JPH11111307A - Separator for solid electrolyte fuel cell and manufacture thereof - Google Patents

Abstract

PROBLEM TO BE SOLVED: To manufacture a separator at low cost, without lowering the quality thereof by forming a glass flow passage structure in an extruded molding of a perovskite compound oxide, including La and Sr or Ca after the extrusion. SOLUTION: A perovskite compound oxide which forms a separator is expressed with the formula A1-x Bx CrO3 , and A is La, B is Sr or Ca, (x) is in the range of 0-0.4. A separator is formed of a ceramic sheet formed in advanced with a groove, having the gas flow passage structure after the extruding and before the burning, and the flow passage structure can be formed without performing post-work. A separator is manufactured by the following method. One hundred pts.wt. of perovskite powder having a particle side of 1-10 μm, 10-25 pts.vol. of binder fine powder of a hydroxide group-containing organic compound having a particle size <=300 μm, 10-20 pts.vol. of plasticizer, 0.3-2.0 pts.wt. of a dispersant in relation to the perovskite powder of 100 pts.wt. and 100-150 pts.vol. of water are mixed to obtain the unburned earth, and this unburned earth is extrusion-molded, and baked after to eliminate the binder and the plasticizer by thermal decomposition.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a solid oxide fuel cell separator comprising a perovskite-type composite oxide formed by an extrusion method and a method for producing the same.

[0002]

2. Description of the Related Art In the development of a separator for a solid oxide fuel cell (hereinafter abbreviated as SOFC), for example, as disclosed in JP-A-6-5295 and JP-A-7-85881, Attempts have been made to significantly reduce the manufacturing cost by simplifying the manufacturing process as well as reducing the thickness of the constituent members and using inexpensive materials.

In a flat type SOFC, the operating temperature (1
Lanthanum chromite (LaCrO ₃ ) -based perovskite-type composite oxide which can be used stably at 2,000 ° C.).

[0004] The flat type SO using the lanthanum chromite
The FC separator has a plurality of grooves for a gas flow path. In order to form the grooves, first, a sheet of lanthanum chromite type oxide is prepared, and after calcining or main firing the sheet, Machined. Therefore, there is a problem that the yield due to cracking during processing is low, and an expensive machining apparatus is required, and it is very difficult to reduce the manufacturing cost.

[0005]

The problem to be solved by the present invention is that SO
An object of the present invention is to provide a grooved ceramic sheet suitable as a separator, which is an important component of FC, at low cost without deteriorating its quality.

[0006]

According to the present invention, there is provided a separator for an SOFC, wherein A is lanthanum, B is strontium or calcium, and X is 0 to 0.4.
A _1-X B _X extrudate perovskite-type composite oxide represented by CrO _3, characterized in that it forms a gas flow path structure after extrusion.

The SOFC separator is an extruded sheet-shaped composite oxide having a relative density of 60% or more and a film thickness of 1 to 3 mm. Such a groove is formed. That is, it is a ceramic sheet in which grooves like the gas flow channel structure are formed before extrusion before extrusion, and the gas flow channel structure can be manufactured without post-processing.

The SOFC separator of the present invention has a uniform thickness and a groove height, and allows both the oxidizing agent and the fuel gas to pass without stagnation.

This SOFC separator comprises 100 parts by volume of perovskite powder having a particle diameter of about 1 to 10 μm, 10 to 25 parts by volume of a binder fine powder of a hydroxyl-containing organic compound having a particle size of 300 μm or less, and 10 to 20 parts by volume of a plasticizer. And 0.3 to 2.0 parts by weight of a dispersant and 100 to 15 parts by weight of water per 100 parts by weight of the perovskite powder.
It is obtained by extruding and kneading the kneaded clay obtained by mixing the mixture with 0 parts by volume, removing the binder and the plasticizer by thermal decomposition, and then firing.

