JPS61141617A - Powdery solid-solution of barium strontium titanate, and production thereof - Google Patents

Abstract

PURPOSE:To obtain novel powdery solid-solution of barium strontium titanate having spherical form, small particle diameter, small specific surface area and sharp particle size distribution, by reacting hydrated titanium oxide with barium hydroxide and strontium hydroxide in the presence of a specific molar amount of water based on the titanium, at a temperature within a specific range. CONSTITUTION:Hydrated titanium oxide is made to react with barium hydroxide and strontium hydroxide at 60-100 deg.C in the presence of 120-10,000mol of water based on 1mol of titanium. The powdery solid-solution of barium strontium titanate produced by the process has spherical form, an average particle diameter of 0.07-0.5mu, a specific surface area of 3-20m<2>/g and <=2.5 times the value calculated from the average particle diameter assuming the true spherical form, and a crystallite diameter of 0.05-0.4mu calculated from the half-value width of the peak of the powder X-ray diffraction pattern.

Description

Detailed Description of the Invention (Field of Industrial Application) The present invention relates to a novel spherical barium/strontium titanate solid solution powder having a small particle size, a small specific surface area, and a narrow particle size distribution, and a method for producing the same. It is. Furthermore, the present invention relates to a novel barium/strontium titanate solid solution powder that can be sintered at low temperatures and a method for producing the same.

Currently, barium/strontium titanate solid solutions are widely applied in the field of electronic components as capacitors, PTC elements, semiconductors, and the like.

(Conventional technology) In recent years, electronic components are becoming increasingly smaller.

For example, there is a desire for smaller capacitors with higher capacitance than other capacitors, and multilayer capacitors are attracting attention as a way to achieve this goal.

Currently, in multilayer capacitors, the distance between electrodes is approximately 10
There is a tendency to make the capacitance as small as ~20μ to promote high capacity.

In order to satisfy this requirement and guarantee the performance and reliability of the capacitor, it is desirable for such ceramic capacitors to have as many particles as possible, which make up the sintered body, uniformly present between the electrodes. For example, 1 for sintering
．． Requiring 300 tll'' or more requires expensive noble metal internal electrodes, which increases the electrode cost.Furthermore, the particles in the sintered body also grow larger, making it necessary to shorten the distance between the electrodes. Failure to do so will hinder the ability to increase the capacity, and variations in bulk, physical properties, and dimensional accuracy will further reduce yields and increase costs.

Therefore, it is strongly desired that the above drawbacks be improved. However, this is also a strong demand for electronic components other than multilayer capacitors. However, these @
A barium/strontium titanate solid solution powder that satisfies these requirements has not been previously known.

Conventionally, barium/strontium titanate solid solution powder has been manufactured industrially by a solid phase reaction method. The solid phase reaction method is a method in which barium carbonate, strontium carbonate, and titanium dioxide are mixed and reacted with each other at a high temperature of 10 QOC or higher to synthesize a barium/strontium titanate solid solution. However, this method is not suitable for carrying out anti-Ct treatment at high temperatures; sintering begins already during powder production, resulting in powder-to-powder adhesion and grain growth; It has the disadvantage that it is difficult to obtain solid solution powders.

Recently, new synthesis methods for barium titanate powder and strontium titanate powder, such as the oxalic acid method, alkoxide method, and hydroxide method, have been proposed, and although the above drawbacks can be considerably improved, the present invention No powder with these characteristics has been obtained. For example, P, Galla
gher et al. @J, λm, Ceram.

8oc,, 46,559-345 (194M)”, 0
．． We report that barium titanate powders with various particle sizes ranging from 0.09 μm to 0.73 μm were synthesized with oxalic acid. Maku, K, 8. Mazdiyasni et al., J. Am. Ceram, Soc., 52, 5.
25-524 (1969)'' reported the synthesis of high-purity barium titanate with a particle size of 50X to 150^ by an alkoxide method.

However, oxalic acid is a method of synthesizing titanate by firing oxalate at 600C or higher, so it is dangerous, and although it is close to the solid phase reaction method, it is easy to cause agglomeration of powder, and it is difficult to produce large quantities. The drawbacks are that the oxalic acid used for this process cannot be recovered and reused, and the cost is high.

