Rational selection of advanced solid electrolytes for intermediate temperature fuel cells

Sammells, Anthony F.; Cook, Robert P.; White, James H.; Osborne, J. J.; MacDuff, Robert C.

doi:10.1016/0167-2738(92)90097-9

Cited by 311 publications

(164 citation statements)

References 11 publications

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“…6). Hence, the concept of free volume [12,23], developed for perovskite-type oxides, cannot be applied for comparison of phases with different structural types. Table 4 lists the ion-migration channel sizes (so-called ''bottlenecks'') for the CaAl 0.5 Fe 0.5 O 2.5þd lattice, estimated from the Rietveld refinement results (Table 2) by assuming linear diffusion pathways between each two neighboring oxygen sites.…”

Section: Ionic Conductivitymentioning

confidence: 99%

“…1), and can be considered as an oxygen-deficient perovskite where the oxygen vacancies are ordered along (0 1 0) planes [11]. These vacancies were assumed to significantly contribute to ionic transport, forming one-dimensional diffusion pathway for oxygen ion migration in the tetrahedral layers [12,13]. On the contrary, experimental data on partially ordered ferrites [6,11,14] suggest that oxygen-vacancy ordering leads to decreasing ionic conduction.…”

Section: Introductionmentioning

confidence: 95%

“…According to simplified perspectives on the role of stereological features on ionic transport, the diffusion may be affected by a number of structural parameters, such as the specific free volume of the unit cell, tolerance factor, or the size and curvature of channels available for mobile oxygen anions [1,12,22,23]. The specific free volume (V sf ) of CaAl 0.5 Fe 0.5 O 2.5þd , estimated as [23] …”

Section: Ionic Conductivitymentioning

confidence: 99%

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Oxygen ionic conduction in brownmillerite CaAl0.5Fe0.5O2.5+

Хартон

Marozau

Vyshatko

et al. 2003

Materials Research Bulletin

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The oxygen permeability of CaAl 0.5 Fe 0.5 O 2.5þd brownmillerite membranes at 1123-1273 K was found to be limited by the bulk ionic conduction, with an activation energy of 170 kJ/mol. The ion transference numbers in air are in the range 2 Â 10 À3 to 5 Â 10 À3 . The analysis of structural parameters showed that the ionic transport in the CaAl 0.5 Fe 0.5 O 2.5þd lattice is essentially along the c axis. The largest ion-migration channels are found in the perovskite-type layers formed by iron-oxygen octahedra, though diffusion in tetrahedral layers of the brownmillerite structure is also possible. Heating up to 700-800 K in air leads to losses of hyperstoichiometric oxygen, accompanied with a drastic expansion and, probably, partial disordering of the CaAl 0.5 Fe 0.5 O 2.5þd lattice. The average thermal expansion coefficients of CaAl 0.5 Fe 0.5 O 2.5þd ceramics in air are 16:7 Â 10 À6 and 12:6 Â 10 À6 K À1 at 370-850 and 930-1300 K, respectively.

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Section: Ionic Conductivitymentioning

confidence: 99%

Section: Introductionmentioning

confidence: 95%

Section: Ionic Conductivitymentioning

confidence: 99%

See 1 more Smart Citation

Oxygen ionic conduction in brownmillerite CaAl0.5Fe0.5O2.5+

Хартон

Marozau

Vyshatko

et al. 2003

Materials Research Bulletin

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“…The free volume is defined as the "unoccupied volume" of the unit cell and is calculated by subtracting the volume occupied by all the ions in the unit cell from the volume of the perovskite unit cell. The critical radius (r crit ), Equation 2, for ionic migration between two anion sites is established by a triangle composed of two A-site cations and one B-site cation 7,8 :…”

Section: Introductionmentioning

confidence: 99%

The effect of Pr co-doping on the densification and electrical properties of Sr-LaAlO3

Villas-Bôas

Souza

2013

Mat. Res.

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Perovskite-type materials have been investigated extensively in the attempt to discover new electrolyte materials for solid oxide fuel cells (SOFC) operating at low temperatures. These materials include LaAlO 3 -based perovskite, which, when adequately doped, presents high ionic conductivity. However, despite the high conductivity of doped LaAlO 3 , two characteristics limit its application as solid electrolyte: low sinterability and p-type electronic conductivity in oxidizing conditions. The purpose of this work was to investigate the effect of Pr co-doping on the densification and electrical conductivity of Sr-doped LaAlO 3 . The addition of Pr eliminated the deficiencies mentioned above. Pr in solid solution acts as a perfect sintering aid because promoted densification without forming secondary phase which should be detrimental for electrical conduction. The addition of Pr also increased the bulk electrical conductivity measured in air atmosphere but had no effect at low oxygen partial pressure. However, the addition of Pr had a strong effect on the grain boundary, improving the ionic grain boundary electrical conductivity at air atmosphere which was attributed to the Pr influence on the space charge layer.

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“…The unit cell free volume (V f ) can be defined as the difference between the total unit cell volume and the sum of volumes occupied by Table 1 The structure Parameters of Reatveld analysis of XRD for Ba2(Zn,Zr)2O5 system individual ions in the unit cell, as follows [9],…”

Section: Electrical Propertiesmentioning

confidence: 99%

Synthesis of new brownmillerite-type systems A2(M,M')2O5 (A = Ba, Sr; M = Zn; M'= Zr, Ce, Ti, Hf, Sn)

Ito

Saito

Takayama

et al. 2010

Trans. Mat. Res. Soc. Japan

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Oxide ion conductor has been desired for application to solid oxide fule cells (SOFCs), which can be operated at temperatures below 873K. In order to obtain a new oxide-ion conductor, di-(M) and tetra-(M') valent cations were co-doped to the In-site of Ba 2 In 2 O 5 which is known to be high oxide-ion conductor at high temperature above 1203K. The A 2 (M,M') 2 O 5 systems (A＝Ba, Sr; M=Zn, ; M'=Zr, Ce, Ti. Hf, Sn) having a brownmillerite-type compositions were prepared by solid state reaction. X-ray diffraction analyses confirmed that only the combinations of (Ba-Zn-Zr), (Ba-Zr-Ce), (Ba-Zn-Hf), (Sr-Zn-Zr), (Sr-Zn-Ti) and (Sr-Zn-Hf) for the A-M-M' in the present systems showed single phases of cubic or orthorhombic perovskite-type structures at room temperature. It was found that the electrical comductivities of the new phases increased with increasing the unit cell free volume.

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Rational selection of advanced solid electrolytes for intermediate temperature fuel cells

Cited by 311 publications

References 11 publications

Oxygen ionic conduction in brownmillerite CaAl0.5Fe0.5O2.5+

Oxygen ionic conduction in brownmillerite CaAl0.5Fe0.5O2.5+

The effect of Pr co-doping on the densification and electrical properties of Sr-LaAlO3

Synthesis of new brownmillerite-type systems A<sub>2</sub>(M,M')<sub>2</sub>O<sub>5</sub> (A = Ba, Sr; M = Zn; M'= Zr, Ce, Ti, Hf, Sn)

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