JPS60161338A - Manufacture of mixed fine particle consisting of batio3 and basn(oh)6 and fine particle of ba(snxti1-x)o3 solid solution - Google Patents

Abstract

PURPOSE:To obtain the titled mixed fine particles having high activity, high sintering properties at low temps., and high purity by mixing an Sn compd. and a Ti compd., adding a Ba salt to the mixture, and allowing the mixture to react in a strongly alkaline aq. soln. CONSTITUTION:An Sn compd. or its hydrolysate and a Ti compd. or its hydrolysate are mixed in a specified ratio. SnCl4, Sn(NO3)4, etc. are used as the Sn compd., and the hydrolysate is obtained by hydrolyzing the aq. soln. of said Sn compd. with an alkaline soln. such as NH4OH. Meanwhile, TiCl4, Ti(SO4)2, etc. are used as the Ti compd., and its hydrolysate is obtained by hydrolyzing the aq. soln. of said Ti compd. with an alkaline soln. such as NH4OH. A Ba salt [Ba(NO3)2, etc.] is added to the mixture in 0.7-2.0mol ratio of Ba/(Sn+Ti), and the mixture is allowed to react at >=about 13pH and about 80 deg.C for >=5min. The formed precipitate is then washed, and dried to obtain the fine particles wherein BaTiO3 fine particles and BaSn(OH)6 fine particles are mixed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention utilizes BaTiO3 and BaTiO3, which are one of the dielectric glazes.
Mixed fine particles consisting of Sn (OH) 6 and Ba (Sn
The present invention relates to a method for producing x Ti 1-y)ot solid solution fine particles.

In recent years, ωF has been investigated from various angles on manufacturing methods for making ceramic materials into fine particles, and one of the applications of the finely divided ceramic particles is in capacitors. BACKGROUND ART As electronic products become smaller and more dense, capacitors, like other electronic components, are required to be smaller and lighter, as well as to have larger capacity and improved high frequency resistance. For this reason, in ceramic capacitors, it is necessary to make the dielectric material finer in order to reduce the thickness of the ceramic layer and provide uniform pressure. Moreover, this fine particle formation also makes it possible to keep the sintering temperature low.

In addition, particles with small and uniform particle diameters are expected to be used as raw materials for electronic materials, piezoelectric materials, transparent ceramic materials, etc., for example, in order to improve sinterability and temperature characteristics.

A solid solution of barium titanate and barium stannate Ba (Snx Ti 1-X)
03 (hereinafter abbreviated as BSTx, the number X is the mol% of Sn
shows. Note that 0<x<1), and conventionally, to obtain this solid solution, BaCO3, 5n02, Ti0z or BaT
A solid phase reaction using i03 and BaSnO3 as raw materials is being carried out. When the BST solid solution obtained by this in-phase reaction is made into fine particles, AI 20
The contamination of impurities such as 3 is unavoidable. Also,
Problems such as uneven molding and an increase in pores after sintering occur due to the non-uniform particle size of the pulverized solid solution fine particles. Furthermore, the solid solution uniformity of the solid solution fine particles obtained in this manner cannot be said to be high, and local compositional fluctuations, that is, portions with a high content of Sn or Ti appear. This is because the particle size of the fine particles after calcination is uneven and relatively large.
This is because the diffusion states of Sn and Ti particles are different. As a result, problems have arisen in terms of dielectric properties, such as a worsening of the expected diffusion phase transition profile, and there is much room for improvement. In addition, at present, single-phase BST is produced by solid-phase reaction.
It is the inner axis that obtains solid solution fine particles, and depending on the composition, 1
It requires a temperature of 500°C or higher. This poses a major problem in obtaining a single phase and in utilizing the dielectric properties of this solid solution fine particle.

Recently, attempts have been made in various fields to improve these problems, one of which is the metal alkoxide method.

