Nonstoichiometric La2-xGeO5-δ monoclinic oxide as a new fast oxide ion conductor

Tatsumi Ishihara, H. Arikawa, Taner Akbay, H. Nishiguchi, Y. Takita

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Abstract

Oxide ion conductivity in La2GeO5-based oxide was investigated and it was found that La-deficient La2GeO5 exhibits oxide ion conductivity over a wide range of oxygen partial pressure. The crystal structure of La2GeO5 was estimated to be monoclinic with P21/c space group. Conductivity increased with increasing the amount of La deficiency and the maximum value was attained at x = 0.39 in La2-xGeO5-δ. The oxide ion transport number in La2GeO5-based oxide was estimated to be unity by the electromotive force measurement in H2 - O2 and N2 - O2 gas concentration cells. At a temperature higher than 1000 K, the oxide ion conductivity of La1.61GeO5-δ was almost the same as that of La0.9Sr0.1Ga0.8Mg0.2 O3-δ or Ce0.85Gd0.15O2-δ, which are well-known fast oxide ion conductors. On the other hand, a change in the activation energy for oxide ion conductivity was observed at 973 K, and at intermediate temperature, the oxide ion conductivity of La1.61GeO5-δ became much smaller than that of these well-known fast oxide ion conductors. The change in the activation energy of the oxide ion conductivity seems to be caused by a change in the local oxygen vacancy structure. However, doping a small amount of Sr for La in La2GeO5 was effective to stabilize the high-temperature crystal structure to low temperature. Consequently, doping a small amount of Sr increases the oxide ion conductivity of La2-GeO5-based oxide at low temperature.

Original languageEnglish
Pages (from-to)203-209
Number of pages7
JournalJournal of the American Chemical Society
Volume123
Issue number2
DOIs
Publication statusPublished - Jan 17 2001

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Oxides
Ions
Temperature
Activation energy
Crystal structure
Doping (additives)
Oxygen
Electromotive force
Force measurement
Partial Pressure
Ion Transport
Oxygen vacancies
Partial pressure
Gases

All Science Journal Classification (ASJC) codes

  • Chemistry(all)

Cite this

Nonstoichiometric La2-xGeO5-δ monoclinic oxide as a new fast oxide ion conductor. / Ishihara, Tatsumi; Arikawa, H.; Akbay, Taner; Nishiguchi, H.; Takita, Y.

In: Journal of the American Chemical Society, Vol. 123, No. 2, 17.01.2001, p. 203-209.

Research output: Contribution to journalArticle

Ishihara, Tatsumi ; Arikawa, H. ; Akbay, Taner ; Nishiguchi, H. ; Takita, Y. / Nonstoichiometric La2-xGeO5-δ monoclinic oxide as a new fast oxide ion conductor. In: Journal of the American Chemical Society. 2001 ; Vol. 123, No. 2. pp. 203-209.
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abstract = "Oxide ion conductivity in La2GeO5-based oxide was investigated and it was found that La-deficient La2GeO5 exhibits oxide ion conductivity over a wide range of oxygen partial pressure. The crystal structure of La2GeO5 was estimated to be monoclinic with P21/c space group. Conductivity increased with increasing the amount of La deficiency and the maximum value was attained at x = 0.39 in La2-xGeO5-δ. The oxide ion transport number in La2GeO5-based oxide was estimated to be unity by the electromotive force measurement in H2 - O2 and N2 - O2 gas concentration cells. At a temperature higher than 1000 K, the oxide ion conductivity of La1.61GeO5-δ was almost the same as that of La0.9Sr0.1Ga0.8Mg0.2 O3-δ or Ce0.85Gd0.15O2-δ, which are well-known fast oxide ion conductors. On the other hand, a change in the activation energy for oxide ion conductivity was observed at 973 K, and at intermediate temperature, the oxide ion conductivity of La1.61GeO5-δ became much smaller than that of these well-known fast oxide ion conductors. The change in the activation energy of the oxide ion conductivity seems to be caused by a change in the local oxygen vacancy structure. However, doping a small amount of Sr for La in La2GeO5 was effective to stabilize the high-temperature crystal structure to low temperature. Consequently, doping a small amount of Sr increases the oxide ion conductivity of La2-GeO5-based oxide at low temperature.",
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AU - Takita, Y.

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N2 - Oxide ion conductivity in La2GeO5-based oxide was investigated and it was found that La-deficient La2GeO5 exhibits oxide ion conductivity over a wide range of oxygen partial pressure. The crystal structure of La2GeO5 was estimated to be monoclinic with P21/c space group. Conductivity increased with increasing the amount of La deficiency and the maximum value was attained at x = 0.39 in La2-xGeO5-δ. The oxide ion transport number in La2GeO5-based oxide was estimated to be unity by the electromotive force measurement in H2 - O2 and N2 - O2 gas concentration cells. At a temperature higher than 1000 K, the oxide ion conductivity of La1.61GeO5-δ was almost the same as that of La0.9Sr0.1Ga0.8Mg0.2 O3-δ or Ce0.85Gd0.15O2-δ, which are well-known fast oxide ion conductors. On the other hand, a change in the activation energy for oxide ion conductivity was observed at 973 K, and at intermediate temperature, the oxide ion conductivity of La1.61GeO5-δ became much smaller than that of these well-known fast oxide ion conductors. The change in the activation energy of the oxide ion conductivity seems to be caused by a change in the local oxygen vacancy structure. However, doping a small amount of Sr for La in La2GeO5 was effective to stabilize the high-temperature crystal structure to low temperature. Consequently, doping a small amount of Sr increases the oxide ion conductivity of La2-GeO5-based oxide at low temperature.

AB - Oxide ion conductivity in La2GeO5-based oxide was investigated and it was found that La-deficient La2GeO5 exhibits oxide ion conductivity over a wide range of oxygen partial pressure. The crystal structure of La2GeO5 was estimated to be monoclinic with P21/c space group. Conductivity increased with increasing the amount of La deficiency and the maximum value was attained at x = 0.39 in La2-xGeO5-δ. The oxide ion transport number in La2GeO5-based oxide was estimated to be unity by the electromotive force measurement in H2 - O2 and N2 - O2 gas concentration cells. At a temperature higher than 1000 K, the oxide ion conductivity of La1.61GeO5-δ was almost the same as that of La0.9Sr0.1Ga0.8Mg0.2 O3-δ or Ce0.85Gd0.15O2-δ, which are well-known fast oxide ion conductors. On the other hand, a change in the activation energy for oxide ion conductivity was observed at 973 K, and at intermediate temperature, the oxide ion conductivity of La1.61GeO5-δ became much smaller than that of these well-known fast oxide ion conductors. The change in the activation energy of the oxide ion conductivity seems to be caused by a change in the local oxygen vacancy structure. However, doping a small amount of Sr for La in La2GeO5 was effective to stabilize the high-temperature crystal structure to low temperature. Consequently, doping a small amount of Sr increases the oxide ion conductivity of La2-GeO5-based oxide at low temperature.

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