JP2001089230A - Powdery composition for production of barium titanate- base sintered compact and sintered compact - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain a powdery barium titanate-base composition which can be sintered at a low temperature and allows an easy control of the Ba to Ti molar ratio of barium titanate. SOLUTION: The powdery composition for the production of a barium titanate-base sintered compact capable of sintering at a low temperature comprises powdery barium titanate whose crystal phase at room temperature is a cubic phase or a middle phase between cubic and tetragonal phases and at least one Ba compound, Sr compound or Pb compound which increases the molar ratio of barium site to titanium in barium titanate in firing. The powdery composition may further contain at least one of compounds of Mg, Ca, Sr, Ba, Pb, rare earth metals, Ti, Zr, Hf, Sn, V, Nb, Ta, Bi, Sb, W, Mo, Cr, Mn, Cu, Ni, Co, Fe, Zn, Al and Si.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a barium titanate-based powder composition used as a dielectric material, a piezoelectric material, a semiconductor, and various other electronic materials, a sintered body using the powder composition, and a method for producing the same.

[0002]

BACKGROUND OF THE INVENTION Barium titanate-based sintered bodies made from raw materials obtained by adding various additives to barium titanate are used as dielectric materials such as multilayer ceramic capacitors, piezoelectric materials, semiconductors, and various other electronic materials. Have been. In recent years, in particular, electronic components have been reduced in size and capacity. For this reason, for example, in a multilayer capacitor,
In order to cope with this problem, the thickness of one dielectric ceramic sintered body layer is reduced to increase the number of layers.

[0003] To reduce the thickness of the sintered body layer, it is necessary to reduce the particle size of crystal grains in the dielectric ceramic sintered body layer. Usually, when sintered at a high temperature, crystal grains grow. For this reason, the raw material powder of barium titanate is required to be a fine powder and capable of being sintered at a low temperature. As a method for producing such barium titanate powder, a solid phase method in which a mixture of titanium oxide and barium carbonate is heated to a high temperature of 1300 ° C. or higher to cause a solid phase reaction is known. However, the solid-phase method has disadvantages that it is difficult to obtain uniform fine particles and it is difficult to sinter at a low temperature.

[0004] On the other hand, the liquid phase method has characteristics that, compared with the solid phase method, uniform and fine powder can be easily obtained, and the obtained barium titanate powder can be easily sintered at a low temperature. It is expected as a method for producing barium titanate powder for low-temperature sintering. As such a liquid phase method, specifically, after reacting TiCl ₄ , BaCl ₂ and oxalic acid in an aqueous solution to form a precipitate of BaTiO (C ₂ O ₄ ) ₂ .4H ₂ O, The oxalate method of thermally decomposing the precipitate, hydrothermal treatment of a mixture of barium hydroxide and titanium hydroxide,
Hydrothermal synthesis method of calcining the obtained reaction product, alkoxide method of hydrolyzing a mixed alkoxide solution of barium alkoxide and titanium alkoxide, and calcining the obtained hydrolyzate, titanium alkoxide in barium hydroxide aqueous solution Hydroxide-alkoxide method of calcining the reaction product obtained by hydrolysis of the other, other coprecipitation method, sol-gel method,
Spray pyrolysis has been proposed. However, even when barium titanate powders obtained by these liquid phase methods are used, although the sintering temperature can be somewhat lower than that of the powder obtained by the solid phase method, the sintering temperature is higher than 1200 ° C. There is a problem that low-temperature sintering is difficult.

As a method of lowering the sintering temperature of barium titanate, the applicant of the present application has focused on the Ba / Ti molar ratio, and if the molar ratio is such that Ba is slightly excessive, the sintering property is reduced. Have been found, and the sintering temperature can be greatly reduced as compared with the prior art, and this is proposed (see Japanese Patent Application Laid-Open No. 10-203867). However, in this method, barium titanate having a predetermined Ba / Ti molar ratio different from each other has to be synthesized each time, and a large amount of labor is required industrially.

Under these circumstances, the present inventors have conducted intensive studies on a method of greatly reducing the sintering temperature of barium titanate, and found that barium titanate powder having a cubic crystal phase at room temperature was obtained. It has been found that when a compound such as Ba is added to such a barium titanate powder, the sinterability is dramatically improved and the sintering temperature can be greatly reduced.

Hitherto, it has been considered that the addition of a Ba compound (for example, barium carbonate) to barium titanate powder does not improve sinterability or rather lowers sinterability.
However, the present inventors have found that such a decrease in sinterability
It was discovered that the crystal phase of barium titanate used was tetragonal. It has been found that adding a Ba compound to cubic barium titanate can significantly lower the sintering temperature.

The use of cubic barium titanate powder as a raw material for sintering is disclosed in JP-A-5-139744, JP-A-6-279110, and JP-A-10-13.
9535. However, none of them aimed at improving the sinterability by focusing on the Ba / Ti molar ratio, and was not always satisfactory for the purpose of low-temperature sintering.

[0009]

SUMMARY OF THE INVENTION The present invention has been made to solve the problems associated with the prior art as described above, and enables low-temperature sintering and facilitates the adjustment of the Ba / Ti molar ratio of barium titanate. It is an object of the present invention to provide a barium titanate-based composition powder that can be controlled.

[0010]

SUMMARY OF THE INVENTION The powder composition for producing a barium titanate-based sintered body capable of being sintered at a low temperature according to the present invention comprises a titanium phase having a cubic crystal or an intermediate phase between cubic and tetragonal at room temperature. It is composed of barium oxide powder and at least one compound selected from a Ba compound, an Sr compound or a Pb compound that increases the molar ratio of barium sites to titanium in barium titanate during firing.

