KR20090023180A - Complex oxide powder, method for preparing the same, ceramic composition using the complex oxide powder and ceramic electronic parts using the ceramic composition - Google Patents

Abstract

A manufacturing method of complex oxide powder is provided to obtain complex oxide powder of which particle diameter is small and crystalline is good using titanium oxide of which a rutilation rate by a line diffraction method is higher than 90% and lower than 100% and a specific surface area is 150 ~ 300 m^2/g. A manufacturing method of complex oxide powder comprises a step of mixing and plasticizing titanium oxide of which a rutilation rate by a line diffraction method is higher than 90% and lower than 100% and a specific surface area is 150 ~ 300 m^2/g and a compound containing a metal element selected in a group consisting of barium, strontium, calcium, magnesium and lead. A determinant diameter of the rutile-type crystal contained in the titanate compound is 10nm or less.

Description

COMPLEX OXIDE POWDER, METHOD FOR PREPARING THE SAME, CERAMIC COMPOSITION USING THE COMPLEX OXIDE POWDER AND CERAMIC ELECTRONIC PARTS USING THE CERAMIC COMPOSITION}

The present invention relates to a composite oxide powder containing a metal element of titanium and at least one metal element selected from barium, strontium, calcium, magnesium, and lead, and a method for producing the same. Moreover, this invention relates to the ceramic composition which sintered the said composite oxide powder, the ceramic electronic component, and laminated ceramic electronic component using the same.

Composite oxide powders, such as barium titanate, strontium titanate, lead titanate, and lead zirconate titanate, are used as raw materials for the sintered compact, and after mixing the composite oxide powder with a binder, the powder layer is coated on a substrate using a method such as sheet forming or printing. And then sintered to form a sintered body (hereinafter sometimes referred to as a ceramic composition). Since the ceramic composition has excellent dielectric properties, piezoelectricity, and semiconductivity, it is used as an electric and electronic industrial material such as a capacitor, a radio wave filter, a complexing element, and a thermistor.

The ceramic composition is attached to and used in various electric and electronic devices as a ceramic electronic component. With the recent miniaturization, weight reduction, high performance, and multifunctionality of electric and electronic devices, the performance demands on such ceramic electronic parts are becoming more stringent. Taking a multilayer ceramic capacitor used in an integrated circuit such as a computer as an example, since the capacitor has a structure in which a plurality of thin layers and internal electrodes of the ceramic composition are alternately superimposed and electrically connected in parallel, miniaturization of the multilayer ceramic capacitor, With the demand for higher capacity and the like, further thinning and high dielectric constant of ceramic compositions are desired. For this reason, the performance requirements of the fine particle formation and the high crystallization of the composite oxide powder which are raw materials of a ceramic composition, and also the quality requirements, such as homogenization and high dispersion, are becoming more remarkable. In addition, although precious metal materials such as platinum, palladium, and silver were used as internal electrodes of the multilayer ceramic capacitor, switching to low-cost non-metallic materials such as copper and nickel is facilitated, and consequently, the composite oxide powder is further cooled at a lower temperature. Even if it can be sintered and sintered in the atmosphere of low oxygen partial pressure, it is not semiconductorized and it is desired to have reduction resistance.

To prepare a composite oxide powder containing a metal element of titanium and at least one metal element selected from barium, strontium, calcium, magnesium, and lead, an oxide or carbonate of each element is mixed and an electric furnace or a rotary kiln is used. The so-called solid phase synthesis method for calcining, the oxalate of each element is synthesized by water, and the so-called oxalate method for calcining, the citrate method for each element is synthesized in water and then calcined, the so-called citrate method for calcining, aqueous solution and alkaline aqueous solution of each element. After mixing, hydrothermal treatment, filtration, washing, and drying, there are so-called hydrothermal synthesis methods and the like. In each method, improvement studies such as fine particle formation and high crystallization of the composite oxide powder are conducted. The main focus of the research is to suppress the decrease in crystallinity caused by the granulation of the composite oxide powder. For example, in the solid phase synthesis method, a barium compound that produces barium oxide by thermal decomposition and an X-ray diffraction method By mixing and firing titanium dioxide having a rutileization rate of 30% or more and a specific surface area of 30 m 2 / g or more, the ratio between the c-axis and a-axis of the crystal lattice that is a fine grain and tetragonal (tetragonality) index ( It describes that barium titanate powder with a high c / a ratio) is obtained (refer patent document 1).

Patent Document 1: Japanese Unexamined Patent Publication No. 2006-306632

In the method described in the above Patent Document 1, by using fine particle titanium dioxide having a specific surface area of 30 m 2 / g or more, barium titanate powder having fine particles and high crystallinity is obtained, but the SEM diameter of the barium titanate powder of the example (scan type The electron microscope diameter) is about 24 to 90 nm, but the c / a axis ratio, which is an index of crystallinity, is about 1.002 to 1.006 (Table 2), which is not necessarily high.

