KR20090095491A - Method for producing perovskite-typed barium titanate powder - Google Patents

Abstract

Provided is a method for manufacturing perovskite barium titanate powder for used in producing electronic components. A method for manufacturing perovskite barium titanate powder for used in electronic components comprises the following step of calcining a mixture of barium carbonate and titanium dioxide in the presence of humid air. The calcination is performed when the humid air is introduced to a furnace. The humid air is prepared by adjusting the temperature of water. The dew point of the humid air is 15 °C or greater. The calcination is performed at the temperature of 700 - 1200 °C.

Description

Manufacturing method of perovskite type barium titanate powder {METHOD FOR PRODUCING PEROVSKITE-TYPED BARIUM TITANATE POWDER}

The present invention relates to a method for producing perovskite-type barium titanate powder, and more particularly, to a method for producing perovskite-type barium titanate powder useful as a raw material for functional ceramics such as piezoelectric materials, optical electronic materials, dielectrics, semiconductors and sensors. .

Perovskite-type barium titanate powder has conventionally been used as a raw material for functional ceramics such as piezoelectric bodies and multilayer ceramic capacitors. However, in recent years, multilayer ceramic capacitors have been required to increase the number of laminated layers and increase the high dielectric constant in order to increase their capacity, and therefore, it is desired to have fine tetragonal tetragons for perovskite-type barium titanate powders.

As one method for producing the perovskite type barium titanate powder, a so-called solid phase method is known in which barium carbonate and titanium dioxide are mixed and the resulting mixture is calcined. In this solid phase method, there is a problem that it is difficult to obtain perovskite-type barium titanate powder which is fine and has high tetragonality.

In addition, in order to improve the tetragonality of the perovskite barium titanate obtained by the solid phase method, the calcining temperature at the time of producing the perovskite barium titanate is increased by calcining a mixture containing barium carbonate and titanium dioxide. Although effective, if the calcination temperature is increased, the growth of particles and the condensation of particles occur, which makes it difficult to refine the perovskite-type barium titanate obtained.

For this reason, for example, Patent Document 1 below discloses a method of mixing barium carbonate and a metal oxide such as titanium dioxide having a specific surface area of 10 m 2 / g or more, and calcining the resulting mixture under an oxygen partial pressure of 2 × 10 ³ Pa or less. Proposed.

Further, Patent Document 2 below discloses a method of calcining barium carbonate and titanium dioxide having a rutileization rate of 30% or less and a BET specific surface area of 5 m 2 / g or more, preferably at an overall pressure of 1 × 10 ³ Pa or less. Is proposed.

In addition, Patent Document 3 proposes a method of calcining a mixture of barium carbonate and titanium oxide in an atmosphere having a temperature of 600 to 1100 ° C and a carbon dioxide partial pressure of 400 to 1000 ppm.

[Patent Document 1] Japanese Patent Application Laid-Open No. 2001-316114

[Patent Document 2] Japanese Patent Application Laid-Open No. 2002-255552

[Patent Document 3] Japanese Unexamined Patent Publication No. 2006-327890

Although various methods for producing perovskite-type barium titanate powder have been studied by the solid phase method as in the conventional art, a perovskite-type barium titanate powder having fine and high tetragonality by a more industrially advantageous method is used. The manufacturing method was desired.

It is therefore an object of the present invention to provide a method for producing perovskite-type barium titanate powder which is fine by an industrially advantageous method in a solid phase method and which has high tetragonality even at the same calcination temperature.

The present inventors made intensive studies in view of the above situation, and as a result, when a large amount of carbon dioxide is present in the furnace when calcining the mixture containing barium carbonate and titanium dioxide, the obtained perovskite-type barium titanate powder includes Since barium carbonate is formed on the surface and inside, the perovskite-type barium titanate powder having low characteristics as a ferroelectric is produced and the ratio of c-axis to a-axis (c / a), which is an index of tetragonal crystals, is also produced. When the generation of carbon dioxide gas is suppressed, the perovskite-type barium titanate powder which is fine and has a high tetragonality even at the same calcination temperature can be produced. Further, when calcination is performed in the presence of humidified air, the carbon dioxide gas is in humidified air. It is effectively absorbed by water vapor and because of this, it is possible to reduce the concentration of carbon dioxide gas during calcination, and the resulting perovskite The sky-type barium titanate powder was fine and found to have high tetragonality even at the same calcination temperature, and came to complete the present invention.

