JPH0248490B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) The present invention relates to a method for producing high purity 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 high-purity, highly reactive fine powder raw materials with a narrow particle size distribution. Particularly high purity is important not only for the electrical properties of the device but also for the electrical properties of the device. It is also important in terms of reliability, such as changes over time.

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

(Problems to be Solved by the Invention) However, even in the coprecipitation method useful for preparing lead-containing oxide fine powder, if a halogen is contained in the starting material solution, its removal is a problem. Generally, water washing is performed to remove halides and other impurities from the produced precipitate, but the removal cannot be said to be complete.

In addition, the solubility of the precipitate generated during the reaction with the precipitant is large, making it difficult to achieve the desired composition, such as metal components.
In order to precipitate components such as alkaline earth metals such as Mg and alkali metals such as Li, or to prevent them from dissolving during cleaning, a large amount of solvent, such as alcohol, must be added. However, it is expensive and cannot be said to be an industrially advantageous method.

In other words, a method that does not require a cleaning step and does not contain chlorine components is desired.

(Means for solving the problem) The inventors conducted research on a method for removing halogen compounds from conventional lead-containing oxide fine powder. By treating the precipitate obtained by reacting the containing solution or suspension with a precipitant with hot water,
The present invention was achieved based on the knowledge that lead-containing oxide fine powder containing no halide can be obtained. That is, in producing a lead-containing oxide fine powder, the present invention involves: (a) reacting a solution or suspension containing various metals and halogens to form a lead-containing oxide with a precipitant under stirring to form a slurry; (b) heating the precipitate obtained in the above step to a temperature of 250 to 450°C;
(c) adding and mixing lead compound powder to the powder obtained in the above step; (d) adding and mixing the powder obtained in the above step with the powder obtained in the above step; The powder mixture is heated to a temperature of 600~
This is a method for producing high-purity lead-containing oxide fine powder, which is characterized by combining each step of firing at 1000°C.

The present invention will be explained in more detail below.

First, we will explain step by step starting from step (a).

In the present invention, 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, as a solution containing these metal components,
Examples include inorganic acid solutions such as hydrochloric acid solutions and hydrofluoric acid solutions, and mixed solutions of these and formic acid, oxalic acid, alkoxides, and the like. Examples of methods for preparing the solution include the general method of dissolving salts of the various metals mentioned above 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 refers to various metal components or compounds thereof that constitute the lead-containing oxide, such as oxides, It is a liquid in which at least one powder of salt, hydroxide, oxalate, etc. is dispersed and suspended.

Examples of the liquid used for this dispersion and suspension include water, alcohol, and the like, in addition to the above-mentioned solutions.

The properties of the powder used for dispersion and suspension are important, and fine powder with good suspension and dispersibility is preferred.

Precipitating agents include inorganic bases such as aqueous ammonia, various salts such as ammonium carbonate and ammonium oxalate, organic bases such as methylamine and ethylamine, water, alcohol solutions, etc. Additives such as hydrogen oxide, hydrazine, etc. that improve the efficiency of precipitation formation can also be added.

The term "slurry-like material" as used in the present invention means a mixture of the above-mentioned suspended powder containing the various metal components and a precipitate produced by reacting with a precipitant, or a precipitate obtained by reacting with a precipitant. It is.

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 it is preferable to stir sufficiently.

A precipitate can be obtained by removing the supernatant liquid from the slurry thus obtained by a method such as filtration. This precipitate may or may not be washed.

Next, in step (b), the precipitate is heat treated.

In the present invention, hot water treatment refers to applying heat and steam to the precipitate at the same time, and there is no difference in the effect even if the supernatant liquid part is removed or if it is dried and volatilized. However, it goes without saying that using the former is thermally advantageous.

Hot water treatment can be carried out by applying steam at a temperature of 200 to 450°C. Hydrothermal treatment only removes halogens and other impurities;
The precipitate is converted into an oxide by heat treatment at ~1200°C. Hydrothermal treatment has difficulty removing impurities at temperatures below 200°C, and is thermally uneconomical at temperatures above 450°C.

