WO2003004415A1

WO2003004415A1 - Barium titanate powder and method for production thereof

Info

Publication number: WO2003004415A1
Application number: PCT/JP2002/006719
Authority: WO
Inventors: Koji Tokita; Matsuhide Horikawa
Original assignee: Toho Titanium Co., Ltd.
Priority date: 2001-07-04
Filing date: 2002-07-03
Publication date: 2003-01-16
Also published as: JPWO2003004415A1

Abstract

A method for producing a tetragonal fired barium titanate powder having an average particle diameter of 0.05 to 0.5 μm, a Ba/Ti atomic ratio of 1.003 to 1.006, particularly preferably 1.003 to 1.005 and an ignition loss of 0.5 % or less, which comprises preparing a tetragonal fine barium titanate powder having an average particle diameter of 0.05 to 0.5 μm, a Ba/Ti atomic ratio of 1.003 to 1.009 by means of the liquid phase process, and firing the powder at 930 to 980˚C. The fired barium titanate powder produced by the method has high crystallinity, exhibits high dielectric property, and is reduced in the content of an alkali metal component such as Na, and thus can be suitably used as a material for forming a dielectric layer of a monolithic ceramic capacitor or the like.

Description

Description Barium titanate powder and method for producing the same

The present invention relates to an improved barium titanate powder having excellent dielectric properties and used as a dielectric material for electronic components such as multilayer ceramic capacitors and PTC thermistors, and a method for producing the same. Background art

Barium titanate is widely used in electronic materials such as dielectric materials for multilayer ceramic capacitors. Recently, the barium titanate particles, which are the material for forming the dielectric layer, are as small as possible, specifically 0.5 m or less, in order to increase the number of layers, miniaturization, and capacity of capacitors. There is a demand for a barium titanate material having a crystallinity of preferably 0.4 or less, high crystallinity, and a low content of alkaline metal components such as Na ions and K ions.

Barium titanate obtained by the solid phase method has disadvantages such as a large particle size of several meters and a wide particle size distribution even when crushed. For this reason, various liquid phase methods such as a hydrothermal synthesis method, a low-temperature direct synthesis method, a gel sol method, and an oxalic acid method have been proposed in many documents. Although the liquid phase method is costly, it has the advantage that spherical fine particles with a particle size of 1 m or less can be easily obtained, but the crystallinity is not easily increased. There is a problem that it is difficult to remove metal.

For example, JP-A-5-330824 discloses that a titanium compound and a barium compound are mixed at a BaZTi ratio of 0.95 to 1.05, hydrogen peroxide is added thereto, and a wet reaction is carried out. It is disclosed that after obtaining a cubic barium titanate powder having a particle diameter of 0.2 to 5 and calcining at 900 to 1300 ° C., a truly spherical barium titanate can be obtained. Based on the advantages of the liquid phase method, which allows barium titanate with a small particle diameter to be obtained, there have been introduced many examples of methods for producing spherical fired barium titanate powder with a particle size of 0.1 to 0.2 m by low-temperature firing. I have. JP-A-60-81023 and JP-A-60-90825 disclose that a reaction is carried out by reacting hydrous titanium oxide and barium hydroxide in a dilute aqueous solution at 60 to 110 ° C. : Calcined barium titanate powder of! ~ 0.2 at 800 ° C, then into tablets and fired at 1200 ° C to obtain calcined titanate with relative density of 93% and particle size of about 0.5m Examples of producing barium materials have been reported.

In order to remove alkali metals such as Na from the barium titanate powder obtained by the liquid phase reaction, Japanese Patent Application Laid-Open No. 5-178619 discloses that the reaction product is not less than 300 ° C., preferably 400 ° C. It introduces a method of heating at ~ 700 ° C, washing with water of pH 7 ~ 10, and separating by filtration. Also, JP-A-61-146713 discloses that barium titanate obtained by a hydrothermal reaction is washed with hot water, the powder is calcined at 800 ° C, then washed with acetic acid water, and further washed with pure water. How to do is introduced. However, even with water washing or hot water washing, the Na content cannot be easily removed. Also, in severe cleaning, there is a risk that even when baked titanium titanate is used, the leaching of the barrier occurs during water cleaning. Incidentally, J. Mater. Res., Vol. 10, o. 2, p. 3106 reported an example in which barium titanate obtained by a liquid phase reaction contained 400 ppm of Na. I have. As described above, although many liquid phase processes have been reported, little attention has been paid to strict control of the BaZT i ratio. Even if the BaZTi ratio is not taken into account, it is difficult to stably produce a highly crystalline barium titanate powder with an average particle size of 0.5 / m or less in practice. . Furthermore, it was difficult to remove the Na content as an impurity. Disclosure of the invention