MEANS TO SOLVE THE PROBLEM As a result of earnestly researching the method of manufacturing the composite oxide powder which is more crystallinity especially a barium titanate powder, the rutile ratio of the titanium oxide used as a raw material of a solid-phase synthesis method is higher than 90%, and is 100% or less, When the specific surface area is 150 to 300 m 2 / g, the same crystal structure of the rutile type enables uniform reaction, and also has a high specific surface area, thereby increasing the reactivity and having a desired crystallinity and particle diameter. It was found that an oxide powder was obtained.

Furthermore, when the crystallite diameter of the rutile crystal of the titanium oxide was 10 nm or less, the reactivity was further increased to find that the desired composite oxide powder was obtained.

In addition, it was found that the titanium oxide was suitable for drying the product obtained by neutralizing titanium tetrachloride at a temperature of 150 ° C. or lower, thereby completing the present invention.

That is, the present invention

(1) In the group consisting of titanium oxide having a rutile rate of 90% or more and 100% or less and a specific surface area of 150 to 300 m 2 / g and barium, strontium, calcium, magnesium and lead determined by X-ray diffraction; A method for producing a composite oxide powder, characterized by mixing and firing a compound containing at least one metal element selected,

(2) a composite oxide powder having a particle diameter in the range of 0.06 to 0.15 µm, especially a barium titanate powder having a c / a ratio of 1.0075 to 1.010, produced using the method described in (1) above,

(3) a ceramic composition obtained by sintering the composite oxide powder or barium titanate powder of (2) above,

(4) A ceramic electronic component having a ceramic composition as described in the above (3) and an electrode formed to face each other with the ceramic composition interposed therebetween, a plurality of layers containing a ceramic composition, and an electrode formed between the layers of the ceramic composition. Multilayer ceramic electronic components and the like.

In the method for producing a composite oxide powder such as barium titanate, the present invention provides a rutile ratio obtained by X-ray diffraction as a titanium oxide of a raw material of higher than 90%, 100% or less, and a specific surface area of 150 to 300 m 2. By using / g titanium oxide, a composite oxide powder having a small particle diameter and good crystallinity is obtained.

Specifically, barium titanate powder having excellent tetragonality in which the particle diameter is in the range of 0.06 to 0.15 µm and the c / a ratio is in the range of 1.0075 to 1.010 is obtained.

In addition, since the crystallinity of the composite oxide powder is good, low-temperature sintering resistance and reduction resistance can be improved, and the filling rate when the sintered body is used can be improved, and characteristics such as dielectric properties and piezoelectric properties can be improved. For this reason, when the ceramic composition which sintered the composite oxide powder by the method of this invention is used, the ceramic electronic component, especially laminated ceramic electronic component which satisfy | fills miniaturization, light weight, high performance, and multifunctionalization is obtained using the outstanding characteristic.

The present invention provides a method for producing a composite oxide powder in which a compound containing titanium oxide and at least one metal element selected from the group consisting of barium, strontium, calcium, magnesium and lead is mixed and calcined. The rutile ratio obtained is higher than 90%, 100% or less, and uses a titanium oxide having a specific surface area of 150 to 300 m 2 / g. Although a titanic acid compound is preferable because a reactivity is so large that a specific surface area is large, since it becomes difficult to manufacture such a titanium oxide when it is too large, a specific surface area is preferable 160-250 m <2> / g, and 160-200 m <2> / g is more preferable. The specific surface area is obtained by nitrogen adsorption by the BET method.

Said titanium oxide contains what is called an oxide of titanium (titanium dioxide), or a hydroxide of titanium, a hydrous oxide, and a hydroxide, and can use at least 1 sort (s) chosen from it. In addition, the titanium oxide generally has rutile crystals, anatase crystals and brookite crystals from X-ray diffraction peaks. The titanium oxide of the present invention has many rutile crystals among the above three types of crystal structures, and the rutile ratio of the titanium oxide obtained by the X-ray diffraction method is higher than 90%, 100% or less, and is used. % Is more preferable, and rutile ratio 100% of the extent to which the X-ray-diffraction peak of an anatase crystal and a brookite crystal is not recognized is still more preferable. The rutile rate of titanium oxide refers to the ratio of rutile crystals contained in the titanium oxide and refers to the presence or absence of rutile crystals, anatase crystals, brookite crystals by X-ray diffraction (using CuKα rays). It confirms and the content rate of the rutile type crystal | crystallization with respect to said 3 types of crystal form is calculated | required. Further, the crystallite diameter of the rutile crystal can be obtained from the half value width of the X-ray diffraction peak of the (110) plane of the rutile crystal using the Syrah's formula (Formula 1). As crystallite diameter of a rutile type crystal, a smaller thing is preferable from a reactive viewpoint, 10 nm or less is more preferable, and 1-10 nm is still more preferable.

