JPH0365515A - Production of powdery lead-containing oxide - Google Patents

Abstract

PURPOSE:To enable production of a fine sinterable powder having a narrow particle size distribution at a low cost by calcining constituent components having a specified particle size in production of a perovskite-type lead-containing compound oxide represented by ABO3. CONSTITUTION:In production of a perovskite-type lead-containing compound oxide represented by ABO3 (A is Pb and B is Ti, Mg, Nb, Ni, Zn, Zr, Fe, etc.), a powder having <=0.6mum average particle size of the B site component compound or of both the A and B site compounds is calcined at <=1000 deg.C. By grinding the above obtained fine particle compounds in the presence of a surfactant using the wet grinding method, grinding hours can be reduced and coagulation or sintering between mutual particles during drying and calcination can be prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Field of Application] The present invention relates to a method for producing fine lead-containing perovskite oxide powder.

[Prior Art] Conventionally, a solid phase reaction method and a coprecipitation method are known as methods for producing powder for lead-containing perovskite oxide ceramics.

These internal solid phase reaction methods are methods in which constituent compounds are simply mixed and calcined to obtain oxide powder. Although this method allows production of oxides with various desired compositions at relatively low cost, it has the disadvantage of poor sinterability because the resulting oxide powder has a large particle size and a wide particle size distribution.

In addition, in the coprecipitation method, a mixed solution containing constituent element ions is
Co-precipitate the constituent components by adding a precipitate forming liquid such as alkali,
In this method, this coprecipitate is dried and calcined to obtain an oxide powder. According to this method, an oxide powder with a relatively narrow particle size distribution can be obtained, but the p
Since the precipitate formation conditions for each 1+X'I component ion differ depending on l+, it is often difficult to co-precipitate with a desired composition.

In order to overcome these difficulties of the coprecipitation method, a coprecipitation method using an alkoxide as a raw material has been proposed.

According to this method, a coprecipitate having a desired composition can be obtained, and the oxide powder obtained by calcining the coprecipitate has a small particle size and a narrow particle size distribution. However, this method is disadvantageous from a technical and economic point of view because it must be handled in a non-aqueous system and the alkoxide itself is expensive.

As described above, each of the conventional techniques has both advantages and disadvantages.

As a raw material powder for lead-containing perovskite oxide ceramics, there is a demand for a powder that is inexpensive and has excellent sinterability and can be sintered at a relatively low temperature.

It is known that the sinterability of ceramics is greatly influenced by the state of the raw material powder as well as its chemical composition. Raw material powders with excellent sinterability that can be sintered at low temperatures include:
It is necessary that the particles be fine, and in order to suppress abnormal grain growth that occurs during sintering, a raw material powder with a particle size distribution as narrow as possible is desired. The advantage of being able to sinter lead-containing perovskite oxide ceramics at low temperatures is, for example, in multilayer capacitors using this, in addition to being able to use inexpensive materials such as silver for internal electrodes, it also suppresses grain growth during sintering. , suppression of compositional fluctuations during sintering, etc.

For these reasons, there is a need for a method that can produce at low cost a fine, easy-to-burn, lead-containing perovskite oxide powder with a narrow particle size distribution.

[Problems to be Solved by the Invention] The purpose of the present invention is to improve the drawbacks of the conventional method for producing lead-containing perovskite oxides, and to produce a fine and easily sinterable lead-containing perovskite oxide with a narrow particle size distribution. An object of the present invention is to provide a manufacturing method that allows powder to be manufactured at low cost.

[Means for solving problems]

As a result of intensive studies to solve the above-mentioned problems, the present inventors have developed a method for producing perovskite-type oxides represented by the general formula ABO3 (A represents lead). By calcining a powder with a particle size of 0.6 μm or less, or a compound containing an A-site component and a compound containing a B-site component with an average particle size of 0.6 μm or less at a temperature of 1000°C or less, fine particles can be obtained. We have discovered that it is possible to produce lead-containing perovskite-type oxide powder. Further, by wet-pulverizing the compound to be subjected to calcination in the presence of a surfactant, the average particle size can be relatively easily reduced to 0.6μ or less, and lead-containing perovskite obtained by calcination of this compound can be obtained. The present inventors have discovered that the type oxide powder is fine and has a narrow particle size distribution, and that by sintering this oxide powder, it is possible to produce lead-containing perovskite type oxide ceramics with high sintered density. The present invention will be explained in detail below.

Perovskite-type oxides are generally represented by oxides of A-site components and B-site components, that is, ABO3. There are many combinations of these A site components and B site components. As the A-site component of the ABO, for example, Pb5H
There are a, Ca, La, etc., and the B site components are:
TI, Mg, Nb, N1, Zn, Zr.

There are Fe etc.

