JP4462013B2 - Solid electrolyte for use in solid oxide fuel cells - Google Patents

Description

  The present invention relates to a solid electrolyte for a solid oxide fuel cell having high strength.

  In general, since solid oxide fuel cells can use hydrogen gas, natural gas, methanol, coal gas, or the like as fuel, they can promote the use of alternative energy for petroleum in power generation and use waste heat. Because it can be done, it is attracting attention from the viewpoint of resource saving and environmental problems. This solid electrolyte fuel cell has a high temperature type with an operating temperature of 900 to 1000 ° C and a low temperature type with an operating temperature of 600 to 800 ° C. A fuel electrode current collector is stacked on the other side of the solid electrolyte, a separator having an air inlet is stacked outside the oxygen electrode current collector, and fuel is introduced outside the fuel electrode current collector. It has a basic structure in which separators having a mouth are stacked. Since the oxygen electrode current collector functions as a flow path for flowing air, which is an oxidant gas, conductive ceramics such as lanthanum chromite in which a gas passage is formed, platinum mesh, silver polymorph, etc. Is used. In order to increase the power generation capacity of the solid oxide fuel cell, the oxygen electrode current collector, the fuel electrode current collector, the solid electrolyte, and the separator all have a plate-like structure.

As the solid _{electrolyte, (La 1-x Sr x} ) (Ga 1-y-z Mg y Co z) O 3 ( provided that, x: 0.05~0.3, y: 0~0.29 , z: 0.01-0.3, y + z: 0.025-0.3) is known, this solid electrolyte has high ionic conductivity, and this solid electrolyte is La ₂ O ₃ powder, SrCO ₃ powder, Ga ₂ O ₃ powder, MgO powder and CoO powder are prepared as raw material powders, and these raw material powders are (La _1-x Sr _x ) (Ga _1-yz Mg _y Co _z ). O ₃ (x: 0.05 to 0.3, y: 0 to 0.29, z: 0.01 to 0.3, y + z: 0.025 to 0.3) After mixing, pre-baking is performed at a temperature of 500 to 1300 ° C. in the atmosphere. The obtained mixture is pulverized and formed into a plate-like compression molded body by cold isostatic pressing, and the obtained plate-like compression molded body is sintered at a temperature of 1200 ° C. or higher (preferably 1300 ° C. or higher). This is known (see Patent Document 1).
Japanese Patent Laid-Open No. 11-335164

Recently, solid oxide fuel cells have also been made an attempt to load such a large vehicle, a conventional _{(La 1-x Sr x)} (Ga 1-y-z Mg y Co z) O 3 ( where x: 0.05 to 0.3, y: 0 to 0.29, z: 0.01 to 0.3, y + z: 0.025 to 0.3)) Attempts have been made to load batteries on large vehicles. However, conventional _{(La 1-x Sr x)} (Ga 1-y-z Mg y Co z) O 3 ( provided that, x: 0.05~0.3, y: 0~0.29 , z: 0 .01-0.3, y + z: 0.025-0.3) was not strong enough, and it was necessary to further increase the strength.