Equation 1: D _HKL = K ＊ λ / βcosθ

D _HKL : crystallite diameter (Å)

λ: wavelength of X-ray

β: half width of diffraction peak

θ: Bragg's angle

K: constant (= 0.94)

On the other hand, according to an electron micrograph, the primary particle diameter of a titanium oxide is estimated to be about 1-15 nm, and the primary particle may aggregate and form secondary particle. The shape of the secondary particles of the titanium oxide may be any shape, for example, granular, spherical, substantially spherical, fusiform or the like can be used. In the case of a granular form, spherical shape or substantially spherical shape, when the particle diameter is represented by the maximum diameter (number average), 10-300 nm is preferable, 20-150 nm is more preferable, 30-120 nm is still more preferable. In addition, the fusiform refers to a shape resembling a weight to pull out a thread, and is shaped like a columnar with sharp ends. For this reason, fusiform forms include what is generally said to be needle-like, rod-shaped, columnar, columnar, polygonal, and the like. The length connecting the both ends of the particles is the major axis diameter and the length of the thickest part of the column is the minor axis diameter, and the ratio between the number average (average major axis diameter) of the major axis diameter and the number average (average minor axis diameter) of the minor axis diameter is measured. If it is ratio, the larger one is preferable, and it is preferable that it is 1.5 or more specifically. On the other hand, when titanium oxide becomes microparticles | fine-particles, since it is difficult to enlarge an axial ratio, about 1.5-5 are more preferable, and about 1.5-4 are more preferable. 10-300 nm is preferable, as for the average long-axis diameter of a titanium oxide, 20-150 nm is more preferable, 30-120 nm is still more preferable. Several secondary particles of the titanium oxide may further aggregate to form aggregated particles. The secondary particle shape, average major axis diameter, and average minor axis diameter of such titanium oxide can be observed by measuring with an electron microscope.

For example, granular particles may aggregate to form larger porous aggregated particles, and fusiform particles may form aggregated particles resembling star candy.

Regarding the aggregated particles of the titanium oxide, the particle diameter (50% accumulated diameter (median diameter)) in water can be measured by the following method, and in the present invention, about 0.06 to 0.20 µm is preferable from the viewpoint of reactivity of solid phase synthesis. Do.

Measurement method of particle size distribution in water

(1) The slurry of titanium oxide is adjusted to pH 10.8 with an aqueous sodium hydroxide solution, and then dispersed in a paint shaker for 15 minutes.

(2) An aqueous sodium hydroxide solution is added to 300 ml of water to which 0.3 mg of hexamethalin sodium is added in terms of P ₂ O ₅ to adjust the pH to 10.5 to obtain a dispersion medium for measurement.

(3) A few drops of said measurement dispersion medium and the dispersion liquid (titanium oxide slurry) produced with the paint shaker were added to a 1-liter polyethylene container, and it stirred, and prepared suspension.

(4) The suspension is irradiated with ultrasonic waves for 1 minute with an ultrasonic generator (manufactured by Sharp, UT-500) to disperse the sample.

(5) The particle size distribution of the sample in the obtained dispersion liquid is measured using a laser diffraction scattering type particle size distribution measuring apparatus (manufactured by HORIBA, LA-910).

Titanium oxide used in the present invention is preferable that the TiO ₂ purity of at least 99 wt% purity and 99.5% by weight is more preferable, and at least 99.9 wt% more preferred. TiO ₂ purity refers to the sum of moisture, ignition loss component (Ig-Loss), chlorine, and impurities other than carbon (for example, elements such as silicon, iron, aluminum, niobium, sodium, and their oxide equivalents). It is shown by the numerical value subtracted from 100 (%). Elements such as silicon are analyzed by fluorescence X-ray method, ICP emission spectrometry, or atomic absorption method.

The titanium oxide used in the present invention can be produced by a liquid phase method or a gas phase method, and conditions for producing desired titanium oxide such as rutileization rate and specific surface area are appropriately selected. The liquid phase method is a method of hydrolyzing and neutralizing a solution of a titanium compound such as titanium sulfate, titanium sulfate, titanium tetrachloride, titanium alkoxide, etc., because a specific surface area is high and the crystallite diameter of the rutile crystal is easily obtained. desirable. As a specific liquid phase method, the hydrous titanium oxide obtained by neutralizing or hydrolyzing titanium tetrachloride, titanium sulfate, etc. in base compound aqueous solutions, such as alkali metal hydroxides, such as sodium hydroxide, an ammonium compound, an ammonium carbonate compound, and an amine compound, is mentioned, for example. After heat-processing, it can filter and wash, and then it can obtain by heat-processing in strong acid aqueous solutions, such as hydrochloric acid. As said base compound, sodium hydroxide is the most preferable at the point of rutile-ization rate, etc., In order to remove sodium sufficiently, it is preferable to carry out the etc. with acid. In addition, when the hydrochloric acid treatment is carried out in the presence of titanium trichloride, fine titanium oxide fine particles having a large major axis diameter and a small crystallite diameter are obtained, which is a preferable method. The obtained product is fractionated and dried. If the drying temperature is too high, the specific surface area decreases, so the drying temperature is preferably 150 ° C or lower. As another method, a method of neutralizing titanium tetrachloride can be used. While stirring the titanium tetrachloride solution, a neutralizing agent is added to neutralize the titanium tetrachloride. As the neutralizing agent, alkali metal hydroxides such as sodium hydroxide, ammonium compounds, ammonium carbonate compounds, amine compounds and the like can be used. Also in this method, when alkali metal hydroxide is used as a neutralizing agent, it is preferable to carry out littering with an acid in order to sufficiently remove the alkali metal. The product thus obtained is fractionated and dried in the same manner as above. If the drying temperature is higher than 150 ° C, the specific surface area of the neutralized product tends to be lowered, which is not preferable. The minimum temperature of drying may be any temperature as long as drying temperature is possible.

