KR100523960B1 - Method for preparing (Pb(Fe1/2Nb1/2)O3) powders using liquid columbite under supercritical fluid condition - Google Patents

Abstract

The present invention relates to a method for producing a ferroelectric ferro-buscate lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) powder, and more specifically, to a liquid colombite method under a supercritical fluid state. A method for producing a perovskite lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) powder for an electronic material having a lobite crystal structure. The perovskite lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) powder according to the present invention is a Pb-Fe-based colloid in a double reaction vessel for a liquid columbite method. The reaction mixture of Pb compound, Fe compound and ethanol is added for the bite synthesis, the reaction mixture of Nb compound and ethanol is added to the outside of the double reaction vessel and reacted, and the electrical properties are prepared by the method according to the present invention. It is possible to prepare a direct crystalline ferrocusphate lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) powder without formation of a secondary reaction pyrochlore phase which significantly lowers the amount of .

Description

     Method for preparing (Pb (Fe1 / 2Nb1 / 2) O3) powders using liquid columbite under supercritical fluid condition} under supercritical fluid conditions

The present invention is a secondary product pyrochlore which is an intermediate product that lowers the electrical properties when synthesizing a perovskite lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) powder widely used as an electronic material. The liquid columbite method, which suppresses the production and synthesizes ternary functional ceramic powders in one reaction, has been proposed.

A double reaction vessel was installed inside the autoclave to synthesize the Pb-Fe compound inside the double reaction vessel, and the Nb compound was separated and reacted to inhibit the Nb-based pyrochloro phase reaction. A bussky lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) powder was prepared.

Synthesis of an oxide having a Pb-base complex perovskite structure produces an intermediate product pyrophase that is poorly decomposed due to the high reactivity of the Nb-based compound. In order to prevent this, the liquid colombite method using supercritical fluid reaction was developed to propose a new technique for preparing powder for samsung system.

The present invention is a ferro-busky type lead-based composite oxide (Pb (Fe_1/2Nb_1/2) O₃) The present invention relates to a method for producing a powder, and more particularly, to a perovskite lead-based composite oxide (Pb (Fe) for an electronic material having a perovskite crystal structure using a liquid colombit method under a supercritical fluid state._1/2Nb_1/2) O₃) It relates to a method for producing a powder.

In the composite perovskite structure having A (B'B ") O ₃ type, B 'and B" are alternately positioned at the corners of eight perovskite unit cells to form a large cubic unit cell. In general, these compounds have a structure that makes up the rules of A (B ′ _1/2 B ″ _1/2 ) O ₃ and A (B ′ _2/3 B ″ _1/3 ) O ₃ . Where B 'is a low valence cation such as Mg ²⁺ , Fe ³⁺ , Ni ²⁺ , Sc ³⁺ , Zn ²⁺ , and B ″ is a high valence cation such as Nb ⁵⁺ , Ta ⁵⁺ , W ^6+, etc. The structure of the composite perovskite is shown in FIG.

Recently, studies on the production of fine powders for electronic ceramics have been conducted on how to achieve the reliability of ceramic sintered bodies, and the perovskite-based dielectrics used for them in accordance with the rapid progress of high performance and miniaturization in electronic ceramics. There is an increasing demand for raw material powders such as ferrite-based magnetic materials to be adapted to high performance. Reliability represents the improvement of the process, and the material needs to be improved for homogeneity and reproducibility of the sintered body. It is the microstructure that influences the physical properties of the material, and in order to improve it, it is important to remove defects after sintering, but it is practically impossible and control of the molding process is important because the cause comes from the molding process. The preparation of the powder is also of great importance as it is highly dependent on the physical properties of the powder.

Preferred raw material powders for electronic ceramics include (1) high purity, (2) chemically homogeneous, (3) densified primary particles and homogeneous structure, and (4) primary particles. Small particle size, (5) good particle size distribution, and (6) spherical shape are required. In order to cope with this, a lot of solid phase methods and wet chemical techniques have been studied. .

On the other hand, the production method of fine powder is divided into two, the first is a mechanical size reduction process (size reduction process), which is a method of finely dividing the first large lump using a ball mill. This is mainly aimed at breaking the aggregation and controlling the particle size distribution. Furthermore, the grinding increases the surface energy of the powder, but when the particle size is somewhat small, the grinding energy changes the properties of the powder. When the powder is prepared by a solid phase reaction, which is a commonly used method, the composition becomes chemically heterogeneous, and mechanical grinding is used to effectively produce particles having a diameter of 1 μm or less.

