Solid electrolyte, method of producing same and fuel cell using same

• US 6,447,944 B1
• Filed: 08/22/2000
• Issued: 09/10/2002
• Est. Priority Date: 08/30/1999
• Status: Active Grant

• Current Assignee: Nissan Motor Co., Ltd.
• Original Assignee: Nissan Motor Co., Ltd.
• Inventors: Munakata, Fumio, Akimune, Yoshio, Shinohara, Mikiya
• Primary Examiner(s): WEINER, LAURA S
• Application Number:
  US09/642,652
• Time in Patent Office: 749 Days
• Field of Search: 429/33, 429/304, 429/30, 429/46, 252/62.2
• US Class Current: 429/495
• CPC Class Codes: C04B 2235/3206 Magnesium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3213 Strontium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3215 Barium oxides or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3224 Rare earth oxide or oxide forming salts thereof, e.g. scandium oxide
• CPC Class Codes: C04B 2235/3225 Yttrium oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3227 Lanthanum oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3284 Zinc oxides, zincates, cadmium oxides, cadmiates, mercury oxides, mercurates or oxide forming salts thereof
• CPC Class Codes: C04B 2235/3286 Gallium oxides, gallates, indium oxides, indates, thallium oxides, thallates or oxide forming salts thereof, e.g. zinc gallate
• CPC Class Codes: C04B 2235/5436 micrometer sized, i.e. from 1 to 100 micron
• CPC Class Codes: C04B 2235/5445 submicron sized, i.e. from 0,1 to 1 micron
• CPC Class Codes: C04B 2235/656 characterised by specific heating conditions during heat treatment
• CPC Class Codes: C04B 2235/6567 Treatment time
• CPC Class Codes: C04B 2235/786 Micrometer sized grains, i.e. from 1 to 100 micron
• CPC Class Codes: C04B 35/01 based on oxide ceramics
• CPC Class Codes: C04B 35/6262 of calcined, sintered clinker or ceramics
• CPC Class Codes: C04B 35/62655 Drying, e.g. freeze-drying, spray-drying, microwave or supercritical drying
• CPC Class Codes: C04B 35/62675 characterised by the treatment temperature
• CPC Class Codes: H01M 2300/0074 Ion conductive at high temperature
• CPC Class Codes: H01M 8/124 characterised by the process of manufacturing or by the material of the electrolyte
• CPC Class Codes: H01M 8/1246 the electrolyte consisting of oxides
• CPC Class Codes: Y02E 60/50 : Fuel cells
• CPC Class Codes: Y02P 70/50 : Manufacturing or production processes characterised by the final manufactured product

Abstract

A solid electrolyte used in a cell and represented by the following formula:

La_(1−x−y)Ln_xA_yGa_(1−z)B_zO_{3−0.5(x+y+z)}

where Ln is at least one element selected from the group consisting of Gd, Sm and Nd; A is Ba; B is Mg; x is 0.1; y is 0.1; and z is 0.2, wherein the solid electrolyte is formed of particles whose means diameter is within a range of from 4 to 10 μm, the solid electrolyte being produced by a method comprising: (a) mixing lanthanum oxide, gallium oxide, oxide of at least one rate earth element selected from the group consisting of Gd, Sm and Nd, barium oxide and magnesium oxide to form a mixture; (b) firing the mixture in air at a temperature ranging from 1100 to 1200° C. for a time ranging from 2 to 8 hours to accomplish synthesizing a compound material; (c) pulverizing the compound material; (d) compacting the pulverized compound material; (e) adjusting mean diameter of the pulverized compound material within a range of from 0.5 to 0.8 μm; and (f) sintering the compacting compound material in air at a temperature ranging from 1400 to 1500° C. for a time ranging from 2 to 8 hours to form the solid electrolyte.

Claims

1. A solid electrolyte represented by the following formula:

2. A solid electrolyte as claimed in claim 1, wherein said solid electrolyte is formed of particles whose means diameter is within a range of from 2 to 10 μ

m.

3. A method of producing a solid electrolyte, comprising:

mixing gallium oxide, oxides of rare earth elements, oxide of alkaline earth element, at least one of zinc oxide and magnesium oxide to form a mixture;

firing the mixture at a temperature ranging from 1050 to 1200°

C. for a time ranging from 2 to 10 hours to accomplish synthesizing a compound material;

pulverizing the compound material; and

compacting the pulverized compound material; and

sintering the compacting compound material to form the solid electrolyte.

4. A method as claimed in claim 3, wherein the sintering is accomplished at a temperature ranging from 1350 to 1500°

C. for a time ranging from 2 to 8 hours.

5. A method as claimed in claim 3, wherein the firing and the sintering are accomplished in air.

6. A method as claimed in claim 3, further comprising adjusting mean diameter of the pulverized compound material within a range of from 0.5 to 0.8 μ

m, before the sintering.

7. A solid electrolyte represented by the following formula:

8. A fuel cell comprising:

a solid electrolyte represented by the following formula;