The t1 alkoxide method requires very expensive raw materials and is problematic from an industrial perspective.

Although the hydroxide method is not yet an established technology,
It is attracting attention because the manufacturing process is simple, the raw materials are inexpensive, and the resulting powder has high sinterability. However, it has not been known that the barium/strontium titanate solid solution of the present invention can be produced by the hydroxide method;
Barium titanate with a particle size of about OXμ was obtained by Kubo et al.
Industrialization, Academic Journal, Vol. 71, No. 1 (194B)), and barium titanate with a grain size of 0.02 to 0.05μ (Japanese Patent Application Laid-open No. 59-59721h) and 0.0
Strontium titanate of 1 to 0.02, a (Japanese Unexamined Patent Publication No. 59-59727) is disclosed.

(Problems to be Solved by the Invention) As described in Mayuki, it is difficult to obtain a barium/strontium titanate solid solution having an essentially fine and uniform particle size using conventional methods. The only known barium/strontium titanate solid solution powders are those with large particle sizes, and powders with small particle sizes but poor dispersibility and non-uniform particle sizes and shapes. For large grain size or strongly agglomerated particles, the sintering start temperature must be ttooc or higher, and the relative density must be 1500C or higher to achieve a relative density of t-90- or higher. Requires high temperatures. Powders with poor dispersibility or non-uniform particle size and shape require a uniform packing structure, and sintering will not proceed uniformly, causing variations in dimensions and physical properties. It becomes. Furthermore, ffl fine powder with a particle size of about 0.05μ or less has very poor no-undling properties, making it difficult to obtain a uniform compact, and making it difficult to obtain a highly reliable sintered compact. My friend.

(Elaborate Means to Solve the Problems) After producing barium/strontium titanate solid solution powder with fine and uniform particle size, the inventors conducted extensive research on the hydroxide method, and as a result, Hydrous titanium oxide, barium hydroxide, and strontium hydroxide are heated and reacted while being mixed in the presence of a relatively large amount of water, and the particles have a fine and uniform particle size and a spherical shape, and K is the specific surface area. We have discovered that it is possible to synthesize a barium/strontium titanate solid solution powder with a small amount of #1 and almost no agglomeration, and based on this knowledge, we have accomplished the present invention.

That is, one of the aspects of the present invention is to ``mix hydrous titanium oxide, barium hydroxide, and strontium hydroxide in the presence of water in an amount of 120 to 10,000 times the mole of titanium at a temperature range of 60C or more and less than 110C. This is a method for creating a barium-strontium titanate solid solution characterized by reacting with t-.

In the present invention, as the hydrous titanium oxide, one or more of orthotitanic acid, metatitanic acid, and titanium dioxide is used, and orthotitanic acid is particularly preferred because of its high reactivity. These can be used in solid or gel form. Such hydrous titanium oxide, such as orthotitanic acid, can be easily obtained by treating titanium chloride, sulfate, oxalate, etc. with an alkali, and chloride is particularly preferred. In addition, if metatitanic acid, titanium dioxide #i, and orthotitanic acid are heated, the structural water of orthotitanic acid will be removed one by one, so that 71 degrees of oxidation can be easily obtained.

Both barium hydroxide and strontium hydroxide used in the present invention are generally white-colored hexagons containing water, and they may be used as they are or dissolved in water.

In the present invention, hydrous titanium oxide, barium hydroxide, and strontium hydroxide are combined in the presence of a large amount of water with a 60 to 11
React at 0C.

The amount of water needs to be 120 to 0 times the mole of fO,OG in terms of titanium, and preferably 200 to 2,
000 times the mole. In the presence of a relatively large amount of water, the reaction between hydrous tantanium oxide, barium hydroxide, and strontium hydroxide proceeds mildly, so the resulting powder has a particle size of 0.07 to 0.5μ, The crystallites are large, there are no pores, the specific surface area is small, and there is almost no agglomeration, and the particle shape is spherical and the particle size distribution is uniform. Become something. As the amount of water decreases, the fluidity of the mixture decreases, and when the amount of water decreases by 120 times, the fluidity can no longer be maintained, making it difficult to produce a powder with a spherical shape and uniform particle size. However, because the reactivity of hydrous titanium oxide, barium hydroxide, and strontium hydroxide increases, the particle size is 0.05.
It is small, less than μ, has small crystallites, has pores, has a large specific surface area, and therefore begins to form a powder with strong cohesiveness. Furthermore, if a large amount of water is added, exceeding 10,000 times the molar amount, the concentration of the entire reaction system decreases and the reactivity decreases, making it difficult to carry out the reaction any longer.