The second method is a particle growth process, which is a method of growing a very small particle, which is a reaction involving a liquid phase, which forms particles by nucleation and growth in ions and molecules, That is, it is easy to make ultra-fine particles of less than 1㎛ according to the control of the production conditions by the wet chemical method, and the particle size distribution can be controlled.

In the wet chemistry method in which the liquid phase is involved in the second manufacturing method, to obtain a powder in solution, a precipitant is added to obtain a precipitate, and then pyrolyzed to obtain powder. The precipitate thus obtained is different in composition due to the difference in reactivity unlike in the solution state. In addition, because the powder obtained is amorphous, the particles grow during heat treatment or partial sintering, which adversely affects the physical properties of the powder.

Since the discovery of ferroelectric BaTiO ₃ in 1940, ceramic capacitors have been demanding miniaturization and diversification of products due to the rapid development of the electronics industry. In particular, research has been actively conducted on multilayer multilayer capacitors with smaller capacitance and higher capacitance than monolayer type. have. Such dielectric material is BaTiO _3, SrTiO _3, CaTiO ₃ there coming alkaline earth titanate material such as is commonly used by these materials, so have to use more than 1300 ℃ sintering temperature, Pt, Pd or expensive internal electrode in these alloys The substance must be used.

In order to improve these economic problems, research on low-temperature sintering by adding sintering aids such as LiF to BaTiO ₃ has been conducted, but the sintering temperature could be lowered by about 100 ~ 300 ℃, but the dielectric properties were significantly lowered. This remained.

In the two aspects of low temperature sintering and dielectric improvement, composite perovskite structure oxides represented by the general formula of A (B'B ") O ₃ have been actively developed as multilayer ceramic capacitor materials. Sky oxide having a crystal phase agent they have been already widely used as a known BaTiO _3, because of the properties of a high dielectric constant and low-temperature sintering as compared with the multilayer capacitor and the LC filter material or the like. Pb (Mg _1/3 Nb _2/3) O ₃ , Commonly known Pb-based composite perovskite oxides, such as Pb (Zn _1/3 Nb _2/3 ) O ₃ and Pb (Fe _1/2 Nb _1/2 ) O ₃ , are directly derived from the oxides in the manufacturing process. An intermediate, pyrochlore phase is formed, which is not prepared. In addition, these oxides are difficult to control the precise phase due to the volatilization of PbO, and in particular, the formation of an intermediate phase such as a pyrochloro phase significantly reduces the dielectric constant, making it difficult to manufacture.

In order to suppress the formation of the pyrochloro phase, various methods such as the columbite method, the sol-gel method, the pechinis method and the citrate method have been proposed. In addition to the incorporation of impurities, PbO volatilization during the calcination process is so severe that the composition is not stoichiometric, and the reaction process is complicated to control the process, making it difficult to apply to small electronic components such as multilayer capacitors. have. Wet chemistry, such as the sol-gel method, has been studied in order to improve the problems of the solid state reaction method. The sol-gel method has been widely studied because it can control the volatilization of PbO relatively well, the composition can be easily controlled in a wide range, the reproducibility is excellent, and the cost of the device is relatively low, but the powder produced is amorphous. As a result, it is necessary to heat-treat to obtain crystalline, so that the crystallization characteristics are greatly influenced by drying conditions and heat treatment conditions in the process, and it has a disadvantage that it contains many organic substances. It will adversely affect the physical properties. Therefore, there is a need for a new process to improve these problems.

Supercritical fluid is a single fluid phase that is neither a liquid phase nor a gas phase, and has advantages such as liquid phase reactivity and gas phase permeability, low viscosity, and high solute diffusion coefficient. By using the characteristics of the supercritical fluid with such a fast reaction rate, and separating the reaction vessel under such a supercritical fluid state, it is possible to suppress the formation of a highly reactive pyrochloro phase at a low temperature, while maintaining a high purity and fine crystalline ferrobuskite type. Lead Composite Oxides (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) The powder can be obtained in a relatively simple way.

As a result, high performance and miniaturization of electronic ceramics leads to perovskite lead-based composite oxides (Pb (Fe _1/2 Nb _1/2 ) O ₃ ). There is a need for new methods of manufacturing that improve the disadvantages of the prior art in preparing powders.

