JP2000044244A - PRODUCTION OF Sr DOPED LANTHANUM CHROMITE POWDER AND INTERCONNECTOR FOR SOLID ELECTROLYTE TYPE FUEL CELL USING SAME - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain Sr doped lanthanum chromite powder of a specified composition capable of firing at a low temp. and excellent in denseness and electronic conductivity by forming a polyester contg. La, Sr and Cr by a complex polymn. method, thermally decomposing it and calcining the resultant powder. SOLUTION: In the complex polymn. method, La, Sr and Cr are highly dispersed in the state of a complex with a complex forming agent such as citric acid, ethylene glycol is added and a finely and highly dispersed polymer is formed by condensation polymn. reaction. This polymer is thermally decomposed by heating at 350-600 deg.C and the resultant powder is calcined at 1,100-1,300 deg.C to obtain the objective Sr doped lanthanum chromite powder having a uniform compsn. represented by the formula La1-XSrX+YCrO3 (where 0<X<0.4 and 0<Y<=0.1). Since the Sr rich compsn. and the complex polymn. method are used in combination, the objective interconnector excellent in denseness and electronic conductivity is obtd. even when the lanthanum chromite powder is fired in the air at 1,400-1,500 deg.C.

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 Sr dopantran chromite powder suitable as an interconnector for a solid oxide fuel cell (hereinafter also referred to as SOFC).

[0002]

2. Description of the Related Art Conventionally, as a raw material synthesis method of lanthanum chromite ceramics, a powder mixing method and the like are often used as seen in JP-A-8-55629. The details found in the publication are as follows. Lanthanum chromite is used as the interconnector material of the SOFC. As a method for synthesizing the raw material powder of the lanthanum chromite, a powder mixing method is used, and La, Cr, oxides of other additional elements and the like are mixed in a ball mill, and a lanthanum chromite powder is obtained by a process such as heat treatment. . Further, in order to obtain the sintered body, after being subjected to press molding, firing is performed at a firing temperature of 1500 ° C. or higher. Most of the fired bodies have a conductivity of 30 S / cm or less.

As sintering aids for lanthanum chromite, Ca, Mg and the like are used in addition to Sr.
It is considered to be excellent in durability and the like, and is expected as an interconnector material for SOFC.

[0004]

In a raw material synthesizing method such as a conventional powder mixing method, a firing temperature of 1500 ° C. or higher is required in order to obtain a dense lanthanum chromite which is difficult to be sintered. . If the firing temperature is high, the firing cost is high, and when various types of ceramics are present, such as in a solid oxide fuel cell, there are problems such as thermal damage to other materials.

SUMMARY OF THE INVENTION The present invention has been made to solve the above-mentioned problems, and an object of the present invention is to provide a lanthanum chromite which can be fired at a low temperature of 1500 ° C. or less, and has excellent denseness and electronic conductivity. An object of the present invention is to provide a raw material powder synthesis method.

[0006]

Means for Solving the Problems] To achieve the above _{object, La 1-X Sr X +} Y CrO 3, 0 <X <0.4,0 <Y
≦ 0.1, La, Sr, C
r, a decomposition step of thermally decomposing the polyester to obtain powder, and a calcining step of calcining the powder to obtain La _1-X Sr _{X + Y} CrO ₃ powder. I decided to include it.

La _1-X Sr _{X + Y} CrO ₃ , 0 <X <0.
A high sintering property is ensured by the Sr-rich composition of 4,0 <Y ≦ 0.1, and the sintering property is further improved by using a complex polymerization method, which is a finer and highly dispersed raw material synthesis method. A method for synthesizing high Sr dopantran chromite powder was used.

[0008]

DESCRIPTION OF THE PREFERRED EMBODIMENTS A typical application of the present invention is
This is an interconnector for OFC.

Generally, lanthanum chromite is considered to be difficult to sinter, and a firing temperature of 1600 ° C. or more is required to obtain a dense body.

In the present invention, by synthesizing lanthanum chromite powder having high sinterability, lanthanum chromite having excellent denseness and excellent electronic conductivity suitable for interconnectors for SOFCs and the like is fired at a firing temperature of 1400 ° C. to 1500 ° C. It is possible to manufacture.