The present inventors have, from the viewpoint as described _{above, (La 1-x Sr x} ) (Ga 1-y-z Mg y Co z) O 3 ( provided that, x: 0.05 to 0.3, Research was conducted to further increase the strength of the solid electrolyte comprising y: 0 to 0.29, z: 0.01 to 0.3, y + z: 0.025 to 0.3). as a result,
(I) Raw material powders such as La ₂ O ₃ powder, SrCO ₃ powder, Ga ₂ O ₃ powder, MgO powder and CoO powder are (La _1-x Sr _x ) (Ga _1-yz Mg _y Co _z ) O ₃ (x: 0.05 to 0.3, y: 0 to 0.29, z: 0.01 to 0.3, y + z: 0.025 to 0.3) and mixed. After that, pre-fired in an air atmosphere at a temperature of less than 1300 ° C., the pre-fired mixture is pulverized, and formed into a plate-like compression-molded body by cold isostatic pressing, and the obtained plate-like compression-molded body is obtained. A solid electrolyte made of an oxide sintered body obtained by sintering at a temperature of 1300 ° C. or higher in an air atmosphere in which the oxygen content is lower than that of normal air is (La _1-x Sr _x ) (Ga _{1 -y-z Mg y Co z)} O 3 ( provided that, x: .05 to 0 .3, y: 0 to 0.29, z: 0.01 to 0.3, y + z: 0.025 to 0.3), and a base of an oxide sintered body having a perovskite crystal structure in, very few of Mg and Co content _{(La 1-x Sr x)} (Ga 1-y-z Mg y Co z) O 3 ( however, 0.3 <x <0.7, y <0.01 , Z <0.01, y + z <0.02), and has a structure in which fine oxide particles are precipitated and uniformly dispersed. The fine oxide particles are precipitated and uniformly dispersed in the substrate. The solid electrolyte composed of an oxide sintered body having a texture having a higher strength than the conventional solid electrolyte,
(B) Research results such as that the fine oxide particles uniformly dispersed in the substrate are preferably in the range of an average particle size of 0.5 to 10 μm are obtained.

The present invention has been made based on the results of such research,
(1) (La _1-x Sr _x ) (Ga _1-yz Mg _y Co _z ) O ₃ (where x: 0.05 to 0.3, y: 0 to 0.29, z: 0. 01~0.3, y + z: in the matrix of the oxide having a perovskite crystal structure having a composition consisting of _{0.025~0.3), (La 1-x} Sr x) (Ga 1-y-z Mg _y Co _z ) O ₃ (where 0.3 <x <0.7, y <0.01, z <0.01, y + z <0.02), fine oxide grains having a uniform dispersion A high-strength solid electrolyte for use in a solid oxide fuel cell made of an oxide sintered body having a texture
(2) The fine oxide particles are characterized by a high-strength solid electrolyte for use in the solid oxide fuel cell according to (1) above having an average crystal grain size: 0.5 to 10 μm. is there.

The oxide sintered bodies constituting the solid electrolyte for use in the solid oxide fuel cell of the present invention are La ₂ O ₃ powder and SrCO ₃ powder each having an average particle size of 0.05 to ₃ μm as a raw material powder. , Ga ₂ O ₃ powder, MgO powder and CoO powder are prepared as raw material powders, and these raw material powders are (La _1-x Sr _x ) (Ga _1-yz Mg _y Co _z ) O ₃ (where x: 0.05 to 0.3, y: 0 to 0.29, z: 0.01 to 0.3, y + z: 0.025 to 0.3), and after mixing, air atmosphere ( In general, atmospheric components are oxygen: 20.99%, nitrogen: 78.03%, argon: 0.94%, carbon dioxide: 0.03%, hydrogen: 0.01%, other, neon , Helium, krypton, xenon, etc.) Temperature: Pre-baked at less than 1300 ° C., the pre-baked agglomerates are pulverized, and formed into a plate-shaped molded body by a cold isostatic press or a doctor blade method. It is obtained by sintering at a temperature of 1300 ° C. or higher (preferably 1400 to 1450 ° C.) in an air atmosphere containing less oxygen (that is, an air atmosphere having an oxygen content of less than 20.99%).

The thus produced of the present invention _{(La 1-x Sr x)} (Ga 1-y-z Mg y Co z) O 3 ( provided that, x: 0.05~0.3, y: 0~0 . 29, z: 0.01 to 0.1, y + z: 0.035 to 0.3) and uniformly dispersed in the base of the oxide sintered body having a perovskite crystal structure (La _{1 -x Sr x) (Ga 1-} y-z Mg y Co z) O 3 ( however, 0.3 <x <0.7, y <0.01, z <0.01, y + z <0.02) When the oxide sintered body is used as a solid electrolyte, it is more preferable that the fine oxide particles having an extremely small Mg and Co content composition have an average crystal grain size: 0.5 to 10 μm. Most of the oxide grains are precipitated along the grain boundaries of the substrate, but some of the oxide grains may be precipitated in the crystal grains.

