Phase stability and oxygen transport characteristics of yttria- and niobia-stabilized bismuth oxide

Joshi, A. V.; Kulkarni, Sneha A.; Nachlas, Jessie; Diamond, Jordan; Weber, Neill; Virkar, Anil V.

doi:10.1007/bf00585430

Cited by 32 publications

(12 citation statements)

References 16 publications

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“…A clear bend in the conductivity slopes at approximately 625 C was also observed, similar to the one observed by Berezovsky et al [35]. Of the compositions with various Nb 5þ contents, Bi 0.76 Y 0.20 Nb 0.04 O 1.5þd obtained the highest conductivities of 0.09 and 0.29 Scm À1 at 600 and 700 C respectively, which are much higher than those in the d-Bi 2 O 3 systems with a single dopant of Y 3þ or Nb 5þ such as the Bi 0.75 Y 0.25 O 1.5 and Bi 0.75 Nb 0.25 O 1.5 ceramics as reported in the literature [8,27,36]. The conductivity of the Bi 0.76 Y 0.24Àx Nb x O 1.5 ceramics showed a tendency of decreasing with increasing Nb 5þ concentration due to the fact that the incorporation of Nb 2 O 5 in the Bi 2 O 3 lattice diminished the oxygen vacancies according to the following equation [36]:…”

Section: Resultsmentioning

confidence: 59%

“…Though the conductivity of the Nb 2 O 5 -stabilized Bi 2 O 3 was less than one-fifth of the conductivity of the Y 2 O 3 -stabilized Bi 2 O 3 in the literature [36], the electric conductivities of the Bi 0.76 Y 0.24Àx Nb x O 1.5 Fig. 4(d), the electrical conductivity of the Y 2 O 3 and Sc 2 O 3 co-doped Bi 2 O 3 ceramics escalated with the increase in temperature and in the Sc 3þ content of the Bi 0.76 Y 0.24Àx Sc x O 1.5 ceramics.…”

Section: Resultsmentioning

confidence: 96%

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The phase stability and electrical conductivity of Bi2O3 ceramics stabilized by Co-dopants

Wang

Hsu

Tsai

et al. 2012

Journal of Power Sources

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Section: Resultsmentioning

confidence: 59%

Section: Resultsmentioning

confidence: 96%

The phase stability and electrical conductivity of Bi2O3 ceramics stabilized by Co-dopants

Wang

Hsu

Tsai

et al. 2012

Journal of Power Sources

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“…Eo(RL + Ret + Re(l) + Re(a)) (RL + Rct)(Ri(I, + Ri (2)) + (Re(D + Re (2))(Ri(l) + Ri(2) + RL + Rot) [20] Finally, substitution of Eq. [18] and [:20] in Eq.…”

Section: [19]mentioning

confidence: 98%

Theoretical Analysis of Solid Oxide Fuel Cells with Two‐Layer, Composite Electrolytes: Electrolyte Stability

Virkar

1991

J. Electrochem. Soc.

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126

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Theoretical analysis of solid oxide fuel cells (SOFCs) using two-layer, composite electrolytes consisting of a solid electrolyte of a significantly higher conductivity compared to zirconia (such as ceria or bismuth oxide) with a thin layer of zirconia or thoria on the fuel side is presented. Electrochemical transport in the two-layer, composite electrolytes is examined by taking both ionic and electronic fluxes into account. Similar to most electrochemical transport phenomena, it is assumed that local equilibrium prevails. An equivalent circuit approach is used to estimate the partial pressure of oxygen at the interface. It is shown that thermodynamic stability of the electrolyte (ceria or bismuth oxide) depends upon the transport characteristics of the composite electrolyte, in particular the electronic conductivity of the air-side part of the electrolyte. For example, the greater the electronic conductivity of the air-side part of the electrolyte, the greater is the interface partial pressure of oxygen and the greater is the thermodynamic stability. The analysis shows that it would be advantageous to use composite electrolytes instead of all-zirconia electrolytes, thus making low-temperature (~600-800~ SOFCs feasible. Implications of the analysis from the standpoint of the desired characteristics of SOFC components are discussed.The current SOFC technology is based on stabilized zirconia electrolytes which are stable in fuel (reducing) environment. The ionic conductivity of zirconia, however, is too low below about 950~ Consequently, most of the SOFCs are operated at -1000~ It is well known that the efficiency of a fuel cell is greater at lower temperatures. In this regard, the need for the development of solid electrolytes with substantially higher ionic conductivity compared to zirconia has been long recognized. Several researchers have demonstrated that CeO2 doped with alkaline earth or rare earth oxides exhibits ionic conductivity up to two orders of magnitude higher than zirconia at comparable temperatures (1-9). Ceria, however, exhibits a significant electronic conduction which is undesirable. Moreover, the electronic transference number increases in the presence of reducing atmospheres. Theoretical analysis of fuel cell operation with mixed conducting solid electrolytes has been conducted by Ross and Benjamin (10)

