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|Title:||Investigations of thermally stimulated polarization current in polyetherimide|
Kaushik, B K
Quamara, J K
Thermally stimulated polarization currents
|Abstract:||Thermally stimulated polarization currents (TSPC) have been investigated in polyetherimide (PEI) in the temperature region 10º-200ºC under various polarizing fields, ranging from 12-176 kV/cm with different heating rates. The TSPC spectra show a pronounced peak (P₁) around 25º-30ºC and a shoulder peak (P₂) in certain cases around 90º-110ºC attributed to the dipolar nature of ether linkages and carbonyl groups (>C=O), respectively. A steady rise in current is observed beyond 120ºC due to the dominance of large conduction currents. During successive cooling, the current retains its positive polarity and peak P₂ is observed around 110ºC. The peak P₁ disappears during second TSPC cycle owing to the temperature dependence of saturation polarization, confirming the dipolar nature of this peak. In few cases the corresponding thermally stimulated depolarization current (TSDC) characteristics have also been recorded, which are found to consist of two peaks P₁ and P′₂ located around 20º and 160ºC, respectively. The peak P₁ is consistent with the TSPC peak observed around 25º-30ºC whereas peak P′₂ corresponds to ⍺β-relaxation. The thermal variation of dielectric constant of PEI has also been deduced from the TSPC spectra. The experimental observations are in general agreement with the theoretical predictions.|
|Appears in Collections:||IJPAP Vol.46(07) [July 2008]|
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