JPH059023A - Production of powder of perovskite type compound oxide - Google Patents

Abstract

PURPOSE:To directly produce powder of a perovskite type compd. oxide from a mixture of alkoxides, compd. alkoxide or a hydrolyzate of the mixture or compd. alkoxide as a precursor of the perovskite type compd. oxide without passing through a troublesome process such as sintering or pulverization. CONSTITUTION:Barium titanate powder is formed with hot plasma from a sol of a precursor of barium titanate as a perovskite type compd. oxide.

Description

Detailed Description of the Invention

[0001]

FIELD OF THE INVENTION The present invention relates to a method for producing a perovskite type complex oxide powder. More specifically, for functional materials, for example, the sinterability, crystallinity, dispersibility, uniformity, and fluidity required for forming ferroelectric thin films such as capacitors, piezoelectric thin films, or protective films for solid resistors. The present invention relates to a method for producing a perovskite type complex oxide powder having excellent properties such as properties.

[0002]

2. Description of the Related Art Conventionally, a perovskite type complex oxide powder is produced from a material such as a precursor obtained by a solid phase method or a coprecipitation method through binder mixing, sintering and pulverization steps. The method is known. However, any of the manufacturing methods requires a large amount of energy when sintering the material and the raw material such as the precursor for manufacturing the perovskite-type composite oxide powder, and there is a possibility that impurities are mixed during the pulverization of the sintered product, There are various problems such as the possibility of structural crystal strain due to physical force. Therefore, we also tried a method that does not involve a crushing step, that is, a method of adding an inhibitor to suppress grain growth due to sintering, or a method of holding the sintering to the degree of calcination, which is the state before the grain growth significantly progresses. Has been. The former method of adding a grain growth inhibitor has an adverse effect on the product characteristics, for example, when a dielectric thin film is formed, depending on the type of the inhibitor to be added, adversely affects the dielectric characteristics, and unexpected impurities are mixed. Therefore, the kind and addition method of the grain growth inhibitor are limited, and the design of the product to be produced is also limited. Even if the latter is limited to calcination, the sintering of the raw material is incomplete, so it must be re-sintered at a high temperature before use. When molding as a product, shrinkage of the raw material during the sintering process Due to such factors, cracks are likely to occur and special caution is required.

On the other hand, a hydrothermal synthesis method and a sol-gel method for obtaining a perovskite type composite oxide powder without a sintering or crushing process have been devised. However, the production of perovskite-type composite oxide powder by the hydrothermal synthesis method, which includes the step that requires reaction conditions of approximately several tens of atmospheric pressure and 200 ° C. or higher, involves a considerable amount of research at the laboratory level. However, in the case of industrialization, the manufacturing equipment becomes complicated, which is not practical. Further, in the latter method of producing a perovskite-type composite oxide powder by the sol-gel method using an alkoxide, since a highly pure alkoxide can be obtained by distillation or the like, a high-purity perovskite-type composite oxide powder can be produced. Therefore, in recent years, attention has been paid to the microfabrication technology in the field of electronic materials and research has been conducted, but the size of the particles produced is extremely small, and secondary agglomeration is likely to occur, which makes handling complicated. Therefore, in order to further increase the particle diameter, a heat treatment of at least 1000 ° C. or higher is required, but it is possible to carry out the calcination at a relatively low temperature as compared with the case of producing by the usual solid phase method or coprecipitation method. However, since the particle size produced is smaller than that produced by the solid phase method or coprecipitation method, there is a drawback that the firing time is long, and in some cases a crushing step is also necessary. Therefore, energy saving cannot be expected.

In any of these manufacturing methods, the perovskite type complex oxide powder obtained in multiple steps has a drawback that it is inferior in dispersibility, fluidity and the like.

[0005]

DISCLOSURE OF THE INVENTION In view of the above, the present inventors have a drawback in the conventional production of perovskite type complex oxide powder, that is, a large amount of energy is required for sintering and pulverization, and it is a multistep process. , And the resulting powder was thoroughly studied in order to overcome the drawbacks of poor dispersibility and fluidity, using a thermal plasma method, which is a known method, and using a metallic element that is a precursor material. It has been found that a perovskite type complex oxide powder can be directly produced from a mixture of alkoxides or a complex alkoxide, and further, a hydrolysis product thereof without going through a complicated process of calcination for a long time and, in some cases, pulverization. Further, it was found that spherical perovskite type complex oxide powder can be produced under specific thermal plasma conditions. In addition, it was also known that ultra-fine particles of perovskite-type complex oxide can be obtained by further appropriately selecting the thermal plasma conditions.

