JP2866416B2 - Method for producing perovskite-type composite oxide powder - Google Patents

Description

BACKGROUND OF THE INVENTION (FIELD OF THE INVENTION) This invention relates to compounds of the general formula ABO composite perovskite oxide powder represented by _3, especially perovskite rate high, particles with excellent fine sinterability The present invention relates to a method for producing a powder.

(Prior Art) Composite perovskite oxides are widely used as functional ceramics such as piezoelectrics, dielectrics, semiconductors, and sensor materials. Recently, the improvement of functionality or the addition of new functions has been actively promoted, and there has been a demand for reducing the size of particles, improving the uniformity of composition, and imparting low-temperature sinterability to raw material powders.

BACKGROUND ART Conventionally, a solid phase synthesis method and a coprecipitation method have been known as methods for producing a composite perovskite oxide powder. Hereinafter, these methods will be outlined.

(A) Solid-phase synthesis method This method is a method of weighing, mixing and calcining the compounds of each raw material component. This is the most common,
Since it is a high-temperature reaction, there is a disadvantage that the lead component evaporates and the composition tends to be non-uniform, and it is difficult to obtain fine particles. Further, in a system containing Nb, it is difficult to obtain a perovskite single phase by a usual method, and a pyrochlore phase is mixed. Since the pyrochlore phase impairs the sinterability and significantly deteriorates the electrical properties of the sintered body, some measures have been proposed to reduce this phase.

For example, SLSwrartz, TRShrout et al.
In the production of g _1/3 Nb _2/3 ) O ₃ , MgO + Nb ₂ O ₅ → MgNb ₂ O ₆ (calcination temperature about 1000 ° C.) 1 / 3MgNb ₂ O ₆ + PbO → Pb (Mg _1/3 Nb _2/3 It has been reported that a single-phase perovskite phase can be obtained by a two-stage calcination method of O ₃ (calcination temperature of about 900 ° C.). (Mater.Res.Bull. 1
In 7.1245 (1982)) normal stage firing method, by performing repeated firing and crushing, the proportion of the perovskite phase increases, that of the perovskite single phase in this method difficult to obtain.

In any case, the solid phase synthesis method has problems in terms of finer particles and uniformity of composition.

(B) Coprecipitation method In this method, a mixed solution of each component is prepared, and the mixed solution is brought into contact with a precipitation solution such as an alkali to obtain a coprecipitate, which is dried and dried.
It is a method of calcining.

Even in this coprecipitation method, a perovskite single-phase powder is difficult to obtain, and secondary particles are formed during precipitation, drying, or calcination, and the obtained powder has poor sinterability.

As described above, a method for obtaining a powder of Nb-containing lead-based composite perovskite oxide having a single phase of perovskite and easy sintering has not been established, and its development is awaited.

(Problems to be Solved by the Invention) An object of the present invention is to satisfy the sinterability and uniformity in the production of a composite perovskite-type oxide powder containing Nb, which is difficult to obtain a perovskite single phase in the conventional production method. Another object of the present invention is to provide a method for efficiently producing fine powder of single phase perovskite.

(Means for Solving the Problems) The present invention provides a compound represented by the general formula AB comprising the following steps:
The gist is a method for producing a composite perovskite oxide represented by O ₃ .

A step of mixing and reacting a solution containing Nb and a solution containing at least one other component B to form a homogeneous solution of an Nb-B component system.

A step of causing Pb or a solution containing at least one of Pb and another A component to react with an aqueous alkali metal solution in a reaction vessel to form a hydroxide precipitate of Pb or Pb and another A component.

A step of adding the solution generated in the step to the reaction vessel to form a hydroxide precipitate of Nb and the B component.

 A step of causing a hydrothermal reaction in the reaction vessel.

 Filtration, washing and drying.

 The step of calcining and crushing the powder.

Note that A and B in the above general formula ABO ₃ are the following elements, respectively, and O is oxygen.

A: Pb or Pb and at least one kind of Ba, Sr, Ca, La, Li B: Nb and at least one kind of Zn, Mg, Zr, Ti, Ni, Fe, W, Mn Composite represented by this ABO ₃ Some examples of the specific composition of the perovskite-type oxide will be described below. The Pb (Mg _1/3 Nb
_2/3) In addition to O _3, there is something like the following.

Pb (Ni _1/3 Nb _2/3 ) O ₃ , Pb (Zn _1/3 Nb _2/3 ) O ₃ Pb (Mg _1/3 Nb _2/3 ) O ₃ -PbTiO ₃ -PbZrO ₃ , Pb (Fe _1/2 Nb _1/2 ) O ₃ , Pb (Co _1/3 Nb _2/3 ) O ₃ , Pb (Ni _1/3 Nb _2/3 ) O ₃ -PbTiO ₃ -PbZrO ₃ , Pb (Mg _{1 / 3 (} Nb _2/3 ) O ₃ —PbTiO ₃ (Function) FIG. 1 schematically shows the steps of the method of the present invention. The following will be described with reference to this figure.

