm ⁻¹ . The dielectric constant at 25 ° C. was 900. The temperature characteristic at that time did not satisfy the X7R characteristic of the EIA standard. This is because MgO, Ho ₂ O ₃ , and BaSiO ₃ diffuse into the barium titanate due to low crystallinity. The Ba / Ti molar ratio was 0.007 smaller than that before washing, suggesting that Ba elutes simultaneously with K.

Comparative Example 5:
Barium titanate was synthesized in the same manner as in Example 1 except that TMAH having a carbonate group concentration of 1000 mass ppm was used instead of TMAH having a carbonate group concentration of 60 mass ppm. The ratio of the actual yield to the theoretical yield was 99.4%. The sample crystallized by holding at 880 ° C. for 2 hours was examined in the same manner as in Example 1. As a result, the specific surface area was 8.3 m ² / g and the c / a ratio was 1.0058. The dielectric constant at 25 ° C. was 1400. The temperature characteristic at that time did not satisfy the X7R characteristic of the EIA standard. This is because MgO, Ho ₂ O ₃ , and BaSiO ₃ diffuse into the barium titanate due to low crystallinity.

In the TEM photograph of the barium titanate powder, vacancies, which are defects due to desorption of hydroxyl groups, are observed. It is the graph which showed the processing temperature dependence of a BET specific surface area. It is the graph which showed the processing temperature dependence of c / a. It is the graph which showed the primary particle size dependence of c / a. It is the graph which showed the processing temperature dependence of the lattice axis length.

Claims (21)

  Barium titanate, which is a single crystal and contains 20% or more of the entire particles, in which particles having no pores of 1 nm or more are present in the grains.   The barium titanate according to claim 1, wherein the number of particles having no pores of 1 nm or more in the grains is 50% or more of the whole particles.   The barium titanate according to claim 1, wherein the number of particles having no pores of 1 nm or more in the grains is 80% or more of the whole particles. The barium titanate according to any one of claims 1 to 3, wherein the BET specific surface area is 0.1 m ² / g or more. The barium titanate according to any one of claims 1 to 4, wherein no steep peak is detected in the vicinity of 3500 cm ^-1 by infrared spectroscopy after heat treatment at 700 ° C. From the group consisting of Sn, Zr, Ca, Sr, Pb, Ho, Nd, Y, La, Ce, Mg, Bi, Ni, Al, Si, Zn, B, Nb, W, Mn, Fe, Cu, and Dy barium titanate according to any one of claims 1 to 5 (including 0 mol%) containing at least one element of less than 5 mol% relative to BaTiO ₃ the chosen.   The barium titanate according to any one of claims 1 to 6, wherein the barium titanate is powder.   The barium titanate according to any one of claims 1 to 7, wherein barium titanate is synthesized by wet synthesis.   A slurry containing the barium titanate according to any one of claims 1 to 8.   A paste containing the barium titanate according to any one of claims 1 to 8.   A dielectric material comprising the barium titanate according to any one of claims 1 to 8.   A dielectric ceramic containing the barium titanate according to any one of claims 1 to 8.   A piezoelectric material comprising the barium titanate according to any one of claims 1 to 8.   A piezoelectric ceramic containing the barium titanate according to any one of claims 1 to 8.   A dielectric film containing the barium titanate according to any one of claims 1 to 8.   A capacitor comprising the dielectric material according to claim 11.   A capacitor comprising the piezoelectric material according to claim 13.   A capacitor comprising the dielectric film according to claim 15.   An in-substrate capacitor comprising the dielectric film according to claim 15.   A printed wiring board comprising the dielectric film according to claim 15. An electronic device including the capacitor according to any one of claims 16 to 19.

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