As the Ba compound, barium oxide,
At least one compound selected from the group consisting of barium peroxide, barium carbonate, barium hydroxide, barium acetate, barium oxalate, and barium alkoxide;
Examples of the r compound include at least one compound selected from strontium oxide, strontium peroxide, strontium carbonate, strontium hydroxide, strontium acetate, strontium oxalate, and strontium alkoxide. Examples of the Pb compound include lead oxide, carbonate At least one compound selected from lead, lead hydroxide, lead acetate, lead oxalate, and lead alkoxide is exemplified.

In the powder composition for producing a barium titanate-based sintered body which can be sintered at a low temperature, the barium titanate powder has a Ba / Ti molar ratio in the range of 0.950 to 1.050, The (Ba + Sr + Pb) / Ti molar ratio of the composition is in the range of 0.990 to 1.180, and the (Ba + Sr + Pb) / Ti molar ratio of the powder composition is larger than the Ba / Ti molar ratio of the barium titanate powder. Is preferred. When the molar ratio is adjusted to such a value, the sinterability is greatly improved, and although a sintering temperature of 1250 ° C. or more was conventionally required, even if the sintering temperature is 900 to 1150 ° C., the theoretical density is 85% % Can be manufactured.

[0013]

DETAILED DESCRIPTION OF THE INVENTION Hereinafter, the present invention will be described specifically. The powder composition according to the present invention comprises a barium titanate powder whose crystal phase is cubic or an intermediate phase between cubic and tetragonal at room temperature, and at least one compound selected from a Ba compound, an Sr compound or a Pb compound. It consists of:

Barium titanate powder First, the barium titanate powder used in the present invention will be described. In the present invention, as the barium titanate powder, barium titanate whose crystal phase is cubic at room temperature or an intermediate phase between cubic and tetragonal is used. Originally, barium titanate is orthorhombic below about 0 ° C., tetragonal between about 0 ° C. and the Curie point of about 120 ° C., and has a Curie point of about 120 ° C.
It is known that a cubic crystal is formed at a temperature of not less than ° C. Thus, the room temperature stable phase of barium titanate is tetragonal.

By the way, among barium titanate powders, there are known those in which the crystal phase measured at room temperature does not originally show a tetragonal crystal which is stable at room temperature but shows a cubic crystal which is called a pseudo cubic crystal ( The term “quasi-cubic” is a term used in part to distinguish it from a regular cubic which is shown at a temperature of about 120 ° C. or higher of the Curie point. Since it is a cubic crystal, the term pseudo cubic is not used, but is unified to the term cubic.)

It is also known that by subjecting such cubic barium titanate to a heat treatment at a temperature of 400 to 1200 ° C. or higher, the crystal phase measured at room temperature shifts from cubic to tetragonal. . In the process of shifting the crystal phase from a cubic system to a complete tetragonal system, an intermediate phase appears as a tetragonal system in which the difference between the lattice constants c and a is reduced. This intermediate phase is that (100) plane and (001) plane, (200) plane and (002) plane, and (400) plane and (004) plane are not completely branched in powder X-ray diffraction. Is determined from The barium titanate powder used in the present invention may be in an intermediate phase from cubic to complete tetragonal.

JCPDS (Joint Committee on Powder)
According to Diffraction Standard) card 5-0626, the perfect tetragonal c / a is 1.011. Accordingly, the crystal phase used in the present invention is cubic crystal at room temperature or c of barium titanate which is an intermediate phase between cubic and tetragonal
/ A (axial ratio between lattice constant c and lattice constant a) is 1.011
It is sufficient that the ratio is less than 1.000 or more, and in particular, c / a is 1.
008 or less, more preferably 1.000 or more.

The measurement of the c / a ratio is performed by precise measurement of the lattice constant by powder X-ray diffraction. As a method for synthesizing such barium titanate powder having a cubic crystal phase measured at room temperature, a hydroxide-alkoxide method (Bu
lletin of the Chemical Society OF Japan, Vol. 47, No.
1168 to 1171 (1974)), alkoxide method (J. Am. Cera)
m. Soc., Vol. 52, pp. 523-526 (1969)), hydrothermal method (Chemical Society of Japan, No. 6, pp. 985-990 (1975)), oxalate method (J. Am. Ceram. Soc., Vol. 49, pp. 291-295 (19
66)) and co-precipitation method (Industrial Chemistry Magazine, Vol. 71, pp. 114-118 (1968)).

Hereinafter, a method for producing a cubic barium titanate powder will be described by taking the barium hydroxide-alkoxide method as an example. If a barium titanate powder having a cubic crystal phase at room temperature can be obtained, the production method will be described. Is barium hydroxide-
It is not limited to the alkoxide method. The barium hydroxide-alkoxide method is a method of preparing a barium titanate powder by mixing and hydrolyzing an aqueous barium hydroxide solution and a titanium alkoxide.

The aqueous barium hydroxide solution is Ba (OH) _2.
It is prepared by dissolving barium hydroxide hydrate, such as 8H ₂ O, barium hydroxide anhydride, or barium oxide in water.
A barium hydroxide aqueous solution may be prepared by hydrolyzing barium alkoxide, and BaCl ₂ or Ba (N
Ba (OH) ₂ .nH ₂ obtained by adding an alkali such as caustic soda to a water-soluble barium salt such as O ₃ ) ₂ and reacting the same.
O may be prepared by dissolving in water.

