JP3412186B2 - Preparation of composite perovskite oxide powder - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing composite perovskite type oxide fine powder. More specifically, the present invention relates to a method for producing a complex perovskite type oxide which has high surface activity and is easily sintered and fine.

[0002]

2. Description of the Related Art With the recent miniaturization of electronic equipment, there is a strong demand for miniaturization of electronic components, and the demand for miniaturized monolithic ceramic components is increasing year by year. In order to meet these needs, fine powders that can be sintered at low temperature and that are homogeneous are required. The powder produced by the conventional method has problems such as coarse particle size, lack of homogeneity, and high firing temperature, and is not fully satisfactory. There are numerous proposals for the method for producing the lead-containing composite perovskite type oxide powder, which are roughly classified as follows. Oxide solid phase method A method in which the oxides, carbonates, etc. of the constituent elements are mixed and calcined in the solid phase to obtain raw material powder. Coprecipitation method pH of mixed aqueous solution containing water-soluble compound of element
Is adjusted to coprecipitate each hydroxide, and the coprecipitated oxide is calcined to obtain a raw material powder. Organic metal method A method for obtaining a raw material powder by calcination of a precipitated powder produced by thermal decomposition or hydrolysis of an organic solvent containing an alkoxide of a component element and an organic solvent-soluble compound.

[0003]

The oxide solid phase method is a method that can inexpensively produce raw material powders having various compositions, and is a method that is widely used industrially. Has a large particle size, a wide particle size distribution, and different particle shapes, so that the formability and sinterability during porcelain production are poor, and it is difficult to obtain a high density porcelain. In this method, a pyrochlore phase is produced as a by-product, and a composite perovskite single phase is not formed,
It is necessary to calcine at high temperature to eliminate this by-product phase. Therefore, the generated powder becomes a powder having low surface activity, so that it does not sinter unless it is fired at a high temperature. Since firing is carried out at a high temperature, there are many inconveniences such as composition deviation due to evaporation of lead during firing. Moreover, it is very impossible to uniformly disperse the raw material powder at the molecular level. Further, since the raw material powder produced is coarse, mechanical pulverization becomes necessary to make it usable. There is also a problem of mixing impurities from this crushing process.

The coprecipitation method is a method for relatively easily obtaining a raw material powder having a uniform particle shape and particle size, and is also used industrially. However, in this method, the solubility product of the hydroxide varies depending on the type of metal element,
It is difficult to produce stoichiometrically controlled coprecipitated hydroxides for various compositions. Since the pH regions which are precipitated as hydroxides of the constituent elements are different, the hydroxides of the constituent elements are generated in the ascending order of pH, so that not all elements are generated at the same time. Therefore, in this method, the dispersibility is improved as compared with the oxide solid-phase method, but rather than coprecipitation, the hydroxide precipitates of the respective elements are mixed in a fairly uniformly dispersed state. Therefore, even with this method, it is impossible to perform uniform dispersion at the molecular (atomic) level. The dried cake obtained by this method after washing and dehydration is a densely aggregated mass. Therefore, the agglomerates are in a state close to sintering that is not easily crushed in the calcination step. Therefore, it is difficult to obtain a fine oxide powder only by performing a simple pulverization process. As with the oxide solid-phase method, a crushing device with large energy must be used, and the problem of mixing impurities cannot be avoided. Therefore, this method is not good.

The organometallic method is a method for obtaining a highly sinterable powder having a small particle size of the oxide powder to be produced and a uniform stoichiometric composition with a uniform particle shape.
This method is widely used in laboratories to synthesize powders of standard composition. However, the raw material alkoxide is extremely expensive, it is impossible to synthesize an organic solvent-soluble alkoxide depending on the metal species, or there are many points such as lead alkoxide that is extremely harmful, Not an industrial method. Also, alkoxides are very sensitive to moisture and are therefore very difficult to handle. In order to carry out the reaction, it is necessary to consider a device considering the humidity in the atmosphere, which makes the device itself expensive.

[0006]

Means for Solving the Problems As a result of intensive research for solving the above-mentioned problems, the present inventors have found that the surface of a surface of a precursor compound is treated by heat-treating an acidic precursor solution containing a raw material compound, tartaric acid and hydrogen peroxide. The inventors have found that a highly active and easily sinterable composite perovskite type oxide can be economically obtained, and have completed the present invention.

That is, the present invention contains a lead compound, a Me compound (Me is at least one metal element selected from the group of divalent metals), a titanium compound, a zirconium compound, a niobium compound, tartaric acid and hydrogen peroxide. A general formula: Pb (Me _1/3 Nb _2/3 ) O ₃ -Pb (ZrxTi _1- x) O ₃ (wherein Me is divalent) The present invention provides a method for producing a composite perovskite type oxide powder represented by the formula: at least one metal element selected from the metal group, and the range of x is 0 ≦ x ≦ 1.

