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Dielectric and Li transport properties of electron conducting and non-conducting sputtered amorphous Ta2O5 films
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.
Uppsala University, Disciplinary Domain of Science and Technology, Technology, Department of Materials Science.ORCID iD: 0000-0002-8279-5163
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2001 (English)In: Electrochimica Acta, ISSN 0013-4686, E-ISSN 0019-4686, Vol. 46, no 13-14, 2041-2046 p.Article in journal (Refereed) Published
Abstract [en]

Two types of sputtered thin film amorphous tantalum oxide (Ta2O5) were studied: one electron conducting Ta2O5 (ec-Ta2O5) and the other non-conducting Ta2O5 (nc-Ta2O5). The as-deposited films were characterized by impedance spectroscopy (IS) and isothermal transient ionic current (ITIC) measurements. From IS, the dc conductivity 2×10−14 S/cm was obtained for the ec-Ta2O5 film at an applied ac potential of 50 mV whereas a value ≤1×10−17 S/cm was obtained for the nc-Ta2O5 film. Li conducting properties were studied using the galvanostatic intermittent titration technique and ITIC measurements on the intercalated samples. Despite the very dissimilar dc conductivities of the as-deposited films, the two Ta2O5 samples showed surprisingly similar Li ion conducting properties for small Li/Ta2O5 ratios. The Li ion mobility was in the range 1.1×10−9–3.0×10−9 cm2/V s for both films. However, the Li storage behaviour as well as the chemical diffusion coefficient differed. For the nc-Ta2O5 film a plateau was observed in the equilibrium potential vs. composition curve for Li/Ta2O5 ratios between 7×10−5 and 2×10−3. This plateau was likely to have been caused by attractive interactions between the intercalated ions, possibly large enough to cause phase separation. The attractive interactions were shown to suppress the chemical diffusion coefficient in this composition range.

Place, publisher, year, edition, pages
2001. Vol. 46, no 13-14, 2041-2046 p.
National Category
Engineering and Technology
Identifiers
URN: urn:nbn:se:uu:diva-89903DOI: 10.1016/S0013-4686(01)00412-1OAI: oai:DiVA.org:uu-89903DiVA: diva2:161753
Available from: 2002-05-15 Created: 2002-05-15 Last updated: 2016-11-30Bibliographically approved
In thesis
1. Charged Particle Transport: As Information Source about Ion Conductors, Dielectric Materials, and Drug Delivery Systems
Open this publication in new window or tab >>Charged Particle Transport: As Information Source about Ion Conductors, Dielectric Materials, and Drug Delivery Systems
2002 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

This thesis treats charged particle transport, mostly in solid materials but also, to some extent, in aqueous media. Three major types of materials have been investigated; dielectric materials, ion conductors, and drug-delivery systems.

The frequency-dependent dielectric permittivity of sputtered amorphous thin film tantalum oxide (Ta2O5) has been determined by using impedance spectroscopy. A new interpolation formula has been derived, that interpolates between the two power-law regions at low and high frequencies usually observed in the dielectric spectrum. This formula is based on a regular-singular-point (RSP) analysis of the conduction process, and the power-laws in the dielectric spectrum are interpreted in terms of RSPs of the underlying rate equation for the corresponding polarization-current response function.

Lithium transport properties of Ta2O5 have been analyzed by using the galvanostatic intermittent titration technique and by isothermal transient ionic current measurements. Chemical and component diffusion coefficients for intercalated lithium have been extracted. Moreover, the ion conduction process has been analyzed theoretically, and expressions for transient ionic currents derived, both for single ion-conducting layers and for three-layered structures of ion conductors.

Electrical measurement techniques have also been applied to pharmaceutical systems. The alternating ionic current technique has been developed as a tool for determining the release of electrically charged drug substances in aqueous media. Tablets made of agglomerated micronized cellulose have been investigated, and sodium chloride has been used as a model drug. An attempt has been made to describe the combined drug dissolution and drug release processes in mathematical terms.

Place, publisher, year, edition, pages
Uppsala: Acta Universitatis Upsaliensis, 2002. 82 p.
Series
Comprehensive Summaries of Uppsala Dissertations from the Faculty of Science and Technology, ISSN 1104-232X ; 725
Keyword
Materials science, Materialvetenskap
National Category
Materials Engineering
Research subject
Engineering Science
Identifiers
urn:nbn:se:uu:diva-2103 (URN)91-554-5347-3 (ISBN)
Public defence
2002-06-07, the Hägg Lecture Hall at the Ångström Laboratory, Uppsala, 09:30
Opponent
Available from: 2002-05-15 Created: 2002-05-15Bibliographically approved

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Frenning, GöranNiklasson, Gunnar AStrømme Mattsson, Maria

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