The concentration of the aqueous barium hydroxide solution used is not particularly limited as long as barium hydroxide is dissolved. The solubility of barium hydroxide per 100 g of water was 1.67 g at 0 ° C., 4.29 g at 25 ° C.,
It is 101.4 g at 80 ° C. Since the solubility of barium hydroxide is low near room temperature, to increase the solubility,
It may be heated to 90 ° C. before use. In this case, the barium hydroxide aqueous solution has a barium concentration of 0.1 to 3 mol /.
It is practical and economical to prepare in the range of kg.

The raw materials used in preparing the aqueous barium hydroxide solution include not only highly purified specially purified products but also general industrial grade products. Titanium alkoxide can be produced by a known method.
For example, it can be manufactured by blowing ammonia gas into titanium tetrachloride dissolved in alcohol to remove NH ₄ Cl by-produced.

The titanium alkoxide [Ti (O
R) ₄ , R = alkyl group] is not particularly limited, and any type can be used. Considering practicality, R is preferably a linear or branched alkyl group having 1 to 6 carbon atoms. Representative alkyl groups include, but are not limited to, methyl, ethyl, normal propyl, isopropyl, normal butyl, isobutyl, normal pentyl, normal hexyl, and the like. The titanium alkoxide used may be a purified high-purity product or a general industrial grade product.

The organic solvent for dissolving the titanium alkoxide is not particularly limited as long as the titanium alkoxide is soluble. Alcohols such as methyl alcohol, ethyl alcohol, isopropyl alcohol and normal butyl alcohol, and fats such as hexane, heptane and octane can be used. Organic solvents such as aromatic hydrocarbons, aromatic hydrocarbons such as benzene, toluene, and xylene can be used, and these can be used alone or as a mixture of two or more. The concentration of the titanium alkoxide solution dissolved in the organic solvent is 0.1 to 3 m
ol / kg, preferably in the range of 0.5 to 2 mol / kg.

When a water-insoluble solvent such as benzene, toluene or xylene is used as the organic solvent for dissolving the titanium alkoxide, methyl alcohol,
It is desirable to add a water-soluble solvent such as ethyl alcohol, isopropyl alcohol, and normal butyl alcohol. If such a water-soluble solvent is added,
Since the compatibility with the aqueous barium hydroxide solution can be improved, the hydrolysis can be performed uniformly, and the hydrolysis rate is increased, so that fine particles can be prepared. As a method of adding the water-soluble solvent, when added to the titanium alkoxide, or when added to an aqueous barium hydroxide solution, or when added simultaneously with hydrolysis,
Either case may be used. The amount of the water-soluble solvent depends on the concentrations of the titanium alkoxide solution and the aqueous barium hydroxide solution, but is preferably about 0.2 to 5 times the volume of water in the aqueous barium hydroxide solution. Appropriate.

When a titanium alkoxide which is liquid at room temperature, such as titanium isopropoxide and titanium normal butoxide, is used, the reaction between the titanium alkoxide and barium hydroxide can be carried out without using an organic solvent. . In consideration of the operability, it is preferable to dissolve and use in the above-mentioned organic solvent. The particle size of the obtained barium titanate powder, the concentration of barium hydroxide aqueous solution,
And the rate of hydrolysis of the titanium alkoxide. Specifically, a fine powder can be obtained by increasing the concentration of the aqueous barium hydroxide solution or increasing the hydrolysis rate of titanium alkoxide.

The slurry of the hydrolyzate obtained by mixing and reacting the aqueous barium hydroxide solution with the titanium alkoxide can be subjected to filtration, centrifugation, drying under reduced pressure, and solid-liquid separation such as a spray dryer to remove a precipitate. it can. Further, Sr, Ba, Pb compounds and the like described later may be directly added to the hydrolyzate slurry without performing solid-liquid separation.

The drying of the precipitate obtained by the solid-liquid separation is as follows:
General methods such as ventilation drying, vacuum drying and freeze drying can be employed. The drying temperature of the precipitate is preferably as low as possible in order to prevent agglomeration.
A range of 0 ° C. is preferred. Although the obtained dry powder can be used as it is as a cubic barium titanate powder, it is preferably calcined at a temperature in the range of 400 ° C. to 1150 ° C. as necessary.

Normally, the barium titanate powder immediately after drying is a cubic crystal having a swelled lattice (lattice constant a = 4.028-
(About 4.030 °) indicates barium titanate. The lattice of the cubic barium titanate gradually shrinks by the heat treatment, and the lattice constant a measured at room temperature is 4.0.
It changes from about 05 to 4.010 °. For example, when the particle size of the dried powder as observed by electron microscopy is as small as 0.05 μm, the heat treatment at 700 to 800 ° C. causes the crystal phase measured at room temperature to start changing to a tetragonal crystal, and becomes a crystal phase showing the intermediate phase. When calcined at 900-1000 ° C,
The crystal phase measured at room temperature becomes completely tetragonal. The particle size of the dried powder as observed by electron microscopy was 0.3.
In the case of about 2 μm, the crystal phase measured at room temperature starts to change to a tetragonal crystal by the heat treatment at 800 to 900 ° C., becomes a crystal phase showing the intermediate phase, and further becomes 1150 to 1200
When calcined at ° C., the crystal phase measured at room temperature changes to a perfect tetragon. For this reason, the calcining temperature is appropriately selected according to the particle size of the obtained barium titanate powder.