The present inventors have completed the present invention as a result of further studies based on such findings.

[0007]

Means for Solving the Problems That is, according to the present invention, in the following general formula (1), the metal element A is a group IB, a group IIA, a group IIB, a group IIIA, or IVB of the periodic table of elements. Tribe, first
Alkoxide of at least one metal element selected from VB group and VIII group, and at least one metal element of B metal element selected from IVA group, IVB group and VB group of the periodic table of elements A perovskite-type composite oxide powder represented by the following general formula (1) is produced by subjecting a mixture of elemental alkoxides, a complex alkoxide of element A and element B, and a hydrolysis product thereof to thermal plasma. It provides a way to do it. However, the metal elements in the present invention include Group IB and Group IIA of the Periodic Table of Elements.
Group, Group IIB, Group IIIA, Group IVA, Group IVB, Group VB
Group VIII. General formula (1) ABO ₃

In the present invention, the above-mentioned A element is, for example, Cu, Mg, Ca, Sr, Ba, Zn, Cd, Sc,
Y, La, Ce, Pr, Nd, Sm, Eu, Gd, T
b, Dy, Ho, Er, Tm, Yb, Lu, Pb, B
Examples thereof include i, Fe, Co and Ni, and more preferable examples include Mg, Ca, Sr, Ba and Pb, but the present invention is not limited thereto. Examples of the B element include Ti, Zr, Hf, Sn,
Although Sb etc. can be mentioned, it is not limited to this.

As the A element, a group IB of the periodic table of the elements, a group
Group IIA, Group IIB, Group IIIA, Group IVB, Group VB, Group V
Alkoxides of at least one element selected from Group III and Group IVA and I of the Periodic Table of Elements as element B
A mixture of alkoxides of at least one element selected from VB group and VB group, a complex alkoxide of A element and B element, and a hydrolysis product thereof may be used, but as a single alkoxide Is magnesium methoxide, magnesium ethoxide, magnesium propoxide, magnesium butoxide, calcium methoxide, calcium ethoxide, calcium propoxide, calcium butoxide, strontium methoxide, strontium ethoxide, strontium propoxide, strontium butoxide, barium methoxide, Barium ethoxide, barium propoxide, barium butoxide, lead methoxide, lead ethoxide, lead propoxide, lead butoxide, titanium methoxide, titanium ethoxide, titanium Propoxide, titanium butoxide, zirconium methoxide, zirconium ethoxide, zirconium propoxide, zirconium butoxide, hafnium methoxide, hafnium ethoxide, hafnium propoxide, hafnium butoxide,
Tin methoxide, tin ethoxide, tin propoxide,
Examples thereof include, but are not limited to, tin butoxide, antimony methoxide, antimony ethoxide, antimony propoxide, and antimony butoxide. In this case, as the alkoxide, one kind or two or more kinds of the central metal and the halogen atom may be bonded, but one kind and one or less kinds are preferable.

Further, complex alkoxides include barium titanium methoxide, barium titanium ethoxide, barium titanium propoxide, barium titanium butoxide, strontium titanium methoxide, strontium titanium ethoxide, strontium titanium propoxide, strontium titanium butoxide, magnesium titanium methoxide. , Magnesium titanium ethoxide, magnesium titanium propoxide, magnesium titanium butoxide,
Examples thereof include, but are not limited to, calcium titanium methoxide, calcium titanium ethoxide, calcium titanium propoxide, calcium titanium butoxide, and the like. In this case, as the alkoxide, one kind or two or more kinds of a central metal and a halogen atom may be bonded, but one kind and one kind are preferable.
Less than or equal to one is good.

When the alkoxides are mixed, the method is not particularly limited as long as the alkoxides are uniformly mixed, but if the compatibility between the alkoxides is poor or if the alkoxides are solid, a solvent may be added if necessary. It may be dissolved. In this case, a known solvent or water is appropriately used as the solvent. The organic solvent may be any of methanol, ethanol, methyl ethyl ketone, acetone, etc., if necessary.