The sinterability can be further improved by doping lanthanum chromite with Sr as a sintering aid and making the stoichiometric composition Sr-rich.

In the present invention, a complex polymerization method is used to improve the sinterability of the raw material other than the composition. With a complexing agent such as citric acid, La, Sr, and Cr are finely and highly dispersed in a solution in a complex state. An ester forming aid such as ethylene glycol is added to the solution, and a polymer in which La, Sr, and Cr are fine and highly dispersed is obtained by a condensation polymerization reaction. By subjecting this polymer to heat treatment, the bond of the polymer is decomposed, and a desired Sr doptolan tandemite can be obtained as a more uniform composition. This uniform composition of Sr doptoran chromite has high sinterability.

By using the above composition and raw material synthesizing method, it is possible to realize sintering of Sr doptolan chromite at a lower temperature.

[0014]

Embodiments of the present invention will be described below.

EXAMPLE 1 Raw Material Synthesis Method Using Pressed Body
Effects of Sr-rich and Sr-rich compositions As an example of the embodiment of the present invention, La _0.7 Sr _{0.3 + Y} Cr
Raw materials of O ₃ , 0 ≦ Y ≦ 0.15 were synthesized by a complex polymerization method and a powder mixing method, and a press fired body was prepared using the raw material powders and evaluated.

(1) Synthesis of Raw Materials by Complex Polymerization Each nitrate of La, Sr, and Cr was used as a starting material and dissolved in a state in which ethylene glycol and citric acid were added. By heating the above solution at 150 to 170 ° C, a polyester compound was obtained. Further, a powder obtained by a thermal decomposition process in which the above polyester compound is heat-treated at 350 ° C. to 600 ° C. and pulverized several times is heated to 1100 ° C. to 1300 ° C.
By calcining at ℃, a raw material powder having a desired composition was obtained.

(2) Raw Material Synthesis by Powder Mixing Method Each oxide of La, Sr, and Cr is used as a starting material, and each oxide is mixed by a ball mill for 50 hours. By calcining at ℃, a raw material powder having a desired composition was obtained.

(3) Preparation of pressed body: 1 wt% of PVA was added as a binder to the raw material powder synthesized by the above-described complex polymerization method and powder mixing method, followed by uniaxial pressing to obtain a 50 mm × 5 mm × 5 mm. A pressed body was produced.

(4) Firing The above pressed body was fired at 1400 ° C. × 10 hours in an air atmosphere.

(5) Evaluation: The press fired body was measured for relative density by the Archimedes method and conductivity at 1000 ° C. in an air atmosphere by the DC four-terminal method.

FIG. 1 is a view showing the relative density of a pressed body produced by the complex polymerization method and the powder mixing method according to the composition of Example 1. As shown in FIG. 1, even at a low-temperature baking at 1400 ° C., a dense body having a relative density exceeding 90% can be produced by using the complex polymerization method and the Sr-rich composition together. A more desirable rich amount is 0.03 ≦ Y ≦
0.08.

FIG. 2 is a diagram showing the conductivity of a pressed body produced by the complex polymerization method and the powder mixing method according to the composition of Example 1 at 1000 ° C. in the atmosphere. As shown in FIG. 2, it is possible to produce a pressed body having a high electrical conductivity exceeding 30 S / cm even at a low temperature of 1400 ° C.

Example 2: Sr doping amount by pressing body
Relation of firing temperature As an example of the embodiment of the present invention, La _1-X Sr _{X + 0.05} Cr
A raw material of Sr-rich lanthanum chromite having a composition of O ₃ , 0 ≦ X ≦ 0.4 was synthesized by a complex polymerization method, and a pressed fired body was prepared using the raw material powder and evaluated.

(1) Synthesis of raw materials by complex polymerization method The synthesis of raw materials by (1) complex polymerization method in Example 1 is followed.

(2) Preparation of Pressed Body: This is based on (3) Preparation of Pressed Body in Example 1.

(3) Firing The above pressed body was fired in an air atmosphere at 1400 ° C. to 1500 ° C. × 10 hours.

