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(Reference retrieved automatically from Web of Science through information on FAPESP grant and its corresponding number as mentioned in the publication by the authors.)

Charge carrier concentration and mobility in alkali silicates

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Souquet, Jean-Louis [1] ; Ferreira Nascimento, Marcio Luis [2, 3] ; Martins Rodrigues, Ana Candida [4]
Total Authors: 3
[1] ENSEEG, Lab Electrochim & Physicochim Mat & Interfaces, F-38402 St Martin Dheres - France
[2] Univ Fed Bahia, Inst Humanities Arts & Sci, Vitreous Mat Lab, BR-40170115 Salvador, BA - Brazil
[3] Univ Fed Bahia, Polytech Sch, PEI Postgrad Program Ind Engn, PROTEC, BR-40210630 Salvador, BA - Brazil
[4] Univ Fed Sao Carlos, Lab Mat Vitreos, Dept Mat Engn, BR-13565905 Sao Carlos, SP - Brazil
Total Affiliations: 4
Document type: Journal article
Source: Journal of Chemical Physics; v. 132, n. 3 JAN 21 2010.
Web of Science Citations: 23

The respective contributions of the charge carrier concentration and mobility to the ionic conductivity in glasses remain an open question. In the present work we calculate these two parameters from conductivity data as a function of temperature below and above the glass transition temperature, T(g). The basic hypothesis assumes that ionic displacement results from the migration of cationic pairs formed by a partial dissociation, which is a temperature-activated process. Below T(g) their migration would follow a temperature-activated mechanism, while a free volume mechanism prevails above this temperature, leading to a deviation from the Arrhenius behavior. Expressions are formulated for the variation in ionic conductivity as a function of temperature in the supercooled and glassy states. Fitting the experimental data with the proposed expressions allows for the determination of characteristic parameters such as the charge carrier formation and migration enthalpies. Based on these values, it is then possible to calculate the charge carrier concentration and mobility in the entire temperature range. At room temperature, the mobility of effective charge carriers is estimated close to 10(-4) cm(2) s(-1) V(-1) for alkali disilicates glasses under study, while the ratio between the number of effective charge carriers and the total number of alkali cations is estimated to be from 10(-8) to 10(-10), comparable to the concentration of intrinsic defects in an ionic crystal or dissociated species from a weak electrolyte solution. (AU)

FAPESP's process: 07/08179-9 - Kinetic processes in glasses and glass ceramics
Grantee:Edgar Dutra Zanotto
Support type: Research Projects - Thematic Grants