Hydrolysis is carried out by adding a hydrolyzing agent to a mixture of alkoxides or complex alkoxides.
Alternatively, it is carried out by adding a mixture of alkoxides or complex alkoxides into the hydrolyzing agent. As the hydrolyzing agent, an acid or alkaline aqueous solution, water, and the like can be used, but the hydrolyzing agent is not limited to these. The acid or alkali may be any of inorganic acids, organic acids, organic amines, hydroxides, etc., for example, nitric acid, phosphoric acid, sulfuric acid, hydrochloric acid as the inorganic acid, and formic acid, oxalic acid, acetic acid, propionic acid as the organic acid. As succinic acid, malic acid, tartaric acid, citric acid, adipic acid, mutic acid, benzoic acid, salicylic acid, phthalic acid, isophthalic acid, terephthalic acid, trimellitic acid, sebacic acid, pyromellitic acid, stearic acid, organic amines Examples thereof include trimethylamine and dimethylamine, and examples of hydroxides include ammonium hydroxide, sodium hydroxide and potassium hydroxide, but are not limited thereto.

In the present invention, when a mixture of alkoxides or a complex alkoxide is hydrolyzed by a hydrolyzing agent, the sol solution or the produced gel may be in the form of slurry or lump depending on the conditions of hydrolysis. It can be used. When it becomes a slurry or a lump, the gel may be appropriately crushed before use.

The above-mentioned alkoxide of each element or the composite alkoxide containing two or more kinds of metal elements is
It may be prepared by adding an element capable of substituting the element A or the element B as a metal compound, for example, a metal oxide.
Further, various metal oxides or glass may be added to the alkoxide solution. When these are added and mixed, various metal oxides or glasses may be added at the time of preparing or hydrolyzing the alkoxide of the above-mentioned element and mixed in the alkoxide or hydrolysis product. Of course, it is not necessary that the mixed additives are completely melted in the alkoxide or the hydrolysis product, but it is preferable that the additives are melted. Further, the alcohol necessary for preparing the alkoxide or the composite alkoxide may be a mixture of different alcohols, for example, a mixture of methanol and ethanol.

A mixture of an alkoxide of at least one kind of metal element selected from the A element and an alkoxide of at least one kind of element selected from the B element, or a complex alkoxide of the A element and the B element, and their hydration. By introducing a decomposition product or the like into the thermal plasma, a perovskite-type composite oxide powder having high crystallinity represented by the following general formula (1) can be obtained, and further, under specific thermal plasma conditions, Spherical perovskite-type composite oxide powder having good crystallinity can also be produced, and ultrafine particles of perovskite-type composite oxide can be obtained by further appropriately selecting thermal plasma conditions. General formula (1) ABO ₃

The thermal plasma source used is preferably, but not limited to, high frequency induction plasma, microwave induction plasma, or direct current arc plasma.

[0017]

When the perovskite-type composite oxide represented by the above-mentioned general formula (1) or the perovskite-type composite oxide which is kept to a degree of calcination by the conventional manufacturing method is supplied into the thermal plasma flame, thermal plasma is generated. Spherical or nearly spherical powders can be produced depending on the conditions and particle size conditions of the raw materials, but only powder with low crystallinity can be obtained, and in order to obtain the required composition of the powder, strict heat treatment is required. It is necessary to control the plasma conditions, which is technically difficult. The cause of this is that the supplied material is heated in a thermal plasma flame at the same time as it is supplied and is melted at an extremely high temperature, so that the perovkite-type complex oxide powder shown in the general formula (1) releases oxygen. It is thought that this is because the structural changes such as the decomposition and the reduction are easily promoted.

On the other hand, as in the present invention, an alkoxide or a mixture of two or more alkoxides, which is a precursor of a perovskite type complex oxide, or a mixture of two or more alkoxides, or a mixture of two or more types, is used as a feed material for a thermal plasma flame. When a mixture of alkoxides or a hydrolysis product thereof is used, highly crystalline, perovskite type complex oxide powder having good dielectric properties, and further spherical or nearly spherical powder can be produced, and produced. It is relatively easy to adjust the composition of the perovskite type complex oxide powder to the required value.

This is considered to be as follows. That is, when an alkoxide such as a precursor of a perovskite type complex oxide or a mixture of two or more kinds of alkoxides, a complex alkoxide, a mixture of two or more kinds of complex alkoxides, or a hydrolysis product thereof is used. When ultra-high temperature is applied in thermal plasma, the thermal decomposition reaction of the alkoxide or the thermal decomposition reaction and dehydration reaction of the organic substance remaining in the gel, which is a hydrolysis product, and the perovskite-type composite oxide formed by thermal decomposition. Although the decomposition or vitrification reaction occurs before or after the reaction, the perovskite-type composite oxide that is being generated from the ultrahigh temperature due to thermal plasma may be due to the slow thermal decomposition reaction or dehydration reaction, or due to the thermal decomposition reaction or dehydration reaction. Because it is protected, decomposition that causes structural changes is suppressed, and High sex, dielectric properties good perovskite-type composite oxide powder is estimated to be produced.

