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Charge carrier concentration and mobility in alkali silicates

Texto completo
Souquet, Jean-Louis [1] ; Ferreira Nascimento, Marcio Luis [2, 3] ; Martins Rodrigues, Ana Candida [4]
Número total de Autores: 3
Afiliação do(s) autor(es):
[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
Número total de Afiliações: 4
Tipo de documento: Artigo Científico
Fonte: Journal of Chemical Physics; v. 132, n. 3 JAN 21 2010.
Citações Web of Science: 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)

Processo FAPESP: 04/10703-0 - Crescimento de cristais em vidros óxidos: testes de modelos e do possível desacoplamento entre difusão iônica e fluxo viscoso
Beneficiário:Marcio Luis Ferreira Nascimento
Linha de fomento: Bolsas no Brasil - Pós-Doutorado
Processo FAPESP: 07/08179-9 - Processos cinéticos em vidros e vitrocerâmicas
Beneficiário:Edgar Dutra Zanotto
Linha de fomento: Auxílio à Pesquisa - Temático
Processo FAPESP: 07/03563-5 - Jean Louis souquet | Institut National polytechnique Grenoble - França
Beneficiário:Ana Candida Martins Rodrigues
Linha de fomento: Auxílio à Pesquisa - Pesquisador Visitante - Internacional