Improvement of the electrolytic properties of Y2O3-based materials using a crystallographic index

Toshiyuki Mori, Jong Heun Lee, Jiguang Li, Takayasu Ikegami, Graeme Auchterlonie, John Drennan

Research output: Contribution to journalArticle

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Abstract

Y2O3 is a c-type rare earth oxide with a fluorite-related structure. This material has been used to refractory because of its high thermal stability and excellent resistance to hydration. In this study, the effective index was suggested in order to improve the electrolytic properties of Y2O3-based oxide. (CexY1-x)2O3+δ (x = 0.25 and 0.3) and [LaaSrbCe0.25Y(1-a-b)]2 O3+δ (a = 0.05, 0.1 and 0.15, b = 0, 0.006 and 0.0125) were prepared as the examples with intermediate and high index, respectively. The specimens with high index value such as (La0.15Ce0.25Y0.60)2O3.25 and (La0.1Sr0.0125Ce0.25Y0.6375)2O3.24 consisted of two phases such as c-type and fluorite, although (Ce0.25Y0.75)2O3.25 with intermediate index value had a single phase of c-type rare earth oxide. Microanalysis indicates that a grain in the (La0.1Sr0.0125Ce0.25Y0.6375)2O3.23(7) sintered body consists of c-type and fluorite phases. An interface between c-type and fluorite phases is coherent in a grain. This suggests that this effective index guides the crystal structure in the specimen to fluorite and the examined composition introduces the interface between c-type and fluorite in the microstructure. The electrochemical properties of specimens including Y2O3 were characterized on the basis of the suggested index. The electrical conductivity of Y2O3-based materials increased with an increase of the index. The apparent activation energy of Y2O3-based materials decreased with increasing index. The ionic transport number of oxygen of the specimens was improved by enhancement of the index, confirming validity of the index. The oxide ionic conductive region of (La0.1Sr0.0125Ce0.25Y0.6375)2 O3.23(7) with high effective index extended up to PO(2) = 10-18 atm at 800 °C, although the specimens with low or intermediate index showed p- or n-type semi-conduction in the same PO(2) region at 800 and 1000 °C. These results suggest that the interface between c-type and fluorite phases also contributes to improve the electrolytic properties in the grain. It is concluded that the improvement of electrolytic properties in Y2O3-based materials is attributable to the microstructure with interface between two phases in a grain and the fluorite structure guided by the suggested index.

Original languageEnglish
Pages (from-to)277-291
Number of pages15
JournalSolid State Ionics
Volume138
Issue number3-4
DOIs
Publication statusPublished - 2001 Jan 1
Externally publishedYes

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Fluorspar
fluorite
Oxides
Rare earths
oxides
Microstructure
Microanalysis
Electrochemical properties
rare earth elements
Hydration
Refractory materials
Thermodynamic stability
Activation energy
Crystal structure
microstructure
Oxygen
refractories
microanalysis
hydration
Chemical analysis

ASJC Scopus subject areas

  • Electrochemistry
  • Physical and Theoretical Chemistry
  • Energy Engineering and Power Technology
  • Materials Chemistry
  • Condensed Matter Physics

Cite this

Improvement of the electrolytic properties of Y2O3-based materials using a crystallographic index. / Mori, Toshiyuki; Lee, Jong Heun; Li, Jiguang; Ikegami, Takayasu; Auchterlonie, Graeme; Drennan, John.

In: Solid State Ionics, Vol. 138, No. 3-4, 01.01.2001, p. 277-291.

