JPH0255375B2 - - Google Patents

Description

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

In general, many lead-containing oxides are useful as electroceramics, such as ferroelectric materials, piezoelectric materials, and pyroelectric materials.

As electroceramic parts become smaller and more sophisticated, there is an increasing demand for highly reactive fine powder raw materials with high purity and narrow particle size distribution. This is because, when forming a thin film by, for example, a doctor blade method, excellent fine powder is required to improve surface roughness and improve the quality of the film.

(Prior art) Conventionally, the method for producing lead-containing oxide powder is as follows:
Compound powders such as oxides and carbonates containing various metals that should constitute the lead-containing oxide are weighed and mixed to achieve the desired composition, then calcined, and the solid phase reaction by crushing and calcining is repeated many times. There is a so-called solid-phase method for manufacturing.

With this method, it is difficult to produce highly pure powder due to impurities mixed in during pulverization. Furthermore, the particle size of powder that can be efficiently produced by pulverization is limited to a few micrometers, and the particle size tends to be non-uniform, resulting in poor reactivity.

As a method for improving these drawbacks of the solid phase method, a coprecipitation method is known in which a powder is produced using a solution as a starting material, and this method has the advantage that fine powder with a generally narrow particle size distribution can be obtained.

(Problems to be Solved by the Invention) Regarding the application of the coprecipitation method, which is useful for preparing lead-containing oxide fine powder, it is difficult to prepare a solution of some of the metals that should constitute the lead-containing oxide, or Even if the solution is easy to prepare, it may not be industrially advantageous because it contains metal components that make the solution preparation process complicated and expensive.

For example, metal components such as Nb and Ta are fluoric acids,
It dissolves only in oxalic acid, tartaric acid, etc.
Fluoric acid has many problems in handling, such as the material of the equipment.
Furthermore, oxylic acid, tartaric acid, etc. have the disadvantage of being relatively expensive. On the other hand, metal alkoxide solutions are often complicated to synthesize and expensive.

In addition, even if the metal component is easy to prepare a solution, the solubility of the precipitate formed during the reaction with the precipitant makes it difficult to achieve the desired composition, such as alkaline earth metals such as Mg and alkali metals such as Li. hard. That is, in order to precipitate these components, it is necessary to use a large amount of precipitant in order to increase the pH of the precipitate, which is not industrially advantageous.

Further, examples of metal components that increase the solubility of the precipitate by increasing the precipitate pH include Al,
Examples include amphoteric metals such as Zn.

As mentioned above, when applying the coprecipitation method, it is often difficult to set precipitation conditions common to all the metals that should constitute the lead-containing oxide.
This has been pointed out as a problem in the conventional technology, and it is an object of the present invention to solve the problem.

(Means for Solving the Problems) Among the various metal components other than lead that should constitute the lead-containing oxide, the inventors have determined that, for metal components that have the above-mentioned problems during solution preparation or precipitate formation, The inventors have discovered that the above-mentioned problems can be solved by using a compound powder containing the metal component as a suspension in a solution of the remaining metal, and have arrived at the present invention.

That is, in the production of lead-containing oxide fine powder, the present invention uses alkaline earth metals, alkali metals,
A suspension of a compound powder containing at least one metal selected from the group consisting of Al, Zn, Nb, and Ta in a solution of the remaining metal is reacted with a suspending agent under stirring. 450~
A step of calcining at 1200°C to obtain a powder, a step of adding and mixing lead compound powder to the powder obtained in the above step, and a step of mixing the powder mixture obtained through each of the above steps.
This is a method for producing lead-containing oxide fine powder, which is characterized by combining the steps of firing at 600 to 1000°C.

First, specific examples of various metals that should constitute the lead-containing oxide include Pb, Zr, Ti, Mg, Nb,
Sn, Zn, Sb, Al, Fe, Ta, Co, Ni, Bi, Li,
Sr, Ba, Ca, Se, La, Cu, Y, Yb, Te, Re,
Examples include CD and In.

