Au Catalyzed Structural and Electrical Evolution of Ni/Au Contact to GaN

Kim, C.C.; Kim, J.K.; Lee, J.L; Je, Jung Ho; Yi, Min-Su; Noh, Do Young; Hwu, Y.; Ruterana, P.

doi:10.1002/1521-396x(200111)188:1<379::aid-pssa379>3.0.co;2-u

Cited by 3 publications

(3 citation statements)

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“…On this occasion, the suppressed arc instead of the half-tear shaped spectrum will also be expected, which has usually been confirmed in most 3 PB limited electrodes like LSM. 34 In view of those implications of the Gerischer behavior, it seems that D and k are most possibly well balanced also in those Sr20-40 specimens. k is progressively reduced by Sr doping as D is.…”

Section: Resultsmentioning

confidence: 99%

“…Those results are consistent with the ones reported by Aguadero et al 24 According to the fitting results, the small capacitances and the large characteristic frequencies for the HF arcs of Sr30 and Sr40 indicate that those arcs can be reasonably associated to a charge transfer process. [34][35][36] The incorporation of oxygen into cathode lattice has been taken into account in the ALS element. Meanwhile, the electron transfer from current collector to the cathode must not be the case because Sr30 and Sr40 possess higher electrical conductivities than LNO.…”

Section: Resultsmentioning

confidence: 99%

“…The surface exchange process is carried out in several sequent steps as shown above. The reaction orders are calculated using the routine reported elsewhere by Heuveln et al 34,49,50 and listed after each elementary reaction. Burriel et al 51 observed that the surface exchange reaction was 2 orders of magnitude faster in a-b plane than along c-axis in the (001)-oriented epitaxial LNO thin film.…”

Section: Oxygen Surface Exchange: Omentioning

confidence: 99%

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Oxygen Reduction Reaction Kinetics in Sr-Doped La₂NiO_4+δRuddlesden-Popper Phase as Cathode for Solid Oxide Fuel Cells

Guan

Zhang

et al. 2015

J. Electrochem. Soc.

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In this paper, electro-catalytic reduction of oxygen in Sr-doped lanthanum nickelates, La 2-x Sr x NiO 4+δ (0 ≤ x ≤ 0.4) RuddlesdenPopper (R-P) phase, has been investigated. The oxygen reduction reaction (ORR) kinetics is evaluated via electrochemical impedance spectroscopy (EIS) with the symmetric cell configuration. The maximum performance is achieved with the un-doped La 2 NiO 4+δ , ∼0.13 cm 2 at 800 • C. Sr doping decreases the electrode performance progressively. Further detailed analysis indicates that bulk ionic diffusion and surface oxygen exchange co-limit the ORR of those cathodes. Sr substitution leads to both lowered bulk diffusion and surface exchange rates. With high Sr content (x = 0.3, 0.4), oxygen ion transfer resistance between nickelate/electrolyte is observed. As for the surface exchange process, oxygen adsorption is suggested to be the main rate-limiting step (RLS) according to the reaction orders, which is retarded further by the oxidation of Ni 2+ to Ni 3+ as Sr content increases. The possible role of incorporation process in determining the overall reaction rate is also discussed.Intermediate temperature (600∼800 • C) solid oxide fuel cells (ITSOFCs) have attracted increasing interest because of the relaxed requirement for sealing, interconnects and thermal expansion matching. However, the lowered operating temperature usually leads to poorer performance due to the increased electrolyte resistance and the retarded electrode reaction kinetics. In order to improve the cathode performance of IT-SOFCs, mixed ionic and electronic conductors (MIEC) have been brought up as potential electrode materials. The fast ionic conduction in MIEC could transport oxygen vacancies from electrolyte to 3-dimension of the cathode network, thereby enlarging the electrochemically reactive area. 1 Recently, K 2 NiF 4 type La 2 NiO 4+δ (LNO)-based oxides with higher oxygen ionic conductivity than conventional LaCoO 3 -based perovskites such as (LaSr)(CoFe)O 3-δ (LSCF), have also been proposed as possible candidates for IT-SOFCs cathode application. [2][3][4][5][6][7][8][9][10][11] The lattice structure of LNO is composed of perovskite alternating with LaO rock salt layers. Oxygen hyperstoichiometry is confirmed and associated to the incorporation of oxygen atoms into the interstitial sites of LaO layers. [12][13][14][15] The ionic conductivity of such materials mainly results from the in-plane transport of interstitial oxygen in the LaO layers. [16][17][18][19] La and/or Ni site element substitution have been used to tailor the materials in attempt to improving certain physical parameters, such as the surface exchange (k), bulk diffusion (D) coefficients and electrical conductivity. Despite excellent oxygen surface exchange and bulk diffusion properties, un-doped LNO did not show superior ORR performance, which is believed to relate to low electronic conductivity of such material. Sr substitution for La in LNO is confirmed to improve the electronic conductivity beneficially, 20 while the ionic conductivity is decre...

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Section: Resultsmentioning

confidence: 99%