Examples of lead-containing perovskite oxides whose A-site component is pb include Pb CMg+/v Nb2/v
) 03, Pb (Ni+/x Nb2/3) 03
, PbTiOs, Pb (Zn+/3Nb273)
In addition, two-component systems, three-component systems, etc. in which 2.3 types of perovskite-type oxides are combined are also known.

In the present invention, it is essential to calcinate the powder having an average particle size of 0.6 μm or less of the B site component compound or ASB site component compound at 1000° C. or less. The ASB site component compound mentioned here includes oxides, hydroxides, carbonates, etc. of the component element represented by ASB. Moreover, those produced by common synthesis techniques such as a coprecipitation method, an alkoxide method, and a hydrothermal synthesis method can be used. For example, the coprecipitation method or the alkoxide method is a method in which a precipitant is added to a solution of components of a lead-containing oxide, and the resulting precipitate is dried to obtain a powder. A, Bff 1 minute element hydroxides, carbonates, sulfates, acetates, nitrates, formates, oxalates, metal alkoxides, etc. can be adjusted by adding them to water or alcohol.

In addition, as the precipitating agent used here, ammonia,
In addition to oxalic acid, sodium hydroxide, etc., amines and the like can be used.

In the present invention, if a compound containing at least a B site component of the component compound to be subjected to calcination has an average particle diameter of more than 0.6 μm, high temperatures (1000 In addition, the particle size of the oxide obtained by calcination is large and the particle size distribution is wide.

The finer the particle size of the component compound, the more preferable it is, but making the particle size more fine than necessary requires a long time for the pulverization process, which is not necessarily practical for industrial production. Therefore, in the present invention, the particle size of the component compound subjected to calcination is 0.1 to
A thickness in the range of 0.6 μm is desirable.

In general, there are methods for making particles into fine particles, such as pulverization using a ball mill, but the pulverization time can be shortened by wet pulverization in the presence of a surfactant. The use of surfactants not only suppresses agglomeration between particles, increases pulverization efficiency, and shortens pulverization time, but also prevents aggregation of particles or This is thought to have the effect of suppressing sintering. It is surmised that these effects are effective in obtaining powder with a small particle size and narrow particle size distribution.

As the surfactant used here, various surfactants such as anionic surfactants, cationic surfactants, amphoteric surfactants and nonionic surfactants can be used.
When contamination with impurities such as Na and CI is undesirable, for example, acrylic acid oligomer ammonium salts and acrylic esters are useful.

In addition, in order to improve the dispersibility of oxide particles obtained by calcination, it is necessary to
By adjusting l+, it is possible to improve the dispersibility of the particles by imparting an electric charge to the particle surface, thereby increasing the pulverization efficiency. There are no particular restrictions on the pH adjustment method at this time, but Na5C
If contamination with impurities such as No. 1 is undesirable, it is desirable to use, for example, ammonia. As a method for pulverizing the oxide obtained by the above method, a general ball mill, vibration mill, etc. can be used. As the material of the balls, zirconia, alumina, resin-coated balls, agate stones, etc. can be used, but it is preferable to use balls with as small a diameter as possible in order to improve the grinding efficiency. As the medium, water or an organic solvent such as alcohol can be used.

In the pulverization treatment in the present invention, each of the A and B site component compounds may be pulverized and then mixed, or the mixed powder may be pulverized after each compound is mixed.

The slurry obtained by the above pulverization process can be filtered and dried, or a dry powder can be obtained by evaporating the medium using an evaporator or the like.

As for the method of firing the obtained mixed powder into lead-containing perovskite oxide powder, in order to complete the oxidation reaction sufficiently quickly, it is preferable to perform firing in an oxygen-containing gas atmosphere. It can be baked.

The calcination temperature in the present invention may be 1000°C or less, as long as it can form a perovskite phase. When the calcination temperature exceeds 1000° C., the particles obtained become large, and the charcoal particles are likely to sinter with each other to form secondary particles, resulting in a wide particle size distribution. However, if the temperature is less than 700° C., it is difficult to obtain a perovskite production rate of 95% or more, for example. The obtained powder has a particle size of 1 μm or less,
- There is little sintering between charcoal particles and it can be crushed relatively easily.

By molding and sintering the powder obtained according to the present invention, a lead-containing perovskite-type oxide ceramic having a high sintered density can be obtained.

As this molding method, a known mold molding method, slip cast molding method, or the like can be used.

Further, the sintering temperature may be any temperature between 900°C and 1300°C, but the powder obtained by the present invention is fine, has a narrow particle size distribution, and has excellent sinterability, and has a sintering temperature of 8 g/c11 at a temperature of 1000°C or lower. 'High sintered density can be obtained.

[Effects of the Invention] According to the present invention, a perovskite-type oxide powder can be obtained at a relatively low temperature, and the obtained powder has a fine particle size and a narrow particle size distribution. The powder obtained according to the present invention has excellent sinterability, and can be used to produce products with a high sintering density of 8 g/cm3 or more at a sintering temperature of 1000°C or less, such as ceramic capacitors, pressed bodies, etc. It has excellent properties as a raw material powder for electronic ceramics.