Metal alkoxide refers to a compound in which the hydrogen atom of an alcohol is replaced with a metal.As a method for synthesizing Ba(Zrx Ti 1-X)03 by this metal alkoxide method, for example, Japanese Patent Publication No. 58-2220 discloses There are some, but this method uses Ba (Snx Ti 1-x)
There have been no reports yet on the synthesis of Oa. However, metal alkoxides, which are organometallic compounds used in this synthesis method, have many problems in practical application, including the fact that they are much more expensive than raw materials used in ordinary solid-phase reaction methods.

On the other hand, the present applicant has developed a method for synthesizing BaT 103 (%
7-147226) and the synthesis method of Ba5n(OH)6 (
Japanese Patent Application No. 58-49765) has been proposed, but it is conceivable that based on this synthesis method, both may be synthesized separately and then mixed to obtain solid solution fine particles. However, when using this method, it is not simple to mix them in the desired proportions.

That is, since both compounds are accompanied by something that causes loss of M amount, such as adsorbed water, during synthesis, it is not possible to immediately mix them only using the weighing section. Therefore, it is necessary to perform a heat-generating treatment to eliminate the amount loss, and then mix the components to the desired ratio.

The present invention provides a method for producing mixed fine particles of BaTiO3 and BaSn(OH)6 and Ba(SnxT-x)03 solid solution fine particles, which can solve the problems mentioned above. It is.

The present invention relates to a Sn compound or its hydrolysis product and T.
After mixing the i compound or its hydrolysis product in a predetermined ratio, add a Ba field, react in a strong alkaline aqueous solution at a temperature near the boiling point, etc. to sufficiently remove alkali ions, filter, and dry. BaTiO3 fine particles and B
This is a manufacturing method for obtaining fine particles in which a5n(OH,)e fine particles are mixed.

Next, BaTiO3 obtained by the above operation and Barn
Ba(SnxTi1-X)03 solid solution fine particles can be obtained by heat-treating mixed fine particles consisting of (OH)e.

Here, as Sn compounds, 5nC14, 5n(NO
3) 4, Sn(SO4)2, 5n(SOwa2 ・2H
20 etc., and hydrolysis products of Sn compounds include:
The aqueous solution was mixed with NH40H1LiOI-1, Naα-(,
Those hydrolyzed with an alkaline solution such as KOH can be used. However, if sulfate groups -804 are present, it is necessary to remove the sulfate groups by sufficiently repeating decantation and filtration after hydrolysis. Also, soluble stannate Na25n03 ・3H
20, K2Sn03, 3H20, etc. may be used.

As the Ti compound, TiCl4, Ti(SO4)z, etc. can be used, and as the hydrolysis product of the Ti compound, a product obtained by hydrolyzing the water bath solution with the above-mentioned alkaline solution can be used. However, when using Ti(SO4)2, it is necessary to remove the sulfate group 804, so 1
It is then hydrolyzed with an alkali to produce Ti02.nH2O, which is then used after repeated decanting/filtration.

Ba salts include Ba(NO3)z, Ba(OI-i
)2, BaCl2, Ba(CH3COO)2, etc. can be used. 8: These hydrolysis products may also be used.

The reaction conditions for synthesizing mixed fine particles consisting of BaTiO3 and Ba5n(OH)6 are as follows: pl-(of a strongly alkaline aqueous solution is 13.0 or higher, preferably 132 or higher, and the reaction temperature is 80°C or higher, preferably 90°C). C or more, reaction time is 5 minutes or more, preferably 30 minutes or more, and Ba/ (
The molar ratio of Sn+Ti is in the range of 0.7 to 2.0, preferably around 1.0.