First Step A solution containing Nb and a solution containing a component B other than Nb are mixed and reacted. The reaction temperature at this time is preferably from 40 to 80 ° C. If the temperature is too low, the reaction is slow, and if it is too high, the evaporation of the solvent (water, alcohol, etc.) increases, which is not good.

The raw material used in this reaction is not particularly limited as long as it is soluble, and is selected from, for example, chlorides, oxychlorides, nitrates, carbonates, hydroxides and acetates, oxalates, alkoxides and the like. . Usually, it is used as an aqueous solution.If it is hardly soluble in water, it may be dissolved using an acid or a suitable solvent.In the case of an insoluble raw material, it can be used as a suspension solution. is there.

Desirable starting compounds include Nb ₂ O, NbCl ₅ , Pb (N
O ₃ ) ₂ , PbO, Mg (NO ₃ ) ₂ , MgCl ₂ , TiCl ₄ , TiO ₂ , NiCl
₂ , Ni (NO ₃ ) ₂ , Fe (NO ₃ ) ₃ , FeCl ₃ , CoCl ₂ , Co (N
O ₃ ) ₂ .

In the first step, it is one of the features of the method of the present invention that the component B of the general formula ABO ₃ is reacted in advance. That is, for the purpose of suppressing the reaction between Pb and Nb that causes the pyrochlore phase, compounds of Nb and other B components are generated before Nb comes into contact with Pb.

Second Step In this step, hydroxide precipitate is formed by reacting Pb or a mixed solution of Pb and another A component with an aqueous alkali metal solution, for example, an aqueous KOH solution.

Third Step In this step, the homogeneous solution of the Nb-B component system produced in the first step is added to the hydroxide precipitate of the Pb-A component system produced in the second step and the aqueous alkali metal solution. The reaction produces a hydroxide precipitate of the Nb-B component system.

In the first step, since the Nb-B component-based compound is generated in advance, the direct reaction between Pb and Nb is suppressed, and therefore, the generation of the pyrochlore phase is eliminated, and a perovskite single phase powder is obtained.

The aqueous alkali metal solution used in the second and third steps is preferably a liquid having a concentration in the range of 1 to 15 mol /. If the concentration is too high, the alkali metal remains in the powder finally obtained, which may have adverse effects such as deterioration of sinterability.

Fourth step This step is a step for causing a hydrothermal reaction. This reaction is preferably carried out at a temperature of 100 to 200 ° C. and a pressure from atmospheric pressure to about 15 atm.

This fourth step is another major feature of the method of the present invention. Even if the fourth step is omitted and the process proceeds to the next fifth and sixth steps, it is difficult to obtain a perovskite single-phase powder. This is believed to be due to compositional non-uniformity.

Fifth Step This step is a step of filtering, washing, and drying the generated precipitate, and the conditions may be ordinary conditions.

Sixth step This is a step of calcining and pulverizing the powder obtained in the fifth step.
The calcination is performed to improve the crystallinity of the powder obtained in the previous step, that is, to increase the ratio of the perovskite phase and adjust the particle size. If the calcination temperature is too low, the effect of calcination is insufficient, and if it is excessively high, the powder becomes coarse and does not become fine even by crushing.
Usually, the range of 500 to 1000 ° C is preferable.

The disintegration is performed in order to reduce the particles coarsened or agglomerated in the calcination to, for example, about 0.5 μm in average particle diameter.

The powder produced through the first to sixth steps has extremely excellent properties as a raw material for producing a functional ceramic such as a piezoelectric or derivative element.

〔Example〕

An example in which a powder of Pb (Mg _1/3 Nb _2/3 ) _0.65 Ti _0.35 O ₃ was produced will be described.

(Step) magnesium nitrate _{[Mg (NO 3) 2 · 6H} 2 O ] was 18.4g water 10
To an aqueous solution dissolved in 0 ml, 31.g of an aqueous solution of titanium tetrachloride (TiCl ₄ ) (Ti content: 16.7%) was mixed and stirred at room temperature for 20 minutes.
A homogeneous solution of magnesium and titanium was obtained. To this solution, 60 ml of an alcohol solution containing 36.9 g of niobium pentachloride (NbCl ₅ ) is added with stirring, and the mixture is reacted at 60 ° C. for 30 minutes to obtain Mg-Ti-Nb
Yielded a homogeneous solution of

(Step) To an aqueous solution in which 140 g of potassium hydroxide (KOH) was dissolved in 300 ml of water, an aqueous solution in which 133.0 g of lead nitrate [Pb (NO ₃ ) ₂ ] was dissolved in 250 ml of water was added. Produced a hydroxide precipitate.

