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Doctoral Thesis
DOI
10.11606/T.54.1992.tde-09042014-144141
Document
Author
Full name
Neri Alves
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1992
Supervisor
Committee
Giacometti, José Alberto (President)
Faria, Roberto Mendonça
Kawano, Yoshio
Oliva, Glaucius
Varela, Jose Arana
Title in Portuguese
Estudo da polarização ferroelétrica no copolímero P (VDF/TrFE)
Keywords in Portuguese
Corrente constante
P(VDF-TrFE)
Polarização ferroelétrica
Abstract in Portuguese
Usando-se a técnica do triodo de corona com corrente constante estudaram-se as propriedades ferroelétricas dos copolímeros P(VDF-TrFE) contendo diferentes teores de VDF. Descrevem-se as metodologias usadas na preparação de amostras por solução, a caracterização por raios X e DSC e a determinação do grau de cristalinidade. Apresentam-se o princípio de funcionamento da técnica do triodo de corona com corrente constante e a equivalência das curvas de potencial de superfície com as curvas de histerese. Mostra-se que a condução elétrica pode ser desprezada quando as medidas são realizadas em atmosfera com baixo valor de umidade. O valor do campo coercivo e da polarização remanente foram determinados a partir das curvas de subida do potencial de superfície, sendo o valor da polarização diretamente proporcional ao grau de cristalinidade das amostras. Esses resultados foram analisados supondo-se que os filmes de P(VDF-TrFE) podem ter duas fases cristalinas. Também são discutidos os modelos teóricos usados para interpretar as curvas de subida do potencial de superfície.
Title in English
Study of ferroelectric polarization in P(VDF/TrFE) copolymer
Keywords in English
Constant current
Ferroelectric polarization
P(VDF-TrFE)
Abstract in English
Ferroelectric properties of P(VDF-TrFE) copolymers having different contents of VDF were investigated using the corona triode with constant current. The casting procedure for the sample preparation, the characterization by X rays and DSC, and the determination of the degree of crystalinity were presented. The corona triode method allowing to charge samples with a Constant current and the equivalence between the potential buildup curves and hysteresis curves are presented. The coercive field and the remanent polarization were determined from the potential buildup curves and it was found that the polarization is linearly dependent on the degree of crystalinity. Results were discussed taking into account two different crystaline phases which could exists in P(VDF-TrFE). Also, it was presented theoretical models aiming to fit the potential buildup curves.
 
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NeriAlvesD.pdf (4.66 Mbytes)
Publishing Date
2014-04-11
 
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