The heat treatment conditions applied to the mixed fine particles consisting of BaTiO3 and Ba5n(OH)6 are as follows:
It depends on the sweetness of the Sn/Ti molar ratio, but if the Sn/Ti molar ratio is close to 1, the temperature may be about 1260°C to 1350°C, and if the Sn/Ti molar ratio is close to 10, the temperature may be 1400°C.
It is necessary to raise the temperature to about 1460°C. however,
These heat treatment conditions are applied when the purpose is to obtain single-phase l3ST solid solution fine particles, and when used for other purposes, the heat treatment conditions may be the temperature during synthesis of mixed fine particles, depending on the purpose of use. The heat treatment temperature can be set by

As mentioned above, according to the present invention, BaTiO3 and BaS
After wet-synthesizing mixed fine particles consisting of n (OH) 6, BST solid solution fine particles can be obtained at a heat treatment temperature that is about 150'C lower than in conventional solid phase reaction methods. This BS
Since T solid solution fine particles have high uniformity in particle size, they have high activity and high sinterability at low temperatures. Furthermore, since the particles are of high purity with very little compositional variation, they have excellent dielectric properties of 11%. Furthermore, since the diffusivity of Sn and Ti in the mixed value particles is high, it is possible to immediately start the main firing with one heat treatment without requiring calcination. This is Ba
Sn (Q)l) 6 becomes amorphous during the heat treatment, and then BaSnO3 is formed.
It is presumed that this is because the fine particles diffuse unilaterally into the BaT i03 fine particles. According to the present invention, since mixed fine particles are obtained in crystalline form during synthesis, filtration is easy and productivity is high. In addition, since the starting materials are inexpensive, it is economically advantageous compared to other wet synthesis methods such as the metal alkoxide method.

The present invention will be explained below based on examples.

Examples Example 1 Approximately 200 g of TiCl4 was added to ice water with stirring to make a water bath solution, and then transferred to a volumetric flask to make a total volume of 1000 cc. Next, a portion is taken from this solution and an excess of aqueous ammonia is added to precipitate TiO2.

After subjecting this precipitate to a heat treatment of approximately 1000°C, a volume measurement is performed to determine the exact concentration of the T1Cl4 standard solution in the volumetric flask (in this case, 0.9595moQ, 7
g). On the other hand, as a Sn compound in which the B site of the ABO3 peropus powerite type compound has been changed to 5nout, B
ST 50 (i.e. Ba(SnO,5Tio,s
)03), 30.67 nJ of the above 'I'1C14 standard solution and 7.848 g of Na 2Sn03 ・3H20 were accurately sampled with beer force, and then Ba(
Add and dissolve 15.38 g of NO3)z.

Next, add a pre-adjusted 5N-KOH solution to adjust the pH.
13.6 to obtain a cloudy white liquid with a total solution amount of 400 mg.

This solution is stirred while boiling and aged for 7 hours. After formation, impurities such as alkali ions are removed by repeating kneading and canation of the white precipitate 10 times using hot water. Next, this precipitate is separated by filtration and dried at 90° C. for a day and night to obtain a fine powder.

As a result of analyzing the fine particle powder obtained by the above operation by X-ray diffraction (copper target, nickel filter), the X-ray diffraction pattern was found to be ASTM card 5-0626 (B,
4Ti(J3) and 9-s3(BaSn(OH)6
) was obtained. Therefore,
This fine particle powder contains BaT i03 fine particles and Ba5n (
It was confirmed that it was a mixture of OH)6 fine particles. This mixed fine particle has a stoichiometric BaTiO3:Ba5n (
OH)6=1:1. Scanning electron micrographs of this mixed fine particle are shown in FIGS. 1 and 2 (magnification true). Needle crystals of 20-30ttm are Ba5n(OH)s
The fine spherical crystals of 0.1 to 0.2 μm are Ba
It is TiO3.

Next, the mixed fine particle powder is heat treated at 1260° C. for 3 hours. The fine particle powder thus obtained was analyzed by X-ray diffraction in the same manner as above, and the results are shown in FIG. This X-ray diffraction pattern is similar to that of BS obtained by conventional solid-phase reaction method.
This corresponds to the X-ray diffraction pattern (Fig. 4) of T50 (BaSn (which also contains 01()6 fine particles)), and it was confirmed that these fine particles were BST50. BST 50 was prepared as follows: BaCO3, TiO2, and 5n02 were taken at a molar ratio of Ba:Ti:Sn = 1:0.5:0.5, and the total amount was 0.1. m O・e, then put into a polyethylene bottle and add about 30cc of water.Next, after mixing and crushing in a ball mill for 15 hours, 1415°
BST50 is obtained by heat treatment at C. Therefore,
According to the in-phase reaction method, 150° C.
A higher temperature is required.