(Step) The homogeneous solution formed in the step was added to the suspension containing the precipitate formed in the step while stirring, and reacted at room temperature for 30 minutes to form a hydroxide precipitate of Mg-Ti-Nb.

(Step) The suspension containing the precipitate was transferred to an autoclave and reacted at a pressure of 8 atm and a temperature of 180 ° C. for 5 hours to produce and precipitate a target oxide.

(Step) The generated precipitate was filtered, sufficiently washed with water at room temperature, and then dried at 120 ° C for 15 hours.

(Step) The powder obtained in the step was calcined in air at 800 ° C. for 2 hours, and was crushed by a ball mill.

The powder obtained by the above process [Pb (Mg _1/3 Nb _2/3 ) _0.65 Ti
_0.35 O ₃ ) is almost a single phase of perovskite and has a particle size of 0.
5 μm, total amount was about 95 g.

FIG. 2 is an X-ray diffraction pattern of the powder obtained by the method of the above example.

As comparative examples, X-ray diffraction patterns of powders produced by a method different from the method of the present invention are shown in FIGS. The manufacturing conditions of this comparative example are as follows.

(Comparative Example 1 FIG. 3) Using PbO, MgO, TiO ₂ , and Nb ₂ O ₅ as raw materials, firing was performed at 1000 ° C. for 1 hour by a general solid-phase method to obtain a powder having the same composition as that of the example. Synthesized. FIG. 3 is an X-ray diffraction pattern of the powder.

(Comparative Example 2 ... FIG. 4) The same raw materials as in the example were not used to carry out the process, but Mg, Nb, and Ti solutions were separately added in the process and synthesized. To obtain a powder. FIG. 4 shows the X-ray diffraction pattern.

(Comparative Example 3 FIG. 5) A powder was produced using the same raw materials as in the example, without performing the steps, and under the same other conditions as in the example. FIG. 5 shows an X-ray diffraction pattern of the powder.

Table 1 shows the particle sizes and perovskite conversion rates of the powders synthesized in the above Examples and Comparative Examples.

From the X-ray diffraction patterns shown in FIGS. 2 to 5, the perovskite conversion rate was determined from the peak intensity I _Pe of the (110) plane of the perovskite.
And Pyrochlore (222) peak intensity I _Py Was evaluated.

Example 1 in Table 1 is the powder obtained in the above example, and Examples 2 to 4 are powders obtained in the same manner and having different compositions.

As is clear from Table 1, the powder obtained in the examples of the present invention is almost a single phase of perovskite, and has a fine particle size of 0.5 μm or less.

In the comparative example, a perovskite single phase powder was not obtained,
In Comparative Example 2 having a relatively small particle size, the perovskite conversion rate is extremely poor.

(Effect of the Invention) The method of the present invention is particularly useful as a component B among the perovskite-type composite oxides of the general formula ABO ₃ whose use is expanding in recent years.
It is suitable for the production of those containing Nb. According to this method,
The formation of a pyrochlore phase is suppressed, and a fine powder of a perovskite single phase can be produced.

The present invention makes a great contribution to the production of ceramic dielectrics, piezoelectrics, and the like having excellent physical properties.

[Brief description of the drawings]

FIG. 1 is a view for explaining the steps of the method of the present invention, FIG. 2 is an X-ray diffraction pattern of the powder obtained in an example of the present invention, FIG. 3, FIG. 4 and FIG. 3 is an X-ray diffraction pattern of the powder obtained in the example.

Claims (1)

(57) [Claims] 1. A general formula ABO ₃ comprising the following steps (where A is: Pb or at least one component of Pb and Ba, Sr, Ca, La, Li; B is Nb, Zn, Mg , Zr, Ti, N
i is a component of at least one of Fe, W, and Mn, and O is oxygen). A step of mixing and reacting a solution containing Nb and a solution containing at least one other component B to generate a uniform solution of Nb and the component B; A step of causing Pb or a solution containing at least one of Pb and another A component to react with an aqueous alkali metal solution in a reaction vessel to generate a hydroxide precipitate of Pb or Pb and another A component. A step of adding the solution generated in the step in the reaction vessel to form a hydroxide precipitate of Nb and B components. A step of causing a hydrothermal reaction in the reaction vessel. Filtration, washing and drying. The step of calcining and crushing the powder.