Next, solutions containing these metal components are not particularly limited, but examples thereof include inorganic acid solutions such as nitric acid solutions, hydrochloric acid solutions, and sulfuric acid solutions, oxalic acid solutions,
Examples include organic acid solutions such as formic acid solutions, alkoxide solutions, and mixed solutions thereof.

Examples of methods for preparing solutions include the general method of dissolving various salts in water, synthesis of alkoxides, and dissolution in alcohol.

On the other hand, the suspension as used in the present invention refers to a liquid in which solid particles are uniformly dispersed, and specifically, among the various metal components other than lead that should constitute the lead-containing oxide, alkaline metals, alkali metals, Al,
A liquid in which powders of compounds containing metals belonging to the group consisting of Zn, Nb, and Ta, such as oxides, carbonates, hydroxides, and oxalates, are dispersed and suspended in a solution of the remaining metals. .

The characteristics of the powder used for dispersion and suspension are important, and a fine powder that does not dissolve in the liquid to be dispersed and suspends and has good suspension and dispersibility is preferable. The particle size is
It is preferably 1 μm or less. Further, as a method for suspending, in addition to a general method using a stirrer, it is preferable to use a homogenizing device such as a homogenizer, and it is important to ensure sufficient suspension.

Precipitating agents include inorganic bases such as aqueous ammonia, various salts such as ammonium carbonate and ammonium oxalate, water and alcohol solutions of organic bases such as methylamine and ethylamine, and hydrogen peroxide. , hydrazine, etc.
It is also possible to add additives that improve the efficiency of precipitate formation.

The term "slurry" as used in the present invention means a mixture of a precipitant produced by reacting the powder containing various suspended metal components with a precipitant.

The reaction method of the solution or suspension with the precipitant is to add the precipitant to the solution or suspension while stirring, or to sequentially add the solution, suspension, and precipitant to a slurry production tank. methods, etc. Stirring is important when reacting this solution or suspension with a precipitant, and suspension is preferably sufficiently stirred by the method described above.

The solution portion of the slurry thus obtained is removed by a method such as filtration.

It is preferable to wash the precipitate under the same conditions as those used for forming the precipitate or to use a solution with a higher pH than that to prevent elution during washing.

It is desirable to wash thoroughly to remove impurities such as Cl ^- and NO ³ in the precipitate. It is also effective to prevent precipitated particles from agglomerating together by washing with ethanol, acetone, etc. after removing impurities.

Drying methods include normal heat drying, vacuum drying, spray drying, vibration fluidized drying,
Methods include drum dryers and film evaporators.

Preventing agglomeration of powders is important in obtaining fine powders, and in this respect it is effective to perform crushing using a ball mill, vibrating ball mill, jet mill, etc. before and/or after calcination.

If the calcination temperature is lower than 450°C, it will be insufficient to remove moisture etc. from the precipitate, and it will be difficult to achieve the desired composition when weighing and charging in the next step. Further, if the temperature is higher than 1200°C, there is a problem that agglomeration occurs due to sintering of powders and reactivity decreases. Furthermore, calcining at high temperatures is not practical in terms of energy. Therefore, the calcination temperature is preferably 450 to 1200°C, more preferably 600 to 1000°C.

The above is the specific content of step (a).

Next, examples of the lead compound used in step (b) include lead oxide (PbO, Pb ₃ O ₄ ), lead carbonate, basic carbonate, lead hydroxide, lead oxalate, lead formate, and the like.

Regarding the powder characteristics of the lead compound powder, a fine powder with good mixability is preferable.

As a mixing method, a general method using a mortar or a ball mill may be used, and wet mixing using alcohol, acetone, etc. is more efficient and preferable than dry mixing.

The amount of lead compound powder to be mixed should be 8 mol% or less in excess of the stoichiometric amount to form the desired phase, in order to form the desired phase and to increase the reactivity of the powder. more effective.