According to the present invention, the temperature range of the reaction is preferably 60C.
It is above 110C. If the reaction temperature is lower than 60C, the reaction rate between hydrous titanium oxide, barium hydroxide, and strontium hydroxide is extremely slow and impractical. 9, which not only increases the equipment cost, but also
This is because the particles produced undergo grain growth, making it difficult to produce powder with fine and uniform particle size.

Furthermore, in the present invention, it is preferable to perform mixing in order to make the powder shape spherical and to make the particle size distribution uniform. The reaction time is not particularly limited as long as it is longer than the time required to complete the reaction.

In the present invention, the molar ratio of the mixture of barium hydroxide and strontium hydroxide to hydrous titanium oxide is 1 to 1.
It is desirable to set it to 10. If the molar ratio is less than 1, a large amount of unreacted hydrous titanium oxide will remain. Well done,
Even if the molar ratio is made larger than t-10, the effect of addition will hardly increase and this will cause an increase in cost. A more preferred molar ratio is 1.3-5. According to the present invention, barium and strontium (D% ratio t',
By changing the molar ratio of barium hydroxide and strontium hydroxide added during the reaction], it can be arbitrarily changed from 0 to 1 (however, 0 and 1 are excluded).

The reaction of the present invention is inhibited by the presence of carbon dioxide.

Therefore, it is of course necessary to pay sufficient attention to the absence of carbon dioxide when carrying out the reaction, and to remove the hydrated titanium oxide, barium hydroxide, and strontium hydroxide used in the reaction, as well as the water used to disperse and dilute them, in advance. It is desirable to remove carbon dioxide gold.

The barium/strontium nine titanate solid solution obtained in this way is processed in a conventional manner by washing with water, filtration, drying, and if necessary, calcined at an appropriate temperature, then washed with a weak acid, washed with water, and subjected to F treatment. , dried.

Another aspect of the present invention is that the average particle size is 0.07 to 0.
5 μ, the specific surface area is 5 to 20 trt/f, and the value does not exceed 2.5 times the value calculated from the average particle size assuming that the particle shape is a true sphere], and the peak in the powder X-ray diffraction image. The crystallite diameter calculated from the half-value width is 0.05μ or more and 0.4μ or less,
This is a titanate/barium strontium solid solution powder characterized by its spherical shape. As a specific example of the manufacturing method, it can be obtained by applying the manufacturing method of the present invention, but it is not particularly limited thereto.

The spherical shape in the present invention refers to the shape of each particle as a whole resembling a sphere, as seen in the scanning electron micrograph of the drawing.

The barium/strontium titanate solid solution of the present invention is
Scanning electron microscope (e.g., Hitachi, Ltd.)
450 model scanning electron microscope), the particle size and shape can be measured.

The barium/strontium titanate solid solution of the present invention is
The average particle size is in the range of 0.07 to 0.5μ, but all particles have the same particle size as #1, and the standard deviation value is 1.
5 or less. In the present invention, the average particle diameter i and standard deviation value α determined by scanning electron microscopy are calculated by measuring the particle diameter χ=1− of n particles visible within a unit field of view and using the following formula.

, Σ χL b=1 χ =□ Furthermore, in the barium/strontium titanate solid solution of the present invention, all particles have a spherical shape. The value is less than 1.

The dispersibility of the powder can be determined by measuring the particle size distribution. The particle size distribution can be easily measured using, for example, Micron Fort Sizer 8KA-sooo manufactured by Seishin Enterprise Co., Ltd. The present inventors dispersed barium/strontium titanate solid solution powder in inopropyl alcohol, added a trace amount of PEGt as a dispersant, and measured the particle size distribution.