If the barium titanate powder is homogeneous and fine, abnormal grain growth during sintering is suppressed and the activity is high, so that it can contribute to the improvement of sinterability. Specifically, it is desirable that the average particle diameter is in the range of 0.01 to 1.0 μm. Ba compound, Sr compound or Pb compound Next, Ba added to the above-mentioned barium titanate powder
At least one compound selected from a compound, an Sr compound and a Pb compound will be described.

The Ba compound, Sr compound or Pb compound to be added is selected from compounds which increase the molar ratio of barium sites to titanium in barium titanate during firing. Such a compound is not particularly limited as long as it decomposes to an oxide in the heat treatment after addition and mixing to barium titanate and in the sintering process. Specifically, barium oxide, barium peroxide, Ba compound such as barium carbonate, barium hydroxide, barium acetate, barium oxalate, barium alkoxide, strontium oxide, strontium peroxide, strontium carbonate, strontium hydroxide, strontium acetate,
Examples include Sr compounds such as strontium oxalate and strontium alkoxide, and Pb compounds such as lead oxide, lead carbonate, lead hydroxide, lead acetate, lead oxalate, and lead alkoxide.

These Ba compounds, Sr compounds and Pb compounds may be used alone or in combination of two or more. That is, a combination of a Ba compound and an Sr compound, a combination of an Sr compound and a Pb compound, a combination of a Pb compound and a Ba compound, or a combination of a Ba compound, an Sr compound, and a Pb compound may be used.

Powder Composition The powder composition for producing a barium titanate-based sintered body according to the present invention comprises a barium titanate powder having a cubic crystal or an intermediate phase between cubic and tetragonal at room temperature. , Ba compound, Sr compound or Pb compound. The barium titanate powder used has a Ba / Ti molar ratio of 0.950 to 1.05.
0, preferably in the range of 0.950 to 1.000. In the case of barium titanate having a Ba / Ti molar ratio of 0.950 or less, B added to improve sinterability
If the added amount of the a-compound, Sr-compound, and Pb-compound is too large, uniform dispersion becomes difficult, and the microstructure of the obtained sintered body becomes non-uniform. When the molar ratio of Ba / Ti is 1.050 or more, Ba compound, Sr compound, Pb
Even if a compound is added, the effect of improving sinterability is small.

B which increases the molar ratio of barium sites to titanium in barium titanate during calcination
The amount of the at least one compound selected from the compounds a, Sr and Pb added to the barium titanate powder is such that the composition after the addition has a molar ratio of (Ba + Sr + Pb) / Ti of 0.990 to 1.180; Preferably 1.000
It is desirably in the range of １．１1.180.

At this time, the (Ba + Sr + Pb) / Ti molar ratio after the addition of the Ba compound, the Sr compound or the Pb compound is determined by the Ba / Ti molar ratio of the barium titanate powder before the addition of the Ba compound, the Sr compound and the Pb compound. The condition is that it is larger. By setting the (Ba + Sr + Pb) / Ti molar ratio in such a range, the sinterability of barium titanate can be significantly improved. For example, although a sintering temperature of 1250 ° C. or higher was conventionally required, if the (Ba + Sr + Pb) / Ti molar ratio is within the above range, the relative density is 85% even at a sintering temperature of 900 to 1150 ° C.
Thus, a densification of preferably 90% or more is achieved.

Although the theoretical density slightly fluctuates according to the molar ratio of (Ba + Sr + Pb) / Ti, the relative density is determined by JC
PDS (Joint Committee on Powder Diffraction Stan
dard) Calculated for convenience as a percentage (%) based on the theoretical density of 6.012 g / cm ³ calculated from the lattice constant of BaTiO ₃ having the stoichiometric composition described in 5-0626 of the card.

Japanese Patent Application Laid-Open No. Hei 6-279110 discloses that BaTiO ₃ , SrTiO ₃ , PbTiO ₃ and CaT
A powder composition consisting of iO ₃ is disclosed. Also,
Japanese Patent Application Laid-Open No. Hei 6-279110 discloses BaTiO _3.
Are pseudo-cubic, and SrTiO ₃ , PbTiO ₃
And the addition of at least one of CaTiO ₃ as a carbonate and oxide precursor (eg, SrCO ₃ and TiO ₂ ). However, JP-A-6-279110 discloses any technical idea of adding a Ba compound, a Sr compound or a Pb compound that increases the molar ratio of barium sites to titanium in barium titanate during firing. is not. That is, in Japanese Unexamined Patent Publication No. Hei 6-279110, the carbonate of Sr, Pb or Ca added to pseudo-cubic BaTiO ₃ and TiO ₂ are burned into SrTi
The formation of O ₃ , PbTiO ₃ and CaTiO ₃ alone does not increase the molar ratio of barium sites to titanium in barium titanate.

Ba compound added in the present invention, S
The particle size of the r compound and the Pb compound, and the method of adding the
There is no particular limitation. However, the added Ba
The smaller the particle size of the compound, the Sr compound or the Pb compound is, the more preferable it is because it can be uniformly mixed and dispersed with the barium titanate powder. Ba compound, Sr compound,
As a method of adding and mixing the Pb compound, either dry mixing or wet mixing can be selected. Since barium titanate is a fine powder, wet mixing using a ball mill, a vibration mill, an attrition mill, or the like with water or an organic solvent as a medium is preferable. When the Ba compound, the Sr compound, and the Pb compound are dissolved in water or an organic solvent, they can be added to the barium titanate powder as a solution.

