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Master's Dissertation
DOI
10.11606/D.54.1985.tde-11092007-102959
Document
Author
Full name
Ervino Carlos Ziemath
Institute/School/College
Knowledge Area
Date of Defense
Published
São Carlos, 1985
Supervisor
Committee
Aegerter, Michel André (President)
Ferreira, Guilherme Fontes Leal
Morato, Spero Penha
Title in Portuguese
Medidas dielétricas em cristal de KCN a ultrabaixas freqüências
Keywords in Portuguese
Constante dielétrica
Cristais iônicos
Instrumentação
Abstract in Portuguese
Realizamos medidas dielétricas a baixas freqüências (10-2-40Hz) em cristais de KCN empregando uma ponte de ultra-baixas freqüências, bem como a altas freqüências (50-104 Hz) empregando uma ponte de capacitância comercial (General Radio). As curvas de perda dielétrica mostraram um bom ajuste entre altas e baixas freqüências. Obtivemos picos de perda dielétrica num intervalo de cinco décadas e entre 53 e 78K. Os picos destas curvas foram ajustados segundo uma equação de Arrhenius, e obtivemos uma energia de ativação de 0,148 eV e um tempo de relaxação característico de 6,53 x 10-15s para os dipolos CN-. Para temperaturas entre 53 e 59K observamos o aparecimento gradual de um segundo pico de perdas de 25Hz. Sua origem ainda não é conhecida, mas isto sugere que o cristal de KCN pode apresentar propriedades de um dielétrico composto, com dois mecanismos de relaxação distintos.
Title in English
Dielectric measurements of KCN crystal at ultra-low frequencies
Keywords in English
Dielectric constant
Instrumentation
Ionic crystals
Abstract in English
Dielectric measurements were performed at low frequencies (10-2- 40Hz) with an ultra-low frequency bridge in KCN crystals , as well as at high frequencies (50-10-4 Hz) employing a commercial capacitance bridge (General Radio). The dielectric loss curves show a good adjustment between the high and low frequencies. We obtain dielectric loss peaks in a window of five decades and in the range of 53 and 78 K. The peaks of these curves were fitted with an Arrhenius expression giving for the CN- dipoles an activation energy of 0,148eV and an attempt relaxation time of 6,53x10-15. At temperatures between 53 and 59K we observed the gradual appearing of a second loss peak for frequency of 25Hz. Its origin is not yet known butt his suggestt that the KCN, crystal may present compound dielectric properties , with - two distinct relaxation mechanisms.
 
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ErvinoZiemath.pdf (3.18 Mbytes)
Publishing Date
2007-09-13
 
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