JPH0881219A - Synthesis of lanthanum-based oxide powder having perovskite-type structure - Google Patents

Abstract

PURPOSE: To obtain lanthanum-based oxide powder having perovskite-type structure by heating at a low temperature in good productivity, by preparing a mixed aqueous solution of a water-soluble lanthanum compound and a prescribed water-soluble compound, forming a precursor of an oxide under specific conditions and then heating. CONSTITUTION: A mixed aqueous solution of a water-soluble lanthanum compound (e.g. LaCl3 ) and a prescribed water-soluble compound (e.g. SrCl2 O.H2 O and MnCl2 .H2 O) is prepared. The mixed aqueous solution is blended with a solution of hydrazine to form a precursor of an oxide containing La and a fixed element. Then the precursor is heated at 1,000 deg.C for 15-60 minutes to give oxide [e.g. La1-x Srx MnO3 ((x) is 0.1-0.5)] powder.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention relates to a method for synthesizing a lanthanum-based oxide powder having a perovskite structure.

[0002]

2. Description of the Related Art Lanthanum oxides having a perovskite type crystal structure exhibit high electrical conductivity. As a method for synthesizing this lanthanum-based oxide powder, a solid-phase reaction method has been conventionally known. This method will be described by taking lanthanum strontium manganite (La _1-X Sr _X MnO ₃ ) as an example. First, lanthanum oxide, strontium carbonate, and manganese oxide are put in a ball mill together with ethanol, and pulverized and mixed. After thorough pulverization and mixing, the mixture is dried to evaporate ethanol to prepare a ternary mixture. Next, this ternary mixture is heat-treated at a high temperature of about 1500 ° C. to form La _1-x Sr _x MnO ₃ . However, since only one heat treatment is a chemical reaction (solid-phase reaction), a single-phase La _1-x Sr _x MnO ₃ cannot be obtained. Therefore, the ball mill treatment is performed again to increase the contact area between the particles, and then the heat treatment is performed at a high temperature of about 1500 ° C.
After repeating this a few times, the completely generated La _1-X
Sr _X MnO ₃ is put into a ball mill and pulverized to obtain La _{1 -X} Sr _X MnO ₃ powder having a single phase of perovskite. Therefore, in order to obtain a single-phase La _1-X Sr _X MnO ₃ powder by the solid-phase reaction method, there is a problem that it is necessary to repeat the heat treatment and the pulverization by the ball mill at a high temperature of about 1500 ° C. It was

As another method, a wet method using a metal alkoxide is known. However, in this method, the metal alkoxide is expensive, the manganese alkoxide yield is poor, the synthesis is difficult, and the treatment cost of the waste liquid generated during the synthesis is high, and the manufacturing cost is high. Moreover, it was necessary to perform heat treatment at a temperature of about 1350 ° C. for about 10 hours.

Therefore, an object of the present invention is to solve the above problems and to provide a method for synthesizing lanthanum-based oxide powder which is excellent in productivity and is inexpensive in manufacturing cost.

[0005]

In order to solve the above problems, the method for synthesizing a lanthanum-based oxide powder having a perovskite structure according to the present invention comprises (a) a water-soluble lanthanum compound and a predetermined water-soluble compound. Of preparing a mixed aqueous solution of a polar compound, (b) adding a hydrazine solution to the mixed aqueous solution to prepare a precursor of an oxide containing lanthanum and a predetermined element, and (c) heating the precursor. And a step of producing an oxide powder.

By the above method, lanthanum-based oxide powder having a perovskite type structure can be produced by using inexpensive hydrazine without repeating grinding by a ball mill. The heat treatment temperature is also the conventional temperature (about 1350 to about 1350).
Lower temperature (about 1000 ° C) than 1500 ° C is required, and production cost can be reduced.

[0007]

EXAMPLES Examples of producing a lanthanum-based oxide powder having a perovskite structure according to the present invention will be described below with reference to the accompanying drawings. [First Example, FIG. 1] In the first example, lanthanum strontium manganite (hereinafter, referred to as La _1-X Sr _X MnO ₃ ) will be described as an example.

As shown in FIG. 1, lanthanum chloride (LaCl ₃ ) was prepared as a water-soluble lanthanum compound, and strontium chloride (SrC) was combined with this lanthanum compound.
1 ₂ · H ₂ O) and manganese chloride (MnCl ₂ · H ₂ O) are prepared. The desired composition of these three compounds is dissolved in water. This mixed aqueous solution is acidic with a pH of 2.

Next, the hydrazine ((NH ₂ ) ₂ .H ₂ O) solution is added dropwise to the mixed aqueous solution while heating and stirring the mixed aqueous solution. A white precipitate forms as soon as the hydrazine solution is added dropwise. The reason for stirring the mixed solution is to keep the concentration of hydrazine in the solution constant. This white precipitate is almost amorphous powder containing lanthanum strontium and manganese.

Next, 1000 parts of this amorphous precursor are added.
Crystallized perovskite type single phase La _1-X Sr _X MnO ₃ powder (X = 0.1
0.5). Further, by selecting appropriate heat treatment conditions, it is possible to obtain La _1-x Sr _x MnO ₃ powder having a uniform particle size of 0.01 to 20 nm. Therefore, the powder produced according to the present invention is suitable as a high quality ceramic and a starting material for thermal spraying used for forming a film.