The barium titanate-based powder composition according to the present invention contains Mg, Ca, Sr,
Ba, Pb, rare earth metal, Ti, Zr, Hf, Sn,
V, Nb, Ta, Bi, Sb, W, Mo, Cr, Mn,
A compound of at least one element selected from Cu, Ni, Co, Fe, Zn, Al, and Si (hereinafter, a third component compound) may be included.

The third component compound is not particularly limited as long as it decomposes to an oxide in the heat treatment and sintering process after mixing. For example, oxides, hydroxides, acetates, oxalates, carbonates, nitrates, alkoxides and the like of the exemplified elements can be mentioned. Also, 2
When adding more than one kind, for example, SrTiO ₃ ,
It may be a composite oxide such as CaTiO ₃ or BaZrO ₃ or a precursor thereof.

Such a third component compound may be simultaneously added to the barium titanate powder together with the Ba compound, Sr compound or Pb compound.
After adding the compound, the Sr compound or the Pb compound, the compound may be added to the barium titanate powder. As a method of adding and mixing the third component compound, any of the above-described dry mixing and wet mixing can be selected.

The barium titanate-based powder composition according to the present invention thus obtained is molded and fired to obtain a barium titanate-based sintered body. When molding the barium titanate-based powder composition according to the present invention, the powder composition may be directly molded and then sintered, or may be calcined and then molded.

The molding method is not particularly limited, and known techniques such as press molding, hydrostatic molding, tape molding such as doctor blade method, extrusion molding, injection molding, and casting are applicable. Further, these molding methods may be combined. When the barium titanate-based powder composition is prepared by wet mixing, the obtained barium titanate-based powder composition slurry is not dried, an organic binder is added, and directly into a sheet by a method such as a doctor blade method. It can also be molded.

The sintering of such a molded product is carried out by preparing a barium titanate powder having a cubic crystal phase at room temperature,
When it is composed of at least one compound selected from a Ba compound, an Sr compound and a Pb compound,
A sintered body having a relative density of about 85% or more of the theoretical density can be obtained at a sintering temperature lower than the conventional one such as 1150 ° C.
The sintering may be performed at a temperature of 1150 ° C. or higher. The sintering temperature depends on the particle size of the barium titanate powder used as the main raw material.
Densifies at low temperatures. For example, when the particle size of the barium titanate powder is 0.05 μm, the sintering temperature is 900 to 1100 ° C., and when the particle size is 0.2 μm, the sintering temperature is 900 to 1150 ° C. A sintered body having a high density is obtained.

In the powder composition obtained by further adding the third component compound to such a powder composition, the sintering temperature is appropriately selected within a temperature range of 900 to 1350 ° C. As the sintering atmosphere, conditions such as atmospheric pressure, pressurization, decompression, oxidation, and reduction can be appropriately selected and combined. The heating rate is usually in the range of 0.1 to 50 ° C./min, preferably 0.5 to 20 ° C./min, and the sintering holding time is 1 to 20 hours, preferably 2 to 8 hours. Appropriate.
It is also possible to maintain the temperature for a certain period of time or change the rate of temperature rise during the temperature rise.

[0046]

As described above, according to the present invention, the sintering temperature is increased by adding at least one of Ba compound, Sr compound and Pb compound to barium titanate powder having a cubic crystal phase at room temperature. Can be greatly reduced. In addition, since the method may be mixed with the barium titanate powder, the labor can be reduced industrially.

Therefore, according to the present invention, it is possible to easily perform low-temperature sintering of a barium titanate-based sintered body, reduce the production cost due to the energy saving effect, and suppress the grain growth. The excellent effect that can be obtained is exhibited.

[0048]

EXAMPLES Examples of the present invention will be described below.
The present invention is not limited to these embodiments.

[0049]

Example 1 [Preparation of cubic BaTiO ₃ powder] 15.78 g (0.05 mol) was added to 58 g of ion-exchanged water from which CO ₂ had been removed.
High purity _{Ba (OH) 2 · 8H 2} O were added, and warmed dissolved in 80 ° C.. The high-purity Ba (OH) ₂ .8H ₂ O is Sr
Purified to a content of 100 ppm or less was used.

This solution was cooled to 60 ° C. in N ₂ gas, and 50.25 g of a 1 mol / kg titanium tetraisopropoxide [Ti (O i-Pr) ₄ ] isopropyl alcohol solution [titanium tetraisopropyl 14.284 g (0.05025 mol) as a propoxide, corresponding to a Ba / Ti molar ratio of 0.995], and stirring was continued for 2 hours under reflux.

The heating was further continued to evaporate the solvent, and the obtained precipitate was evaporated to dryness under reduced pressure, dried at 60 ° C., crushed in a mortar, and sized with a 100-mesh sieve. Barium acid powder was obtained. X-ray diffraction analysis of the obtained barium titanate powder showed that the powder was cubic Ba.
It was confirmed to be TiO ₃ . Moreover, the Ba / Ti molar ratio of the obtained barium titanate powder was determined by a glass bead method using fluorescent X-rays. Its analysis value is 0.995
Met.

[Preparation of Barium Titanate-Based Molding Powder Composition] Next, 3.88 parts by weight of BaCO ₃ was added to 100 parts by weight of the obtained barium titanate powder, and mixed in acetone using a mortar. And dried at 60 ° C, then 100
The particles were sized with a mesh to prepare a barium titanate-based molding powder composition. Table 1 shows the properties of the obtained powder composition.