The lead compound used in the present invention is lead acetate,
Lead nitrate, lead carbonate, basic lead carbonate, basic lead acetate, lead hydroxide, lead oxide and the like can be used. As the titanium compound, titanium tetrachloride, titanyl oxynitrate, titanium isopropoxide and the like can be used. As the zirconium compound, zirconium oxynitrate, zirconium chloride, zirconium oxyacetate, zirconium hydroxide, zirconium carbonate, zirconium nitrate or the like can be used. As the niobium compound, niobium hydroxide or niobium oxide can be used. As the Me compound, an acetate salt of at least one metal element selected from the group of divalent metals represented by Me, particularly a basic acetate salt (eg, basic zinc acetate),
Inexpensive compounds such as chlorides, nitrates, carbonates, especially basic carbonates (eg basic zinc carbonate, basic nickel carbonate, basic magnesium carbonate) can be used. Me
Is preferably selected from the group of divalent metals consisting of Mg, Ni, Zn and Co.

In the present invention, each raw material compound is used in a proportion corresponding to the desired composition of the composite perovskite type oxide powder. Tartaric acid is usually used in a molar amount of 1 to 3 times the total molar number of Ti and Nb constituting the composite perovskite compound. Preferably, a molar amount of 1.5 to 2 is suitable. The hydrogen peroxide solution is usually used in a molar ratio of 4 to 8 with respect to the total molar number of Ti, Zr and Nb. Preferably, 5 to 6 times is appropriate. Pure water is used as the solvent of the precursor solution. Besides, those containing organic solvents such as ethanol and methanol can be used. The pH of the precursor solution is usually adjusted to 3 or less.
For adjusting the pH, nitric acid, acetic acid, hydrochloric acid or the like is used, and preferably nitric acid is used.

The heat treatment of the precursor solution is preferably 650.
Perform at ~ 750 ° C. The heat treatment is preferably carried out by blowing the precursor solution into a heating cylinder heated to 650 to 750 ° C. in a mist form from a two-fluid nozzle and thermally decomposing it. Alternatively, the precursor solution may be atomized by a two-fluid nozzle or an atomizing method into a heating cylinder heated to 100 to 200 ° C. to obtain dry fine particles, and the fine particles may be calcined at 650 to 750 ° C. Good. Further, the obtained composite perovskite type oxide may be further subjected to a secondary heat treatment in order to obtain powder characteristics suitable for the purpose of use. Further, particularly when at least one compound other than Pb used as a raw material is a chloride, for example, when NiCl ₂ and ZnCl ₂ are used, it is preferable to use the precursor solution in a state of being heated to 40 to 60 ° C. .

[0011]

EXAMPLES The present invention will be described in more detail with reference to Examples and Comparative Examples, but the present invention is not limited thereto. Example 1 0.2 mol of lead nitrate was dissolved in 200 cc of pure water, 0.0266 mol of nickel acetate was dissolved in 100 cc of pure water, 0.073 mol of zirconium oxynitrate was dissolved in 100 cc of pure water, and titanium isopropoxide was 0.047 mol. Was added to 150 cc of nitric acid acidic solution containing 6.5 cc of hydrogen peroxide solution (concentration of 30%) to prepare a stable complex solution, and then niobium hydroxide of 0.
A stable complex solution of perniobic acid is prepared by adding 05332 mol, 0.15 mol of tartaric acid, 42 cc of hydrogen peroxide solution and 100 cc of pure water. The prepared solutions of each of the above elements were mixed, and pure water was added to 1000 cc to prepare a transparent orange-red precursor solution. This precursor solution is 700
1200 hours per hour into a vertical pyrolysis furnace prepared at ℃
The target composite perovskite type oxide powder was obtained by spraying in a mist at a speed of cc and conducting thermal decomposition. After being blown into the vertical pyrolysis furnace, the residence time in the 700 ° C. zone is about 1 minute. XRD analysis and specific surface area of the obtained oxide powder
(SS) measurement was performed. From the XRD analysis results, the perovskite production rate and the pyrochlore production rate were calculated. The analysis results are shown in FIG. 1 and Table 1.

Comparative Example 1 Lead oxide, titanium oxide, zirconium oxide, nickel oxide and niobium oxide were accurately weighed, mixed and ground, and calcined at 700 ° C. for 10 minutes so that the composition was the same as that of the example. A composite perovskite type oxide powder of was obtained. Analysis was performed as in the example. The results are shown in FIG. 2 and Table 1.