Example 2 TiCl4 standard solution (0
, 9595mog/Q). Next, about 260g
After adding 5nCI4 into ice water with stirring to make an aqueous solution, transfer it to a volumetric flask and bring the volume up to 1000c.
Let it be c. Then, as in the case of TiO14, a portion of this solution was collected and an excess of ammonia water was added to give 5n.
After precipitating 02, heat treatment was performed at 1000°C for about 3 hours,
Determine the exact concentration of the 5nC14 standard solution by performing a gravimetric measurement (in this case it was 0.9015moQ/Q). Then 5n so that BST 50 is obtained
C1,i standard solution 32.64 mQ and T i Cl 4
Ba (NO3) in a solution containing 30.67 mQ of standard solution
After dissolving 15.38 g of 2, pH was adjusted with NaOH solution.
Adjust to 13.7. This solution is stirred while boiling and aged for about 6 hours.

After formation, impurities such as alkali ions are removed by repeating kneading and canation of the white precipitate 10 times using hot water. Next, this precipitate was separated by filtration, and 9
A fine particle powder is obtained by drying at 0° C. for a day and night.

The results of X-ray diffraction analysis of the fine particle powder obtained by the above operation were the same as those shown in FIG. 3, and it was confirmed that this fine particle powder was a mixture of BaTiO3 fine particles and Ba5n(OH)e fine particles. Further, according to a scanning electron micrograph of this fine particle powder, fine particles having a shape similar to that shown in FIGS. 1 and 2 could be observed.

Next, this fine particle powder was subjected to heat treatment for 3 hours at different temperatures, and the change in lattice constant was investigated. The results are shown in FIG. From this graph, the two-phase mixed state continues up to 1260°C, but after 1260°C, the single-phase BST
It turned out to be 50. From this state of phase change,
While the lattice constant of the first phase BaSnO3 changes completely up to nearly 1260°C, the @2 phase BaTiO3
The lattice constant gradually changes from around 1000'C due to the diffusion of 4Sn, and Ba(Sn) changes gradually in the range 0≦x<0.5.
There is a clear tendency for X of nx Ti 1□)03 to increase. This means that during the diffusion phenomenon caused by heat treatment, Ba5
R1 clearly shows that nQ3 diffuses unilaterally.

Example 3 BaTiO3 and BaSn synthesized in the same manner as Example 1
A mixed fine particle powder consisting of (Oi() 6 is prepared.

Next, this powder is heat-treated at 1400°C to obtain BST solid solution fine particles. On the other hand, BST solid solution fine particles obtained by a conventional dry solid phase reaction method (heat treatment temperature: 1430° C.) are also prepared. And against both of them, N17
4, 1°DS=0.15mm R8”l°SS noslit condition, scanning speed of 1/40/min, time constant 1
Surface index (100) (200) (300) (
X-ray measurements were performed on the diffraction pattern of 400). On the other hand, using the Si powder as a standard sample, the integral width β using only the BST solid solution sample is calculated using the method of Jones, and βCOSθ/λ-5in gives the average strain l.
A graph plotting θ/λ is shown in FIG. The straight line A represents the solid solution fine particles according to the present invention, straight &! B indicates solid solution fine particles obtained by solid phase reaction method. In this graph, the slope of the straight line is 2η (η - Δd/d), so the BST solid solution fine particles obtained by this method, which has a very small slope, have less fluctuation in the lattice constant and therefore less compositional fluctuation. You can see that it is very small. On the other hand, BST solid solution fine particles produced by the solid phase reaction method have a composition variation of 0.
400<x(0,600), and it can be seen that the compositional variation is extremely large.