The object of the present invention is that the manufacturing process is simpler than the powder prepared by the conventional solid phase reaction method, the colombite method, the sol-gel method, the oxalate method, and the direct crystalline at low temperature while suppressing the formation of the pyrochloro phase. Excellent perovskite lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) It is to provide a method for producing a powder.

The production method of the present invention for achieving the above object is a perovskite lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) by the liquid colombit method in a supercritical fluid state A method for preparing a powder, comprising the steps of: providing a double reaction vessel in an autoclave, a reaction mixture of Pb-Fe compound and ethanol, and a reaction mixture of Nb compound and ethanol; And separating and adding the reaction mixture to the outside and inside of the double reaction vessel in the autoclave and performing supercritical reaction for 2 hours or more at a reaction temperature of 243 ° C., which is a supercritical state of ethanol.

Oxides having a Pb-base composite perovskite structure are widely used as MLCC materials due to high dielectric constant and low firing temperature, but have a disadvantage in that an intermediate phase of pyrochloro is produced when prepared by the solid phase synthesis method. Pb (Fe _1/2 Nb _1/2 ) O ₃ , Pb (Mg _1/3 Nb _2/3 ) O ₃ , Pb (Zn _1/3 Nb _2/3 ) O ₃ , Pb (Ni _1/3 Nb Pb-base composite oxides, such as _2/3 ) O ₃ , form a pyrochloro phase during calcination, which causes a decrease in the final electrical properties.

The Columbit method is a solid state reaction, which is accomplished by double calcination. First, the Pb compound and the Fe compound are calcined to first form a colombite phase for transferring to the perovskite structure, and then the formed colombite phase and the Nb compound are mixed and calcined again to form a perovskite lead-based composite oxide (Pb ( Fe _1/2 Nb _1/2 ) O ₃ ) Prepare a powder. Incorporation of impurities in these two calcination processes can be made, and the cost of calcination at high temperatures is also high.

On the other hand, in the liquid colombite method, a mixture of Pb and Fe compounds for forming a colombite phase in a double reaction vessel with the use of a highly reactive supercritical fluid reacts with an Nb compound inside and outside. The highly reactive Nb compound reacts with PbFeO ₅ on the columbite formed inside together with the supercritical fluid to form ferro-buskite-type lead-based complex oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) in the inner container. Since the powder is produced, the direct crystalline ferrobussky lead-based complex oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) is suppressed while suppressing formation of the secondary phase pyrochloro phase at a low temperature. Powders can be prepared.

Hereinafter, the present invention will be described in more detail.

The liquid colombite method in a supercritical fluid state causes synthesis reaction and crystallization by the action of heat and pressure of a high-temperature solvent, but fine grains can be obtained because it does not grow grain more than necessary. In addition, the particles are dense, the composition and structure are uniform, hardly agglomerate, and close to the ideal conditions for ceramic powder. Under such a supercritical fluid state, the liquid colombite method is suitable for preparing microcrystals without calcining and pulverizing in preparing Pb-based composite perovskite-based powder having an A (B'B ") O ₃ structure. Crystalline powders can be prepared directly without formation of the merchant pyrochloro phase.

Supercritical fluid is defined using the apparatus of FIG. 1 as a condensed gas state that exists at conditions above the critical temperature and pressure of each material. Supercritical fluids are liquid or gaseous, not a single fluid phase, and have all the advantages of liquid phase reactivity and gas phase permeability, low viscosity, no surface tension, and high solute diffusion coefficient. The critical conditions of fluids usable in the present invention are listed in Table 1 below.

Table 1.

Fluid Boiling Point (℃) Critical temperature (℃) Critical pressure (atm) ^* Critical density (g / cm 3) Methanol 64.6 239.4 79.9 0.272 ethanol 78.3 243.0 63.0 0.276 1-propanol 97.2 263.5 51.0 0.275 2-propanol 82.2 235.1 47.0 0.273

* 1 atm = 1.013 × 10 ⁵ Pa

The critical density (= 0.276 g / cm 3) of ethanol, which is widely used in laboratory reactions, is about one third of the liquid density (= 0.796 g / cm 3) (see Table 1).

In general, the reaction rate is closely related to the mobility of solute molecules. The mobility of the solute in the general solution state is 10 ^-5 cm 2 / sec, which has no significant relationship with temperature. However, when the supercritical fluid state exceeds the critical temperature and the critical pressure of the solvent, the mobility of the solute molecules is increased up to 100 times from 10 ^-4 to 10 ^-3 ㎠ / sec. Complementary crystalline powder can be obtained directly.