On the other hand, the gas phase synthesis method of titanium oxide is a method of oxidizing titanium tetrachloride gas with oxygen gas or hydrolyzing titanium tetrachloride gas with water vapor, and a method of easily obtaining high purity titanium oxide. The method of hydrolyzing with water vapor is more preferable because titanium oxide having a high specific surface area and high rutylation rate is easily obtained.

Compounds containing at least one metal element selected from the group consisting of barium, strontium, calcium, magnesium and lead, which are one raw materials for producing the composite oxide powder (hereinafter sometimes referred to as metal compounds), are usually What is used by the solid phase synthesis method can be used without exception, and oxides, hydroxides, carbonates, etc. of these metal elements can be used. As the metal compound, carbonate is preferably used. As a carbonate, you may use what is obtained by neutralizing by adding carbonic acid compounds, such as alkali carbonate and ammonium carbonate, or blowing carbonic acid gas, into aqueous solutions of water-soluble salts, such as the chloride, nitrate, and acetate of the said metal element. Although the metal compound is relatively soft and easily pulverized by the titanium oxide during mixing with the titanium oxide, the particle diameter of the metal compound also affects the properties of the composite oxide powder. It is preferable because it is effective for atomization. For example, when the specific surface area by BET method is represented as an index of fine particles, about 5 m 2 / g or more is preferable, about 10 m 2 / g or more is more preferable, and about 20 m 2 / g or more is more preferable.

Said titanium oxide and a metal compound are mixed to make a raw material powder. Both mixing amounts can be set suitably according to the composite oxide powder made into the objective. For example, to prepare a composite oxide powder having a perovskite structure represented by the general formula ABO ₃ , at least one metal atom (A) selected from the group consisting of barium, strontium, calcium, magnesium and lead is It is represented by the atomic ratio with respect to Ti atom (B) of a titanium oxide, Preferably it mixes in the range of 0.9-2.0, More preferably, it is the range of 0.95-1.05, More preferably, it is the range of 1.000-1.035. When the above atomic ratio is less than 0.9, it is not preferable because a complex oxide powder having a desired composition is hard to be obtained, and excess components remain in the complex oxide to easily inhibit characteristics such as dielectric property and piezoelectricity. In addition, polybarium titanate, specifically, of Ti / Ba, such as BaTi ₂ O ₅ , BaTi ₄ O ₉ , BaTi ₅ O ₁₁ , Ba ₂ Ti ₉ O ₂₀ , Ba ₄ Ti ₁₃ O ₃₀ , Ba ₆ Ti ₁₇ O _40, and the like. In order to produce barium titanate having an atomic ratio X having a composition formula of two or more, it is preferable to mix the respective raw materials so that the predetermined atomic ratio X is in the range of (X × 0.95) to (X × 1.05).

At the time of this mixing, a zirconium compound may be added to produce a zirconate titanate according to required properties of the ceramic composition. If necessary, as an additive, for example, rare earth elements such as lanthanum, cerium, gardium, terbium, dysprosium, holmium, erbium, ytterbium, boron, aluminum, silicon, manganese, iron, nickel, copper, zinc, niobium, yttrium You may add elements, such as tungsten and bismuth, suitably. These additives may be oxides, hydroxides, carbonates, or other compounds. The addition amount can be set suitably according to the objective.

Mixing should just be a degree to which titanium oxide and a metal compound are mixed uniformly to some extent, and a mixing degree can be adjusted suitably. As the mixing method, any of dry mixing and wet mixing may be used. For example, a fixed mixer such as a screw mixer, a ribbon mixer, a fluidized mixer, a rotary mixer such as a cylindrical mixer, a twin cylindrical mixer, or the like can be used. have. In addition, before mixing, the titanium oxide and the metal compound may be pulverized before mixing, or may be mixed at the same time during the pulverization, using a pulverizer such as a compression pulverizer, an impact compression pulverizer, a shear pulverizer, or a friction pulverizer. The finer the raw material powder is, the more likely the composite oxide powder is to become fine particles. Therefore, the raw material powder is preferably pulverized. For example, wet mills such as pole mills, bead mills, and colloid mills can be preferably used. have. When the mixed state is in a wet state or suspended state (slurry state) using a wet mill or the like, it may be fractionated, dried and pulverized as necessary.