The barium/strontium titanate solid solution of the present invention is
The average particle size measured by particle size distribution measurement is approximately the same as the average particle size measured by scanning electron microscopy, and the particle size distribution is narrow, with a standard deviation value of 2.0 or less. However, in the present invention, the average particle diameter a and the standard deviation value α determined by the particle size distribution measuring pressure are calculated by the following method.

z=,5. j'4-χL In the above formula, %ZL is the particle size, the arithmetic average of the micro measurement range and both ends, PL is the volume fraction occupied by particles with particle size χ, n
is the number of minute measurement ranges.

In the present invention, the crystallite diameter can be determined by measuring the half-width of a peak in a powder X-ray diffraction image and substituting it into the trap of Scherrer's equation. In the above formula, L
is the crystallite diameter, λ is the X-ray wavelength, β is the half-width of the peak, θ
is the diffraction angle of X-rays and the Ki constant, which is set to 0.9 in the case of the present invention. The value of the half-width β is determined by assuming that the peak shape of the powder X-ray diffraction image to be measured is a Cauchy distribution and correcting it using a silicon crystal.

Regarding the barium/strontium titanate solid solution powder provided by the present invention, the crystallite diameter calculated using the above formula is:
This shows good agreement with the average particle diameter measured by the scanning electron microscope observation. That is, one particle is generally made up of one to several crystallites.

The specific surface area can be measured using a gas adsorption type specific surface area measuring device, for example, Two Buttomatic 1800 manufactured by Carlo Erba Co., Ltd.

The specific surface area of the barium/strontium titanate solid solution powder of the present invention is in the range of 3 to 207 rt/S',
The particle size calculated assuming that the barium/strontium titanate solid solution powder is spherical and has no micropores or irregularities is:
The average particle diameter is not less than 40% of the average particle diameter measured by the scanning electron microscopy, and they are in close agreement. Therefore, from this point of view, does the barium/strontium titanate solid solution powder provided by the present invention have pores? It can be confirmed that the particles are almost spherical in shape and have no stagnation.

(Effects of the Invention) The barium/strontium titanate solid solution powder of the present invention has a relative density of 9 at 1200C after being molded and sintered.
0 or more capsules. This is made by molding and sintering known barium/strontium titanate solid solution powder with a relative density of 90%.
It is 100 C or more lower than the temperature at which the above can be achieved, and is extremely useful in practice as barium titanate powder for low-temperature sintering. In particular, in multilayer capacitors, barium/strontium titanate solid solution powder for low-temperature sintering is in high demand in order to improve overall electrical insulation and reduce electrode costs.The barium/strontium titanate solid solution powder provided by the present invention We fully satisfy this request,
It is extremely useful.

(Example) Next, the present invention will be explained in more detail with reference to Examples.

Example 1 0.5 mol of gel-like orthotitanic acid with a water content of 95% was put into a reactor together with 2 tons of water. Nitrogen gas was blown into the mixture to replace the inside of the reactor with nitrogen, and the reactor was allowed to stand for 20 hours while flowing nitrogen gas. Barium hydroxide (octahydrate) 285P and strontium hydroxide (octahydrate) 80f
't-Dissolve in 2 tons of 90C water, boil, filter to remove barium carbonate, and add orthotitanic acid and water, taking great care under nitrogen gas to avoid exposure to air. The mixture was placed in a reactor that had been left unattended. While flowing nitrogen gas into the reactor, the mixture was stirred and mixed and heated for 1 hour in an oil bath to carry out the reaction. After the reaction was completed, the supernatant was left to stand for about 5 minutes, the supernatant liquid was removed, and the mixture was further added to hot water 51, washed with stirring, and then filtered. This washing and filtration operation was repeated three times. After washing with a total of 9L of hot water, washing with 0.2N acetic acid O,SZ and filtering, further washing with pure water and filtration was repeated 5 times. After that, it was dried in air at 100C for 20 hours. The thus obtained powder was subjected to scanning electron microscopy, X-ray diffraction analysis, specific surface area measurement, and particle size distribution measurements.

The average particle size obtained by electron microscopy was 0.24μ, and the standard deviation was 1.41. The powder obtained from X-ray diffraction analysis is a homogeneous solid solution of cubic barium titanate and strontium titanate, and the amount of barium nine is approximately 60,000, and the amount of strontium is approximately 4
0 chi de atatsu 几. Furthermore, the crystallite diameter determined from the X-ray peak width was 0.1 μ, indicating extremely high crystallinity.

