JPH04315772A - Manufacture of interconnector for solid electrolyte fuel cell - Google Patents

Abstract

PURPOSE:To form a thin film of lanthanum chromate on a lanthanum manganate sintered body through a wet process. CONSTITUTION:Slurry of calcium-doped lanthanum chromate having A-sites in excess is applied as a thin film on a porous body made from alkaline earth metal-doped lanthanum manganate having defects in A-sites and is sintered in an oxidation atmosphere. A nonplanar interconnector can be obtained readily by application of slurry of lanthanum chromate using vacuum suction method.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an interconnector for solid electrolyte fuel cells.

0002

[Prior Art and Problems to be Solved by the Invention] Interconnectors for solid electrolyte fuel cells have a temperature of 1,000℃.
be stable in both redox and redox atmospheres at high temperatures;
In addition, it is required to have a certain level of electronic conductivity. The manufacture of such interconnectors mostly involves the use of alkaline earth metals (Ca, Sr, Mg, etc.)
Lanthanum chromate (LaCrOx) doped with is used. However, such LaCrOx is difficult to sinter, and cannot be sintered by conventional methods unless the temperature is raised to 1,600° C., so it has not always been easy to manufacture interconnectors.

[0003] For this reason, the following methods have been attempted in the past.

1. A method of sintering LaCrOx alone and joining it with other parts.

2. Lanthanum manganate (LaMnOx)
) or by a dry process such as CVD, EVD, or thermal spraying on a porous electrode material such as Ni/ZrO2 cermet.
A method of forming aCrOx thin film.

In the former case, the thickness of the film is limited due to internal resistance constraints, so the film area cannot be increased, and the shape is limited to a flat plate. On the other hand, the latter method has the disadvantage that the equipment cost is high because it is a dry process.

A co-sintering method using Ca-doped LaCrOx was also attempted, but due to the movement of the CaO phase, LaMn
There was a drawback that sintering of Ox and Ni/ZrO2 cermets was hindered.

The object of the present invention is to solve the above-mentioned drawbacks and to solve the problem of La
The present invention provides a method for forming a LaCrOx thin film on a MnOx sintered body by a wet process. This method also has the advantage that large-area or non-planar interconnectors can be easily obtained.

[0009]

[Means for solving the problem] A slurry of calcium-doped lanthanum chromate with an excess of A sites is applied in a thin film onto a porous body made of alkaline earth metal-doped lanthanum manganate having A-site defects, and this is oxidized. Sinter in the atmosphere.

Preferably, the lanthanum chromate slurry is applied by vacuum suction.

[0011]

[Action] Lanthanum chromate doped with excessive Ca at the A site (for example, La0.70Ca0.35CrOx
; where x is 3±δ) is known as an easily sinterable lanthanum chromate. Using this slurry, a thin film is formed on a porous body made of lanthanum manganate doped with an alkaline earth metal and having A-site defects, and when this is fired at about 1,300°C, the porous lanthanum manganate A dense thin film of lanthanum chromate forms on the body. At this time, lanthanum manganate does not resinter (lanthanum manganate does not resinter unless the temperature is raised to approximately 1,350°C). Excess Ca in lanthanum chromate creates a CaO phase between particles, and this However, since LaMnOx has already been sintered, it is not adversely affected. In addition, in terms of reaction with LaMnOx, Ca is coordinated to the A-site defects in LaMnOx, so that it is less likely to be adversely affected.

Furthermore, by applying the lanthanum chromate slurry by vacuum suction, it is possible to form a film on a curved surface such as a cylinder.

[0013]

【Example】

Example 1 Sr-doped lanthanum manganate with A-site defects [(La0.9Sr0.1)0.9MnO3±δ
] on the porous cylinder of La0.70Ca0.35CrO
Slurry of 3±δ powder (average particle size 2 μm) (LaCaC
A film containing 50 to 70% by weight of rOx powder (others being water, polyvinyl alcohol, and surfactant) was formed by vacuum suction, dried at room temperature, and then calcined in air at 1,300° C. for 5 hours. As a result, a dense film of LaCaCrOx with a thickness of 30 μm was obtained.

[0014] The obtained film was treated at 1,100°C for 500 hours, but no practically harmful changes were observed in the electrical or mechanical properties.

Comparative Example 1 A slurry was applied onto the same porous cylinder as in Example 1 without vacuum suction, and the same firing was performed, but the resulting film was gas permeable and the dense film was I couldn't get it. Comparative Example 2 An experiment similar to Example 1 was conducted using calcium-doped lanthanum chromate (La0.84Ca0.16CrO3±δ) powder that did not have an excess of A sites, but no sintering occurred.

Comparative Example 3 When a similar experiment was carried out using a porous cylinder of strontium-doped lanthanum manganate (La0.9Sr0.1MnO3±δ) with no A-site defects, the A-site was excessive due to Ca doping, and air Since the H2O inside was absorbed and La(OH)3.nH2O was produced, the strength of the cylinder was significantly reduced.

[0017]

According to the present invention, a lanthanum chromate thin film can be formed on a lanthanum manganate sintered body by a wet process. Therefore, equipment costs can be kept low.

Furthermore, due to the movement of the CaO phase, LaMnOx
The sintering of the material is not hindered.

Furthermore, a non-planar interconnector can be easily obtained by applying a slurry of lanthanum chromate by a vacuum suction method.

Claims (3)

[Claims] Claim 1: A solid electrolyte in which a slurry of calcium-doped lanthanum chromate with an excess of A sites is applied in a thin film form on a porous body made of alkaline earth metal-doped lanthanum manganate having A-site defects, and the slurry is sintered. A method for manufacturing a fuel cell interconnector. 2. The method according to claim 1, wherein the lanthanum chromate slurry is applied by vacuum suction. 3. The method according to claim 2, wherein the surface of the lanthanum manganate porous body to which the lanthanum chromate slurry is applied is not flat.