[Example] Examples will be described below, but the present invention is not limited thereto.

Example I A Pb (Mg+zi Nb2/i ) 03 (hereinafter abbreviated as PMN) based perovskite oxide was produced by the following method.

PbO: 45.091g, MgO: 2.715
g, Nbz 05: 17.745g in 2ml1
lφ zirconia ball 125ml and distilled water 70m
1 and put it in a polyethylene pot and heat it in a vibrating mill for 50I.
I! The resulting slurry was evaporated to dryness using an evaporator to obtain a mixed powder.

The average particle diameter of the obtained mixed powder was determined by API using a centrifugal sedimentation type particle size distribution analyzer, and was found to be 0.52 μm.

Next, this powder was calcined at 850°C for 2 hours.

The X-ray diffraction chart of the obtained powder is shown in FIG. 1, and from the intensity of this main peak, 97.1% was P)IN-based perovskite. Further, as a result of observation using an electron microscope, the particle size of the obtained powder was 0.2 to 0.8 μm.

Example 2 PbO: 45.091g 1 MgO: 2.
715g: Nb 20s: 17.745g
was placed in a polyethylene pot together with 125 ml of 2 m+++φ zirconia balls and 70 ml of distilled water.

In this practical example, a dispersant (trade name rD manufactured by Hoechst)
ispcx A-40J) Add Ig and mix with a vibration mill.
Wet milling was carried out for 00 hours. Next r? The slurry
The mixture was evaporated to dryness using an evaporator to obtain a mixed powder. The average particle size of the obtained 11Z combined powder was determined by centrifugal sedimentation particle size 71i.
The result of measurement using an A11I measuring machine was 0.47 μm.

Next, this powder was calcined at 850°C for 2 hours. The X-ray diffraction chart of the obtained powder is shown in FIG. 2, and from the intensity of this main peak, 98.3% was PMN-based perovskite. (The relationship between calcination temperature and perovskite ratio is shown in FIG. 7) Furthermore, as a result of observation using an electron microscope, the particle size of the obtained powder was 0.3 to 0.5 μm.

Example 3 Mg0: 3.317g, Nb2O5: 21.6
83 g was placed in a polyethylene pot together with 501 ml of 2 φ zirconia balls and 30 ml of distilled water. Furthermore, a dispersant (manufactured by Hoechst, trade name: rDIspex^-4)
0J) was added and subjected to wet pulverization in a vibration mill for IO hours, and the resulting slurry was evaporated to dryness in an evaporator to obtain a mixed powder.

The average particle diameter of the obtained mixed powder was 0.47 μm as measured using a centrifugal sedimentation type particle size distribution analyzer. Next, this powder was calcined at 900° C. for 2 hours.

(The obtained powder is referred to as Powder-A) PbO: 50g is packed into 100m of zirconia balls with a diameter of 2.
1 and 55+ el of distilled water were placed in a polyethylene pot and wet-pulverized for 1 hour in a vibrating mill to obtain a slurry 1'). This slurry was filtered and dried.

(The obtained powder is referred to as powder-B) III obtained powder = A: 15.607g, powder-
B: 34.393 g was placed in a polyethylene pot together with 2 mF 6 φ zirconia balls 1201!11 and 70 ml of distilled water, and wet milling was performed in a ball mill for 5 hours. The resulting slurry was evaporated to dryness in an evaporator to obtain a mixed powder.

Next, the obtained mixed powder was calcined at 850° C. for 2 hours.

The X-ray diffraction chart of the obtained powder is shown in FIG. 3, and from the intensity of this main peak, 99.5 to 100% was PMN-based perovskite. Further, as a result of observation using an electron microscope, the particle size of the obtained powder was 0.3 to 0.8 μm.

Example 4 0.2PbTi030.2Pb (Mg+, tNb2
．． ) O) 0. GPb (My i+, i Nb23)
03 (abbreviated as PT PMN PN) type perovskite oxide was manufactured. PbO: 102.4
47g, MgO: 1.235g, Nb2O5:
32.237g, NIO: (i, 794g, T
iO2: 7.298g was placed in a polyethylene pot with 200ml of 21111iφ zirconia balls and 150il of distilled water, and a dispersant (Hoechst > l
3 g of split product name (rl) ispcx A-40J) was added and subjected to wet crushing in a vibration mill for 100 hours, and the resulting slurry was evaporated to dryness in an evaporator to obtain a mixed powder. The average particle size of the obtained mixed powder is based on the centrifugal sedimentation particle size distribution aF.
The result of measurement using I-seiiso was 0.41 μm.