Thus, the raw material powder thus obtained is preferably granulated in order to obtain an appropriate particle size in a solid phase synthesis reaction using, for example, fluidized bed firing or a gas flow firing method, which will be described later. The granulation can be carried out by conventional methods such as layer granulation, stirring granulation, disintegration granulation, compression granulation, extrusion granulation and droplet solidification granulation. In the case of a suspended state (slurry state) using a wet grinder or the like, spray drying using a spray dryer or the like is preferably carried out to dry granulation. Granulation by spray drying is preferable because it not only prevents scattering of the raw material powder and uneven gas contact, but also the granular powders of the granulated powders are relatively matched, so that uniform solid phase synthesis can be expected. The average particle size of the granulated powder can be arbitrarily adjusted in consideration of the flowable size or the degree of scattering, and for example, it may be about 1 to 10000 µm, and preferably about 5 to 3000 µm, since the scattering is less, it is preferable. It is more preferable in it being about 1000 micrometers, and it is still more preferable in it being about 20-500 micrometers. The granulated powder may be any shape, such as spherical shape, substantially spherical shape, plate shape, cube shape, cuboid shape, rod shape, or hollow shape having a space inside the powder, but a shape that is easy to flow is preferable, for example, spherical shape, approximately spherical shape, hollow shape Shapes such as phases are preferred. In addition, organic compounds, such as surfactant, resin, and a dispersing agent, can also be mix | blended as needed at the time of grinding | pulverization, mixing, and granulation. When the resin is added during granulation, particularly during spray drying, it acts as a binder to adjust the particle size of the granulated powder, and in addition, the resin is made porous by the voids generated and decomposed at the time of firing to generate gas from the inside of the granulated powder (eg For example, since carbon dioxide gas etc.) can also be discharged, it is preferable. The material used is not specifically limited, According to the objective, it selects suitably and uses a required amount. For example, an aqueous acrylic resin, an aqueous melamine resin, an aqueous urethane resin, etc. can be used as resin, and it is preferable to add about 1-20 weight% with respect to raw material powder.

Next, said raw material powder and granulated powder which granulated it (Hereinafter, a raw material powder and granulated powder may be called a raw material powder etc.) are injected into a baking apparatus. The firing apparatus to be used may be a firing furnace used in a conventional solid phase synthesis method or the like and a heating furnace used in other inorganic chemical fields, particularly in the ceramics field, and may be a vacuum firing furnace, a reduced pressure firing furnace, a raw material powder, etc. The fluidized bed kiln which can be baked while flowing, and the gas distribution type kiln can be used preferably. Although baking temperature and baking holding time can be set suitably according to a composite oxide powder, what is necessary is just about 500-1100 degreeC, for example, what is necessary is just to hold | maintain baking time about 0.5 to 10 hours, for example. Moreover, after baking is complete | finished, although it cools to extraction temperature, the rate of cooling can be set suitably and you may cool slowly or rapidly.

When the raw material powder or the like is injected into the firing apparatus and the temperature rise is started from the room temperature until the predetermined firing temperature is reached, the reaction between the titanium oxide and the metal compound or the decomposition of the organic compound is usually carried out from the temperature range in the middle thereof. Carbon dioxide gas, steam, etc. are generated. When this carbon dioxide gas etc. are exhausted out of a baking apparatus, since composite oxide powder with higher crystallinity is obtained, it is preferable. Specifically, it is preferable to fire the raw material powder or the like under a atmospheric pressure using a vacuum firing furnace or a reduced pressure firing furnace, more preferably, under a atmospheric pressure of 1 × 10 ³ Pa or less, and a voltage of 1 × 10 ¹ It is more preferable to carry out under an atmospheric pressure of ˜1 × 10 ³ Pa. Moreover, in order to exhaust carbonic acid gas etc. out of a baking apparatus, the gas distribution type baking furnace which bakes while circulating gas, for example, baking furnaces, such as a rotary electric furnace and a fixed floor electric furnace, can be used. The gas to be used may be the same as the gas used in the fluidized bed kiln described later.

