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Master's Dissertation
DOI
10.11606/D.54.1976.tde-18082014-170256
Document
Author
Full name
Jan Frans Willem Slaets
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1976
Supervisor
Title in Portuguese
Ponte de ultra baixa frequência para medidas dielétricas: aplicações e eletretos
Keywords in Portuguese
Eletretos
Medidas dielétricas
Ultra-baixa freqüência
Abstract in Portuguese
Analisa-se no presente trabalho o problema das medidas de relaxação dielétrica a U.B.F. (Ultra Baixa Frequência). Propõe-se um modelo de ponte para tais medidas capaz de varrer o intervalo 10-3 Hz-10Hz, baseada na medida de fase conforme a discussão original de Van Turnhout e colaboradores. Analisa-se também os principais problemas experimentais com tal equipamento de U.B.F. e descreve-se a sua construção e funcionamento. Analisa-se também o modelo teórico de correlação entre medidas de U.B.F. e descarga de eletreto com correntes termo-estimulado. Em particular calculamos uma correção para a expressão integral dado por Van Turnhout e colaboradores que leva em conta a influência da energia de ativação na correlação entre as duas técnicas. Tal conversão é significante para valores da energia de ativação menor que 0,5eV e que ocorrem experimentalmente com frequência
Title in English
Ultra low frequency bridge for dielectric measurements in electrets
Keywords in English
Dielectric measurements
Electrets
Ultra-low frequency
Abstract in English
In the present work we investigate the problem of U.L.F. (Ultra Low Frequency) dielectric relaxation. An experimental model is proposed for a bridge covering the range of 10-3Hz-10Hz, based on phase shift measurements originally proposed by Van Turhout and collaborators. We also analyze the main experimental problems with such U.L. F. measurements and describe its construction and performance. We have also investigated the theoretical correlation between U.L.F. dielectric relaxation and electret thermal stimulated currents. We calculate in particular, a correction for the integral expression given by Turnhout and collaborators that takes into account the value of the activation energy in the relation between the two techniques. The correction is important for values of the activation energy below 0,5eV, which occur frequently in dielectric relaxation processes
 
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Publishing Date
2014-08-18
 
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