The reason for heat treatment after hot water treatment is to oxidize the precipitate and remove water etc. in the precipitate. If this is insufficient, the target composition may be used when weighing and preparing in the next step. is difficult. When the heat treatment is performed at a temperature lower than 450°C, removal of water etc. in the precipitate and oxidation of the precipitate are insufficient. Furthermore, if the temperature is higher than 1200°C, there is a problem that agglomeration occurs due to sintering of powders and reactivity decreases. Also, it is not practical at high temperatures in terms of energy.

The hot water treatment time is not particularly limited, but is 5
The time is preferably 5 to 30 minutes, more preferably 5 to 30 minutes.

In addition, what is necessary is just to heat-process what was hot-water-treated at the temperature of 450-1200 degreeC for 5 minutes - 5 hours.

A specific example of hydrothermal treatment is to supply water vapor at a temperature of less than 200°C or fine droplets to a heat treatment device at a temperature of 200°C or more, such as an electric furnace or a rotary kiln, together with a precipitate and a carrier gas, and leave it there for a predetermined period of time. Exhaust the exhaust gas out of the system. In this case, it is preferable to fluidize using a rotary kiln or the like to improve contact.

It is preferable to provide a trap on the discharge side to collect the generated halide gas, and the trap must be capable of absorbing the halide gas. A specific example thereof is an alkaline solution such as caustic soda. Note that it is preferable to crush the precipitate in advance using a ball mill, vibration mill, jet mill, etc. before the hot water treatment.

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

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

The mixing method may be a general method using a pot or a ball mill, and in particular, dry mixing using alcohol, acetone, etc. is more effective 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.

In this step (c), trace amounts of additives, such as
MnO ₂ , Fe ₂ O ₃ , SrCO ₃ , SrO, CaO, BaO,
BaCO ₃ , NiO, Al ₂ O ₃ and the like can be added.

Next is step (d), but the firing temperature in this step is
At temperatures lower than 600°C, the efficiency of the reaction is low. On the other hand, 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 700-1000℃.
The temperature is 900°C, more preferably 750 to 850°C.

(Function) One of the features of the present invention is that the powder properties are improved by reacting the lead compound afterwards. That is, if a lead compound is produced simultaneously with other components and subjected to high temperature treatment, the lead compound will melt and the powder will tend to form strong agglomerations, resulting in poor powder properties. Another feature of the present invention is that powders made of components other than lead can be treated at high temperatures by reacting with lead compounds later on, thereby making it possible to efficiently remove chlorine impurities.

(Example) Example 1 A zirconyl chloride aqueous solution with a metal concentration of 1.02 mol/metal and a titanium tetrachloride aqueous solution with a metal concentration of 1.63 mol/metal are mixed so that the atomic ratio of Zr:Ti is 0.125:0.4375, and the metal is added to the solution. Mg powder and metallic Mn powder were added with stirring so that the atomic ratio of Ti:Mg was 30:10:1 to obtain a purple solution.

Separately, a strongly acidic solution of niobium with a metal concentration of 0.422 mol/metal was prepared using niobium hydroxide precipitation.

The purple solution containing Zr, Ti, Mg and Mn was added to this solution at an atomic ratio of Nb:Mg of 2:1 to obtain a brownish-brown solution.

This solution was sprayed with stirring into a coprecipitation tank maintained at pH 9.0 with ethanol (precipitation aid) and aqueous ammonia (precipitant) to form a precipitate. The amount of ethanol (precipitation aid) added at this time was 50% by volume based on the content in the coprecipitation tank.

The formed precipitate is filtered, and the obtained precipitate is heated to
It was dried at 80°C.

After crushing the dry refining material, approximately 150 g of the dry refining material was placed in a tubular electric furnace with an inner diameter of 40 mmφ, and subjected to hot water treatment by applying steam at a temperature of 350°C for 30 minutes, and then heated to a temperature of 900°C.
Thermal decomposition was carried out for 1 hour. In the case of hot water treatment, steam at a temperature of about 110°C was poured into the furnace for 30 minutes, and a NaOH solution with a concentration of 0.1 mol/min was used as a trap on the outlet side.

The following method was used to quantitatively analyze the chlorine content of the obtained powder. Approximately 0.1 g of powder was placed in a tube furnace with an inner diameter of 30 mm and maintained at a temperature of 900° C. for 30 minutes.
At this time, air was flowed into the tube furnace at a rate of 350 ml/min using water vapor generated from a water tank maintained at a temperature of 95° C. as a carrier gas. Note that the concentration is on the outlet side.
It was trapped with a 0.6 mol/aqueous sodium carbonate solution and quantified by ion chromatography.

