Point-defect thermodynamics and size effects

Maier, Joachim

doi:10.1016/s0167-2738(00)00618-4

Cited by 86 publications

(53 citation statements)

References 24 publications

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“…As in ZrO 2 and YSZ, forming surface vacancies in CeO 2 and GDC is more favorable than bulk vacancies, as has been found previously [29]. Experimentally, vacancy formation enthalpy in CeO 2 has been found to be 1.8eV for nanocrystalline samples and to decrease strongly as the crystal size decreases [30].…”

Section: Vacancy Formation Energysupporting

confidence: 72%

First Principles Study of Oxygen Incorporation Reactions in Oxides

Holme

Prinz

2010

Trans. Mat. Res. Soc. Japan

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The oxygen incorporation reaction, and its opposite, the oxygen deletion reaction, may be rate limiting reactions in solid oxide fuel cells. This study examines the insertion and deletion reactions in the popular solid oxide fuel cell electrolyte and electrode materials (. A Kröger-Vink diagram is constructed for SOFC anode and cathode operating conditions, and defect equilibrium considerations are used to explain the experimental result that oxygen incorporation in bilayer electrolytes shows higher surface exchange rates. Quantum simulations of the incorporation reaction and vacancy formation energetics support this conclusion.Simulations of oxygen incorporation in perovskites agree with experimental trends in reactivity LSCF > LSM > LMO, and suggest the reason to be due to structural rather than electronic properties. A new model of oxygen deletion at the anode is proposed and shown to have lower energy barriers than sequential deletion and reaction with hydrogen to form the hydroxide ion.

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Section: Vacancy Formation Energysupporting

confidence: 72%

First Principles Study of Oxygen Incorporation Reactions in Oxides

Holme

Prinz

2010

Trans. Mat. Res. Soc. Japan

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“…Furthermore, we observed several orders conductivity enhancement in epitaxial YSZ grown on MgO and SrTiO 3 single crystals in a recent work [9]. Studies of the mechanisms for ionic conduction in nanomaterials [10,11] have shown that the mobility of ions can be increased through grain boundaries and interfaces, resulting in orders of magnitude greater diffusivity [12,13].…”

Section: Introductionmentioning

confidence: 76%

Concentration-dependent ionic conductivity and thermal stability of magnetron-sputtered nanocrystalline scandia-stabilized zirconia

et al. 2010

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Nanocrystalline (nc) scandia-stabilized zirconia (SSZ) electrolytes with scandia contents of 5.9 to 15.9 mol% were synthesized by reactive magnetron sputtering. For scandia content ≥ 9.1 mol%, the as-deposited films were pure cubic phase with <111> texture, while traces of tetragonal phase was found for lower Sc content. Single-line profile analysis of the 111 X-ray diffraction peak yielded an out-of-plane grain size of ~10 nm and a microstrain of 2.0-2.2%, regardless of scandia content, for films deposited at 400 °C and a bias of -70 V. Films deposited at higher bias voltages showed a reduced grain size, yielding a grain size of ~6 nm and a microstrain of ~2.5% at -200 V and -250 V with additional incorporation of argon. Temperature-dependent impedance spectroscopy of the SSZ films showed that the in-plane ionic conductivity had a maximum close to 10.7 mol% and decreased almost an order of magnitude as the scandia -content was increased to 15.9 mol%. The activation energy for oxygen ion migration was determined to be between 1.30 -1.43 eV. In addition, no 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 45 46 47 48 49 50 51 52 53 54 55 56 57 58 59 60 61 62 63 64 65 2 dependence on grain size was observed. The above observations suggest a bulk mechanism for ionic conduction. *Manuscript Click here to view linked References

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“…It is clearly due to conduction along the interfaces, which the TEM shows are well ordered. Therefore it could be due to space charge effects at the surface of the grains, and an example of the model proposed by Maier and co-workers [85][86][87]. …”

Section: Lithium Niobatementioning

confidence: 99%

Structure and dynamics in nanoionic materials

Chadwick

Savin

2006

Solid State Ionics

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Nanomaterials, materials with particle dimensions less than 100 nm, show a range of unusual properties when compared with their bulk counterparts. Atomic transport is one of these properties and nanomaterials have been reported as having exceptionally high diffusion coefficients. In the case of ionic materials the atomic transport is important in a number of technological applications where they are used as solid electrolytes, for example in sensors, batteries and fuel cells. Hence ionic nanomaterials often referred to as nanoionics, can offer the means of producing electrolytes with improved performance. This contribution will examine the mechanisms of atomic transport in nanoionics in two model materials, zirconia and lithium niobate. Since an understanding of these mechanisms is dependent on knowledge of the microstructure of the materials consideration will also be given to the structural characterisation of the materials, with a focus on X-ray absorption spectroscopy. The use of this technique to characterise mesoporous a-Fe 2 O 3 is also discussed.

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Point-defect thermodynamics and size effects

Cited by 86 publications

References 24 publications

First Principles Study of Oxygen Incorporation Reactions in Oxides

First Principles Study of Oxygen Incorporation Reactions in Oxides

Concentration-dependent ionic conductivity and thermal stability of magnetron-sputtered nanocrystalline scandia-stabilized zirconia

Structure and dynamics in nanoionic materials

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