That is, the method for producing perovskite-type barium titanate powder to be provided by the present invention, in the method for producing a perovskite-type barium titanate powder by calcining a mixture containing barium carbonate and titanium dioxide, humidifying the calcination It is characterized by performing in the presence of air.

According to the present invention, it is possible to produce perovskite-type barium titanate powder which is fine by an industrially advantageous method and has high tetragonality even at the same calcination temperature. The manufactured perovskite-type barium titanate powder is particularly useful as a raw material for functional ceramics for electronic components such as piezoelectric materials, optical electronic materials, dielectrics, semiconductors, and sensors.

EMBODIMENT OF THE INVENTION Hereinafter, this invention is demonstrated based on preferable embodiment.

The method for producing perovskite-type barium titanate powder according to the present invention is a method for producing a perovskite-type barium titanate powder by calcining a mixture containing barium carbonate and titanium dioxide, wherein the calcination is performed in the presence of humidified air. It is characterized by performing.

The barium carbonate of the raw material used in the present invention can be used without particular limitation as long as it is industrially available, but if the BET specific surface area is 10 m 2 / g or more, preferably 30 to 50 m 2 / g, it is fine and has high tetragonality. It is preferable at the point that a perovskite type barium titanate can be manufactured.

In addition, the barium carbonate to be used has the above-described physical properties, and in addition, when the average particle diameter obtained from scanning electron micrograph (SEM) observation is 0.1 μm or less, preferably 0.03 to 0.05 μm, fine and tetragonality is achieved. It is preferable at the point which can manufacture a high perovskite type barium titanate.

In addition, in this invention, the average particle diameter shows the value of the average calculated | required from the scanning electron microscope observation (SEM) about 1000 samples extracted arbitrarily, unless there is particular notice.

Titanium dioxide of the other raw material can be used without particular limitation as long as it is industrially available, but a BET specific surface area of 5 m 2 / g or more, preferably 8 to 50 m 2 / g, is fine and tetragonal perovskite type It is preferable at the point which can produce barium titanate.

In addition, the titanium dioxide to be used has the above-described physical properties, and the perovskite-type barium titanate having fine and tetragonality is used when the average particle size obtained from SEM observation is 0.1 µm or less, preferably 0.03 to 0.05 µm. It is preferable at the point that it can manufacture.

In addition, since the barium carbonate and titanium dioxide obtain a high purity perovskite-type barium titanate powder, it is preferable to use a high purity one, and the particle shape of these raw materials can be used without particular limitations in the form of needles, spheres, granules, or amorphous forms. have.

In the reaction operation of the present invention, first, the barium carbonate and titanium dioxide are mixed uniformly to obtain a homogeneous mixture.

The mixing ratio of barium carbonate and titanium dioxide is 0.99 to 1.01, preferably 0.995 to 1.005 in the molar ratio (Ba / Ti) of Ba and Ti. The reason is that if the molar ratio (Ba / Ti) of Ba and Ti is less than 0.99, titanium becomes rich, and the tetragonal perovskite-type barium titanate cannot be obtained, while the molar ratio (Ba / Ti) of Ba and Ti is If it exceeds 1.01, barium will become rich, and the tetragonal perovskite barium titanate will not be obtained, which is undesirable.

In the present invention, when the perovskite-type barium titanate powder is used, a compound containing Ca or / and Sr atoms, which are partially substituted for Ba atoms, which are A site elements, and Zr as a partial replacement of Ti atoms, which are B site elements Compounds containing atoms can be contained in the mixture. In this case, the content of Ca or / and Sr atoms which are partially replaced by Ba is not particularly limited, but is preferably set to less than 50 mol% as Ca or / and Sr atoms relative to Ba atoms. On the other hand, the content of the partially substituted Zr atom of Ti is not particularly limited, but is preferably set to less than 50 mol% as the Zr atom relative to the Ti atom. The mixing ratio of Ti and Zr (B site element) to Ba and Ca and / or Sr (A site element) is 0.99 to 1.01, preferably 0.995 to 1.005 in molar ratio (A site element / B site element). desirable. In addition, as the compound containing Ca, Sr, Zr atoms, these carbonates, oxides, organic acid salts, and the like can be used, and physical properties and the like are not particularly limited, but are fine in view of dispersibility of each raw material. desirable.