Next is step (c), the firing temperature in this step is
At temperatures lower than 600℃, the efficiency of the reaction is low;
At temperatures higher than 1000°C, lead compounds tend to melt and form solid agglomerates of powders, making it difficult to form fine powders. Therefore, the firing temperature is 600-1000℃, preferably 700-900℃
More preferably, the temperature is 750 to 850°C.

(Example) The present invention will be further specifically explained below with reference to Examples.

Example 1 A zirconyl chloride aqueous solution with a metal concentration of 1.02 mol% and a titanium tetrachloride aqueous solution with a metal concentration of 2.03 mol% were prepared.
Mix Zr:Ti so that the atomic ratio is 0.125:0.4375, add metal Mn powder to this solution while stirring so that the Ti:Mn atomic ratio is 30:1,
A solution containing Zr, Ti and Mn was obtained.

Mn: Niobium oxide powder with a particle size of 0.3 μm and magnesium oxide powder with a particle size of about 0.2 μm are added to this solution.
Using a homogenizer, suspend and disperse Nb and Mg so that the atomic ratio is 0.05:2:1.
A suspension was obtained in which a compound powder containing Mg was suspended in a solution containing Zr, Ti, and Mn. This suspension was dropped using a liquid pump into a precipitation layer maintained at pH 7 with aqueous ammonia to obtain a slurry. At this time, sufficient stirring was performed using a homogenizer.

Furthermore, 1 ml of hydrogen peroxide solution was added to 100 ml of the slurry.

The obtained slurry was thoroughly washed and filtered using 0.1N diluted ammonia water. Analysis of the metal components in the filtrate revealed that only Mg was eluted, but the amount eluted was only 0.06% based on the molar amount charged. Next, after drying at a temperature of 80°C, it was crushed in a wet ball mill using acetone and calcined at a temperature of 900°C for 3 hours to obtain a powder.

When this powder was observed with a scanning electron microscope, it was confirmed that it was a fine powder with a uniform particle size of about 0.4 μm.

Next, for 96.2600g of this powder, lead oxide (Pb
223.2000 g of O) were wet mixed using acetone.

After that, the above powder mixture was heated to 780°C.
A lead-containing oxide powder was obtained by firing for a period of time. As a result of scanning electron microscope observation, this powder was found to be a fine powder with extremely uniform particle size of approximately 0.4 μm.

Further, purity analysis revealed that carbon, chlorine, and impurity metals were less than 10 ppm, indicating high purity.

In addition, in order to evaluate the reactivity of the lead-containing oxide fine powder, 3.0 g of the fine powder was molded at a molding pressure of 1000 kg/cm ³ with a diameter of 20 mm.
When the material was formed into a disk shape of mmφ and sintered at a temperature of 1150° C. for 1 hour, the sintered density was 7.89 g/cm ³ , and a sintered body having approximately the theoretical density was obtained.

When this sintered body was crushed and subjected to powder X-ray diffraction, it was found to be a single complex perovskite phase.
Analysis using an X-ray microanalyzer revealed that the constituent metals were uniform with no segregation.

Example 2 In the solution containing Zr, Ti, and Mn used in Example 1,
Further, a solution was prepared by mixing an aqueous solution of strontium chloride with a metal concentration of 1.0 mol/mole so that the atomic ratio of Zr:Sr was 0.125:0.05.

Using this, a calcined powder containing Zr, Ti, Mg, Mn, Nb, and Sr was obtained by the same operation as described in Example 1 below.

The elution of metal components in the filtrate during precipitation formation was the same as in Example 1.

The obtained powder was a fine powder with a uniform particle size of about 0.4 μm.

For 101.441g of this fine powder, lead monoxide (Pb
212.0400 g of O) were wet mixed using acetone. After that, the above mixed powder was heated to 780°C.
A lead-containing oxide fine powder was obtained by firing for a period of time. The characteristics of this fine powder were almost the same as those of Example 1.