As another method, the method of baking while flowing a raw material powder etc. using a fluidized bed kiln is more preferable. The fluidized state is preferably a fluidized state that forms a homogeneous fluidized bed (complete fluidized bed), and may be a rich fluidized bed in which bubbles are formed in the fluidized bed, or a part of raw material powder or the like forms a fixed bed and the remainder is in a fluidized state. do. The adjustment of the fluid state can be carried out at the particle size of the raw material powder or the like and the flow rate (flow rate) of the gas to be vented. When the gas is aerated from the generation start temperature range such as carbon dioxide gas to the end generation temperature range for at least a part of the period, preferably all the periods, the carbon dioxide generated is flowed out of the firing apparatus while the raw material powder is flowed. It is preferable because it can exhaust efficiently. In addition, if necessary, the gas may be vented from the step of starting temperature rise, the gas may be vented until the end of firing after the end of the generation, and the gas may be vented until the obtained composite oxide powder is taken out. Although the generation start temperature of carbonic acid gas differs according to the kind, composition, additives, etc. of the metal compound to be used, when the raw material powder etc. are thermally analyzed, the generation start temperature and generation end temperature of carbon dioxide gas can be grasped | ascertained. For example, it is thought that generation | occurrence | production start temperature of the carbon dioxide gas of the raw material powder which mixed titanium oxide and barium carbonate becomes about 500 degreeC. In addition, since generation | occurrence | production end temperature is considered to be about 850 degreeC, it is preferable to ventilate a gas between about 500-850 degreeC.

As the gas to be vented, a gas used in a conventional fluidized bed kiln can be used. However, if carbon dioxide gas is contained, it is not preferable because it affects the crystallinity of the composite oxide powder and the like, and it contains a gas or carbon dioxide gas having a low carbon dioxide gas content. It is better to choose a gas that does not. For this reason, it is preferable to use the gas of 0-0.5 volume% of carbonic acid gas content, More preferably, the carbonic acid gas content is 0-0.1 volume%, More preferably, the carbonic acid gas content is 0-0.05 volume%. . As such a gas, for example, nitrogen, argon, helium, air, oxygen, synthetic air, dry air (dry air), compressed air and the like can be used, and one kind of gas selected from these or two or more kinds of mixed gases can be used. Can be used. Although air, synthetic air, dry air (dry air), and compressed air contained a small amount of about 400 ppm of carbon dioxide, it was confirmed that this amount had no effect. Moreover, when air, synthetic air, dry air (dry air), and compressed air are used, since raw material powder etc. are hard to be reduced at the time of baking, it is easy to obtain a homogeneous composite oxide powder, and it is preferable. Since the gas to be vented is heated before it is introduced into the sintering device, it is preferable because it can prevent the rapid temperature drop of the sintering device. Moreover, although at least one part of carbon dioxide gas etc. which generate | occur | produces with the gas ventilated can be exhausted out of a baking apparatus, on the other hand, the gas ventilated can also be circulated and the carbon dioxide gas content in the circulating gas at that time is made into the said range. It is preferable.

By the above method, a perovskite structure such as a composite oxide powder having fine particles and high crystallinity, such as barium titanate, strontium titanate, lead titanate, lead zirconate titanate, calcium modified barium titanate, and rare earth element-modified barium titanate A compound having a compound of the foregoing and a barium polycarbonate having an atomic ratio of Ti / Ba having a composition formula of 2 or more can be produced. The particle diameter of the composite oxide powder is preferably in the range of 0.01 to 0.3 μm, more preferably in the range of 0.015 to 0.2 μm, still more preferably in the range of 0.01 to 0.15 μm, most preferably The range of 0.06-0.15 micrometers is obtained. The particle diameter (d) of the composite oxide powder is assumed to be spherical and is obtained by the following equation 2 using the specific surface area a (m 2 / g) by the BET method.

Equation 2. d = (6 / ρ) / a

However, ρ is specific gravity, and in the case of barium titanate powder, ρ = 5.90 is used.

In addition, the crystallinity of the obtained composite oxide powder is measured by X-ray diffraction and evaluated from the peak height or half value width of the diffraction peak by any crystal plane. To judge. Particularly in the case of barium titanate powder, it is judged from the ratio of the c-axis to the a-axis (c / a axis ratio) of the crystal lattice, but the larger the c / a ratio, the higher the crystallinity of the tetragonal barium titanate. Specifically, according to the method of the present invention, the c / a ratio can be in the range of 1.0075 to 1.010, more preferably 1.0080 to 1.010. The composite oxide powder having low crystallinity, particularly barium titanate powder of less than 1.006, lacks ferroelectricity for use as an electronic component. Therefore, in order to increase the c / a ratio, additional heat treatment is required, resulting in grain growth. do. The theoretical value of the c / a axis ratio of tetragonal barium titanate is computed from the values of a = 3.994 and c = 4.038 as c / a = 1.011, and the c / a axis ratio of cubic barium titanate is 1.000.