[Sintering test] This powder composition was subjected to ² ton / cm ²
After molding under hydrostatic pressure at a pressure of, the obtained molded body was heated at a heating rate of 1 ° C./min and calcined at normal pressure for 4 hours at the temperature shown in Table 2. Table 2 and FIG. 1 show the bulk density and relative density (percentage of the theoretical density) of the sintered body at each firing temperature.

[0054]

Example 2 The barium titanate powder prepared in Example 1 was calcined at 700 ° C. X-ray diffraction analysis of the obtained barium titanate powder confirmed that the powder was cubic BaTiO ₃ . next,
With respect to 100 parts by weight of the obtained barium titanate powder, B
4.08 parts by weight of aCO ₃ was added, mixed in acetone using a mortar, dried at 60 ° C., and sized with 100 mesh to prepare a barium titanate-based molding powder composition.

Table 1 shows the properties of the obtained powder composition.
Using this powder composition, molding was performed in the same manner as in Example 1, and a sintering test was performed. The results are shown in Table 2 and FIG.

[0056]

Example 3 Similarly to Example 2, the barium titanate powder prepared in Example 1 was calcined at 700 ° C., and 100 parts by weight of the obtained barium titanate powder was mixed with Ba (OH) ₂
6.53 parts by weight of 8H ₂ O was added, mixed in acetone using a mortar, dried at 60 ° C., and sized with 100 mesh to prepare a barium titanate-based molding powder composition.

Table 1 shows the properties of the obtained powder composition.
Using this powder composition, molding was performed in the same manner as in Example 1, and a sintering test was performed. The results are shown in Table 2 and FIG.

[0058]

Example 4 The barium titanate powder prepared in Example 1 was calcined at 800 ° C. X-ray diffraction analysis of the obtained barium titanate powder confirmed that the powder was BaTiO ₃ , an intermediate phase between cubic and tetragonal crystals. Next, the obtained barium titanate powder 10
4.08 parts by weight of BaCO ₃ was added to 0 parts by weight,
The mixture was mixed in acetone using a mortar, dried at 60 ° C., and then sized with 100 mesh to prepare a barium titanate-based powder composition for molding.

Table 1 shows the properties of the obtained powder composition.
Using this powder composition, molding was performed in the same manner as in Example 1, and a sintering test was performed. The results are shown in Table 2 and FIG.

[0060]

Example 5 As in Example 2, the barium titanate powder prepared in Example 1 was calcined at 700 ° C., and SrCO ₃ was added in an amount of 3.006 with respect to 100 parts by weight of the obtained barium titanate powder. A weight part was added, mixed in acetone using a mortar, dried at 60 ° C., and then sized with 100 mesh to prepare a barium titanate-based powder composition for molding.

Table 1 shows the properties of the obtained powder composition.
Using this powder composition, molding was performed in the same manner as in Example 1, and a sintering test was performed. The results are shown in Table 2 and FIG.

[0062]

Example 6 Similarly to Example 2, the barium titanate powder prepared in Example 1 was calcined at 700 ° C., and PbO was added to 100 parts by weight of the obtained barium titanate powder.
Add 62 parts by weight, mix using a mortar in acetone,
After drying at 60 ° C., the mixture was sized with a 100 mesh to prepare a barium titanate-based molding powder composition.

Table 1 shows the properties of the obtained powder composition.
Using this powder composition, molding was performed in the same manner as in Example 1, and a sintering test was performed. The results are shown in Table 2 and FIG.

[0064]

Example 7 Similarly to Example 2, the barium titanate powder prepared in Example 1 was calcined at 700 ° C., and 100 parts by weight of the obtained barium titanate powder was mixed with 2.04 parts of BaCO ₃ . Parts by weight, 1.53 parts by weight of SrCO ₃ are added,
The mixture was mixed in acetone using a mortar, dried at 60 ° C., and then sized with 100 mesh to prepare a barium titanate-based powder composition for molding.

Table 1 shows the properties of the obtained powder composition.
Using this powder composition, molding was performed in the same manner as in Example 1, and a sintering test was performed. The results are shown in Table 2 and FIG.

[0066]

Comparative Example 1 In the same manner as in Example 2, the barium titanate powder prepared in Example 1 was calcined at 700 ° C., and the obtained barium titanate powder was sized at 100 mesh without adding anything. did. Table 1 shows the properties of the barium titanate powder.
After the barium titanate powder was subjected to isostatic pressing at a pressure of ² ton / cm ² , the obtained molded body was heated at a heating rate of 1 ° C./min, and calcined under normal pressure at the temperature shown in Table 2 for 4 hours. The bulk density and relative density of the sintered body were evaluated.

The results are shown in Table 2 and FIG.

[0068]

Example 8 [Preparation of cubic BaTiO ₃ powder] To 117 g of ion-exchanged water from which CO ₂ had been removed, 15.78 g (0.05 mol) of high-purity Ba (OH) ₂ .8H ₂ O was added, and 80 ° C. And dissolved. As Ba (OH) ₂ .8H ₂ O, a high-purity product whose Sr content was purified to 100 ppm or less was used.

This solution was cooled to 60 ° C. in N ₂ gas, and 50.35 g of a 1 mol / kg titanium tetra-n-butoxide [Ti (On-Bu) ₄ ] toluene solution at a concentration of 1 mol / kg was stirred.
[17.137 g as titanium tetra n-butoxide
(Equivalent to 0.993 as a molar ratio of Ba / Ti), and the mixture was stirred under reflux for 1 hour.