The method of mixing barium carbonate and titanium dioxide is performed by a mechanical means in which strong shearing force is applied by the wet method or the dry method so that the barium carbonate and titanium dioxide are uniformly mixed in the above ratio.

The wet process is operated with devices such as ball mills, bead mills, disper mills, homogenizers, vibrating mills, sand grind mills, attritors, and powerful stirrers. In addition, as a dry method, apparatuses, such as a high speed mixer, a super mixer, a turbo spare mixer, a Henschel mixer, a nuter mixer, and a ribbon blender, can be used. Among these, in the present invention, the preparation by the wet method is particularly preferable in that a homogeneous mixture is obtained and a dielectric having a high dielectric constant is obtained.

As a solvent used by wet mixing, water, methanol, ethanol, propanol, butanol, toluene, xylene, acetone, methylene chloride, ethyl acetate, dimethylformamide, diethyl ether, etc. are used, for example. Among these, when alcohol, such as methanol, ethanol, propanol, butanol, is used, it is preferable at the point that a change in composition is small, and the dielectric ceramic itself obtained also has a high dielectric constant.

Moreover, a dispersing agent can be added to a slurry at the time of the said wet mixing as needed for the purpose of improving dispersibility. In addition, after performing a mixing process by wet, the method of drying every slurry with a spray dryer can be applied as desired.

In addition, these uniform mixing operations are not limited to the illustrated mechanical means. Further, the mixing operation may be performed at the same time as the particle size adjustment using an apparatus capable of simultaneously mixing and pulverizing a jet mill or the like.

In the method for producing the perovskite type barium titanate powder of the present invention, the mixture obtained by uniformly mixing the barium carbonate and titanium dioxide is calcined.

The calcination temperature is 700 to 1200 ° C, preferably 800 to 1000 ° C. The reason is that if the calcination temperature is less than 70 ° C., the solid phase reaction which changes to perovskite-type barium titanate does not occur, and it is easy to be in an unreacted state. It is not desirable because barium tends to cause particle growth. The calcination time is at least 4 hours, preferably 6 to 30 hours. In the present invention, in the calcination, the mixture is usually calcined at 700 to 1200 ° C, preferably 800 to 1000 ° C, and then the calcined product is crushed and granulated as desired, and then usually 700 to 1200 ° C, Preferably, calcination may be performed at 800 to 1000 ° C, and in order to make the calcination homogeneous, the calcination may be pulverized once and then calcined.

The firing furnace used for calcination can use a batch type or a continuous electric furnace and a gas furnace, As an example, a roller hearth kiln, a rotary kiln, a pusher furnace, etc. are mentioned. .

In the method for producing the perovskite-type barium titanate powder of the present invention, it is particularly important to perform the above calcination in the presence of humidified air in the atmosphere.

In specific operation, calcination can be performed while introducing humidified air into the firing furnace.

As the humidified air, air which has been passed through water adjusted to a temperature, humidified air, or air humidified by mixing water vapor with air can be used.

The moisture content of the humidified air is not particularly limited, but when humidified air having a dew point of 15 ° C. or higher, preferably 20 to 26 ° C., particularly preferably 21 to 25 ° C., is generated in the kiln in the solid phase reaction. It is especially preferable at the point which absorbs a carbon dioxide gas efficiently.

1 is a graph showing a humidity chart and showing a relationship between the temperature (° C.) and the amount of saturated water vapor (humidity 100%) (g) contained in 1 m 2 of dry air. The relationship between the amount of saturated steam in FIG. 1 and temperature is shown in Table 1 below. In addition, the temperature (degreeC) of Table 1 shows a dew point.