As is clear from the above description, it is an issue to produce a fired tetragonal barium titanate powder having a high crystallinity, a high purity, a high dielectric constant, and an average particle size of 0.05 to 0.5 by a liquid phase method. Met. Above all, controlling the Ba / Ti ratio and achieving low-temperature firing were the biggest technical issues. Therefore, the object of the present invention is

1) To provide a raw material for producing fired barium titanate powder having high crystallinity;

2) To provide a fired barium titanate powder having high crystallinity and high dielectric properties; 3) To provide a calcined barium titanate powder having a small alkali metal component such as Na;

4) providing a method for producing the calcined powder by a liquid phase method,

It is in.

The term “green calcined barium titanate” as used in the present invention refers to a so-called green material (green) to the extent that barium titanate obtained by synthesis is dried. On the other hand, calcined barium titanate refers to It refers to raw material that has been subjected to heat treatment (also called calcination) at a higher temperature, that is, at least 500 ° C or more and 980 ° C or less. This includes those that have been crushed or have been crushed and washed. The fired barium titanate powder of the present invention is appropriately mixed with other components and sintered at a normal firing temperature (about 110 to 1300 ° C.) to form a desired dielectric material. To be served.

The present inventors have conducted intensive studies to achieve the above object,

(i) The BaZT i atomic ratio (hereinafter referred to as the Ba / T i ratio unless otherwise specified) is in a very narrow range, specifically 1.003 to 1.009, especially 1. Obtaining a barium titanate powder controlled to 003 to 1.005 and firing it to obtain a fired barium titanate with high crystallinity;

(ii) The firing can be performed at a temperature much lower than conventionally known, so that the growth of particles can be suppressed, and the average particle size is not more than 0.5 m. To obtain a tetragonal calcined barium titanate powder having an extremely fine specific Ba / Ti ratio, such as 0.3 to 0.1 m,

(iii) that the Na content can be extremely effectively reduced during the firing process;

(iv) The obtained calcined powder was found to have extremely high crystallinity, and to exhibit extremely excellent dielectric properties, thereby completing the present invention.

Hereinafter, the contents of the present invention will be described.

A first invention according to the present invention is an unfired barium titanate powder obtained by subjecting a titanium compound and a vacuum compound to a liquid phase reaction, and having an average particle size (here, 350 ° C The crystal is characterized by having a particle size of 0.05 to 0.5 / m and a BaZT i ratio of 1.003 to 1.009, measured by degassing for 30 minutes at a temperature. It is an unfired barium titanate powder having a cubic structure. The unburned The barium titanate powder is suitable as a raw material powder for producing the barium titanate powder of the second invention described below.

The second invention has an average particle size of 0.05 to 0.5 m, a BaZT i ratio of 1.003 to 1.006, a loss on ignition of 0.5% by weight or less, and a square crystal structure. It is a barium titanate powder that has been calcined.

Furthermore, the third invention of the present invention relates to a method for producing a highly crystalline and fine barium titanate powder, wherein (i) a titanium compound and a barium compound are subjected to a liquid phase reaction in an aqueous alkali solution to obtain an average particle diameter. A first step of producing a green cubic barium titanate powder having a cubic crystal structure having a 0.05 to 0.5 ^ m and a BaZT i ratio of 1.003 to 1.009; Baking the unfired barium titanate powder at 930 to 980 ° C, characterized by comprising a second step, (iii) an average particle size of 0.05 to 0.5 mm, Ba / Ti ratio This is a method for producing a calcined barium titanate powder having a tetragonal crystal structure with a loss on ignition of 1.003 to 1.006, a loss on ignition of 0.5 wt% or less.