Example 4 TiC+4 and 5n produced in the same manner as Examples 1 and 2
Using a standard solution of CI 4, BST 10, 20.
30.40.50.60.70180.90 is obtained by adding appropriate Ba salt and mixing, and then reacting in a strong alkaline aqueous solution to obtain nine types of fine particle powders. X kneading 4 obtained for these fine particle powders
Although the peak intensity of the pattern differs depending on the composition, it was confirmed that all the patterns were mixed fine particles consisting of 13aTi03 and Barn (OH,)6. The mixed fine particles of the above nine glazes were heat-treated at 1460°C for 3 hours.However, depending on the composition, solid solution fine particles can be obtained at a much lower temperature than this temperature, but if the Sn content is A high heat treatment temperature is required for those with a large amount of BaTiO3 and those with a composition very close to BaTiO3$111.The lattice constant of each BST solid solution fine particle prepared in this way is N
Fig. 7 shows the results calculated using the high angle side (90° or more) of the number of bolts.

The lattice constant of the BST solid solution fine particles wet-synthesized according to the present invention closely follows the Vegard side. In addition, when trying to obtain such a result using the traditional in-phase reaction method,
It is clear that a very high processing temperature of 1500° C. or higher is required.

Example 5 FIG. 8 shows a scanning electron micrograph of BST 50 solid solution fine particles obtained by heat-treating the mixed fine particles according to the present invention prepared in the same manner as in Example 1 at 1260° C., which is the lowest temperature at which a single phase is formed. and FIG. 9 (enlarged photograph) K are shown. In addition, scanning electron micrographs of BST 50 solid solution fine particles obtained by heat treatment at 1410°C, which is the lowest temperature at which a single phase is obtained by the in-phase reaction method shown in Example 1, are shown in Figures 10 and 1.
Shown in Figure 1 (enlarged photo). As is clear from FIGS. 8 to 11, the BST solid solution fine particles prepared according to the present invention are
On the other hand, BST solid solution fine particles created by the solid phase reaction method enter the sintering stage from secondary agglomeration, and have a particle size of 0.5 to 5.0 μ. It can be seen that it is non-uniform. These comparisons demonstrate the superiority of the simple synthesis method according to the present invention over conventional solid phase reaction methods.

[Brief explanation of the drawing]

Figures 1 and 2 are BaT i03 and Ba5n(OH)
FIGS. 3 and 4 are scanning electron micrographs of mixed fine particles consisting of B5150 synthesized by the present invention and the solid-phase reaction method, respectively, and FIG. 5 is a scanning electron micrograph of mixed fine particles composed of A characteristic diagram showing the relationship between heat treatment temperature and lattice constant, Figure 6 shows the relationship between heat treatment temperature and lattice constant.
7 is a characteristic diagram showing the relationship between the composition and lattice constant of BST solid solution fine particles, and FIGS. 8 and 9 are scanning electron micrographs of BST 50 according to the present invention. FIGS. 10 and 11 are scanning electron micrographs of BST 50 synthesized by the striped solid phase reaction method. Figure 3 Figure 5 @ Figure 6 S various θ/λ [Sue 1] Figure 7 Btx (S*xTt1-x)03t>χ[-] 10th
Figure 2 (Xi, 500)

Claims (1)

[Claims] 1. After mixing the Sn compound or its hydrolysis product and the Ti compound or its hydrolysis product, Ba
BaTiO3 and B a S n (OH) 6 characterized by adding salt and reacting in a strong alkaline aqueous solution
A method for producing mixed fine particles consisting of: 2. From BaTiO3 and BaSn (OH) 6 obtained by mixing a Sn compound or its hydrolysis product and a Ti compound or its hydrolysis product, adding Ba salt, and reacting in a strong alkaline aqueous solution. Ba characterized by performing MII heat treatment on mixed fine particles consisting of
(Snx Ti1-X)03 (0<x<1) Method for producing solid solution fine particles.