The heating was further continued, and toluene and n-butyl alcohol were distilled off, and the mixture was stirred in an aqueous slurry at 100 ° C. for 2 hours. The resulting precipitate was evaporated to dryness under reduced pressure to give 8
After drying at 0 ° C., the mixture was sized with a 100-mesh sieve to obtain barium titanate powder. This powder was calcined at 800 ° C. for 1 hour to obtain a calcined powder. X-ray diffraction analysis of the obtained powder confirmed that the powder was cubic BaTiO ₃ . Moreover, when the Ba / Ti molar ratio of the calcined powder was determined by a glass bead method using fluorescent X-rays, the analysis value was 0.993.

Table 1 shows the powder characteristics of the barium titanate thus obtained. [Preparation of barium titanate-based molding powder composition] Next, 4.08 parts by weight of BaCO ₃ was added to 100 parts by weight of the obtained barium titanate powder, and the mixture was mixed in acetone using a mortar. After drying at 0 ° C, the powder was sized with a 100 mesh to prepare a barium titanate-based molding powder composition.

Table 1 shows the properties of the obtained powder composition. [Sintering test] After this powder composition was subjected to isostatic pressing under a pressure of ² ton / cm ² , the obtained molded body was heated at a rate of 10 ° C / min.
And fired at normal pressure for 3 hours at the temperature shown in Table 2. Table 2 and FIG. 2 show the bulk density and relative density of the sintered body at each firing temperature.

[0073]

Example 9 A barium titanate-based molding powder composition was prepared in the same manner as in Example 8, except that 2.04 parts by weight of BaCO ₃ was added to 100 parts by weight of the obtained barium titanate powder. Was prepared. Table 1 shows the properties of the obtained powder composition.

This powder composition was molded in the same manner as in Example 8, fired, and subjected to a sintering test. The results are shown in Table 2 and FIG.

[0075]

Example 10 In Example 8, 3.06 SrCO ₃ was added to 100 parts by weight of the obtained barium titanate powder.
A barium titanate-based molding powder composition was prepared in the same manner as in Example 8 except that parts by weight were added. Table 1 shows the properties of the obtained powder composition.

This powder composition was molded in the same manner as in Example 8, fired, and subjected to a sintering test. The results are shown in Table 2 and FIG.

[0077]

Example 11 A barium titanate-based molding powder composition was prepared in the same manner as in Example 8, except that 4.62 parts by weight of PbO was added to 100 parts by weight of the obtained barium titanate powder. Was prepared. Table 1 shows the properties of the obtained powder composition.

This powder composition was molded in the same manner as in Example 8, fired, and subjected to a sintering test. The results are shown in Table 2 and FIG.

[0079]

Example 12 In Example 8, 1.53 parts of SrCO ₃ was added to 100 parts by weight of the obtained barium titanate powder.
A barium titanate-based molding powder composition was prepared in the same manner as in Example 8, except that 2.31 parts by weight of PbO and 2.31 parts by weight of PbO were added. Table 1 shows the properties of the obtained powder composition.

This powder composition was molded in the same manner as in Example 8, fired, and then subjected to a sintering test. The results are shown in Table 2 and FIG.

[0081]

Comparative Example 2 A barium titanate-based molding powder composition was prepared by sizing with a mesh of 100 without adding anything to the obtained barium titanate powder.
Table 1 shows the properties of the obtained powder composition. Using this powder composition, molding was performed in the same manner as in Example 8, followed by firing,
A sintering test was performed.

The results are shown in Table 2 and FIG.

[0083]

EXAMPLE 13 3.2 parts of BaCO ₃ were added to 100 parts by weight of barium titanate powder (average particle size: 0.2 μm), which is a cubic and tetragonal mesophase synthesized by a commercially available hydrothermal method.
3 parts by weight, mixed in a mortar in acetone,
After drying at 0 ° C., the mixture was sized with a 100 mesh to prepare a barium titanate-based molding powder composition.

The properties of the obtained powder composition are shown in Table 1.
This powder composition was molded in the same manner as in Example 8, fired, and then subjected to a sintering test. The results are shown in Table 2 and FIG.
Shown in

[0085]

Example 14 A barium titanate-based molding powder composition was prepared in the same manner as in Example 13 except that 2.42 parts by weight of SrCO ₃ was added to 100 parts by weight of barium titanate powder. Prepared. Table 1 shows the properties of the obtained powder composition.

Using this powder composition, it was molded in the same manner as in Example 8, fired, and then subjected to a sintering test. The results are shown in Table 2 and FIG.

[0087]

Example 15 A barium titanate-based molding powder composition was prepared in the same manner as in Example 13 except that 3.66 parts by weight of PbO was added to 100 parts by weight of barium titanate powder. did. Table 1 shows the properties of the obtained powder composition.

Using this powder composition, it was molded in the same manner as in Example 8, fired, and then subjected to a sintering test. The results are shown in Table 2 and FIG.

[0089]

Comparative Example 3 In Example 13, the particle size was adjusted to 100 mesh without adding anything to the barium titanate powder. Table 1 shows the properties of the barium titanate powder. This barium titanate powder was molded in the same manner as in Example 8, fired, and subjected to a sintering test.

The results are shown in Table 2 and FIG.

[0091]

Comparative Example 4 3.83 parts by weight of BaCO ₃ was added to 100 parts by weight of a tetragonal barium titanate powder having an average particle size of 0.5 μm synthesized by a commercially available hydrothermal method, and a mortar was used in acetone. And then dried at 80 ° C and
It was sized with a mesh. This barium titanate powder was molded in the same manner as in Example 8, fired, and subjected to a sintering test.

The results are shown in Table 2 and FIG.