The loss on ignition (also referred to as L) in the present invention refers to the weight (W1) after the barium titanate powder is kept at 110 ± 5 ° C for 60 minutes in the air. Then, the temperature is raised to 110 ° C in air at 10 ° C per minute, and the weight (W2) after holding at 1100 ± 30 ° C for 60 minutes is calculated by the following formula. Value.

L (% by weight) = [(W 1 -W2) / W 1] X 100

Further, the cube as a shape display of the barium titanate powder of the present invention is observed with an electron microscope, and the appearance of the particles is a cube, a rectangular parallelepiped, or a pseudo cube in which the corners of individual particles are slightly missing, Alternatively, it means a pseudo-cuboid. BRIEF DESCRIPTION OF THE FIGURES

FIG. 1 is an electron micrograph showing an unfired barium titanate powder according to the present invention.

FIG. 2 is an electron micrograph showing the fired barium titanate powder according to the present invention. BEST MODE FOR CARRYING OUT THE INVENTION

Hereinafter, embodiments of the present invention will be described.

First, the “green calcined barium titanate powder” of the first invention is a barium titanate powder obtained by a liquid phase reaction between a titanium compound and a vacuum compound. Considering the ease of handling, the diameter is 0.05 to 0.5, preferably a fine powder of 0.07 to 0.4 m, and (b) the ratio of 8 & / 1.009, from the viewpoint of crystallinity, that is, dielectricity, preferably 1.003 to 1.007, particularly preferably 1.004 to 1.006, extremely close to 1.000, but the number of valence atoms is titanium atom It has a composition that is very slightly greater than the number. If the ratio is less than 1.003 or more than 1.009, the fired barium titanate powder produced therefrom has poor crystallinity. In order to further improve the crystallinity of the calcined powder, the BaZT i ratio is from 1.003 to 1.007, more preferably from 1.003 to 1.006, as described above. The unsintered barium titanate powder includes those subjected to a heat treatment of 250 or less mainly for drying. From the unfired barium titanate powder having such a Ba / T i ratio (that is, the raw material powder to be fired), a “fired barium titanate powder” of the second invention described below is obtained. That is, the specific unfired barium titanate powder is subjected to a heat treatment at 930 to 980 ° C, particularly 930 to 970 ° C, thereby obtaining a fired barium titanate powder having extremely high crystallinity as described later. Can be Cubic crystals cannot be obtained below 930 ° C, and grain growth occurs above 980 ° C. Further, as a characteristic feature of the unfired barium titanate powder of the present invention, by firing in this temperature range, the contained aluminum metal such as Na can be removed very effectively. In

Next, the calcined barium titanate powder of the second invention has extremely high crystallinity while being extremely fine particles having an average particle diameter of 0.05 to 0.5 m. The ratio of barium atoms is extremely slightly higher than titanium atoms, with a ratio of 1.003 to 1.006, preferably 1.003 to 1.005, and in a limited range. The structure is tetragonal, and the shape observed with an electron microscope is square, ie, rectangular or cubic crystalline. This is a finely baked powder having a high particle size.

In a further preferred embodiment of the present invention, in addition to the above, the calcined barium titanate powder has a loss on ignition (L) of 0.5% by weight or less, preferably 0.4% by weight or less, particularly preferably 0.4% by weight or less. 3% by weight or less. The calcined barium titanate powder of the present invention is a fine particle having a particle size of 0.5 / m or less, but has a CZa ratio (C-axis length of tetragonal crystal axis length) Is an extremely high crystallinity of 1.009 or more. Moreover, the BET specific surface area, particle size 0.1 approximately at the 4 Paiiota ones ^{1. 5~2. 5m 2 / g,} 0. intended for ^{2 m 3. 5~5. 0m 2 /} g, 0. 1 Even with m, 8 ~: L 0 m ² Z g, relatively small. In addition, despite having small particles, the loss on ignition (L) when heated to 1100 ° C has an extremely thermally stable crystal structure of 0.5% by weight. The particle shape is a cube or a rectangular parallelepiped, and has a shape different from a generally known spherical or potato-like shape. These clearly show excellent crystallinity. An even more excellent point is that, despite being obtained by the liquid phase method, the high purity of the metal component content of the aluminum alloy is not more than 50 ppm and not more than 40 ppm. Despite such a fine fired powder, a cubic or rectangular parallelepiped fired barium titanate powder having high crystallinity has not been known.