2 is a graph for calculating the dew point from the humidity curve. Dew point can be calculated | required based on FIG. 2, curve Hs is a humidity curve of 100% humidity, and curve H1 is a humidity curve of arbitrary humidity a%. However, a represents the humidity of less than 100% humidity. Curve Hs is the same as the curve shown in FIG. Humidified air Ha of temperature t2 and humidity a% contains the steam of the amount of water vapor h2 in temperature t2 of curve H1. Therefore, in order to determine the dew point of the temperature t2 and the humidity a% humidified air A, the water vapor amount h2 is moved in the direction of the saturated water vapor curve Hs, and the temperature t1 at the intersection h1 between the water vapor amount h2 and the curve Hs is the dew point of the humidified air Ha. Becomes

The rate of introduction of humidified air into the kiln depends on the capacity of the kiln, for example, when using a kiln having a capacity of 3L, the solid phase is 1 L / min or more, preferably 2-5 L / min. It is preferable at the point which efficiently absorbs the carbon dioxide gas which generate | occur | produced in the kiln in reaction, and prevents furnace temperature from falling by humidified humidified air. In addition, when the humidified air is introduced into the kiln, the carbon dioxide gas produced during the reaction is introduced into the kiln before the perovskite-type barium titanate is produced by the solid phase reaction of barium carbonate and titanium dioxide. Is particularly preferable in that it can effectively absorb and suppress generation of carbon dioxide gas.

The perovskite-type barium titanate powder after calcination can be made into a product by, for example, washing with an acid solution if necessary, washing with water, drying, pulverizing and classifying. A drying method can use a conventional method and it is not specifically limited, When wet grinding is performed, the method of using a spray dryer can also be applied, for example.

The perovskite-type barium titanate powder obtained in the present invention has a high tetragonality with a ratio of c-to-a-axis (c / a) serving as an index of tetragonal, preferably 1.004 or more, preferably 1.006 to 1.010. Moreover, the preferable physical property of the perovskite-type barium titanate powder obtained by this invention is 0.5 micrometer or more, Preferably it is 0.05-0.3 micrometer, and BET specific surface area is 2 m <2> / g or more, calculated | required by electron microscope observation. It is 3-20 m <2> / g, and it is very high purity, and especially the perovskite type barium titanate powder which is useful as a raw material of functional ceramics for electronic components, such as a piezoelectric body, an optical electronics material, a dielectric, a semiconductor, and a sensor.

Further, if necessary, before calcination, i.e., when mixing barium carbonate and titanium dioxide or after calcination, Sc, Y, La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Contains rare earth elements such as Yb, Lu, and minor component elements containing at least one element selected from Li, Bi, Zn, Mn, Al, Si, Sr, Co, V, Nb, Ni, Cr, B, Fe, and Mg When the compounds are mixed and subsequently calcined, a titanium-based perovskite-type ceramic raw material powder containing an oxide of a minor component element can be obtained.

The combination and addition amount of these subcomponent element containing compounds can be arbitrarily set according to the dielectric properties required for the ceramic raw material powder produced. The addition amount of a specific subcomponent element containing compound is 0.1-5 weight part normally as an element among subcomponent element containing compounds with respect to 100 weight part of perovskite type barium titanate powder. In addition, the said subcomponent element containing compound may be either an inorganic substance or an organic substance. For example, oxides, hydroxides, chlorides, nitrates, oxalates, carboxylates and alkoxides containing the above elements may be mentioned. When a subcomponent element containing compound is a compound containing Si element, silica sol, sodium silicate, etc. can also be used in addition to the said oxide etc.

The perovskite-type barium titanate powder obtained in the present invention can be used as a raw material for producing a multilayer capacitor. For example, first, the perovskite-type barium titanate powder and conventionally known compounding agents such as additives, organic binders, plasticizers, and dispersants are mixed, dispersed and slurried, and solids in the slurry are molded to obtain ceramic sheets. . Subsequently, a conductive paste for forming internal electrodes is printed on one surface of the ceramic sheet, and after drying, a plurality of ceramic sheets are laminated, and then a laminate is formed by pressing in the thickness direction. Furthermore, this laminated body is heat-processed, a binder removal process is performed, and it bakes and produces a fired body. Then, a laminated capacitor can be obtained by apply | coating and baking In-Ga paste, Ni paste, Ag paste, nickel alloy paste, copper paste, copper alloy paste, etc. to this baking body.