[0020]

According to the present invention, it has been carried out conventionally.
It is possible to produce a perovskite-type composite oxide powder having a crystallinity similar to that of the method that goes through the sintering and crushing process, that is, containing a large amount of perovskite-type dielectric crystal phase, and it is possible to achieve labor saving and energy saving. it can.

As is clear from Table 1 shown in the following examples, an alkoxide which is a precursor of a perovskite type complex oxide, a mixture of two or more types of alkoxides, or a complex alkoxide and further two or more types of complex alkoxides. Of the perovskite-type composite oxide powder containing a large amount of perovskite-type dielectric crystal phase, which has a good crystallinity comparable to that of the sintering method, by supplying the mixture thereof, a hydrolysis product thereof, or the like into the thermal plasma. Is obtained.

Therefore, according to the present invention, it is possible to directly and continuously produce a perovskite-type composite oxide powder by using a thermal plasma device. The raw material is provided, and its industrial significance is extremely great.

[0023]

EXAMPLES The present invention will be specifically described with reference to the following examples. However, the scope of the present invention is not limited to the following examples.

Example 1 In a flask equipped with a stirrer, a reflux condenser and a dropping machine, 50 g of finely cut metal barium from which the oxide film on the surface was removed was charged, and further 1000 ml of isopropyl alcohol dehydrated and dried with a molecular sieve in advance. And add
It was heated and refluxed to synthesize barium isopropoxide. To this, commercially available titanium isopropoxide was added so that the ratio of barium to titanium was 1: 1 and refluxed for 2 to 3 hours to prepare a barium-titanium mixed alkoxide solution.

Next, a high-frequency induction thermal plasma is generated, and the sample is added in an amount of 0.01 to 0.5 ml / in this thermal plasma flame.
To supply barium titanate powder. The obtained barium titanate powder was subjected to an X-ray diffraction experiment, and a sharp peak and a broad peak were separated from the X-ray diffraction pattern, and the crystallinity calculated using the formula (2) is shown in Table 1.

Example 2 While the barium-titanium mixed alkoxide solution of Example 1 was further heated by a heating and drying apparatus, excess alcohol solvent was dried. Further, 1000 ml of methoxyethanol that had been dehydrated and dried with a molecular sieve in advance was added, and an ultrasonic vibrator was used to obtain a methoxyethanol solution of the mixed alkoxide. Thereafter, distilled water was added little by little with stirring to prepare a sol-like solution or a partially gelled solution.

Next, a DC arc thermal plasma is generated, and the sample is added in an amount of 0.01 to 0.5 ml / in this thermal plasma flame.
To supply barium titanate powder. The obtained barium titanate powder was subjected to an X-ray diffraction experiment, and a sharp peak and a broad peak were separated from the X-ray diffraction pattern, and the crystallinity calculated using the formula (2) is shown in Table 1.

Example 3 In a flask equipped with a stirrer, a reflux device and a dropping device, 32 g of finely cut metal strontium from which the oxide film on the surface was removed was charged, and further 1000 ml of isopropyl alcohol dehydrated and dried with a molecular sieve in advance. Was added and heated to reflux to synthesize strontium isopropoxide. To this, commercially available titanium isopropoxide was added so that the ratio of strontium to titanium was 1: 1 and refluxed for 2 to 3 hours to prepare a strontium-titanium mixed alkoxide solution.

Next, a microwave induction thermal plasma is generated, and the sample is added in an amount of 0.01 to 0.5 in the thermal plasma flame.
It was supplied at a rate of ml / min to obtain a strontium titanate powder. Table 1 shows the thermal plasma generation conditions at the time of execution.
The obtained strontium titanate powder was subjected to an X-ray diffraction experiment, a sharp peak and a broad peak were separated from the X-ray diffraction pattern, and the crystallinity calculated by using the formula (2) is shown in Table 1.