Next, as already described, the third invention of the present invention is to produce the unfired barium titanate powder of the first invention by a liquid phase method, and to obtain the obtained raw material in 930 to 98 O: This is to produce the fired barium titanate powder of the second invention by firing. Dielectrics manufactured using the fired barium titanate powder of the present invention have extremely excellent dielectric properties and are effective in reducing the size of parts.

(Production of unfired barium titanate)

Hereinafter, a production example of the unfired barium titanate of the present invention will be described more specifically. Titanium compounds as liquid phase reaction raw materials include titanium tetrachloride, oxytitanium chloride, titanium tetrachloride hydrolyzate (titanium hydroxide hydrate, orthotitanic acid, metatitanic acid), peroxotitanic acid, titanyl sulfate, etc. It is. Titanium tetrachloride hydrolyzate is hydrolyzed with alkaline water such as ammonia, or produced by adding water. The resulting hydrochloric acid is obtained by evaporation and separation as a solid or gel. During the reaction, the solid is used as a slurry or a very dilute aqueous solution. Examples of the barium compound include barium chloride, barium hydroxide, barium nitrate, barium sulfate, and barium acetate. Of these, barium chloride or barium hydroxide is preferably used.

One reaction example is described below.

Basically, an aqueous solution of titanium tetrachloride (concentration is about 0.2 to 2.0 mol and this is called liquid I) and an aqueous solution of barium chloride or barium hydroxide (concentration is 0.1 to 1.0 mol Zl, hereafter referred to as solution II), and bringing them into contact with each other in a reaction vessel at a temperature of 90 to 10 O: under strong alkaline conditions.

In order to promote the reaction and ensure the performance of the product, it is important to always keep the reaction system strongly alkaline. Specifically, the pH is maintained at 13 or higher, preferably 13.5 or higher, more preferably 13.8 or higher. More preferably, it is preferable that the solution II is previously prepared as an aqueous alkali solution. During the reaction, a necessary amount of an alkaline aqueous solution is supplied from another system as needed to maintain the predetermined PH. More preferably, before starting the supply of both liquids, an aqueous solution of an aqueous solution adjusted to a predetermined concentration is charged into the reaction vessel in advance, and then the both liquids are supplied to prevent local pH decrease. It is valid. Regarding the supply amounts of both liquids, to produce barium titanate with a BaZT i ratio of 1.03 to 1.009, which is the target product, the supply amounts of the titanium compound and the barium compound to the reaction system must be adjusted. Strict control is important.

Specifically, the molar ratio of both compounds supplied to the reaction vessel is set in the range of 1.05 to 1.10, and both liquids are quantitatively supplied to the reaction vessel at this set value. For example, in order to produce an unfired barium titanate powder having a BaZT i ratio of 1.003 to 1.005, the total supply ratio of both liquids according to this, that is, (barium concentration of liquid II x supply rate) Z (Titanium concentration X supply rate of liquid I) and instantaneous supply ratio are strictly controlled.

When the two liquids are continuously supplied to the reaction vessel at the above ratio, a premixing region having functions such as high-speed stirring and high-pressure spray contact may be provided in order to promote uniform contact. The contacting and the reaction are preferably carried out at a temperature as close as possible to 100 ° C. under normal pressure, ie 80 to 98 t: 110 to 150 ° C. under pressure. As described above, the solution I and the solution II are brought into contact in the reaction vessel with stirring. The resulting slurry liquid containing solid titanium titanate may be continuously withdrawn from the reaction system and moved to another aging vessel (continuous reaction), or may be withdrawn after the reaction is completed in the reaction vessel. Good (batch reaction). The barium titanate thus produced is desirably aged by heating it for a certain period of time while stirring it in a slurry state. The aging treatment is performed at a temperature of 85 to 150 ° C. After aging, the resulting barium titanate particles and water as a solvent are separated by decantation, centrifugation, filtration, or the like. The barium titanate powder separated from the reaction system is washed with water to remove unreacted raw material compounds, alkali components, and the like attached thereto. The production of the unfired barium titanate powder in the present invention is not limited to the above production method.