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“…␦-Bi 2 O 3 , however, is only stable at temperatures ranging from 723°C to 823°C. [9][10][11] The rhombohdral structure as also obtained by adding alkaline-earth oxides into Bi 2 O 3 . Two metastable phases, ␤-Bi 2 O 3 and ␥-Bi 2 O 3 , may also be observed at temperatures below 650°C after fast cooling from ␦-Bi 2 O 3 .…”

Section: Introductionmentioning

confidence: 99%

Effect of water/water vapor on microstructure and phase stability of (Y_0.25Bi_0.75)₂O₃solid electrolytes

Huang

Fung

2003

J. Mater. Res.

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Highly conductive cubic (Y 0.25 Bi 0.75 ) 2 O 3 tends to transform to rhombohedral (Y 0.25 Bi 0.75 ) 2 O 3 when annealed at 600°C for more than 200 h. Although the rhombohedral phase of (Y 0.25 Bi 0.75 ) 2 O 3 was known to be the stable phase at temperatures ഛ600°C, it was found that the annealed (Y 0.25 Bi 0.75 ) 2 O 3 was not thermodynamically stable in the water-containing environment. From x-ray diffraction and transmission electron microscopy analysis, it was observed that the annealed (Y 0.25 Bi 0.75 ) 2 O 3 easily decomposed into monoclinic ␣-Bi 2 O 3 and yttrium hydroxide at a temperature as low as 50°C. The monoclinic ␣-Bi 2 O 3 further reacted with CO 2 and formed Bi 2 O 2 CO 3 . Consequently, the annealed (Y 0.25 Bi 0.75 ) 2 O 3 degraded and became flaky powder. Scanning electron microscopy micrographs of water-reacted (Y 0.25 Bi 0.75 ) 2 O 3 also showed surface swelling and peeling. Such surface deterioration was caused by a large volume increase during the water reaction. Similar reaction was also observed when the annealed (Y 0.25 Bi 0.75 ) 2 O 3 was exposed in the humidified air at 300°C. As the temperature was raised to 500°C, little reaction was observed between water vapor and (Y 0.25 Bi 0.75 ) 2 O 3 . The better stability of (Y 0.25 Bi 0.75 ) 2 O 3 at elevated temperature was observed.

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Phase stability and oxygen transport characteristics of yttria- and niobia-stabilized bismuth oxide

Cited by 32 publications

References 16 publications

The phase stability and electrical conductivity of Bi2O3 ceramics stabilized by Co-dopants

The phase stability and electrical conductivity of Bi2O3 ceramics stabilized by Co-dopants

Theoretical Analysis of Solid Oxide Fuel Cells with Two‐Layer, Composite Electrolytes: Electrolyte Stability

Effect of water/water vapor on microstructure and phase stability of (Y_0.25Bi_0.75)₂O₃solid electrolytes

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Phase stability and oxygen transport characteristics of yttria- and niobia-stabilized bismuth oxide

Cited by 32 publications

References 16 publications

The phase stability and electrical conductivity of Bi2O3 ceramics stabilized by Co-dopants

The phase stability and electrical conductivity of Bi2O3 ceramics stabilized by Co-dopants

Theoretical Analysis of Solid Oxide Fuel Cells with Two‐Layer, Composite Electrolytes: Electrolyte Stability

Effect of water/water vapor on microstructure and phase stability of (Y0.25Bi0.75)2O3solid electrolytes

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Effect of water/water vapor on microstructure and phase stability of (Y_0.25Bi_0.75)₂O₃solid electrolytes