As a result, no chlorine was detected.

When this powder was observed using a scanning electron microscope (SEM), it was found to be a uniform fine powder with a particle size of approximately 0.3 μm.

Lead oxide (PbO) for 96.2600g of this powder
223.2000 g was wet mixed using acetone and then fired at a temperature of 780° C. for 1 hour to obtain a lead-containing oxide powder. This powder is the result of scanning electron microscopy observation.
It was a fine powder with extremely uniform particle size of about 0.3 μm.

Furthermore, an impurity analysis revealed that the metal impurities were 10 ppm or less, indicating high purity.

This fine powder is used to evaluate the reactivity of this powder.
3.0 g was formed into a disk shape with a diameter of 20 mm at a molding pressure of 1000 Kg/cm ² and sintered at a temperature of 1150° C. for 1 hour.

As a result, the sintered density was 7.94 g/cm ³ , and a sintered body having approximately the theoretical density was obtained.

Comparative Example 1 Heat treatment was carried out under the same conditions as in Example 1 except that the hot water treatment at a temperature of 350°C was not performed. The chlorine content of the obtained powder was determined by the method of Example 1 and was found to be 320 ppm, which revealed that it contained a larger amount of chlorine impurities than in Example 1. This shows that the hydrothermal treatment is effective in removing chlorine impurities.

Example 2 Zr, Ti, Mg, Mn and Nb used in Example 1
In addition, the metal concentration of 1.01 mol /
A solution was prepared by mixing strontium chloride aqueous solutions such that the atomic ratio of Zr:Sr was 0.125:0.05.

As a result, Zr, Ti,
A heat treated powder containing Mg, Mn, Nb and Sr was obtained.

Similarly to Example 1, no chlorine was detected in this powder.

The obtained powder was a fine powder with a uniform particle size of about 0.3 μm.

Lead monoxide (PbO) for 101.441g of this fine powder
After wet mixing 212,0400 g with acetone, the mixture was fired at a temperature of 780° C. for 1 hour to obtain a lead-containing oxide fine powder.

The properties of this powder were almost the same as in Example 1.

Example 3 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 combined.
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.

Separately, an acidic solution of Nb with a metal concentration of 0.583 mol/metal was prepared using the precipitation of niobium hydroxide, and the particle size of the particles in the acidic solution of niobium was 0.2 μm.
A homogenizer was used to suspend and disperse a certain amount of magnesium oxide powder so that the atomic ratio of Nb:Mg was 2:1 to obtain a suspension containing Nb and Mg.

Next, the solution containing Zr, Ti, Mn and Nb, Mg
A suspension containing Mg:Mn in an atomic ratio of 20:1 was dropped into a precipitation tank maintained at pH 7 using 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 resulting slurry was filtered, and the resulting precipitate was dried at a temperature of 80° C., crushed, and then treated with hot water under the same conditions as in Example 1 to obtain a powder.

Similarly to Example 1, no chlorine was detected in this 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 (PbO)
223.2000g 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.

(Effects of the Invention) The present invention provides a method for producing a lead-containing oxide fine powder, in which a solution or suspension containing various metals and halogens to constitute the lead-containing oxide is reacted in the presence of a precipitant. By treating the obtained precipitate with hot water, impurities such as halides are removed at 200 to 450℃.
The conventional cleaning process can be omitted or simplified, and a high-purity powder can be obtained by subsequent heat treatment, which can be further reacted with a lead compound to obtain a high-purity powder. This method has the advantage that lead-containing oxide fine powder of 100% can be obtained.

Claims (1)

[Claims] 1. In producing the lead-containing oxide fine powder, (a): A solution or a suspension containing various metals and halogens to constitute the lead-containing oxide is reacted with a precipitant under stirring. (b): The precipitate obtained in the above step is heated to a temperature of 200 to 450°C.
(c): Adding and mixing lead compound powder to the powder obtained in the above step; (d): In the above step, The resulting powder mixture is heated to a temperature of 600~
A method for producing high-purity lead-containing oxide fine powder, characterized by combining each step of firing at 1000°C.