Growth mechanism of anodic tantalum pentoxide formed in phosphoric acid
The formation of anodic tantalum oxide (Ta2O5) in dilute phosphoric acid is quantitatively described using point defect chemistry reactions. Oxide formed in phosphoric acid has a distinct bi-layer structure, where the inner layer is pure Ta2O5, but the outer layer contains phosphate incorporated fro...
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| Veröffentlicht in: | Electrochimica acta 2013-01, Vol.87, p.82-91 |
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| creator | Sloppy, J.D. Lu, Z. Dickey, E.C. Macdonald, D.D. |
| description | The formation of anodic tantalum oxide (Ta2O5) in dilute phosphoric acid is quantitatively described using point defect chemistry reactions. Oxide formed in phosphoric acid has a distinct bi-layer structure, where the inner layer is pure Ta2O5, but the outer layer contains phosphate incorporated from the solution. In the point defect model (PDM) presented herein, the inner layer forms directly from, and grows into the metal, due to the production of oxygen vacancies at the metal/oxide interface. The outer layer forms due to the production of tantalum interstitials at the metal/oxide interface and their subsequent migration to the oxide/solution interface, where they hydrolyze to form Ta2O5. The Faradaic impedance is derived for the point defect reactions, and a bi-layer equivalent electrical analog is used to optimize the model to the measured electrochemical impedance spectroscopy (EIS) data. The oxide thickness and ionic current density have been measured separately, and the PDM parameters correctly predict the oxide thickness and ionic current densities due to the production of tantalum interstitials and oxygen vacancies. |
| doi_str_mv | 10.1016/j.electacta.2012.08.014 |
| format | Article |
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Oxide formed in phosphoric acid has a distinct bi-layer structure, where the inner layer is pure Ta2O5, but the outer layer contains phosphate incorporated from the solution. In the point defect model (PDM) presented herein, the inner layer forms directly from, and grows into the metal, due to the production of oxygen vacancies at the metal/oxide interface. The outer layer forms due to the production of tantalum interstitials at the metal/oxide interface and their subsequent migration to the oxide/solution interface, where they hydrolyze to form Ta2O5. The Faradaic impedance is derived for the point defect reactions, and a bi-layer equivalent electrical analog is used to optimize the model to the measured electrochemical impedance spectroscopy (EIS) data. The oxide thickness and ionic current density have been measured separately, and the PDM parameters correctly predict the oxide thickness and ionic current densities due to the production of tantalum interstitials and oxygen vacancies.</description><identifier>ISSN: 0013-4686</identifier><identifier>EISSN: 1873-3859</identifier><identifier>DOI: 10.1016/j.electacta.2012.08.014</identifier><identifier>CODEN: ELCAAV</identifier><language>eng</language><publisher>Kidlington: Elsevier Ltd</publisher><subject>Anodic ; Anodization ; Chemistry ; Electrochemical impedance spectroscopy ; Electrochemistry ; Exact sciences and technology ; General and physical chemistry ; Mathematical models ; Oxides ; Phosphoric acid ; Point defect model ; Point defects ; Product data management ; Tantalum oxide ; Tantalum oxides ; Vacancies</subject><ispartof>Electrochimica acta, 2013-01, Vol.87, p.82-91</ispartof><rights>2012 Elsevier Ltd</rights><rights>2014 