Next, it was compressed at 850°C for 2 hours.
A line diffraction chart is shown in FIG. 4, and 99% of the intensity of this main peak was PT-PMN-PNN perovskie I. Further, as a result of observation using an electron microscope, the particle size of the obtained powder was 0.2 to 0.5 μm.

Comparative example I A PMN-based perovskite oxide was produced.

PbO: 45.091g lMgO: 2.715g
, NbO20s: 17.747g 20no+
+φ zirconia ball 125ml and distilled water 70m
Put it in a polyethylene pot with 1 and use a ball mill for 10
The slurry obtained by time-based pulverization was evaporated to dryness using an evaporator to obtain a mixed powder.

The average particle diameter of the iIt mixed powder was 0.87 μm as measured using a centrifugal sedimentation type particle size distribution analyzer.

Next, this powder was calcined at 850°C for 2 hours.

The X-ray diffraction chart of the obtained powder is shown in FIG. 5.As can be seen from FIG. 5, a large amount of pyrochlore phase was observed in the powder obtained in this example, and the PMN perovskite had a main peak intensity of 38.7%. %Met. (Figure 7+,: Temporary t, Q
In addition, as a result of observation using an electron microscope, the particle size of the obtained powder was 1 to 1.
The diameter was 4 μm and the distribution was wide.

Comparative example 2 A PMN-based perovskite oxide was produced.

The mixed powder having an average particle diameter of 0.87 μm obtained in Comparative Example 1 was calcined at 1100° C. for 2 hours. FIG. 6 shows an X-ray concavity chart of the obtained powder. As can be seen from Figure 6, a large amount of pyrochlore phase was observed in the product obtained in this example, and PMN
The intensity of the perovskite system was 60.5% of the main peak intensity. Further, as a result of observation using an electron microscope, the particle size of the obtained powder was 2 to 5 μm and the distribution was wide.

Comparative example 3 A PMN-based perovskite oxide was produced.

The mixed powder obtained in Example 2 with an average particle diameter of 0.41 μm was calcined at 1100° C. for 2 hours. The X-ray diffraction chart of the obtained powder is shown in FIG. 7, and from the intensity of this main peak, 98% was PMN-based perovskite.

Further, as a result of observation using an electron microscope, the particle size of the obtained powder was 0.5 to 3 μm, which was larger than the powder obtained in Example 2, and the particle size distribution was wide.

Comparative Example 4 PT-1) A MN-PNN-based perovskite oxide was produced.

PbO: 102.447g5Mg0: 1.23
5g-Nb2O,: 32.237g, NIO:
6.794g, TiO: 7.298g to 201Il
11φ zirconia ball 200ml and distilled water 15
The resulting slurry was placed in a polyethylene pot with 0 ml of water and time-pulverized at IO in a ball mill, and then evaporated to dryness in an evaporator. JI Iy powder was obtained. The average particle diameter of the obtained mixed powder was 0.79 μm as measured using a centrifugal sedimentation type particle size distribution analyzer. Next, this powder was calcined at 850°C for 2 hours. The X-ray diffraction chart of the obtained powder is shown in FIG. 8, and a large amount of pyrochlore phase was observed, and the intensity of PMN-based perovskite was 74.6% of the main peak intensity. Furthermore, as a result of observation using an electron microscope, the particle size of the obtained powder was 1 to 4 μm wide, and the distribution was wide.

Example 5 The powders obtained in Examples 1 to 4 and Comparative Examples 1 to 4 were put into molds each having a diameter of 20 mm, and the pressure was applied to the molds. It was press-molded at ton/cm2 and sintered at 1000°C. The sintered density of the obtained sintered body was measured by the Archimedes method. The measurement results are shown in Table 1.

Table 1 Sintered density g/cm’ Example 1 8.02 Example 2 8. OB Example 3 8.08 Example 4 8.24 Comparative example 1 7, 1.3 Comparative example 2 7.05 Comparative example 3 7.84 Comparative example 4 7.22

[Brief explanation of drawings]

Countries 1 to 4 show X-ray diffraction charts of the powders i' and I in Examples 1 to 4. 5 to 8 show X-ray diffraction charts of the powders obtained in Comparative Examples 1 to 4. FIG. 9 shows the relationship between the calcination temperature and the perovskite ratio in Example 2 and Comparative Example 1. FIG. 10 shows the relationship between the average particle diameter of each component compound and the perovskite ratio during calcination at 850° C. for 2 hours.

Claims (1)

[Claims] 1) A method for producing a perovskite-type oxide represented by the general formula ABO_3 (A represents lead) by calcining a compound containing components constituting each AB site, at least the B site. The average particle size of the compound containing the component is 0.6
A method for producing a lead-containing perovskite oxide powder characterized by calcining a powder of 1000° C. or less at a temperature of 1000° C. or less. The manufacturing method according to claim 1), in which a compound containing the compound is calcined.