In addition, at the time of preparation of a ceramic composition, you may mix an additive with a composite oxide powder as needed. As the additive, depending on the properties required of the ceramic composition, for example, rare earth elements such as lanthanum, cerium, gardium, terbium, dysprosium, holmium, erbium, ytterbium, boron, aluminum, silicon, manganese, iron, nickel, copper , Such as zinc, niobium, yttrium, tungsten and bismuth, may be appropriately used. In addition, as an additive for controlling particle growth and electrical properties of the ceramic composition during sintering, for example, transitions of alkali metals such as lithium, sodium, potassium, iron, manganese, cobalt, nickel, niobium, and the like, in addition to boron and bismuth The compound of elements, such as a metal and also silicon and aluminum, is mentioned. Such additives may be added to the step of pulverizing the composite oxide powder or may be mixed after pulverization. Or you may add at the arbitrary stage of the sintering process of composite oxide powder. The addition amount can set a required amount suitably. The mixer can usually use a mixer used in the field of inorganic chemistry, especially ceramics, or a mixer used in the field of electronic materials. In addition, organic compounds, such as surfactant, resin, and a dispersing agent, can also be added at the time of grinding | pulverization and mixing. In this way, the ceramic composition raw material can be prepared.

The above-mentioned ceramic composition raw material containing at least a composite oxide powder is sintered and used as a ceramic composition, for example as a material of a ceramic electronic component. The ceramic electronic component includes a ceramic composition and electrodes formed to face each other with the ceramic composition interposed therebetween. Moreover, a multilayer ceramic electronic component as a ceramic electronic component is equipped with the some layer containing a ceramic composition, and the electrode formed between the layers of the said ceramic composition. A specific multilayer ceramic electronic component is a multilayer ceramic capacitor provided with a laminated body including a plurality of laminated ceramic composition layers (dielectric layers) and internal electrodes formed along specific interfaces between these ceramic composition layers. Inside the stack, the second inner electrode is similarly connected to the second outer electrode such that the first inner electrode and the second inner electrode as the inner electrode are alternately disposed, and the first inner electrode is electrically connected to the first outer electrode. Each edge is formed in the state exposed to the end surface of a laminated body so that it may be electrically connected. As the electrode, for example, a metal such as platinum, palladium, nickel, silver copper, or an alloy thereof can be used. The thickness of each layer of the ceramic composition of the multilayer ceramic electronic component is preferably as thin as possible, and preferably 1 μm or less.

The ceramic composition and the ceramic electronic component can be manufactured using a conventional method. The ceramic composition may be, for example, mixed with a binder with a ceramic composition raw material containing at least a composite oxide powder, and then press-molded to form a green pellet having a predetermined shape or on a substrate using a method such as sheet molding or printing. A green sheet having a predetermined thickness is formed and then sintered. The ceramic electronic component is, for example, a method of sintering by printing or applying a paste containing an electrode co-metal or the like on both surfaces of the green pellet, or forming the green sheet, and then on the internal electrode metal thereon. The paste etc. which mix | blended this, etc. are printed or apply | coated, and it repeats it several times, and the method of sintering, etc. can be used. Although sintering conditions can be set suitably according to the sintering degree of a ceramic composition raw material, about 1000-1500 degreeC is preferable and, for example, about 1100-1300 degreeC is more preferable. Although sintering time can also be set suitably according to the composition of a ceramic composition raw material, about 0.5 to 10 hours are preferable. The atmosphere at the time of sintering may be an oxygen-containing gas such as oxygen, air, synthetic air, dry air (dry air), or compressed air, but an atmosphere in which the electrode metal is not oxidized is preferable, and a non-oxidizing gas such as nitrogen , Argon, helium and the like can be preferably used, and reducing gases such as hydrogen, carbon monoxide and ammonia can also be preferably used.

Example

Although an Example and a comparative example are given to the following and this invention is demonstrated in more detail, this invention is not restrict | limited by these Examples.

Example 1

Titanium oxide, obtained by neutralizing titanium tetrachloride, dried at a temperature of 130 ° C. (specific surface area 190 m 2 / g measured by the above-described method, 80 nm in average long axis diameter, fusiform titanium dioxide having an aspect ratio of 3, and TiO ₂ purity 99.98 Weigh%, rutile rate 100%, crystalline diameter of rutile crystals 9 nm, 50% cumulative diameter 0.077 μm in water and barium carbonate (specific surface area 30 m 2 / g) were weighed so that the atomic ratio of barium / titanium was 1.000. , Wet milling and mixing using a ball mill, and then the mixed slurry was evaporated to dryness and ground in a mortar to obtain a raw powder.

Subsequently, the obtained raw powder was placed in a 50 cc crucible so as to have a thickness of 20 mm, and the crucible was placed in a fixed floor electric furnace capable of controlling the atmosphere, and the temperature was raised from room temperature to 850 ° C. under an atmospheric pressure under reduced pressure (200 to 500 Pa). It hold | maintained and baked for time, and obtained the barium titanate powder (sample A).

Example 2

In the said Example 1, it carried out similarly to Example 1 except having set baking temperature to 900 degreeC, and obtained the barium titanate powder (sample B) of this invention.

Example 3

In the said Example 1, the barium titanate powder (sample C) of this invention was obtained like Example 1 except having set baking temperature to 950 degreeC.