In addition, the perovskite-type barium titanate powder obtained by this invention is mix | blended with resin, such as an epoxy resin, a polyester resin, a polyimide resin, and a printed wiring board and a multilayer printed wiring board as a resin sheet, a resin film, an adhesive agent, etc., for example. It can use suitably for materials, such as these. Further, the perovskite-type barium titanate powder is a dielectric material of an EL element, a common material for suppressing a shrinkage difference between an internal electrode and a dielectric layer, a base material of an electrode ceramic circuit board or a glass ceramic circuit board, a raw material of a circuit peripheral material, and exhaust. It can be used suitably as a catalyst used at the time of reaction, such as gas removal or chemical synthesis, the surface modifier of the printing toner which gives an antistatic effect or a cleaning effect.

<Example>

Hereinafter, although an Example demonstrates this invention in detail, this invention is not limited to this.

In addition, in the Example, the average particle diameter was calculated | required with the average value calculated | required from scanning electron microscope observation (SEM) about 1000 samples extracted arbitrarily.

Barium Carbonate Sample

As the barium carbonate, a commercially available one having physical properties shown in Table 2 below was used.

Titanium Dioxide Sample

As a titanium dioxide, the commercially available thing which has the physical property shown in following Table 3 was used.

Examples 1 to 3

The barium carbonate sample and the titanium dioxide sample were mixed and treated for 6 hours using a ball mill (bead diameter; 1 mm zirconia bead, solvent: water) as a wet mixer so as to have a molar ratio of Ba / Ti of 1.00. It dried at 130 degreeC for 2 hours, and obtained dry powder.

In a firing furnace including the electric batch furnace shown in FIG. 3, 7 g of the dry powder was heated to a temperature shown in Table 4 below at a temperature increase rate of 2.5 ° C./min under air, and maintained for 6 hours to be calcined.

The inside of the slope of the furnace 1 of the kiln shown in FIG. 3 is covered with an alumina fiber board, and the sample 3 is accommodated in the barrel of the sample container 2 made of alumina in the furnace. Humidified air 6 is introduced into the furnace from the inlet 5, and humidified air is discharged out of the furnace from the outlet 8 of the discharge pipe 7.

At the same time as calcination commences, calcination was carried out while passing air through water heated to 30 ° C. and introducing humidified air A (dew point 21 ° C.) at a rate of 2 L / min. The capacity of the kiln is 3 liters.

In addition, the state of air before heating is 27.8 degreeC, humidity 24%, and dew point of 7 degreeC. The humidified air A humidified by letting it pass through the water heated at 30 degreeC, is 26.1 degreeC, 72% of humidity, and 21 degreeC of dew point by the measured value of the inlet (5).

After the completion of calcination, the mixture was cooled and pulverized to obtain barium titanate powder.

Examples 4-6

A dry powder was prepared in the same manner as in Example 1, and 7 g of the dry powder was heated in an electric batch furnace at a temperature increase rate of 2.5 ° C./min to the temperature shown in Table 4, held for 6 hours, and calcined.

At the same time as calcination commences, calcination was carried out while passing air through water heated to 45 ° C. and introducing humidified air B (dew point 25 ° C.) at a rate of 2 L / min.

In addition, the state of air before heating is 27.8 degreeC, humidity 24%, and dew point of 7 degreeC. The humidified air B humidified by passing through water heated to 45 ° C is 27.1 ° C, humidity 87%, and dew point 25 ° C in the measured value at the inlet 5.

After the completion of calcination, the mixture was cooled and pulverized to obtain barium titanate powder.

Comparative Examples 1 to 3

A dry powder was prepared in the same manner as in Example 1, and 7 g of the dry powder was heated in an electric batch furnace at a temperature increase rate of 2.5 ° C./min to the temperature shown in Table 4, held for 6 hours, and calcined.