(4) Evaluation: The pressed body was subjected to relative density measurement by the Archimedes method and conductivity measurement in the air atmosphere at 1000 ° C. by the DC four-terminal method.

FIG. 3 is a view showing the relative density of a pressed body produced by the complex polymerization method according to the composition of Example 2. FIG.
As shown, when the Sr rich amount Y = 0.05,
1400 ° C. in the range of Sr doping amount X = 0.2 to 0.3
Even at low temperature baking, it is possible to produce a dense body whose relative density exceeds 90%. Even when X = 0.1, if the firing temperature is 1500 ° C., the relative density is 90 °.
%.

FIG. 4 is a diagram showing the conductivity of a pressed body produced by the complex polymerization method according to the composition of Example 2 at 1000 ° C. in the atmosphere. As shown in FIG. 4, when the Sr-rich amount Y is set to 0.05, the Sr doping amount X can be reduced to 30 in the range of 0.2 to 0.3 even by firing at 1400 ° C.
It is possible to produce a pressed body having a high electrical conductivity exceeding S / cm. Further, even when X = 0.1, the firing temperature is set to 15
At a temperature of 00 ° C., the conductivity exceeds 30 S / cm.

As shown in FIGS. 3 and 4, Sr
When the doping amount is increased, at X = 0.4, the denseness and the electrical conductivity decrease. From the above,
When it is intended to obtain a relative density of 90% or more and a conductivity of 30 S / cm or more suitable for an interconnector for SOFC by firing at 1500 ° C. in air, La _1-X Sr _{X + Y} CrO ₃
In the above, the composition is desirably 0.1 <X <0.4, more specifically, 0.2 ≦ X ≦ 0.3.

In the above embodiment, a pressed body is manufactured. However, a slurry is manufactured using the raw material powder,
The slurry is applied to the cathode or anode of the SOFC, and can be applied to the production of an interconnector film for an SOFC by a process of firing.

[0032]

As is apparent from the above description, according to the present invention, in the method of synthesizing Sr doptolan tandem chromite powder, the Sr-rich composition and the complex polymerization method are used in combination, whereby the atmosphere at 1400 ° C. to 1500 ° C. Also in baking, it is possible to produce Sr dope plantan chromite which is excellent in denseness and electron conductivity.

[Brief description of the drawings]

FIG. 1 is a diagram showing a relative density of a pressed body produced by a complex polymerization method and a powder mixing method according to the composition of Example 1.

FIG. 2 is a diagram showing the electrical conductivity of a pressed body produced by a complex polymerization method and a powder mixing method according to the composition of Example 1 in the air at 1000 ° C.

FIG. 3 is a view showing a relative density of a pressed body produced by a complex polymerization method according to the composition of Example 2.

FIG. 4 is a diagram showing the conductivity of a pressed body produced by a complex polymerization method according to the composition of Example 2 in the air at 1000 ° C.

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Masanobu Aizawa 2-1-1 Nakajima, Kokurakita-ku, Kitakyushu-shi, Fukuoka F-term (reference) 4G048 AA05 AB02 AB05 AC06 AD03 AE05 AE08 5H026 AA06 BB00 BB01 BB10 EE13 HH08

Claims (3)

[Claims] 1. The method according to claim 1, wherein La _1−X Sr _{X + Y} CrO ₃ , 0 <X <0.
4,0 <Y ≦ 0.1.
a step of obtaining a polyester containing a, Sr, and Cr; a decomposition step of thermally decomposing the polyester to obtain a powder; and calcining the powder to obtain a La _1-x Sr _{X + Y} CrO ₃ powder. A method for producing Sr doplastan chromite powder, comprising a calcining step. 2. The method according to claim 1, wherein said complex polymerization method comprises La, Sr and Cr.
The method according to claim 1, wherein the method is performed using a raw material solution containing ions and citric acid and ethylene glycol. 3. A sintering temperature Te of 1400 ° C. using the Sr doplastane chromite powder according to claim 1 or 2.
≦ Te ≦ 1500 ° C., an interconnector for a solid oxide fuel cell.