Research output: Contribution to journalArticle

Mori, Toshiyuki ; Lee, Jong Heun ; Li, Jiguang ; Ikegami, Takayasu ; Auchterlonie, Graeme ; Drennan, John. / Improvement of the electrolytic properties of Y2O3-based materials using a crystallographic index. In: Solid State Ionics. 2001 ; Vol. 138, No. 3-4. pp. 277-291.
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N2 - Y2O3 is a c-type rare earth oxide with a fluorite-related structure. This material has been used to refractory because of its high thermal stability and excellent resistance to hydration. In this study, the effective index was suggested in order to improve the electrolytic properties of Y2O3-based oxide. (CexY1-x)2O3+δ (x = 0.25 and 0.3) and [LaaSrbCe0.25Y(1-a-b)]2 O3+δ (a = 0.05, 0.1 and 0.15, b = 0, 0.006 and 0.0125) were prepared as the examples with intermediate and high index, respectively. The specimens with high index value such as (La0.15Ce0.25Y0.60)2O3.25 and (La0.1Sr0.0125Ce0.25Y0.6375)2O3.24 consisted of two phases such as c-type and fluorite, although (Ce0.25Y0.75)2O3.25 with intermediate index value had a single phase of c-type rare earth oxide. Microanalysis indicates that a grain in the (La0.1Sr0.0125Ce0.25Y0.6375)2O3.23(7) sintered body consists of c-type and fluorite phases. An interface between c-type and fluorite phases is coherent in a grain. This suggests that this effective index guides the crystal structure in the specimen to fluorite and the examined composition introduces the interface between c-type and fluorite in the microstructure. The electrochemical properties of specimens including Y2O3 were characterized on the basis of the suggested index. The electrical conductivity of Y2O3-based materials increased with an increase of the index. The apparent activation energy of Y2O3-based materials decreased with increasing index. The ionic transport number of oxygen of the specimens was improved by enhancement of the index, confirming validity of the index. The oxide ionic conductive region of (La0.1Sr0.0125Ce0.25Y0.6375)2 O3.23(7) with high effective index extended up to PO(2) = 10-18 atm at 800 °C, although the specimens with low or intermediate index showed p- or n-type semi-conduction in the same PO(2) region at 800 and 1000 °C. These results suggest that the interface between c-type and fluorite phases also contributes to improve the electrolytic properties in the grain. It is concluded that the improvement of electrolytic properties in Y2O3-based materials is attributable to the microstructure with interface between two phases in a grain and the fluorite structure guided by the suggested index.

AB - Y2O3 is a c-type rare earth oxide with a fluorite-related structure. This material has been used to refractory because of its high thermal stability and excellent resistance to hydration. In this study, the effective index was suggested in order to improve the electrolytic properties of Y2O3-based oxide. (CexY1-x)2O3+δ (x = 0.25 and 0.3) and [LaaSrbCe0.25Y(1-a-b)]2 O3+δ (a = 0.05, 0.1 and 0.15, b = 0, 0.006 and 0.0125) were prepared as the examples with intermediate and high index, respectively. The specimens with high index value such as (La0.15Ce0.25Y0.60)2O3.25 and (La0.1Sr0.0125Ce0.25Y0.6375)2O3.24 consisted of two phases such as c-type and fluorite, although (Ce0.25Y0.75)2O3.25 with intermediate index value had a single phase of c-type rare earth oxide. Microanalysis indicates that a grain in the (La0.1Sr0.0125Ce0.25Y0.6375)2O3.23(7) sintered body consists of c-type and fluorite phases. An interface between c-type and fluorite phases is coherent in a grain. This suggests that this effective index guides the crystal structure in the specimen to fluorite and the examined composition introduces the interface between c-type and fluorite in the microstructure. The electrochemical properties of specimens including Y2O3 were characterized on the basis of the suggested index. The electrical conductivity of Y2O3-based materials increased with an increase of the index. The apparent activation energy of Y2O3-based materials decreased with increasing index. The ionic transport number of oxygen of the specimens was improved by enhancement of the index, confirming validity of the index. The oxide ionic conductive region of (La0.1Sr0.0125Ce0.25Y0.6375)2 O3.23(7) with high effective index extended up to PO(2) = 10-18 atm at 800 °C, although the specimens with low or intermediate index showed p- or n-type semi-conduction in the same PO(2) region at 800 and 1000 °C. These results suggest that the interface between c-type and fluorite phases also contributes to improve the electrolytic properties in the grain. It is concluded that the improvement of electrolytic properties in Y2O3-based materials is attributable to the microstructure with interface between two phases in a grain and the fluorite structure guided by the suggested index.

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