Taking advantage of the supercritical fluid and separating the reaction vessel in a supercritical fluid state as shown in FIG. 2, a mixture of the Pb compound and the Fe compound is placed in the reaction vessel, and the Nb compound is separated from the reaction vessel. A liquid colombite reaction is carried out.

In the present invention, a perovskite lead-based composite oxide having a Pb-based composite perovskite crystal structure of A (B'B ") O ₃ structure using a liquid colombite method under a supercritical fluid state which has not been tried so far ( Pb (Fe _1/2 Nb _1/2 ) O ₃ ) The new manufacturing process for making powder is established.

As described above, the method according to the present invention provides a reaction mixture of a Pb compound, a Fe compound and ethanol, a reaction mixture of an Nb compound and ethanol, and the reaction mixture is introduced into the inside and the outside, respectively, and then reacted at 243 ° C. Supercritical reaction for at least 2 hours at temperature. At this time, the Pb compound, Fe compound, and Nb compound used in the present invention are mixed so that the molar ratio of Pb: Fe: Nb to react is 1: 0.5: 0.5.

In addition, in order to find the supercritical fluid state of ethanol used as a supercritical fluid in the present invention, it is important to adjust the amount of ethanol to 1.75 times the theoretical value (≒ 150cc) to maintain the ethanol supercritical fluid state.

In the supercritical fluid state in which the present invention is carried out, the liquid colombite method has a reaction temperature of 243 ° C. or more and a reaction time of 2 hours or more. In addition to excellent pyrochloro-phase suppression, crystalline ferrocusphite-type lead-based complex oxides (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) Powder may be produced.

The Pb compound used in the present invention is not particularly limited, and in particular, lead acetate (Pb (CH ₃ COO) ₂ ), lead acetate trihydride ((OCH ₃ O) ₂ Pb.3H ₂ O) lead butyrate (Pb ( C ₄ H ₇ O ₂ ) ₂ ), lead hydroxide (3PbO.H ₂ O), lead lactate (Pb (C ₃ H ₅ O ₃ ) ₂ ), lead oxalate (PbC ₂ O ₄ ) and lead tetra Preference is given to any compound selected from the group consisting of acetate (Pb (CH ₃ COO) ₄ ).

In addition, the Fe compound is not particularly limited, in particular, iron acetate ((CH ₃ CO ₂ ) ₂ Fe), iron acetylacetonate ((CH ₃ COCH = COCH ₃ ) ₃ Fe), iron oxalate dihydrate (FeC Preference is given to any one compound selected from the group consisting of ₂ O ₄ .2H ₂ O) and iron oxalate hexahydrate (Fe ₂ (C ₂ O ₄ ) ₃ .6H ₂ O).

In addition, the Nb compound is not particularly limited, in particular, niobium ethoxide (Nb (OC ₂ H ₅ ) ₅ ), niobium (II) oxide (NbO), niobium (IV) oxide (NbO ₂ ), and niobium (V) Preferred is any one compound selected from the group consisting of) oxides (Nb ₂ O ₅ ).

The solvent of the supercritical fluid according to the present invention is selected from the group consisting of water, ethanol, methanol, ethylene, propane, propylene, n-butane, isobutane, benzene, 1-propanol, 2-propanol and n-pantan. desirable.

According to one preferred embodiment of the invention, leadacetate trihydrate ((OCH ₃ O) ₂ Pb.3H ₂ O) as a source of Pb, iron acetylacetonate ((CH ₃ COCH = COCH ₃ ) _{3 as} a source of Fe Fe), niobium ethoxide (Nb (OC ₂ H ₅ ) ₅ ) was used as a source of Nb, 2-methoxyethanol was used as a common solvent, and ethanol was used as a solvent of the supercritical fluid. In addition, the autoclave (Autoclave) device as shown in Figure 2 used in the present invention is made of stainless steel to be used at 400 ℃, 300atm (≒ 30.4Mpa) above the critical point of water. When the temperature is raised, the ethanol used as a solvent evaporates and becomes a supercritical fluid state. At this time, hydrolysis is performed using water generated by decomposition of ethanol at high temperature to obtain a powder. As shown in Table 1, the supercritical state of ethanol is at least 243 ° C. and at least 63 atm (≒ 6.4 Mpa).