INIST-CNRS</rights><lds50>peer_reviewed</lds50><woscitedreferencessubscribed>false</woscitedreferencessubscribed><citedby>FETCH-LOGICAL-c411t-8aba27a9a6d4316bcc450b65536f413bb3fc543a621d5c7c08d76afdb3441a213</citedby><cites>FETCH-LOGICAL-c411t-8aba27a9a6d4316bcc450b65536f413bb3fc543a621d5c7c08d76afdb3441a213</cites></display><links><openurl>$$Topenurl_article</openurl><openurlfulltext>$$Topenurlfull_article</openurlfulltext><thumbnail>$$Tsyndetics_thumb_exl</thumbnail><linktohtml>$$Uhttps://dx.doi.org/10.1016/j.electacta.2012.08.014$$EHTML$$P50$$Gelsevier$$H</linktohtml><link.rule.ids>314,780,784,3550,4024,27923,27924,27925,45995</link.rule.ids><backlink>$$Uhttp://pascal-francis.inist.fr/vibad/index.php?action=getRecordDetail&idt=26791459$$DView record in Pascal Francis$$Hfree_for_read</backlink></links><search><creatorcontrib>Sloppy, J.D.</creatorcontrib><creatorcontrib>Lu, Z.</creatorcontrib><creatorcontrib>Dickey, E.C.</creatorcontrib><creatorcontrib>Macdonald, D.D.</creatorcontrib><title>Growth mechanism of anodic tantalum pentoxide formed in phosphoric acid</title><title>Electrochimica acta</title><description>The formation of anodic tantalum oxide (Ta2O5) in dilute phosphoric acid is quantitatively described using point defect chemistry reactions. Oxide formed in phosphoric acid has a distinct bi-layer structure, where the inner layer is pure Ta2O5, but the outer layer contains phosphate incorporated from the solution. In the point defect model (PDM) presented herein, the inner layer forms directly from, and grows into the metal, due to the production of oxygen vacancies at the metal/oxide interface. The outer layer forms due to the production of tantalum interstitials at the metal/oxide interface and their subsequent migration to the oxide/solution interface, where they hydrolyze to form Ta2O5. The Faradaic impedance is derived for the point defect reactions, and a bi-layer equivalent electrical analog is used to optimize the model to the measured electrochemical impedance spectroscopy (EIS) data. The oxide thickness and ionic current density have been measured separately, and the PDM parameters correctly predict the oxide thickness and ionic current densities due to the production of tantalum interstitials and oxygen vacancies.</description><subject>Anodic</subject><subject>Anodization</subject><subject>Chemistry</subject><subject>Electrochemical impedance spectroscopy</subject><subject>Electrochemistry</subject><subject>Exact sciences and technology</subject><subject>General and physical chemistry</subject><subject>Mathematical models</subject><subject>Oxides</subject><subject>Phosphoric acid</subject><subject>Point defect model</subject><subject>Point defects</subject><subject>Product data management</subject><subject>Tantalum oxide</subject><subject>Tantalum oxides</subject><subject>Vacancies</subject><issn>0013-4686</issn><issn>1873-3859</issn><fulltext>true</fulltext><rsrctype>article</rsrctype><creationdate>2013</creationdate><recordtype>article</recordtype><recordid>eNqFkF1LwzAUhoMoOKe_wd4I3rTmNGnSXo6hUxh4o9fhNElZRtvUpPPj39uxsdvBOZyb530PPITcA82AgnjaZra1esRpspxCntEyo8AvyAxKyVJWFtUlmVEKLOWiFNfkJsYtpVQKSWdktQr-Z9wkndUb7F3sEt8k2HvjdDJiP2K765LB9qP_dcYmjQ-dNYnrk2Hj47Rh4lA7c0uuGmyjvTveOfl8ef5Yvqbr99XbcrFONQcY0xJrzCVWKAxnIGqteUFrURRMNBxYXbNGF5yhyMEUWmpaGimwMTXjHDAHNiePh94h-K-djaPqXNS2bbG3fhcVFMB4WVWcn0cZr7ioJNu3ygOqg48x2EYNwXUY_hRQtbestupkWe0tK1qqyfKUfDg-waixbQL22sVTPBeyAl5UE7c4cHaS8-1sUFE722trXJh6lfHu7K9_bUCWrA</recordid><startdate>20130101</startdate><enddate>20130101</enddate><creator>Sloppy, J.D.</creator><creator>Lu, Z.</creator><creator>Dickey, E.C.</creator><creator>Macdonald, D.D.</creator><general>Elsevier Ltd</general><general>Elsevier</general><scope>IQODW</scope><scope>AAYXX</scope><scope>CITATION</scope><scope>7SR</scope><scope>7U5</scope><scope>8BQ</scope><scope>8FD</scope><scope>JG9</scope><scope>L7M</scope></search><sort><creationdate>20130101</creationdate><title>Growth mechanism of anodic tantalum pentoxide formed in phosphoric acid</title><author>Sloppy, J.D. ; Lu, Z. ; Dickey, E.C. ; Macdonald, D.D.