The reaction product obtained above is dried at 80 to 250 ° C, preferably 100 to 200 ° C, to obtain the unfired barium titanate powder of the present invention. The above reaction products are spherical cubic particles having an average particle diameter of 0.05 to 0.5 δ ^ πι. Through the above operations, the unfired barium titanate powder of the present invention is obtained.

(Production of calcined barium titanate powder)

Hereinafter, a production example of the fired barium titanate powder according to the second invention of the present invention will be described. The fired barium titanate powder of the present invention is obtained by subjecting the unfired barium titanate powder to a heat treatment at 930 to 980 ° C., more preferably 940 to 975 (this heat treatment is referred to as firing in the present invention). It is obtained by doing. The firing atmosphere may be any of air, vacuum, and inert gas. However, it is more suitable to remove chlorine, which is an impurity, in a vacuum or when water vapor is present at a partial pressure of 0.1 to 0.4. The unfired barium titanate powder has a property of being fired at 930 to 980 ° C. Since sintering can be performed at such a low temperature, particle growth that tends to occur during heating can be prevented, and this is an extremely preferable raw material for producing a small-sized sintered powder. If the temperature exceeds 980 ° C, grain growth occurs and crystallinity decreases. In addition, the crystallinity is not improved below 930 ° C.

When the raw material powder is heat-treated at 930 to 980 ° C, a tetragonal rectangular parallelepiped fired barium titanate powder having a loss on ignition of 0.5% by weight or less is obtained. Further, the firing temperature Another feature of the present invention is that alkali metals such as sodium ions contained in the crystals are very effectively removed. As a result, a fine baked barium titanate powder having a low purity and a low alkali metal content such as Na can be obtained. The calcined barium titanate is pulverized by various means as necessary. Preferred pulverizing means include pulverizing means by contact between powders, particularly wet pulverizing means, specifically wet pulverizing means in the presence of a medium such as water, rather than pulverizing using media such as balls and beads. It is preferable for maintaining crystallinity. Next, examples of the present invention will be described to further clarify the effects of the present invention. In addition, the measurement of each physical property and performance in the following Examples and Comparative Examples was measured by the following methods.

• Sintering density: The sintering density was determined based on Archimedes' principle.

• Shape: The morphology of the powder was analyzed by transmission electron microscope (TEM) and scanning electron microscope (SEM).

• Average particle size: determined from the BET specific surface area.

• Ba / Ti ratio: The atomic ratio of Ba / Ti (BaZTi ratio) was determined by X-ray fluorescence analysis.

• Loss on ignition: Determined by weight loss after heating at 110 ° C for 30 minutes.

[Example 1]

(Manufacture of unfired BaZT i powder)

A 0.92N aqueous NaOH solution was charged into a 2-liter reaction vessel made of SUS equipped with a stirrer and kept at 90 ° C. Then, 4 Ot: the heat retained T i C 1 ₄ aqueous solution (T i C 1 ₄ concentration: 0.4 7 2 mol / 1) and, 9 5 ° and held at C B a C 1 ₂ / N A_〇 H solution (B a C 1 ₂ concentration: 0. 2 7 8 mol / 1, N a OH concentration: 2.7 3 Moruno 1) and, T i C 1 ₄ aqueous solution: 7 7 cc / min, B a C 1 ₂ / N a OH aqueous solution: at 1 5 4 cc Z min of the flow rate, and continuously fed into the reaction vessel and held with stirring 9 0 ° C. The molar ratio of the supplied _{B a C 1 2 / Ύ i} C 1 4 1. was 1 8 0. Next, the slurry containing the produced barium titanate was transferred to an aging tank, and kept at 9 for 60 minutes with stirring. Thereafter, ammonia water was added, the supernatant and the precipitate were separated by decantation, and further centrifuged to separate the barium titanate powder. Collected. Next, the recovered barium titanate powder is washed with ammonia water (PH9) at room temperature, washed with water, and then dried by heating at 200 ° C. in a vacuum atmosphere to obtain a BaZT i ratio. However, unfired barium titanate powder (Sample No. BT-1) of 1.003 was obtained.