Therefore, in order to find the supercritical fluid state of ethanol according to the present invention, it is important to adjust the amount of ethanol 1.75 times the theoretical value (≒ 150cc) to maintain the ethanol supercritical fluid state. Powders are prepared by hydrolysis reaction between water and reactant compounds produced in the supercritical fluid state of ethanol and crystallized using the fast reaction rate of supercritical fluid. Directly producing a crystalline powder while inhibiting the formation of the pyrochloro phase.

The present invention will be described in more detail with reference to the following examples and comparative examples, but the scope of the present invention is not limited thereto.

Example 1

99.90% lead acetate [(OCH ₃ O) ₂ Pb], 99.00% iron acetylacetonate [(CH ₃ COCH = COCH ₃ ) ₃ Fe], 99.95% niobium ethoxide [Nb (OC ₂ H ₅ ) ₅ ] Used.

Each starting material was placed in a round flask mixed with a common solvent used to make a stable sol in a glove box in which humidity was controlled to 20% or less in a dry nitrogen gas atmosphere. It was stirred for 1 hour until a stable sol was formed by heating to a temperature to obtain a dispersed sol, the composition of 2-methoxyethanol used as a common solvent with each starting material is shown in Table 2.

Table 2.

Starting material Sheep 2-methoxyethanol Lead acetate 0.008346 16.69 cc Iron acetylacetonate 0.004173 25.04cc Niobium ethoxide 0.004173 41.73cc

The reaction scheme of each sol produced at this time is the same as the following reaction formula (1), (2), (3).

Pb (R'COO) ₂ + 2ROH → Pb (RO) ₂ + 2R'COOH Scheme (1)

Fe (R'COO) (OH) ₂ + 3ROH ↔ Fe (RO) ₃ + R'COOH + 2H ₂ O Scheme (2)

Nb (R "O) ₅ + 5ROH → Nb (RO) ₅ + 5R" OH scheme (3)

R, R 'and R "are alkyl groups

The Pb sol and the Fe sol thus obtained were mixed with 50 ml of ethanol used as a supercritical fluid, and then placed inside the double reaction vessel, and the Nb sol was mixed with 100 ml of ethanol and placed outside the dual reaction vessel. The total amount of ethanol used at this time was 150cc.

After the reaction vessel was placed in an autoclave apparatus, a powder was prepared by maintaining the reaction vessel at a temperature and a pressure of 273 ° C. and 7.3 Mpa for 2 hours.

At this time, the reaction formula in the reaction vessel is the same as the following reaction formula (4).

Pb (RO) ₂ + Fe (RO) ₃ → PbFeO ₅ + 5R Scheme (4)

R, silver alkyl group

In addition, PbFeO ₅ and a reaction scheme of Nb sol disposed outside in the inner container together with ethanol in a supercritical fluid state are shown in the following reaction formula (5).

2 (PbFeO ₅ ) + 10R + Nb (RO) ₅ + 12H ₂ O

→ 2 Pb (Fe _1/2 Nb _1/2 ) (OH) ₆ + 12ROH

¡Æ 2Pb (Fe _1/2 Nb _1/2 ) O ₃ + 12ROH + 6H ₂ O scheme (5)

R, silver alkyl group

The powder produced inside and outside the double reaction vessel was washed with distilled water using a centrifuge, respectively. The washed powder was dried for 24 hours in a dryer at 60 ℃.

As it is shown in Figure 2 as a double reaction inside and outside respectively, the powder obtained in X- ray diffraction device for a container (a) from the inside of the double reactor crystalline ferro booth kite-type lead-based complex oxide (Pb (Fe _1/2 Nb _{1 / 2} ) O ₃ ) It was confirmed that the phase, the amorphous Nb ₂ O ₅ phase from the outside of the double reaction vessel as shown in Figure 2 (b). As a result of measuring each powder generated inside and outside by scanning electron microscope, it can be seen that the inside is spherical with a size of about 0.7-1 μm as shown in Fig. 3 (a). Particle sizes of about 0.7 to 5 μm in each form were confirmed.

Comparative Example 1

99.90% lead acetate [(OCH ₃ O) ₂ Pb], 99.00% iron acetylacetonate from Aldrich [(CH ₃ COCH = COCH ₃ ) ₃ Fe], 99.95% niobium ethoxide from Aldrich Nb (OC ₂ H ₅ ) ₅ ] was used.