Example 4 Excess alcohol solvent was dried while the strontium-titanium mixed alkoxide solution of Example 3 was further heated by a heating dryer. Further, 1000 ml of methoxyethanol that had been dehydrated and dried with a molecular sieve in advance was added, and an ultrasonic vibrator was used to obtain a methoxyethanol solution of the mixed alkoxide. Thereafter, distilled water was added little by little with stirring to prepare a sol-like solution or a partially gelled solution.

Next, high-frequency induction thermal plasma is generated, and the sample is added in an amount of 0.01 to 0.5 ml / in this thermal plasma flame.
To supply strontium titanate powder. The obtained strontium titanate powder was subjected to an X-ray diffraction experiment, a sharp peak and a broad peak were separated from the X-ray diffraction pattern, and the crystallinity calculated by using the formula (2) is shown in Table 1.

The characteristics of the perovskite type complex oxide powders obtained in Examples 1 to 4 were measured by the following methods.

Directly measuring the dielectric properties of the obtained perovskite type complex oxide powder is to measure the dielectric properties of the powder, which is very difficult in terms of measurement technology. Moreover, the reliability of the measured dielectric properties is poor. As is generally known, perovskite-type composite oxides have good crystallinity, that is, those containing a large amount of perovskite-type dielectric crystal phase in the crystal have high dielectric properties, so the prepared perovskite Type complex oxide powder, X
The diffraction pattern was observed by a line diffraction experiment, and its crystallinity was estimated as the crystallinity, which is the degree of crystallinity according to the formula (2), in the range of 2θ = 10 to 40 °, and the perovskite-type composite produced by the conventional method. Compared with oxide powder. Formula (2) Crystallinity = (X / (X + Y)) × 100 X; crystalline integrated intensity Y; amorphous integrated intensity

In the above equation (2), the crystalline integrated intensity is X.
The area integral of the sharp peak of the line diffraction pattern, and the amorphous integrated intensity is the area integration of the broad peak of the X-ray diffraction pattern. A sharp peak and a broad peak were separated from the measured X-ray diffraction pattern, and the crystallinity was calculated using the formula (2).

As the X-ray diffractometer, JDX-8030 manufactured by JEOL Ltd. was used.

Comparative Examples X-ray diffraction experiments of commercially available barium titanate powder and strontium titanate powder were carried out. As a result, Examples 1 and 3 were obtained.
The crystallinity was about the same as

[0037]

[Table 1]

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yusuke Mitsuyoshi             2-3-13, Kyobashi, Chuo-ku, Tokyo Toyo             Nki Manufacturing Co., Ltd.

Claims (6)

[Claims] 1. (I) At least one kind of alkoxide having two or more kinds of metal elements, (II) At least one kind of alkoxide having one kind of metal elements, (I) and / or (II) (however, In the case of only (II), a method for producing a perovskite type complex oxide powder by thermal plasma using a mixture of two or more kinds of metal elements. 2. In the perovskite type complex oxide represented by the general formula (1), the metal element A is a group IB, group IIA, group IIB, group IIIA or group IVB of the periodic table of the elements. , First
At least one selected from Group VB and Group VIII, and the metal element of B is Group IVA or Group IVB of the Periodic Table of Elements.
The method for producing a perovskite-type complex oxide powder according to claim 1, characterized in that an alkoxide having at least one selected from Group VB and Group VB is used. General formula (1) ABO ₃ 3. In the general formula (1), the metal element of A is a group IB, a group IIA, a group IIB or a group IIIA of the periodic table of elements.
Group B, Group IVB, Group VB, Group VIII, and at least one selected from the group B of the periodic table of elements.
At least one selected from IVA, IVB, and VB
The method for producing a perovskite type complex oxide powder according to claim 1, wherein a hydrolysis product of an alkoxide having at least one kind is used. 4. In the general formula (1), the metal element of A is at least one selected from Group IIA and IVB of the periodic table of elements, and the metal element of B is the group of the periodic table of elements. The method for producing a perovskite-type complex oxide powder according to claim 1, wherein an alkoxide having at least one selected from the group consisting of IVA, IVB, and VB is used. 5. In the general formula (1), the metal element A is at least one selected from Group IIA and Group IVB of the periodic table of elements, and the metal element B is a group of the periodic table of elements. The method for producing a perovskite complex oxide powder according to claim 1, wherein a hydrolysis product of an alkoxide having at least one selected from the group consisting of IVA, IVB, and VB is used. 6. The method for producing a perovskite-type complex oxide powder according to claim 1, wherein a high frequency induction plasma, a microwave induction plasma or a direct current arc plasma is used as the thermal plasma source.