Among the molding aids to be blended, organic binders, inorganic binders, etc. can be used as the binder fine powder, but when mixed, they are easily dissolved in water as a solvent and immediately act as binders. It does not react with the perovskite-type powder used, and is easily decomposed and removed from the green body during calcination.To prevent the remaining of unburned carbon and ash, methylcellulose and other organic binders are used. The use of polysaccharide derivatives such as hemicellulose is preferred.

The compounding of this fine powder is the most important factor in enhancing the bonding between perovskite-type powders and maintaining good strength and moldability during extrusion. On the contrary, if the amount is too small, the kneaded clay becomes harder at the time of extrusion, and the extrusion becomes difficult. Therefore, from the viewpoint of moldability and strength, 5 to 30 parts by volume per 100 parts by volume of perovskite type powder,
Preferably it is in the range of 10 to 25 parts by volume.

As the plasticizer to be blended, an organic plasticizer,
Inorganic plasticizers can be used, but as with fine powders,
Upon mixing, it readily dissolves in water as a solvent and immediately acts as a binder, does not react with the perovskite-type oxide complex used, and is easily decomposed and removed from the green body during calcination, In order to prevent unburned carbon and ash from remaining, it is most preferable to use an organic plasticizer, especially a hydroxyl-containing organic compound such as glycerol or polyvinyl alcohol.

The blending of the plasticizer enhances the fluidity of the perovskite-type powder when it is extruded, and is one of the most important factors in maintaining good extrusion pressure and moldability during extrusion.
However, if the amount is too small, the kneaded material becomes harder at the time of extrusion, and a part of the kneaded material stays in the extruder,
Since so-called blockage occurs and it becomes difficult to produce and extrude a uniform molded product, from the viewpoint of moldability and strength, 5 to 40 parts by volume, preferably 10 to 20 parts by volume, per 100 parts by volume of perovskite-type powder. It is the range of the volume part.

As for the dispersant, the perovskite type powder has poor dispersibility when the solvent is water, and thus does not maintain sufficient fluidity. Therefore, in order to maintain fluidity, the amount of the dispersant is preferably 0.3 to 2.0 parts by weight based on 100 parts by weight of perovskite powder.

Regarding the sintering temperature, if the sintering temperature is low, sintering does not proceed, and if the sintering is carried out at more than 1700 ° C., chromium which is a component in the perovskite type oxide composite is reduced as chromium oxide gas. 1350 ° C. to 1650 ° C., preferably 1
450 ° C to 1600 ° C, the maximum temperature holding time is 3
Or 6 hours.

[0016]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below with reference to examples.

EXAMPLE 1 In the structural formula represented by A ₁ -XB _X CrO ₃ , A is lanthanum, and B is strontium. A perovskite type powder in which X was 0.2 was used. The median diameter is 7μ
m.

Mixtures A, B, C and D having the compounding ratios shown in Table 1
Were mixed with a mixer, predetermined water was added, and the mixture was further kneaded with a mixer to obtain a clay. This kneaded clay is extruded using an extruder
Extrusion was performed under the conditions of an extrusion pressure of 1 to 9 kgf / cm ² to obtain a sheet having a thickness of 1 to 3 mm as a green body. At this time, a green body having a groove in advance could be produced by using a comb-shaped die having a groove height of 500 μm shown in FIG. This was dried, placed in a degreasing furnace and calcined to decompose and remove the molding aid. Furthermore,
The calcined body was heated to 1450 to 1600 ° C. in an oxidizing atmosphere to obtain a calcined body.

[0019]

[Table 1] In order to measure the relative density of the molded article, the relative density was measured by the Archimedes method described in "Ceramic Engineering Handbook" edited by The Ceramic Society of Japan, Gihodo Shuppan, pp. 460-461, (1989).

The grooved perovskite-type composite oxide body had a groove structure and the relative density could be increased to 50% or more.

Example 2 The diameter of the particles used in Example 1 was further reduced to improve the sinterability of the particles. A is lanthanum, and B is strontium. The perovskite-type composite oxide represented by A _1-X B _X CrO ₃ has a conductivity of oxygen and oxygen vacancies. A perovskite-type powder was used.

