Transient Response of the System Ta∕Ta[sub 2]O[sub 5]∕Electrolyte

Taylor, D. F.; Dignam, M. J.

doi:10.1149/1.2403251

Cited by 26 publications

(19 citation statements)

References 20 publications

(147 reference statements)

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“…Closely related to the impedance effects are the effects occurring during galvanostatic and potentiostatic transient measurements (2)(3)(4)(5)(6)(7). All these measurements show the presence of a relaxation effect, the relaxation time of which is inversely proportional to the d-c ionic current density.…”

Section: Rs = ';mentioning

confidence: 93%

“…When real and imaginary parts are split we get Re(BF) --BiF § (js/q)2BrF/(~ ~ § (is/q) 2) [3] Ira(BE) = --~(js/q)BrF/(~ § (is/q) 2) [4] These equations are similar to those describing a Debye relaxation with a single relaxation time (16). For low frequencies ~ ~< is/q: Re(BF) --> (Bi § Br)F, the steady-state value of BF, and Im(BF) --> 0.…”

Section: Js'] Qbrf ~J/~f'f/js =---Bf = Bif ~-I~ + Js/qmentioning

confidence: 99%

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Impedance Measurements during Anodization of Aluminum

Wit

Wijenberg

Crevecoeur

1979

J. Electrochem. Soc.

101

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The impedance of a growing anodic oxide layer is inductive in a rcertain frequency range. This effect is related to the occurrence of transients after changes in current density or applied electric field. Measurements on aluminum samples in the frequency range 5 mHz-10 kHz and the current density range 3 X 10-6-5 • ]~O -3 A/cm 2 and in various electrolytes are presented and compared with a theory in which the relaxation effect is ascribed to a buildup of surface charge at the metal-oxide interface.It has long been recognized that the study of nonsteady-state situations during anodization is helpful to an understanding of the mechanism of anodization. A very early measurement was made by Baumann in 1939 (1) who studied the frequency dependence of the impedance during porous oxide formation on aluminum. The techniques used most commonly are: a sudden change of the applied field, which is kept constant afterward (potentiostatic transient); a sudden change of the current density which is kept constant afterward (galvanostatic transient); and the superposition of a small a-c signal on the d-c signal.Potentiostatic transients have been measured on tantalum by Vermilyea (2), Young (3), and Taylor and Dignam (4), and on aluminum by Vermilyea (2) and Dignam and Ryan (5). Galvanostatic transients have been measured on tantalum by Dewald (6), Vermilyea (2), and Young (3) and on aluminum by Goad and Dignam (7). A-C measurements have been performed on aluminum by Baumann (1), Winkel, Pistorius, and van Geel (8), and Goad and Dignam (9), and on tantalum by Taylor and Dignam (4). In all these experiments it was shown that the system after a change does not immediately assume the new steady-state values for current or overpotential, but that it relaxes to the new steady state in a certain time. This relaxation time is inversely proportional to the d-c ionic current density.Several theories have been put forward to explain this relaxation. Bean, Fisher, and Vermilyea (10) ascribe it to a sluggishness in the response of the number of charge carriers, assumed to be metal interstitials, to the variation of the applied field. Their approach has come in for criticism, on the one hand, from Young (3), who showed that it does not satisfactorily describe the acceleration of the ionic current which is found when a potential step is applied, and, on the other hand, from Dignam ( 11), who challenged it on the grounds of free path considerations. Dignam and co-workers (4, 7, 11) consider a relaxation of the dielectric polarization of the oxide to be responsible for the effects. Their approach leads to a set of equations which satisfactorily accounts for the experiments and which is used as a starting point for the theoretical considerations of the present paper. The mechanism, however, by which these polarization changes occur is unclear.The present work presents a continuation and extension of the cited work. It gives the results of impedance measurements during anodization of aluminum in much wider frequency and current ranges than used hi...

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Section: Rs = ';mentioning

confidence: 93%

Section: Js'] Qbrf ~J/~f'f/js =---Bf = Bif ~-I~ + Js/qmentioning

confidence: 99%

Impedance Measurements during Anodization of Aluminum

Wit

Wijenberg

Crevecoeur

1979

J. Electrochem. Soc.

101

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“…The model is limited to steady-state oxide growth and does not consider transients produced by current or potential modulation. 23,24 Additionally, the influence of mechanical strain energy in the film on conduction is not included in the model. 25 …”

mentioning

confidence: 99%

Metal and Oxygen Ion Transport during Ionic Conduction in Amorphous Anodic Oxide Films

Wang

Hebert

1999

J. Electrochem. Soc.

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A mathematical model was developed for ionic conduction in amorphous oxide films. The model is based on a hypothesized "defect cluster" mechanism in which both metal and oxygen ions are involved in transport. Defect clusters are created by inward displacement of oxygen ions around an oxygen vacancy-like defect in response to the vacancy's electric field. Metal ions are assumed to migrate easily in the gap between the first and second layer of oxygen ions around the vacancy. The model includes the polarization of the conductive gap in the applied electric field, the exchange of mobile metal ions in the cluster with stationary metal ions in the surrounding oxide, and space charge generated in the film by clusters and oxide nonstoichiometry. The rate-limiting step is the jump of the oxygen vacancy in the cluster. It was found that polarization of the cluster leads to a stoichiometric excess of metal ions in the cluster and that this excess produces a net transport of metal ions due to the motion of the cluster. The metal ion transport number was found to increase with electric field and to depend on the dielectric constant and cluster size. The field dependence follows that found experimentally. The calculated transport numbers are in quantitative agreement with experimental values for tantalum, niobium, and tungsten oxide but smaller than experimental values for aluminum oxide. The field coefficient in the high-field-conduction-rate expression is also predicted and agrees with experimental values to within 10%.

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“…Under such conditions, they attributed the presence of the medium-frequency inductive behaviour to dielectric relaxation, as proposed previously by Dignam et al. [6]. Lenderink et al studied the impedance response of aluminium in sulphuric acid and in the acetic acid buffer, and they suggested that adsorbed intermediates involved in the reduction of hydrogen ions could cause an inductive behaviour [7].…”

Section: Introductionmentioning

confidence: 70%

Relationship between the inductive response observed during electrochemical impedance measurements on aluminium and local corrosion processes

Yang

Scenini

Stevens

et al. 2018

Corrosion Engineering, Science and Technology

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In situ real-time imaging and electrochemical impedance spectroscopy (EIS) measurements were performed on pure aluminium, aluminium-copper and copper electrodes, with the aim to elucidate the relationship between the shape of EIS spectra and the local processes occurring on the surface of corroding aluminium, with particular attention to the appearance of inductive behaviour. When a stable oxide was present on the aluminium surface, the impedance modulus increased with decreasing frequencies, indicating the absence of inductive behaviour. Conversely, the presence of depassivating condition coupled with the availability of some anodic current, generated localized corrosion and associated hydrogen evolution at the corrosion front (also known as superfluous hydrogen evolution). In these conditions, a clear inductive behaviour was observed, regardless on the source of the anodic current at the corrosion front, i.e. galvanic coupling or external anodic polarization.

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Transient Response of the System Ta∕Ta[sub 2]O[sub 5]∕Electrolyte

Cited by 26 publications

References 20 publications

Impedance Measurements during Anodization of Aluminum

Impedance Measurements during Anodization of Aluminum

Metal and Oxygen Ion Transport during Ionic Conduction in Amorphous Anodic Oxide Films

Relationship between the inductive response observed during electrochemical impedance measurements on aluminium and local corrosion processes

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