A sol for preparing perovskite lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) was prepared using the composition and common solvent as shown in Table 2 of Example 1. After mixing the prepared Pb sol, Fe sol and Nb sol with ethanol used as a solvent of the supercritical fluid, and then removed the inside of the reaction vessel to compare with the liquid colombite method using a double reaction vessel under supercritical fluid After the experiment was put into the reaction vessel.

The total amount of ethanol used at this time was 150cc. After the reaction vessel was placed in an autoclave apparatus, a powder was prepared by maintaining the reaction vessel at a temperature and a pressure of 273 ° C. and 7.3 Mpa for 2 hours. The prepared powder was washed with distilled water using a centrifuge. The washed powder was dried for 24 hours in a dryer at 60 ℃.

It was confirmed that the pyrochloro phase was formed on the dried powder as an X-ray diffractometer as shown in FIG. 5, and as a result of measuring the dried powder with a scanning electron microscope, a spherical particle having a size of about 0.7 to 1 μm as shown in FIG. 6. It was confirmed that the crystalline pyrochloro phase monodispersed.

Hereinafter, the drawings will be described in detail.

Figure 1 is a detailed view of the autoclave used in the present invention, Figure 2 (a) and (b) is an X-ray diffraction graph of barium titanate powder prepared by the liquid colombite method in a supercritical fluid state according to the present invention 3 (a) and 3 (b) show a perovskite lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) prepared by a liquid colombite method under a supercritical fluid state according to the present invention. Electron micrograph of the powder, Figure 4 is a diagram illustrating a perovskite structure, Figure 5 is a comparative example according to the present invention X-ray diffraction graph of the powder prepared under a supercritical fluid state, Figure 6 is a present invention In Comparative Example according to the electron microscope picture of the powder prepared under the supercritical fluid state

As can be seen from the above examples and comparative examples, the ferrobusky type lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) powder prepared by the method according to the present invention is 0.7 to 1 It was synthesized as a uniform spherical crystal of 탆.

Therefore, the ferro-buskite-type lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) powder having such a fine and uniform spherical shape effectively suppresses the formation of a pyrochlore phase as an intermediate phase, while crystalline ferro It is possible to produce a buscote-type lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) powder.

Therefore, the use of the perovskite lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) powder having a uniform spherical shape improves the quality of various related parts used in the electronic and information communication fields. Of course, the production cost of the product can be lowered.

1 is a detailed view of the autoclave equipped with a double reaction vessel used in the present invention

2A and 2B are X-ray diffraction patterns of a perovskite lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) powder prepared by a liquid colombite method under a supercritical fluid state according to the present invention. Analysis graph.

Figure 3a and Figure 3b is a ferro-buscite type lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) prepared by the liquid colombite method in a supercritical fluid state according to the present invention Electron micrograph of powder

4 is a diagram illustrating a perovskite structure.

5 is an X-ray diffraction graph of a powder prepared under a supercritical fluid state as a comparative example according to the present invention.

6 is an electron micrograph of a powder prepared under a supercritical fluid state as a comparative example according to the present invention.

Claims (6)

In the method for producing a perovskite lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) powder by a liquid colombite method in a supercritical fluid state, 0.008346 mol of reed acetate [(OCH ₃ O) ₂ Pb], iron acetylacetonate [(CH ₃ COCH = COCH ₃ ) ₃ Fe] 0.004173 mol, niobium ethoxide [Nb (OC ₂ H ₅ ) ₅ ] 0.004173 mol In a dry nitrogen gas atmosphere, mixed with 2-methoxyethanol 83.46cc and placed in a round flask to make a stable sol in a glove box in which humidity is controlled to 20% or less, and then placed at a temperature of 100 ° C. Heated to stir for 1 hour until a stable sol was formed to obtain a dispersed sol, The Pb sol and Fe sol thus obtained were mixed with 50 ml of ethanol used as a supercritical fluid, and then placed in the interior of the double reaction vessel, and the Nb sol was mixed with 100 ml of ethanol, and then introduced into the exterior of the double reaction vessel. After the reaction vessel was placed in an autoclave apparatus and maintained at a temperature and pressure of 273 ° C. and 7.3 Mpa for 2 hours to prepare a powder, the powder produced inside and outside of the double reaction vessel was washed with distilled water using a centrifuge, respectively. Next, a perovskite lead-based composite oxide (Pb (Fe _1/2 Nb _1/2 ) O ₃ ) by the liquid colombite method in a supercritical fluid state, which is manufactured by drying in a dryer at 60 ° C. for 24 hours. Method for preparing the powder. delete delete delete delete delete