[0093]

Comparative Example 5 The commercially available tetragonal barium titanate powder used in Comparative Example 4 was molded in the same manner as in Example 8 without adding any Ba compound, Sr compound, or Pb compound, followed by firing and firing. A closing test was performed. The results are shown in Table 2 and FIG.

[0094]

Comparative Example 6 4.08 parts by weight of BaCO ₃ was added to 100 parts by weight of tetragonal barium titanate powder having an average particle size of 1.0 μm synthesized by a commercially available solid phase method, and the mixture was mortared in acetone. The mixture was dried at 80 ° C. and sized with 100 mesh. This powder composition was molded in the same manner as in Example 8, fired, and then subjected to a sintering test.

The results are shown in Table 2 and FIG.

[0096]

Comparative Example 7 The commercial tetragonal barium titanate powder used in Comparative Example 6 was molded in the same manner as in Example 8 without adding any Ba compound, Sr compound, or Pb compound, and then fired. A closing test was performed. The results are shown in Table 2 and FIG.

[0097]

[Table 1]

[0098]

[Table 2]

As is clear from the comparison between Examples 1 to 12 and Comparative Examples 1 and 2 (see Table 2 and FIGS. 1 and 2), the barium titanate powder of the cubic system or the intermediate phase of the cubic system and the tetragonal system was used. If a Ba compound, an Sr compound or a Pb compound is added so as to increase the molar ratio of barium sites to titanium, firing at a high relative density of 85% or more even at a low temperature of 900 to 1100 ° C. You can get union.

As is clear from the comparison between Examples 13 to 15 and Comparative Examples 3 to 7 (see Table 2 and FIG. 3), the molar ratio of barium sites to titanium is increased in tetragonal barium titanate powder. Even if such a Ba compound, Sr compound or Pb compound is added, there is no effect of low-temperature sintering, and on the other hand, the molar ratio of barium sites to titanium is increased in cubic and tetragonal mesophase barium titanate powders. It is clear that low-temperature sintering is promoted by adding such a Ba compound, Sr compound or Pb compound.

[Brief description of the drawings]

FIG. 1 is a diagram illustrating a relationship between a sintering temperature and a relative density in Examples 1 to 7 and Comparative Example 1.

FIG. 2 is a diagram illustrating a relationship between a sintering temperature and a relative density in Examples 8 to 12 and Comparative Example 2.

FIG. 3 shows Examples 13 to 15 and Comparative Examples 3 to
FIG. 7 is a diagram illustrating a relationship between a sintering temperature and a relative density in FIG.

 ──────────────────────────────────────────────────の Continued on the front page F term (reference) 4G031 AA03 AA05 AA06 AA07 AA11 AA12 AA13 AA14 AA15 AA16 AA17 AA18 AA19 AA21 AA22 AA23 AA25 AA26 AA29 AA30 AA31 AA32 AA34 AA35 BA09 BA10 CA01 A01 A01 AE01 A01 AE01 5G303 AA01 AA10 AB15 BA12 CA01 CB01 CB03 CB05 CB06 CB09 CB10 CB11 CB13 CB17 CB18 CB21 CB23 CB25 CB28 CB30 CB31 CB32 CB33 CB35 CB36 CB37 CB38 CB39 CB40 CB43 DA05 DA06

Claims (8)

[Claims] 1. A barium titanate powder whose crystal phase is cubic or an intermediate phase between cubic and tetragonal at room temperature, and a Ba compound which increases the molar ratio of barium sites to titanium in barium titanate during firing. , S
A powder composition for producing a barium titanate-based sintered body which can be sintered at a low temperature and comprises at least one compound selected from an r compound and a Pb compound. 2. The Ba compound according to claim 1, wherein said Ba compound is at least one compound selected from barium oxide, barium peroxide, barium carbonate, barium hydroxide, barium acetate, barium oxalate, and barium alkoxide. The powder composition for producing a barium titanate-based sintered body according to the above. 3. The Sr compound is at least one compound selected from strontium oxide, strontium peroxide, strontium carbonate, strontium hydroxide, strontium acetate, strontium oxalate, and strontium alkoxide. The powder composition for producing a barium titanate-based sintered body according to the above. 4. The titanium according to claim 1, wherein said Pb compound is at least one compound selected from the group consisting of lead oxide, lead carbonate, lead hydroxide, lead acetate, lead oxalate, and lead alkoxide. Powder composition for producing barium acid-based sintered body. 5. The barium titanate powder has a Ba / Ti molar ratio in the range of 0.950 to 1.050, and the powder composition has a (Ba + Sr + Pb) / Ti molar ratio of 0.1 to 0.5.
5. The powder composition according to claim 1, wherein a molar ratio of (Ba + Sr + Pb) / Ti of the powder composition is larger than a molar ratio of Ba / Ti of the barium titanate powder. 6. The powder composition for producing a barium titanate-based sintered body according to the above. 6. A powder composition for producing a barium titanate-based sintered body according to any one of claims 1 to 5, and Mg, Ca, S
r, Ba, Pb, rare earth metal, Ti, Zr, Hf, S
n, V, Nb, Ta, Bi, Sb, W, Mo, Cr, M
A powder composition for producing a barium titanate-based sintered body, comprising at least one compound selected from compounds of n, Cu, Ni, Co, Fe, Zn, Al, and Si. 7. A barium titanate-based sintered body obtained by molding and firing the powder composition according to claim 1. 8. A method for producing a barium titanate-based sintered body, comprising molding and firing the powder composition according to claim 1.