Further, the specific surface area was 6.9g/i, and the average particle diameter was 0645μ and the standard deviation was 1°87-eA″) obtained from particle size distribution measurement.

“Example 2 Water content - Jl, 95 flea gelatinous knife, toditanoic acid 1] 55
Mole, Mizuguchi. 51, and put it into the reactor.

This mixture (' + X in -, 7 - 1 yen crab - () was blown into the reactor and kR exchanged 1,2, - in the evening), A13, barium hydroxide (octahydrate) 150> slag and Hydroxide strike 11
Nchiu h. (octahydrate) 1307 min, 9517' water 2
/、Dissolved in PJ〒(11、Boiling gauze、barium carbonate gold removal＼Keru f(Me filtration 1..1P liquid was gently touched t'c
- Don't be busy: Shiw: I put it into the reactor. ♀Water flow; fM "l・goi tr+' mixture = 1.,,':
'ug-"], heat in oil bath for 10cq 5 hours] 5
:reaction? I did it. Reaction complete, real) $ $'iJ l
and lT1'1-like rtc:: t,, -'c powder is processed knee 2, and physical properties are measured.
Average grain size 71 obtained by o city Niyi imitation mirror viewing festival
．． .;:l: 0.18 μ, standard deviation if: 1 of 8. X-ray plane 4. +Powder id obtained from T, cubic,
hll titanate paris? It is a homogeneous solid body of strontium titanate and f- is determined from the peak position of X-rays.
Barium's rough d゛□'j勺 80 person, 2-stroke Li゛, / Chi'l no Mayutamasaku AOLl)
The crystallite diameter is 0.09μC, determined from the peak width of the Xi ray. Further, the specific surface area was 9.2 nT:/f, the average particle diameter obtained from particle size distribution measurement was 0.35 μ, and the standard deviation was 1.75, 7”c.

[Brief explanation of the drawing]

Drawing 0: f shows the crystal structure of the barium titanate/Stonbum solid solution powder synthesized in Example 1. Magnification: 5
0. Ofl This is a 3L type electron microscope with 0x magnification. 2
Supplementary Procedure No. f (Method April 25, 1985, Commissioner of the Japan Patent Office, Mr. Manabu Shiga, List of 6 cases, No. 1359, No. 262676, 2 Name of Invention: Barium Titanate IJN-Rum Solid Solution) 1゛η・
, Az, 1. 'Hil]'s production 9, Tsume method 5 supplementary work ``/relationship with the thief case...% if'f Applicant (0 [15) Asahi Kasei Kuri Co., Ltd. Miyakominato-ku Toramon-]-' [:t 2 Sakazuki□No. 29 Tora,
) Lock order bit 5 (・;・) 17 Correction inscription
“No.-1・” The description of the specification is amended as follows. (11 page 4 lines 17-18 “P, ni, Gallagh
er ----------8oc,, J is corrected by 9 as shown below. ``P.K. Gala/% -CP, Gallagh
Journal of the American Ceramic Society (J, Am, Ceram, 8o
c,,) J(2) Page 5, lines 1-2 “K, S6Ma
zdiyasni −−−−−・−−−−−goc,
Correct IJ as follows.

Claims (2)

[Claims] (1) Average particle size is 0.07~0.5μ, specific surface area is 3~
20 m^2/g, and the value does not exceed 2.5 times the value calculated from the average particle size assuming the particle shape is a straight sphere, and is calculated from the half-width of the peak of the powder X-ray diffraction image. A barium/strontium titanate solid solution powder having a crystallite diameter of 0.05 μm or more and 0.4 μm or less and having a spherical shape. (2) Average particle diameter is 0.07-0.5μ, specific surface area is 3
~20m^2g, and the value does not exceed 2.5 times the value calculated from the average particle size assuming that the particle shape is a straight sphere, and the crystal value is calculated from the half-width of the peak of the powder X-ray diffraction image. In producing a barium/strontium titanate solid solution powder having a particle diameter of 0.05μ or more and 0.4μ or less and a spherical shape, hydrous titanium oxide, barium hydroxide, and strontium hydroxide are mixed in terms of titanium. 120~10,00
A method for producing a barium/strontium titanate solid solution powder, which comprises reacting in the presence of 0 times the molar amount of water in a temperature range of 60°C or higher and lower than 110°C.