Each of the mixing ratios A, B, C, and D shown in Table 2 was mixed by a mixer, predetermined water was added, and the mixture was further kneaded by a mixer to obtain a clay. The kneaded material was extruded with an extruder under the conditions of an extrusion pressure of 1 to 10 kgf / cm ² to obtain a green body having a thickness of 1 to 3 mm. At this time, a green body having a groove in advance could be manufactured by using a comb-shaped die having a groove height of 500 μm as shown in FIG. This was dried, placed in a degreasing furnace and calcined to decompose and remove the molding aid. Furthermore,
The calcined body was heated to 1450 to 1600 ° C. in an oxidizing atmosphere to obtain a calcined body. In order to measure the relative density of the molded article, the measurement was similarly performed using the Archimedes method. The perovskite-type oxide composite with grooves has a groove structure and the relative density can be increased to 80% or more.

[0023]

[Table 2] Example 3 Compared to Examples 1 and 2, the composition was made to be easily sinterable to improve the sinterability of the particles. In the perovskite-type composite oxide represented by A _{1 -X} B _X CrO ₃ , A is lanthanum, and B is changed from strontium to calcium, and X is 0.2 to provide conductivity and oxygen vacancies. Perovskite type powder was used.

The mixtures having the compounding ratios shown in Table 3 were mixed by a mixer, and predetermined water was added, and the mixture was further kneaded by a mixer to obtain a clay. The kneaded material was extruded with an extruder under the conditions of an extruding pressure of 1 to 10 kgf / cm ² to obtain a sheet having a thickness of 1 to 3 mm as a green body. On this occasion,
By using a comb-shaped die having a groove height of 500 μm as shown in FIG. 1, a green body having grooves in advance could be produced. This was dried, placed in a degreasing furnace and calcined to decompose and remove the molding aid. Further, the calcined body was heated to 1450 to 1600 ° C. in an oxidizing atmosphere to obtain a calcined body. In order to measure the relative density of the molded body, the measurement was similarly performed using the Archimedes method.

[0025]

[Table 3] The above-mentioned grooved perovskite-type composite oxide body could increase the relative density to 90% or more.

As a result of using the fired bodies shown in Embodiments 1 to 3 as a separator of a solid oxide fuel cell, the fired bodies can be used as separators having a gas flow path structure without special groove processing. Do you get it.

FIG. 2 shows an electron micrograph of this separator, which could be used without large-scale planar processing.

[0028]

According to the present invention, a gas supply path for supplying an oxide gas and a fuel gas to an electrode without impairing the efficiency can be produced at the time of extrusion molding without performing machining, and the cost involved in production can be increased. Not only can be greatly reduced, but also there is no fear of cracking due to machining after firing.
Product yield can be greatly improved.

[Brief description of the drawings]

FIG. 1 shows a cross-sectional shape of a used die.

FIG. 2 shows an electron micrograph of a perovskite-type composite oxide body that has been extruded and fired without performing groove processing after firing.

Claims (2)

[Claims] An extruded product of a perovskite oxide represented by A _1-X B _X CrO _{3 wherein} A is lanthanum, B is strontium or calcium, and X is 0 to 0.4. A solid oxide fuel cell separator having a gas flow path structure after extrusion. 2. 100 parts by volume of perovskite composite oxide powder having a particle size of 1 to 10 μm, 10 to 25 parts by volume of a binder fine powder of a hydroxyl group-containing organic compound having a particle size of 300 μm or less, and 10 to 20 parts by volume of a plasticizer. A die having a gas passage structure formed by mixing a clay obtained by mixing 0.3 to 2.0 parts by weight of a dispersant and 100 to 150 parts by volume of water with respect to 100 parts by weight of perovskite-type powder A method for producing a separator for a solid oxide fuel cell, wherein the binder and the plasticizer are thermally decomposed and removed, and then fired.