[Example 2]

Drying except that supplying the feed rate of B a C 1 ₂ solution of Example 1 in 156. 0 cc / min, the reaction was carried out in the same conditions as in Example 1, then, a washing净under the same conditions as in Example 1 Was conducted. The molar ratio of the supplied _{B a C 1 2 / T i} C 1 4 1. was 1 93. As a result, an unfired barium titanate powder having a Ba / Ti ratio of 1.004 (sample No. BT-12) was obtained. The Na metal content in the powder was 190 ppm. An electron micrograph of the powder BT-12 is shown in FIG.

[Example 3]

T i C 1 ₄ aqueous solution (T i C 1 ₄ concentration: 0.600 mol 1) _{and, B a C 1 2 / N} a OH solution (B aC 1 ₂ concentration: 0.335 mol Z 1, Na_〇_H concentration : 3. 0 molar Z 1) and, T i C 1 ₄ aqueous 100 c cZ min, at B aC 1 ₂ / NaOH aqueous 2 1 7 cc / min flow rate, the reaction vessel in the same manner as in example 1 , And maintained at 90 ° C with stirring. Molar ratio of _{B a C 1 2 / Ί i} C 1 4 of the supplied raw material compound 1. was 2 1 2. Subsequent washing and drying were performed under the same conditions as in Example 1. As a result, an unfired barium titanate powder (sample No. BT-3) having 1.06 in & 8 was obtained.

[Example 4]

T i C 1 ₄ solution and B a C 1 ₂ / N A_〇_H solution and T i C 1 when continuously subjected feeding into the reactor the ₄ / B a C 1 ₂ molar ratio of 1.230 An unfired barium titanate powder (sample No. BT-4) was obtained in the same manner as in Example 3, except that

[Comparative Example 1]

And T i C 1 ₄ solution and _{B a C 1 2 / N a} OH solution and the time of continuously subjected feeding into the reaction vessel _{T i C 1 4 / B a} C 1 2 molar ratio of 1.160 A barium titanate powder (sample No. BT-5) was obtained in the same manner as in Example 1 except for the above. The Na content of this powder: No. BT-5 was 220 ppm. [Comparative Example 2]

And T i C 1 ₄ solution and B a C 1 ₂ / N A_〇_H _{T i C 1 4 / B a} C 1 2 molar ratio 1. 250 when an aqueous solution is continuously supplied to the reaction vessel A barium titanate powder of Comparative Example 2 (Sample No. BT-6) was obtained in the same manner as in Example 1 except for performing the above.

[Comparative Example 3]

And T i C 1 ₄ solution and _{B a C 1 2 / N a} OH solution and the time of feeding continuously subjected to a reaction container _{T i C 1 4 / B a} C 1 2 molar ratio of 1.320 An unfired barium titanate powder (sample No. BT-7) was obtained in the same manner as in Example 1 except for the above. The Na content of this powder: No. BT-7 was 190 ppm.

Table 1 shows the properties of the unfired barium titanate powders obtained in Examples 1 to 4 and Comparative Examples 5 to 7.

Table 1

(Production of calcined barium titanate powder)

[Examples 5 to 8], [Comparative Examples 4 to 7]

Unfired barium titanate powder in Table 1: No. BT-1, BT-2, BT-5, and BT-7 were fired in an air atmosphere at 930 to 1100 for 1.5 hours. Next, 1.5 cc of aqueous ammonia was added per 100 g of the obtained calcined powder, and the mixture was wet-pulverized. After that, water was separated by filtration, and further heated to 120 ° C and dried. The fired barium titanate powders of Examples 5 to 8 and Comparative Examples 4 to 7 shown in Table 1 were obtained. Tables 2 and 3 show the sample numbers and properties of these calcined barium titanate powders. FIG. 2 shows an electron micrograph of the calcined powder: CBT-2B obtained in Example 7. According to FIG. 2, it is clear that the particle shape is a cube or a rectangular parallelepiped. Table 2

Table 3

Table 3 shows the crystallinity and dielectric properties of each fired powder in Table 2.

X (te t) as a crystallinity (tetragonality) scale shown in Table 3 is a value obtained by the following method. The closer this value is to 1.0, the higher the crystallinity.

