Development of Proton Conductors Using Pyrochlore-Perovskite Phase Boundaries

Speakman, Scott A.; Carneim, Robert D.; Payzant, E. Andrew; Armstrong, T.R.

doi:10.1361/10599490419270

Cited by 16 publications

(9 citation statements)

References 14 publications

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“…Speakman et al have found that solubility of the Y 3+ in the LZO can be more than 2.5 mol%. The lattice parameter of the LZO (doped with Y) by XRD measurements is ∼0.09 % offset from the lattice parameter of the stoichiometric LZO 18 . This is consistent with that of the LZO (doped with Y) calculated based on TEM results in this study.…”

Section: Discussionsupporting

confidence: 91%

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Characterization of Lanthanum Zirconate Formation at the A‐Site‐Deficient Strontium‐Doped Lanthanum Manganite Cathode/Yttrium‐Stabilized Zirconia Electrolyte Interface of Solid Oxide Fuel Cells

Chen

Bourne

Siebein

et al. 2008

Journal of the American Ceramic Society

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Lanthanum zirconate (LZO) formation and growth kinetics between 1273-1673 K at the A-site (La, Sr)-deficient Sr-doped lanthanum manganite (LSM)/yttrium-stabilized zirconia (YSZ) interface were studied using high-resolution transmission electron microscopy-energy-dispersive X-ray spectrometry (HRTEM-EDS). A cross-section TEM sample preparation technique was developed using a dual-beam focused ion beam and an in situ Omniprobe manipulator. The LZO pyrochlore phase was identified at the LSM/YSZ interface by TEM. The LZO is epitaxial with respect to the YSZ phase but not to the LSM phase. EDS results coupled with structural analysis suggest that La diffusion is a critical step in LZO formation. This study shows that LZO formation can occur even for A-sitedeficient LSM with a La composition of 78 mol% (o86 mol%). The activation energy for LZO formation was found to be 16878 KJ/mol. T. Gur-contributing editorThe authors would like to thank the United States Department of Energy for funding under project number DOE project DE-AC05-76RL01830 and Nextech for supplying cathode inks for use in this work.

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Section: Discussionsupporting

confidence: 91%

“…EDS suggests that La diffuses out of the LSM lattice and reacts with Zr 13,17 and/or Y to form a LZO (doped with Y) layer at the LSM/YSZ interface 1,18 (see Fig. 2(b)).…”

Section: Discussionmentioning

confidence: 99%

Characterization of Lanthanum Zirconate Formation at the A‐Site‐Deficient Strontium‐Doped Lanthanum Manganite Cathode/Yttrium‐Stabilized Zirconia Electrolyte Interface of Solid Oxide Fuel Cells

Chen

Bourne

Siebein

et al. 2008

Journal of the American Ceramic Society

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“…Pyrochlores exist in the stable fluorite-type structure with multiple oxygen vacancies available for proton conduction and do not require strontium or barium, so they are, therefore, more chemically durable. For example, lanthanum zirconate (La 2 Zr 2 O 7 ) has been reported to possess reasonable proton conductivity in the 600-1,000°C temperature range [77,78], and substitutional doping of Sr for La and Y for Zr in La 2 Zr 2 O 7 can further increase the conductivity, with the highest gains obtained for a 4 and 8 mol% substitution of Y for Zr [79]. Other pyrochlores, such as (Gd 0.98 Ca 0.02 ) 2 Ti 2 O 7 , have demonstrated high ionic conductivity at high temperature (0.01 S cm −1 at 1,000°C), as well as good electron conductivity [80], while Gd 2 Mo 2 O 7 is reported to possess metallic-like electron conductivities at room temperature [81].…”

Section: Pyrochloresmentioning

confidence: 99%

Review of proton conductors for hydrogen separation

Phair

Badwal

2006

Ionics

223

132

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There is a global push to develop a range of hydrogen technologies for timely adoption of the hydrogen economy. This is critical in view of the depleting oil reserves and looming transport fuel shortage, global warming, and increasing pollution. Molecular hydrogen (H 2 ) can be generated by a number of renewable and fossil-fuel-based resources. However, given the high cost of H 2 generation by renewable energy at this stage, fossil or carbon fuels are likely to meet the short-to medium-term demand for hydrogen. In view of this, effective technologies are required for the separation of H 2 from a gas feed (by-products of coal or bio-mass gasification plants, or gases from fossil fuel partial oxidation or reforming) consisting mainly of H 2 and CO 2 with small quantities of other gases such as CH 4 , CO, H 2 O, and traces of sulphur compounds. Several technologies are under development for hydrogen separation. One such technology is based on ion transport membranes, which conduct protons or both protons and electrons. Although these materials have been considered for other applications, such as gas sensors, fuel cells and water electrolysis, the interest in their use as gas separation membranes has developed only recently. In this paper, various classes of proton-conducting materials have been reviewed with specific emphasis on their potential use as H 2 separation membranes in the industrial processes of coal gasification, natural gas reforming, methanol reforming and the watergas shift (WGS) reaction. Key material requirements for their use in these applications have been discussed.

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“…The first sublattice occupied mainly by La 3+ , second one by Zr 4+ as presented in [19]. It was assumed that the Y 3+ ion substitutes the La 3+ and Zr 4+ in both cationic sublattices [9,12] and thus the formula for pyrochlore solid solution can be presented as (La 3+ ,Y 3+ ,Zr 4+ ) 2 (Zr 4+ ,Y 3+ ,La 3+ ) 2 (O 2− ,Va) 6 [16]. Experimental investigation of phase relations in the La 2 O 3 -rich corner published in our previous work [12] made it possible to recommend dataset-1 because calculated phase diagrams then agree with experimental results.…”

Section: Thermodynamic Modellingmentioning

confidence: 99%

“…The system La 2 Zr 2 O 7 -LaYO 3 was studied by Speakman et al [9]. Based on the chemical composition dependence of the lattice parameters in the La 2 (Zr 1−x Y x ) 2 O 7−x series Speakman et al [9] concluded that Y 3+ substitutes the La 3+ and Zr 4+ ions in their atomic positions. They also synthesized one sample of (La 1−x Y x ) 2 Zr 2 O 7 series with x = 0.05.…”

Section: Introductionmentioning

confidence: 99%