Example 4

The mixed slurry of the titanium oxide and barium carbonate obtained in Example 1 was dried and granulated with a spray dryer. The average particle diameter of the granulated powder was 50 micrometers.

Subsequently, the granulated powder was introduced into a vertical small fluidized bed kiln, and the dry granules (containing about 400 ppm of carbonate gas) were blown at a gas line speed of 1.73 cm / sec as a gas for flow, and the granulated powder was heated to 950 ° C. while flowing the granulated powder. It was hold | maintained for 0.5 hour, and it baked and obtained the barium titanate powder (sample D) of this invention. In addition, aeration of dry air was performed between the whole baking processes from a temperature start to sample acquisition, the granulated powder was made to flow by aeration of dry air, and the carbon dioxide gas which was generated was discharged | emitted out of the system of the fluidized bed kiln.

Example 5

In Example 4 mentioned above, the barium titanate powder (sample E) of this invention was obtained like Example 4 except having made holding time into 1 hour.

Example 6

In Example 4 mentioned above, the barium titanate powder (sample F) of the present invention was obtained in the same manner as in Example 4 except that the holding time was 1.5 hours.

Comparative Example 1

Titanium oxide having a specific surface area of 115 m 2 / g instead of the titanium oxide used in Example 1 (rutinization rate of 100%, crystallite diameter of 13 nm of rutile crystal, heated titanium oxide used in Example 1 at 175 ° C) ) And the barium titanate powder (sample G) was obtained like Example 1 except having heated up to 800 degreeC from room temperature under atmospheric pressure under pressure reduction (200-500 Pa), hold | maintained for 5 hours, and baking.

Thus, the specific surface area a (m <2> / g) was measured for the barium titanate powder of samples A-G obtained by BET method, and the average particle diameter d (micrometer) was calculated | required.

Furthermore, Rietveld analysis was performed using the data obtained by the X-ray diffraction method, and the lattice constants a and c of the tetragonal barium titanate were obtained to calculate the crystallinity evaluation (square crystal) c / a ratio.

From Table 1 of the results, it was found that the barium titanate powder of the present invention has a relatively small particle diameter, high c / a ratio, and excellent tetragonality (tetragonality).

As a result of conducting the experiments described in Examples 1 to 3 several times, it was confirmed that the variation in the quality of the obtained barium titanate powder was small. Further, in the present invention, in addition to barium titanate, an atomic ratio of Ti / Ba to a compound having a perovskite-type structure such as strontium titanate, lead titanate, lead zirconate, lead zirconate titanate, calcium modified barium titanate and rare earth element modified barium titanate is 2 It was confirmed that the barium polytitanate having the above composition formula can be produced in the same manner. Moreover, the superiority of this invention was confirmed also when the obtained composite oxide powder was sintered to obtain a ceramic composition and it was used as the ceramic electronic component.

Since the composite oxide powder of this invention has high crystallinity as microparticles | fine-particles, by sintering it, the ceramic composition which has the outstanding characteristics, such as dielectric property and piezoelectricity, can be manufactured simply and easily. The ceramic composition is expected to be able to satisfy miniaturization, light weight, high performance, and multifunctionality when used in ceramic electronic components, particularly multilayer ceramic electronic components.

1 is an electron micrograph showing the particle structure of the titanium oxide used in Example 1. FIG.

2 is an X-ray diffraction pattern of the titanium oxide used in Example 1. FIG.

Claims (10)

At least one selected from the group consisting of titanium oxides having a rutile rate of 90% or more and 100% or less and a specific surface area of 150 to 300 m 2 / g and barium, strontium, calcium, magnesium and lead determined by X-ray diffraction; A method for producing a composite oxide powder, comprising mixing and firing a compound containing one kind of metal element. The method of claim 1, A method for producing a composite oxide powder, wherein the crystallite diameter of the rutile crystal contained in the titanate compound is 10 nm or less. The method of claim 1, A method for producing a composite oxide powder, wherein the product obtained by neutralizing titanium tetrachloride is dried at a temperature of 150 ° C. or less. The method of claim 1, Said firing is performed under atmospheric pressure of voltage 1 * 10 <^3> Pa or less, The manufacturing method of the composite oxide powder characterized by the above-mentioned. The method of claim 1, Process for producing a composite oxide powder, characterized in that the mixture is calcined in a fluid state. The composite oxide powder whose particle diameter manufactured using the method of Claim 1 is a range of 0.06-0.15 micrometers. Barium titanate powder whose particle diameter manufactured using the method of Claim 1 is 0.06-0.15 micrometers, and whose c / a ratio is 1.0075-1.010. The ceramic composition which sintered at least the composite oxide powder of Claim 6, or the barium titanate powder of Claim 7. The ceramic electronic component provided with the ceramic composition of Claim 8, and the electrode formed so that the said ceramic composition may oppose. A multilayer ceramic electronic component comprising a plurality of layers containing the ceramic composition according to claim 8 and an electrode formed between the layers of the ceramic composition.

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