</author></sort><facets><frbrtype>5</frbrtype><frbrgroupid>cdi_FETCH-LOGICAL-c411t-8aba27a9a6d4316bcc450b65536f413bb3fc543a621d5c7c08d76afdb3441a213</frbrgroupid><rsrctype>articles</rsrctype><prefilter>articles</prefilter><language>eng</language><creationdate>2013</creationdate><topic>Anodic</topic><topic>Anodization</topic><topic>Chemistry</topic><topic>Electrochemical impedance spectroscopy</topic><topic>Electrochemistry</topic><topic>Exact sciences and technology</topic><topic>General and physical chemistry</topic><topic>Mathematical models</topic><topic>Oxides</topic><topic>Phosphoric acid</topic><topic>Point defect model</topic><topic>Point defects</topic><topic>Product data management</topic><topic>Tantalum oxide</topic><topic>Tantalum oxides</topic><topic>Vacancies</topic><toplevel>peer_reviewed</toplevel><toplevel>online_resources</toplevel><creatorcontrib>Sloppy, J.D.</creatorcontrib><creatorcontrib>Lu, Z.</creatorcontrib><creatorcontrib>Dickey, E.C.</creatorcontrib><creatorcontrib>Macdonald, D.D.</creatorcontrib><collection>Pascal-Francis</collection><collection>CrossRef</collection><collection>Engineered Materials Abstracts</collection><collection>Solid State and Superconductivity Abstracts</collection><collection>METADEX</collection><collection>Technology Research Database</collection><collection>Materials Research Database</collection><collection>Advanced Technologies Database with Aerospace</collection><jtitle>Electrochimica acta</jtitle></facets><delivery><delcategory>Remote Search Resource</delcategory><fulltext>fulltext</fulltext></delivery><addata><au>Sloppy, J.D.</au><au>Lu, Z.</au><au>Dickey, E.C.</au><au>Macdonald, D.D.</au><format>journal</format><genre>article</genre><ristype>JOUR</ristype><atitle>Growth mechanism of anodic tantalum pentoxide formed in phosphoric acid</atitle><jtitle>Electrochimica acta</jtitle><date>2013-01-01</date><risdate>2013</risdate><volume>87</volume><spage>82</spage><epage>91</epage><pages>82-91</pages><issn>0013-4686</issn><eissn>1873-3859</eissn><coden>ELCAAV</coden><abstract>The formation of anodic tantalum oxide (Ta2O5) in dilute phosphoric acid is quantitatively described using point defect chemistry reactions. Oxide formed in phosphoric acid has a distinct bi-layer structure, where the inner layer is pure Ta2O5, but the outer layer contains phosphate incorporated from the solution. In the point defect model (PDM) presented herein, the inner layer forms directly from, and grows into the metal, due to the production of oxygen vacancies at the metal/oxide interface. The outer layer forms due to the production of tantalum interstitials at the metal/oxide interface and their subsequent migration to the oxide/solution interface, where they hydrolyze to form Ta2O5. The Faradaic impedance is derived for the point defect reactions, and a bi-layer equivalent electrical analog is used to optimize the model to the measured electrochemical impedance spectroscopy (EIS) data. The oxide thickness and ionic current density have been measured separately, and the PDM parameters correctly predict the oxide thickness and ionic current densities due to the production of tantalum interstitials and oxygen vacancies.</abstract><cop>Kidlington</cop><pub>Elsevier Ltd</pub><doi>10.1016/j.electacta.2012.08.014</doi><tpages>10</tpages></addata></record> |
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| subjects | Anodic Anodization Chemistry Electrochemical impedance spectroscopy Electrochemistry Exact sciences and technology General and physical chemistry Mathematical models Oxides Phosphoric acid Point defect model Point defects Product data management Tantalum oxide Tantalum oxides Vacancies |
| title | Growth mechanism of anodic tantalum pentoxide formed in phosphoric acid |
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