Method for Producing Cerium-Based Composite Oxide, Solid Oxide Fuel Cell, and Fuel Cell System

Patent metadata

Field	Value
Publication number	US-2016344041-A1
Application number	US-201615225138-A
Country	US
Kind code	A1
Filing date	Aug 1, 2016
Priority date	Apr 1, 2011
Publication date	Nov 24, 2016
Grant date	—

Abstract

On the other hand, the possibility of estimating the dopant ratio of a metal element to each ceria crystalline particle using integral-width or half-width obtained by XRD was considered as follows: an XRD peak is shifted depending on the dopant ratio of La to ceria; when La increases, an XRD peak is shifted to a lower angle; in XRD performed on a raw material obtained by mixing ceria crystalline particles having different dopant ratio, peaks corresponding to the respective dopant ratio exist close to each other; as a result, a peak width is widened; accordingly, the dopant ratio of a metal element to each ceria crystalline particles are supposed to vary when integral-width and half-width obtained by XRD are large. Thus, it was revealed for the first time that integral-width and half-width obtained by XRD indicate variations in dopant ratio. It should be noted that from the direct proportional relationship between the dopant ratio x and the integral-width for dopant ratio ranging from 0.35 to 0.45, integral-widths obtained by XRD are derived to be 0.10 to 0.30 for dopant ratio ranging from 0.35 to 0.45, and half-widths are derived to be 0.10 to 0.30 similarly.

First claim

1 . A method for producing a cerium-based composite oxide to be used as a reaction preventing layer of a solid oxide fuel cell to prevent reaction between a fuel electrode layer and an electrolyte layer, comprising the steps of:
mixing a compound including at least one metal element selected from La, Pr, and Nd and a cerium-based compound to obtain a mixture; and firing the mixture to obtain a fired product, the method further comprising a dopant ratio adjustment step of adjusting a dopant ratio of the metal element to each ceria crystalline particle constituting the fired product to limit the dopant ratio to a predetermined range throughout the fired product.

2 . The method according to claim 1 , wherein the metal element in the compound including the metal element mixed with the cerium-based compound is La, and the predetermined range in the dopant ratio adjustment step is from 0.35 to 0.45.

3 . The method according to claim 2 , wherein the dopant ratio adjustment step comprises a step of identifying a cerium-based composite oxide having a dopant ratio in the range of 0.35 to 0.45 through a dopant ratio estimation step of estimating the dopant ratio, and rejecting a cerium-based composite oxide having a dopant ratio outside the range of 0.35 to 0.45.

4 . The method according to claim 3 , wherein in the dopant ratio estimation step, the dopant ratio is estimated based on a distribution of Raman shift peaks.

5 . The method according to claim 4 , wherein a cerium-based composite oxide having a ratio of a peak value at a Raman shift of 610 cm −1 to a peak value at a Raman shift of 565 cm −1 which is more than 0.7 is rejected.

6 . The method according to claim 3 , wherein in the dopant ratio estimation step, the dopant ratio is estimated using any one of an integral-width and a half-width, each obtained by XRD for a predetermined BET value.

7 . The method according to claim 6 , wherein the predetermined BET value is 5 to 10 m 2 /g, and a cerium-based composite oxide having the integral-width of more than 0.3 is rejected, the integral-width being calculated for a peak of (111) planes that appears at 20=approximately 27.6°, the peak being obtained by XRD.

8 . The method according to claim 6 , wherein the predetermined BET value is 5 to 10 m 2 /g, and a cerium-based composite oxide having the half-width of more than 0.3 is rejected, the half-width being calculated for a peak of (111) planes that appears at near 20=27.6°, the peak being obtained by XRD.

9 . A solid oxide fuel cell comprising the cerium-based composite oxide produced by the method according to claim 1 , the cerium-based composite oxide being disposed as a reaction preventing layer between a fuel electrode and an electrolyte.

10 . A fuel cell system comprising the solid oxide fuel cell according to claim 9 .

Assignees

• Toto Ltd

Inventors

• Ando Shigeru
• Ishiguro Akira
• Kawakami Akira
• Shimazu Megumi
• Momiyama Yutaka
• Kakinuma Yasuo

Classifications

• H01M2008/1293

  Fuel cells with solid oxide electrolytes · CPC title

• C04B2235/5409

  expressed by specific surface values · CPC title

• C01P2002/82

  by IR- or Raman-data · CPC title

• C01P2006/12

  Surface area · CPC title

• H01M4/9066

  of metal-ceramic composites or mixtures, e.g. cermets · CPC title