[Crystalline X (t e t)]

The X-ray diffraction peak intensities of the (200) and (002) planes of the crystal are I (200) and I (002), respectively, and the Rabin intensity between the valleys of both peaks is I (ravine), and X (tet ) Is calculated by the following equation.

X (t e t) = 1-1 (r av i n e) / {(I (200) II (002)} [crystalline cZa ratio]

The lengths of the tetragonal C-axis and a-axis are determined by (002) and (200) times of the X-ray diffraction pattern. It is calculated from the folding peak position, and the ratio c / a ratio is calculated by the following formula.

c Z a = c-axis length a-axis length

As is clear from Table 2 and Table 3, when the unfired powders BT-1 and BT-12 of the present invention are fired at 930 to 980 ° C, a fired powder having high crystallinity and a large relative dielectric constant is obtained. can get. Furthermore, it is clear that the Na content in the obtained fired powder is significantly reduced. On the other hand, as in Comparative Example 6 and Comparative Example 7, the calcined powder obtained by calcining the unfired barium titanate powder of 1.01 and 1.017 at 950 ° C. The crystallinity was not sufficient as compared with the example.

(Manufacture of sintered body)

[Example 9]

MnCo3, MgO, MgCo3, CaCo3, SiO2 and a rare earth oxide were added to the calcined powder (No. CBT-2B) having a BaZTi ratio of 1.004 in Example 7. The mixture was heated at 1300 ° C for 2 hours in a reducing atmosphere, and then sintered at 1,000 ° C for 10 hours under a nitrogen gas flow to obtain a sintered body of Example 9. I got

[Comparative Example 8]

Sample of Example 9: Instead of No. CBT-2B, calcined barium titanate powder (No. CBT-5) having a Ba / Ti ratio of 1.001 in Comparative Example 6 was used, and the comparison was performed in the same manner. A sintered body of Example 8 was obtained.

The dielectric properties (relative permittivity) of the sintered bodies of Example 9 and Comparative Example 8 were measured using an LCR meter (model: 4284A type) manufactured by Hewlett-Packard Company, frequency: 1 mm, and applied voltage: The measurement was performed under the conditions of IV. Table 4 shows the measurement results.

Table 4

As is apparent from Table 4, the sintered body (Example 9) manufactured using the fired barium titanate powder of the present invention has a high relative dielectric constant over a wide temperature range, and has a high dielectric constant. Proved to be very suitable as a forming material -ΐ-

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Claims

The scope of the claims

1. The average particle size obtained by subjecting a titanium compound and a vacuum compound to liquid phase reaction is 0.05-0.5 zm, and the atomic ratio of 8 & / c is 1.003-: L. 009 Unfired barium titanate powder characterized by:

2. Barium titanate obtained by the liquid phase reaction is calcined at 930 to 980 ° C, the average particle size is 0.05 to 0.5 ^ m, and the BaZT i atomic ratio is 1.003 to 1. 006. A tetragonal calcined barium titanate powder having a loss on ignition of 0.5% by weight or less.

3. The average particle size is 0.07 ~ 0.4m, 8 & 7 1 atomic ratio is 1.003 ~ 1.005, loss on ignition is 0.3wt% or less, alkali metal content is 50ppm 3. The fired barium titanate powder according to claim 2, wherein

4. (a) Liquid phase reaction between titanium compound and barium compound, unfired cubic crystal with an average particle size of 0.05 to 0.5ΓΠ, 88 / choice and an atomic ratio of 1.003 to 1.009 A first step of producing a barium titanate powder;

(b) a second step of firing the unfired barium titanate at 930 to 980 ° C., wherein the average particle size is 0.05 to 0.5 m and the BaZT i atomic ratio is 1. 003 to 1.006, a method for producing a tetragonal calcined barium titanate powder having a loss on ignition of 0.5% by weight or less.

5. The method for producing a fired barium titanate powder according to claim 4, wherein wet pulverization is performed after the firing in the second step.

6. The calcined barium titanate powder has an average particle diameter of 0.07 to 0.4 m, a BaZ ratio of 1.003 to 1.005 wt% or less, and an alkali metal content of 40 ppm or less. The method for producing a calcined barium titanate powder according to claim 4 or 5, wherein: