JPS6049137B2 - Method for producing stannate - Google Patents

Description

[Detailed description of the invention] The present invention relates to a method for producing divalent metal stannate.

In particular, it relates to a method for producing stannate salts through relatively low temperature reactions. Generally barium titanate BaTiO.

When using a material having a high dielectric constant such as a material for an electronic component such as a capacitor, a technique is known in which various additives are added in order to control the properties as desired. BaTiO is a typical high dielectric constant material. To explain the effect of this additive using as an example, in the case of BaTiOa alone, the Curie point Tc is about 120°C. The dielectric constant at the Curie point is 6000-1000
The dielectric constant at 0 and 25° C. is about 1500. When using this high dielectric constant material BaTiOa in a capacitor, it is necessary to add additives for the following two reasons. In other words, the first reason is the dielectric constant of BaTiO.
This is because the rate is maximum near the Curie point and is relatively small at temperatures around that point, so it is desirable that the Curie point be near the temperature at which electronic components are normally used.

An additive added to BaTiO3 for the purpose of moving the Curie point of BaTiO3, which is usually about 120°C, to around room temperature is called a shifter. The second reason is BaTiO near the Curie point.

The temperature dependence of the dielectric constant of the dielectric constant is large, that is, the dielectric constant changes greatly with a small change in temperature. Therefore, in order to obtain stable dielectric properties, it is necessary to reduce the temperature dependence of the dielectric constant of the dielectric constant. This is something that must be done. For this purpose, a technique using CaTiO3 and MgTiOa as additives is known. This additive is called a depressor. When using BaTiO3 in actual electronic components as described above, it is necessary to use additives such as shifters or depressers.

This also applies to high dielectric constant materials other than BaTiO3. Strontium titanate S is generally used as a shifter.
rTiO3, barium stannate BasnO3, calcium stannate CasnO3, barium zirconate BaZrO, etc. are used.

FIG. 1, FIG. 2, and FIG. 3 show the shifter characteristics of SrTlO3, BaSnO3, and BazrO3 as additives for BaTlO3 (from Kiyoshi Okazaki: Ceramic Dielectric Engineering). As is clear from this figure, when the amount of additive is 15m0'%, the Curie point of BaTiO3 is
In the case of TiO3, it is moved to about 40℃, and BazrO3
In the case of BasnO3, it moves up to about 60°C, but in the case of BasnO3, it moves up to about 20°C, and its dielectric constant is also 12.
000 or more, which is significantly larger than SrTiO3 and BazrO3. Thus, as shown in the example of BasnO3, stannate is extremely effective and important as a shifter.

The properties of the high dielectric constant material obtained can be varied in a variety of ways by changing the properties of the stannate material (purity, Ba/Sn atomic ratio, particle size and its distribution, etc.) or the method of addition. Conventionally, two methods have been used to add stannate salts, such as BasnO3, as shifters.

The first method is like BacO3? In this method, necessary amounts of salt and SnO2 are added to BaTiO3, and the mixture is subjected to calcination, pulverization, and firing to cause a reaction. In this method, BaO and Sn
The reaction with O2 and BaTiO3 does not necessarily proceed completely and uniformly, and variations in properties such as the Curie point or dielectric constant have been observed in each production.

In order to more reliably advance the reaction of BaO and snO2 and stabilize the properties, calcination is sometimes performed at high temperature for a long time, but this requires a large amount of energy in the process, and the calcination is The powder becomes hard, requiring a large amount of energy to grind, and problems such as impurities entering from the grinding device during grinding are likely to occur, resulting in poor properties. For example, if a capacitor is manufactured using BaTiO3 mixed with Fe from the stainless steel material commonly used in pulverizers, the material properties will change over time.
It is known that the dielectric constant decreases. On the other hand, Ba
The second method of adding snO3 is to synthesize only stannate in advance, pulverize it, and then add it to 7BaTi03 and sinter it.

This method is an effective method for ensuring the reaction between stannate and BaTiO3 and stabilizing the properties, but stannate generally requires a high firing temperature of 1300°C or higher, and the temperature must be raised considerably. The reaction does not proceed sufficiently. In addition, the stannate salt obtained in this manner is difficult to crush and has a coarse particle size, and furthermore, it is difficult to control the particle size distribution. Further, as in the first method, impurities are mixed in due to pulverization. In any case, with the conventional addition methods described above, it is difficult to control the properties of the material 7, there are problems in obtaining high-level properties with good reproducibility, and energy consumption is also large.

In recent years, electronic components have been required to be smaller and have more advanced characteristics, and the raw material powder used for them must therefore have a more uniform composition and higher purity fine particles than ever before. It's getting old. Additionally, in manufacturing processes, there is an increasing demand for materials to be manufactured using as little energy as possible. From this point of view, it has been strongly desired to realize a method for producing finely divided stannate having a uniform composition and high purity at a low temperature.

As a result of repeated research into this new method for producing stannate, the inventors have discovered a method for producing fine particles of stannate with uniform composition and high purity at extremely low temperatures.

The gist of the present invention is to directly obtain a hydrous stannate by using a divalent metal alkoxide and a tin alkoxide as starting materials, mixing the two at low temperatures, reacting them, and hydrolyzing them.

Here, monohydrate stannate refers to the compound MsnO3.NH2O and the compound MSn(0H)m. However, M is a divalent metal. Furthermore, 1-alkoxide refers to a derivative in which the hydrogen (H) of the hydroxyl group of an alcohol is replaced with a metal.

Hydrous stannate is MSnO3.NlI. Whether it is obtained as O or MSn(0H)m depends on the reaction conditions and the type of metal, but there is no big difference in its utilization no matter which form it is obtained, and it is necessary to heat it. Anhydrous stannate crystals can be easily obtained. This heating is preferably carried out at a temperature of 200° C. or higher and below the decomposition temperature, but heating can also be carried out at a lower temperature or by vacuum heating. As the heating atmosphere, air, neutral, oxidizing or reducing atmosphere can be used. It is preferable that the divalent metal alkoxide and the tin alkoxide are reacted in a solvent.

Suitable organic solvents include benzene, alcohol, hexane, and the like. When the reaction temperature is higher than the boiling point of the solvent, the reaction can be carried out under pressure in a pressure vessel. It is preferred that the reaction temperature of both alkoxides does not exceed 1000C for most alkoxides.

Although it is not necessary to carry out the reaction by cooling, the preferable reaction temperature is 0°C to 100'C. A particularly desirable reaction temperature is 40°C to 100°C. Hydrolysis can be carried out by adding water into a reaction vessel or by bringing water vapor into contact with the solution.

The reaction temperature for this is practically 0°C to 10°C due to the nature of water.
A temperature of 0° C. is desirable, but in the case of water vapor or gas, a temperature that exceeds this temperature and until the reaction product decomposes can be selected. Types of divalent metals include Ba, Ca, Sr, Mg,
Preferably, it is one or more metals selected from Pb.

The divalent metal alkoxide may be a mixture of alkoxides of two or more metals.

The produced stannate can be used as a crystal. Depending on the drying temperature and other conditions, it becomes an anhydrous stannate or a mixture of an anhydrous stannate and a hydrous stannate. As mentioned above, when used as an additive for a high-permittivity dielectric material, the final form is preferably an anhydrous stannate, but when added, it is not necessarily in an anhydrous state but in a hydrated stannate state. Alternatively, it can be used by heating together with the main material after addition to form an anhydrous stannate. The present invention will be explained in more detail below.

The present invention is to produce divalent metal stannate using metal alkoxide as a starting material. To carry out the present invention, a divalent metal and a tin alkoxide must first be produced. Since divalent metals such as Ba, Ca, Sr, and Mg have high reactivity with alcohol, they can be directly reacted with alcohol to produce alkoxides as shown in the following general formula (1). M+2R0H-+M(0R)
2+↓ (1) (M is a divalent metal.) Heat may be applied to advance the reaction.

Mg reacts slowly with alcohol, so 12, HgCe3
Catalysts such as these may be added, but care must be taken as impurity ions may be mixed in and mercury may be liberated. The reaction between metal and alcohol proceeds from the surface of the metal to the inside, but the reaction may be slowed down because the metal alkoxide formed covers the metal surface.

To prevent this, benzene or other solvents can be added. Since Pb, which is a divalent metal, is difficult to react directly with metal and alcohol, an exchange reaction between lead acetate (Pb(CH3COO)2) and sodium alkoxide NaOR is used as shown in the following formula (2). It is better to synthesize lead alkoxide.

Pb(Cll3COO)2+2Na0R→ P
b(0R)2+2CH3C00Na (2) Furthermore, tin alkoxide also cannot cause the metal and alcohol to react directly, so it is preferable to use tin halide, particularly tin tetrachloride Snce4, as the starting material.

There are several methods for synthesizing tin alkoxide from Snc'4, but a method using anhydrous ammonia is preferred, as shown in the general formula (3). Snce4+4
R0H+4NH3→ Sn(0R)4+4NH4ce...
(3) When producing alkoxide, use alcohol as
Preferred examples include methanol, ethanol, propanol, butanol, and the like.

The type of alcohol used has a great deal to do with the reactivity in producing the alkoxide, but when the produced alkoxide is used as a starting material for the present invention, the type of alkyl group in the alkoxide is not essentially important. Metals, alcohols, and metal hydroxides, which are the starting materials for alkoxides, all have the characteristic that they can be purified using relatively easy physical or chemical methods, and they do not contain any unnecessary ions. Alkoxides synthesized using these as starting materials can be produced at 99.9% without any particular purification.
Purities of 9% or higher can be easily achieved. In order to further increase the purity of the alkoxide, recrystallization is performed for solid alkoxides, and distillation is performed for liquid alkoxides. In order to increase the yield, care must be taken to ensure that each raw material is sufficiently dehydrated. Divalent metal alkoxide M(0R)2 obtained as above, (M is a divalent metal).

) and Sn(0R)4 or their organic solvent solutions are mixed to a desired composition and then hydrolyzed by gradually adding decarbonated distilled water to form a white powder precipitate. This is separated by filtration to obtain hydrous stannate. When this is heated, stannate crystals are obtained. In this synthesis step, the temperature of the reaction system during hydrolysis greatly influences the state of the produced stannate.

That is, when the temperature of the reaction system is room temperature, the stannate salt produced is amorphous and no clear peak appears even when examined by X-ray diffraction. When the temperature is 40° C. or more and 100° C. or less, it is confirmed by X-ray diffraction that the obtained stannate is a crystal of a hydrous oxide composed of MsnO3.RlH2O. In this case, when M is Ba, Ca, Mg, or Sr, n=3, and when M is Pb, n=2 is often included. However, when the temperature of the system exceeds 100'C, the substance produced by hydrolysis is Sn(0H)4, which is a hydroxide.
and M(0H)2 increase. The reason why the hydrolysis products differ depending on the temperature of the reaction system is considered as follows.

That is, it has been conventionally known that when a monovalent metal alkoxide and a tin alkoxide are mixed, a composite alkoxide called MSn(0R)5 is produced. Considering this, it seems that even when the divalent metal alkoxide of the present invention and tin alkoxide are mixed, a composite alkoxide represented by MSn(0R)6 is produced. When the temperature of the system is 100° C. or lower, the generated composite alkoxide MSn(0R)6 is hydrolyzed while maintaining its structure to generate hydrous stannate.

When the temperature of the system is between 40°C and 100'C, crystalline hydrous stannate is produced which can be confirmed by X-ray diffraction. When the system is hydrolyzed at a temperature below 40'C, the product cannot be confirmed to be crystalline by X-ray diffraction, but thermal analysis shows that hydrous stannate is produced. You can check it. However, when the temperature of the system exceeds 100℃, Sn
Considering that (0H)4 and MCO3 or M(0H)2 are generated, MSn(0R)6→M(0R)2+Sn
(0R)4 It is considered that the composite alkoxide MSn(0R)6 is decomposed as shown in (5).

Hydrous stannate becomes stannate when heated, but MSn (0H)
6, when M is Ba, Ca, Mg, Sr, 20
When heated to about 0°C, it changes from hydrous stannate to amorphous.

Furthermore, M becomes a stannate at about 600°C in Ba, Mg, and Sr, and at about 800°C in Ca. When M is Pb, PbSnO3.2H20 is dehydrated at 200°C to become a stannate. The obtained oxide particles are fine particles with a particle diameter of 0.01 to 0.1 μm according to electron microscopic observation.

Because the heat treatment temperature to form 7 oxides is extremely low,
It is easy to loosen the clumps. In addition, the oxide particles obtained by chemical analysis have an atomic ratio of M/Sn of 99.9% or more.
=0.98 to 1.02. As described above, according to the method of the present invention in which a divalent metal alkoxide and a tin alkoxide are reacted and hydrolyzed to obtain a hydrous stannate, the atomic ratio of the divalent metal and tin is extremely close to 1, and the purity is high. of finely divided stannate can be easily obtained. In particular, it is of great industrial value because it can be obtained through a low-temperature reaction process. EXAMPLES Next, the present invention will be explained in more detail with reference to examples, but the gist of the present invention is not limited to the following examples.

[Example 1] High-purity Ba, Mg, Ca, and Sr metals were taken as shown in the middle columns of Table 1, and put into 200 ml of benzene together with 45 g of dehydrated isopropanol, and reacted at 80°C under reflux.

The metal is dissolved in about 2 to 24 hours, respectively, with the evolution of H2.

This reacts with isopropanol to obtain a benzene solution of metal isopropoxide. Furthermore, for each metal alkoxide, tin alkoxide is synthesized as follows. 437.9 g of anhydrous Snce, a special grade reagent, is dissolved in 200 mL of benzene with 70 g of isopropanol, and dry NH3 gas is passed through this solution. A white precipitate of NH4Ce was formed immediately after the gas was introduced, and NH3 began to be discharged from the reaction vessel in about 1 hour, indicating that the alkoxidation reaction was completed. generated N
H4Cf? Separation by filtration yields a benzene solution of tin alkoxide. A metal alkoxide and a Sn alkoxide were mixed so that the atomic ratio was 1, and 8
Reflux the reaction at 0°C for at least 1 hour. Then 80
When 15 ml of decarboxylated distilled water was added little by little while refluxing at °C, a white precipitate was formed. This precipitate was separated by filtration and dried at 120° C. for 1 hour to obtain the powder shown in the lower column of Table 1. The properties of the white powder thus obtained were examined by X-ray diffraction, differential thermal analysis, and thermogravimetric analysis.

In addition, this powder was heated to temperatures of 200, 400, and 600, respectively.
The temperature was changed to 800° C. and the structure of the product was confirmed by X-ray diffraction. Figure 4 shows the results of the differential thermal analysis. Table 2 shows the products. Table 3 shows the products versus heating temperature. The results of X-ray diffraction show that the crystals are hydrated stannate crystals represented by MSn(0H)6, regardless of whether Ba, Ca, Sr, or Mg is used, and no peaks other than hydrated stannate are observed. do not have.

From the results in Figure 4, Ba, Sr, Mg, and Ca are 200 to 4.
Dehydrated at 00'C, approximately 600°C (8
00°C), it can be seen that crystallization occurs. That is, it can be seen that this method produces stannate at low temperatures. Table 3 confirms the above results, and shows that when heated, it becomes amorphous due to the elimination of crystal water, but the
It can be seen that C becomes crystalline when heated (800° C. in the case of Ca). In addition, when the particle size of the obtained stannate powder was measured using an electron microscope, it was found that the particle size was 0.01 to 0.1.
They were microparticles of μm in size.

Furthermore, as a result of chemical analysis, the purity was 99.9% or higher and the atomic ratio was M/Sn = 0.98 when using any metal.
It was ~1.02. [Example 2] 5g of high purity Mg metal
200mt of Bewazen with 35g of dehydrated methanol
The mixture was placed in a container and reacted under reflux at a temperature of 60°C.

A benzene solution of Mg methoxide is obtained in the same manner as in Example 1. Tin methoxide was obtained in the same manner as in Example 1. The atomic ratio of Mg methoxide and Sn methoxide is
The mixture was mixed so that Mg/Sn=1, and the mixture was refluxed at 60° C. for 1 hour or more.

Then, 20 ml of distilled water was decarbonated while refluxing at 60°C.
When added dropwise little by little, a white precipitate forms. This precipitate was separated by filtration and then dried at 120° C. for one hour to obtain 45 g of white powder. When this white powder was measured in the same manner as in Example 1, all the results were exactly the same as those described in Example 1.

[Example 3] 220 g of Pb(CH3COO) and Na isopropoxide NaOC3H71O. 5 g was reacted in 200 ml of benzene to obtain a benzene solution of Pb isopropoxide.

Sn isopronopoxide prepared in the same manner as in Example 1 was mixed so that the atomic ratio was Pb/Sn = 1, and then divided into two parts. One part was mixed at 80'C and the other part was mixed at 25°C. 5 mL of decarbonated distilled water was added dropwise little by little to obtain a white precipitate.

This 5 was separated by filtration and then dried at 100°C for 10 hours. When each of the white precipitates thus obtained was examined by X-ray diffraction, as shown in Figure 5, the precipitates hydrolyzed at 80°C were crystalline, whereas those hydrolyzed at 25°C were amorphous. It was hot. These are the results of thermal analysis of both O and P.
bSnO3.2F [20]. 200℃, 600℃
X-ray diffraction and thermogravimetric analysis were performed on the heat-treated products.
PbsnO3 crystals form at an extremely low temperature of
It became a crystal of nO3.

[Brief explanation of the drawing]

FIG. 1 is a diagram showing changes in Curie point and dielectric constant when SrTiO3 is added to BaTlO3. FIG. 2 is a diagram showing changes in Curie point and dielectric constant when BasnO3 is added to BaTiO3. Figure 3 is B
A diagram showing changes in the Curie point and dielectric constant when BazrO3 is added to aTiO3.

Claims (1)

[Scope of Claims] 1. A method for producing a stannate, comprising the steps of mixing and reacting a divalent metal alkoxide and a tin alkoxide, and hydrolyzing the reaction product to obtain a hydrous stannate. 2. The manufacturing method according to claim 1, wherein a divalent metal alkoxide and a tin alkoxide are reacted in a state dissolved in an organic solvent. 3. The manufacturing method according to claim 1 or 2, wherein the reaction temperature between the divalent metal alkoxide and the tin alkoxide is 0°C to 100°C. 4 The reaction temperature for hydrolysis to obtain hydrated stannate is 0°C
The method for producing a stannate according to any one of claims 1 to 3, wherein the temperature is 100°C. 5. The method for producing a stannate according to any one of claims 1 to 4, wherein the divalent metal is one or more metals selected from Ba, Ca, Sr, Mg, and Pb. 6. The method for producing a stannate according to any one of claims 1 to 5, which includes a step of heating a hydrous stannate. 7. The method for producing a stannate according to claim 6, wherein the treatment temperature in the heating step is 200° C. or higher and lower than the decomposition temperature.