In this way, the powder of La _{1 -X} Sr _X MnO ₃ perovskite single phase is efficiently produced. That is, conventional solid phase reaction or wet method (1350-1500)
It can be produced by heat treatment at a temperature lower than (.degree. C.) (1000.degree. C.) for a short time and using inexpensive materials (lanthanum chloride, strontium chloride, manganese chloride and hydrazine) that are easily available. Further, the waste liquid treatment is simpler in the present invention because it uses an aqueous solution than in the conventional wet method using an organic solvent.

The obtained La _1-X Sr _X MnO ₃ powder is chemically stable in a high temperature oxidizing atmosphere and has high electrical conductivity, and therefore, it can be used as an air electrode of a solid oxide fuel cell. Can be used. That is, La _1-X Sr _X
A film can be formed on the surface of a solid electrolyte of yttria-stabilized zirconia (YSZ) by means of thermal spraying using MnO ₃ powder as a starting material to form an air electrode.

[Second Embodiment to Eighth Embodiment] As shown in Table 1, the second embodiment uses lanthanum chloride, calcium chloride, manganese chloride and hydrazine according to the same procedure as in the first embodiment. _{A 1-X} Ca _X MnO ₃ powder was produced. Similarly, the third embodiment uses La _1-X Mg _X MnO using lanthanum chloride, magnesium nitrate, manganese chloride and hydrazine.
_Three powders were produced. The fourth embodiment uses L-lanthanum chloride, strontium chloride, cobalt nitrate and hydrazine to obtain L
An a _1-X Sr _X CoO ₃ powder was produced. In the fifth example, La _{1 -X} Ca _X CoO ₃ powder was manufactured using lanthanum chloride, calcium chloride, cobalt nitrate and hydrazine. Sixth
In the example, La _{1 -X} Mg _X CrO ₃ powder was manufactured using lanthanum chloride, chromium chloride, magnesium nitrate and hydrazine. The seventh embodiment uses La _1-X Sr _X C using lanthanum chloride, strontium chloride, chromium chloride and hydrazine.
An rO ₃ powder was produced. The eighth example uses lanthanum chloride, calcium chloride, chromium chloride and hydrazine to prepare La.
_{A 1-X} Ca _X CrO ₃ powder was produced.

[0014]

[Table 1]

Thus, the single phase La_1-XCa_XMnO₃
Powder, La_1-XMg_XMnO₃Powder, La_1-XSr_XCoO₃
Powder, La_1-XCa_XCoO₃Powder, La_1-XMg_XCrO₃
Powder, La_1-XSr_XCrO₃Powder, La_1-XCa_XCrO₃
The powder is manufactured efficiently. The obtained La_1-XCa_XMn
O₃Powder, La_1-XMg_XMnO₃Powder and La_1-XCa_XC
oO₃Each powder is chemically safe under a high temperature oxidizing atmosphere.
Since these are stable and have high electrical conductivity, these are the starting points.
Solid electrolyte fuel by forming a film by thermal spraying as a raw material
It can be used as the air electrode of a battery. On the other hand, La
_1-XMg_XCrO ₃Powder, La_1-XSr_XCrO₃Powder and L
a_1-XCa_XCrO₃The powder has high temperature oxidation and reduction, respectively.
It is chemically stable in the original atmosphere and has high electrical conductivity.
Therefore, the same method (d
Thick film is formed by the knacker blade method or extrusion method,
Used as an interconnector for solid oxide fuel cells
be able to.

[Other Examples] The method for synthesizing the lanthanum-based oxide powder having the perovskite structure according to the present invention is not limited to the above-mentioned examples, and various applications can be made within the scope of the invention. You can In particular, as the water-soluble lanthanum compound, in addition to LaCl ₃ .H ₂ O, LaN
It may be O ₃ · H ₂ O or the like.

[0017]

As is apparent from the above description, according to the present invention, by adding a hydrazine solution to a mixed solution of a water-soluble lanthanum compound and a predetermined water-soluble compound, lanthanum-based oxidation of a perovskite single phase is performed. The material powder can be efficiently produced at a low production cost. That is, the temperature of the conventional solid-phase reaction method or wet method (1350-1500
It can be heat-treated at a temperature lower than (.degree. C.) for a short time (1000.degree. C.) and can be manufactured using an inexpensive material that is easily available.

Further, the obtained lanthanum-based oxide powder has a uniform particle size, and is suitable for producing high-quality ceramics and forming a film by thermal spraying even with a single perovskite phase.

[Brief description of drawings]

FIG. 1 is a flowchart showing a method for synthesizing a lanthanum-based oxide powder having a perovskite structure according to the present invention.

Claims (1)

[Claims] 1. A step of preparing a mixed aqueous solution of a water-soluble lanthanum compound and a predetermined water-soluble compound, and a step of adding a hydrazine solution to the mixed aqueous solution to prepare a precursor of an oxide containing lanthanum and a predetermined element. A method for synthesizing a lanthanum-based oxide powder having a perovskite structure, comprising: heating the precursor to produce an oxide powder.