Calcination was performed without introducing air into the kiln.

After the completion of calcination, the mixture was cooled and pulverized to obtain barium titanate powder.

Comparative Examples 4 to 6

A dry powder was prepared in the same manner as in Example 1, and 7 g of the dry powder was heated in an electric batch furnace at a temperature increase rate of 2.5 ° C./min to the temperature shown in Table 4, held for 6 hours, and calcined. In addition, calcination was carried out while introducing carbonate gas into the baking furnace at the rate of 2 L / min at the same time as calcination start.

In addition, carbonic acid gas was used that does not heat. Carbonic acid gas which is not heated is 22.3 degreeC, 37% of humidity, and dew point of 8 degreeC by the measured value of the inlet port 5. As shown in FIG.

After the completion of calcination, the mixture was cooled and pulverized to obtain barium titanate powder.

Comparative Examples 7 to 9

A dry powder was prepared in the same manner as in Example 1, and 7 g of the dry powder was heated up to the temperature shown in Table 4 at a temperature increase rate of 2.5 ° C / min in an electric batch furnace, and maintained for 6 hours to be calcined.

In addition, calcination was performed while introducing air into the baking furnace at the rate of 2 L / min at the same time as calcination start.

In addition, the state of air is 27.8 degreeC, 24% of humidity, and dew point of 7 degreeC by the measured value of the inlet (5).

After the completion of calcination, the mixture was cooled and pulverized to obtain barium titanate powder.

Evaluation of physical properties of barium titanate sample

For the barium titanate samples obtained in Examples 1 to 6 and Comparative Examples 1 to 9, the ratio (c / a) between the c-axis and the a-axis serving as an index of the average particle diameter, the BET specific surface area, and the tetragonal crystal was measured. The results are shown in Table 5 below. In addition, the ratio of c-axis and a-axis was calculated | required by X-ray diffraction.

From Table 5, the barium titanate obtained by calcining by introducing humidified air has a ratio between the c-axis and the a-axis, which are indices of tetragonal, as compared with those obtained by calcining without the introduction of humidified air with the same calcining temperature (c / a ) And high tetragonality.

Industrial availability

Since the present invention can produce fine and highly tetragonal perovskite-type barium titanate powder, the manufactured perovskite-type barium titanate powder is particularly suitable for piezoelectric, optical electronic materials, dielectrics, semiconductors, sensors and the like. It can use as a raw material of the functional ceramic for components.

1 is a graph showing the relationship between the temperature and the amount of saturated water vapor (humidity 100%) contained in 1 m 2 of dry air.

2 is a graph for obtaining a dew point from a humidity curve.

3 is a schematic view showing an embodiment of a firing furnace.

<Brief description of symbols for the main parts of the drawings>

1: as

2: sample container

3: sample

4: introduction tube

5: inlet

6: humidifying air

7: discharge pipe

8: outlet

9: plug

10: Foundation

Claims (7)

A method for producing a perovskite-type barium titanate powder by calcining a mixture containing barium carbonate and titanium dioxide, wherein the calcination is carried out in the presence of humidified air of the perovskite-type barium titanate powder. Manufacturing method. The method for producing a perovskite-type barium titanate powder according to claim 1, wherein the calcination is performed while introducing humidified air into the firing furnace. The method for producing perovskite-type barium titanate powder according to claim 1 or 2, wherein the humidified air is made of air humidified through water adjusted with temperature. The manufacturing method of the perovskite type barium titanate powder of any one of Claims 1-3 whose dew point of the said humidified air is 15 degreeC or more. The method for producing a perovskite-type barium titanate powder according to any one of claims 1 to 4, wherein the calcination is performed at 700 to 1200 ° C. The method for producing a perovskite-type barium titanate powder according to any one of claims 1 to 5, wherein barium carbonate is used having a BET specific surface area of 10 m 2 / g or more. The method for producing perovskite-type barium titanate powder according to any one of claims 1 to 5, wherein titanium dioxide having a BET specific surface area of 5 m 2 / g or more is used.

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