Example 3 A zirconia chloride aqueous solution with a metal concentration of 0.82 mol/metal and a titanium tetrachloride aqueous solution with a metal concentration of 1.02 mol/are mixed so that the atomic ratio of Zr::Ti is 0.125:0.4375, and metallic Mn powder is added to the solution. , Ti:Mn
were added with stirring to give an atomic ratio of 30:1 to obtain a solution containing Zr, Ti, and Mn.

In this solution, add niobium oxide powder with a particle size of about 0.3 μm and magnesium oxide powder with a particle size of about 0.2 μm,
Zr, Ti, and
A suspension containing Mn, Nb, and Mg was obtained. This suspension was dropped into a precipitation tank maintained at pH 7 with aqueous ammonia using a liquid pump to obtain a slurry. At this time, use a homogenizer to stir thoroughly and add 1 ml to 100 ml of slurry.
of hydrogen peroxide solution was added.

The obtained slurry was thoroughly washed and filtered using 0.1N diluted ammonia water. When the metal components in the filtrate were analyzed, only Mg was observed to be eluted, but the amount eluted was only 0.07% based on the molar amount charged.

Next, it was dried at a temperature of 80°C, crushed in a wet ball mill using acetone, and calcined at a temperature of 940°C for 5 hours to obtain a powder.

When this powder was observed with a scanning electron microscope, it was found to be a fine powder with a uniform particle size of about 0.4 μm.

Next, for 96.2600g of this powder, lead oxide (Pb
223.2000 g of O) were wet mixed using acetone. Thereafter, the mixed powder was fired at a temperature of 780° C. for 1 hour to obtain a lead-containing oxide fine powder. The characteristics of this fine powder were almost the same as those of Example 1.

Example 4 The zirconyl chloride aqueous solution and the titanium tetrachloride aqueous solution used in Example 1 were mixed at an atomic ratio of Zr:Ti of 0.50:
Niobium oxide powder with a particle size of about 0.3 μm is mixed in the solution so that the Ti:Nb atomic ratio is 0.49:
Suspend and disperse using a homogenizer so that the Nb-containing compound powder becomes Zr and Ti.
A suspension was obtained in which the compound was suspended in a solution containing. This suspension was mixed with ammonia water to pH 7 using a liquid pump.
A slurry-like material was obtained by dropping the solution into a precipitate-forming layer held at At this time, sufficient stirring was performed using a homogenizer.

The obtained slurry was thoroughly washed and filtered using 0.1N diluted ammonia water. Next, it was dried at a temperature of 80°C, crushed in a wet ball mill using acetone, and calcined at a temperature of 900°C for 3 hours to obtain a powder.

When this powder was observed with a scanning electron microscope, it was found to be a fine powder with a uniform particle size of about 0.4 μm.

Next, add lead oxide (Pb O) to 3.4027g of this powder.
7.5144 g were wet mixed using acetone. Thereafter, the mixed powder was fired at a temperature of 780° C. for 1 hour to obtain a lead-containing oxide fine powder.

The characteristics of this fine powder were almost the same as those of Example 1.

(Effects of the Invention) According to the present invention, components that are difficult to precipitate using conventional coprecipitation methods and preparation of a stock solution for coprecipitation are efficient, and reactivity and uniformity are achieved even though they contain components that cannot be industrially produced. , easily sinterable lead-containing fine powder with excellent dispersibility can be produced.

Claims (1)

[Claims] 1. In producing the lead-containing oxide fine powder, (a) among the various metals other than lead that should constitute the lead-containing oxide, alkaline earth metals, alkali metals,
A slurry obtained by reacting a suspension of a compound powder containing a metal belonging to the group consisting of Al, Zn, Nb, and Ta in a solution of the remaining metal with a precipitant under stirring. (b) Adding and mixing lead compound powder to the powder obtained in the above step, and (c) Adding and mixing the powder mixture obtained through each of the above steps. 600
A method for producing a lead-containing oxide fine powder, characterized by combining the following steps: a step of firing at ~1000°C.