[0013]

[Table 1]

As is clear from the results shown in Table 1 and FIGS. 1 and 2, the composite perovskite type oxide synthesized by the method of the present invention has a higher perovskite generation rate than the powder synthesized by the conventional method and has a fine surface. Clearly, it is a highly active powder. In the conventional method, the reaction did not proceed even though the heating time at 700 ° C. was 10 minutes, and the starting materials of lead oxide, titanium oxide, and zirconium oxide remained as they were. On the other hand, in the method of the present invention, the reaction progress rate is 9 even though the heating time at 700 ° C. is as short as 1 minute.
It is obvious that the method is highly reactive with 0%.

[0015]

The dispersibility of the constituent elements in the oxide solid phase method is not limited to the above, and in the coprecipitation method, all of the constituent elements are not generated instantaneously at the same time, but in order of decreasing pH region. Since there is a problem of uniform dispersion at the atomic level because it precipitates, in the present invention, a mixed solution in which all the elements constituting the complex perovskite type oxide are uniformly dispersed at the ion level in the form of ions, Since it is instantly solidified directly by spray roasting or spray drying, all elements can be uniformly dispersed at the molecular level, and the problem of uniform dispersion of constituent elements is solved. Further, the Ti ion is very unstable and has a property of hydrolyzing to form titanium oxide and precipitate in the heated state (50 to 60 ° C.). However, in the present invention, a stable complex is formed in the coexistence of hydrogen peroxide and tartaric acid. Even if it is formed and heated, it does not cause hydrolysis and is stably present as ions to maintain the state of the uniformly dispersed mixed solution. Also,
Nb does not exist in a stable solution state, but coexistence of tartaric acid and hydrogen peroxide made it possible to make Nb stable in the state of niobate peroxide ion. Therefore, T of the unstable element in question
All the constituent elements including i and Nb can be solubilized, and all the constituent elements can be maintained in a uniformly dispersed state at the molecular level. On the other hand, in the washing process in the precipitation method, there is a problem of composition deviation due to dissolution of the precipitate, but in this method spray roasting and spray drying methods are used and there is no loss due to dissolution, so there is no loss due to dissolution It is possible to obtain oxide powder. Further, the present invention does not require neutralization treatment of the waste liquid after the reaction necessary for the precipitation method or aerobic treatment for BOD countermeasures, so that the cost for these pollution countermeasures is not required and the cost can be reduced.

Further, since an expensive organometallic compound such as alkoxide or acetylacetonate is not used, the desired composite perovskite type oxide powder can be produced at low cost. Further, in the present invention, since the thermal decomposition reaction is carried out by spray roasting, the particle size is 1/2 or less of the sprayed droplets, and the miniaturization by self-breakdown during thermal decomposition works as a synergistic effect. It has made it possible to obtain extremely fine composite perovskite oxide powder. Therefore, the pulverization step for miniaturization of the conventional method is unnecessary. Therefore,
It solves the problem of impurities coming from the conventional grinding process. As is clear from the above description, according to the present invention,
Provided is an economical method for producing a complex perovskite type oxide powder which is fine, easily sinterable and has high surface activity.

[Brief description of drawings]

FIG. 1 is an XR of an oxide powder synthesized by the method of the present invention.
D shows the analysis results.

FIG. 2 XRD of oxide powder synthesized by conventional method
The analysis results are shown.

─────────────────────────────────────────────────── ─── Continuation of the front page (56) Reference JP-A-3-199123 (JP, A) JP-A-2-307825 (JP, A) International publication 91/002697 (WO, A1) (58) Fields investigated (Int.Cl. ⁷ , DB name) C01G 1/00-57/00 C04B 35/626

Claims (7)

(57) [Claims] 1. An acidic precursor containing a lead compound, a Me compound (Me is at least one metal element selected from a divalent metal group), a titanium compound, a zirconium compound, a niobium compound, tartaric acid and hydrogen peroxide. General formula: Pb (Me _1/3 Nb _2/3 ) characterized by heat-treating body solution
O ₃ -Pb (ZrxTi _1- x) O ₃ (in the formula, Me is at least one metal element selected from the group of divalent metals, and the range of x is 0 ≦ x ≦ 1). Method for producing composite perovskite type oxide powder. 2. The method according to claim 1, wherein the divalent metal group comprises magnesium, nickel, zinc and cobalt. 3. The manufacturing method according to claim 1, wherein the heat treatment temperature is 650 to 750 ° C. 4. The method according to claim 1, wherein the pyrolysis is performed by spray roasting. 5. The precursor solution is supplied from a two-fluid nozzle at 650 to 650.
The manufacturing method according to claim 4, wherein the powder is blown in a mist into a heating cylinder heated to 750 ° C. for thermal decomposition. 6. The method according to claim 1, wherein the precursor solution is spray-dried and then calcined. 7. The precursor solution is sprayed into a heating cylinder heated to 100 to 200 ° C. in a mist state by a two-fluid nozzle method or an atomizing method to obtain dried fine particles, and the fine particles are heated to 650 to 650.
The manufacturing method according to claim 6, wherein calcination is performed at 750 ° C.