  The solid electrolyte of the solid oxide fuel cell of the present invention has a higher mechanical strength than the conventional solid electrolyte, and therefore the solid oxide fuel cell using the solid electrolyte of the present invention is sufficient even when subjected to vibrations or the like. Can be used, and it is not necessary to select an installation location.

BEST MODE FOR CARRYING OUT THE INVENTION

Next, the solid electrolyte of the solid oxide fuel cell of the present invention will be described in detail with reference to examples.
As raw material powders, La ₂ O ₃ powder having an average particle diameter of 0.6 μm, SrCO ₃ powder having an average particle diameter of 1.1 μm, Ga ₂ O ₃ powder having an average particle diameter of 0.9 μm, and an average particle diameter of 0. .4 μm MgO powder and CoO powder having an average particle diameter of 1.2 μm were prepared, and these raw material powders were, in mass%, La ₂ O ₃ powder: 53.28%, SrCO ₃ powder: 12.07%, They were blended so as to have a blend composition of Ga ₂ O ₃ powder: 30.65%, MgO powder: 2.47%, CoO powder: 1.53%, and mixed. Next, the obtained mixed powder is formed into a sheet by a doctor blade method, cut into a disk shape, pre-sintered in the atmosphere at a temperature of 1250 ° C. for 6 hours, and the pre-baked aggregate is pulverized. The present invention solid electrolytes 1 and 2 and the conventional solid electrolyte 1 are formed by forming into a plate-like molded body by cold isostatic pressing or a doctor blade method and sintering the obtained plate-like molded body under the conditions shown in Table 1. Was made.

The cross sections of the obtained solid electrolytes 1 and 2 of the present invention and the conventional solid electrolyte 1 are polished and etched, and then the etched surface is taken in a COMP (secondary electron image) photograph and dispersed in the substrate by image analysis. The average particle size of the fine oxide particles was measured, and the component composition of the fine oxide particles dispersed in the solid electrolyte substrate was measured by EPMA (electron beam microanalyzer). Indicated.
Further, the bending strengths of the present solid electrolytes 1 and 2 and the conventional solid electrolyte 1 were measured, and the results are shown in Table 3.

In order to make it easier to understand the structure of the solid electrolyte of the present invention, a photograph of the structure of the solid electrolyte 1 of the present invention by COMP is shown in FIG. 1, and an explanatory view of the structure photograph is shown in FIG. In the explanatory diagram of FIG. 2, fine grains indicated by oblique lines are (La _1-x Sr _x ) (Ga _1-yz Mg _y Co _z ) O ₃ (where 0.3 <x <0.7, y < Fine oxide grains having a composition of 0.01, z <0.01, y + z <0.02).

  From the results shown in Table 1, although the present solid electrolytes 1 and 2 have the same component composition as that of the conventional solid electrolyte 1, the present solid electrolytes 1 and 2 are stronger than the conventional solid electrolyte 1. It is understood that is superior.

It is the structure | tissue photograph by COMP of the solid electrolyte of this invention. It is explanatory drawing of the structure | tissue photograph of FIG.

Claims (3)

_{(La 1-x Sr x)} (Ga 1-y-z Mg y Co z) O 3 ( provided that, x: 0.05~0.3, y: 0~0.29 , z: 0.01~0 .3, y + z: 0.025 to 0.3) in an oxide substrate having a perovskite crystal structure, (La _1-x Sr _x ) (Ga _1-yz Mg _y Co _z ) O ₃ (where 0.3 <x <0.7, y <0.01, z <0.01, y + z <0.02) A high-strength solid electrolyte for use in a solid oxide fuel cell, characterized by comprising an oxide sintered body. The high-strength solid electrolyte for use in a solid oxide fuel cell according to claim 1, wherein the oxide particles have an average crystal grain size of 0.5 to 10 µm. A solid oxide fuel cell comprising the high-strength solid electrolyte according to claim 1.

Images