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|Title:||Dielectric spectroscopy of 100 MeV Ag ion irradiated polyetherimide|
Quamara, J K
|Keywords:||High energy heavy ion irradiation;Polyetherimide;Dielectric spectroscopy|
|Abstract:||The dielectric constant (′) and loss factor (Ɛ′′) have been measured in pristine and 100 MeV Ag ion irradiated (fluences: 5.610¹⁰, 1.810¹¹ and 1.810¹² ions/cm2) polyetherimide (PEI) in the temperature region 30-250C at different frequencies ranging from 200 Hz to 5 MHz. There is an overall increase in Ɛ′ in irradiated samples. This shows the dominance of interfacial polarization arising from the large number of radiation induced defect sites and free radicals. However, the increase in Ɛ′ is not directly proportional to the fluence of irradiance. There is a sudden decline in ′ at intermediate fluence (1.810¹¹ions/cm²) which is due to the occurrence of new secondary radiation induced crystalline (SRIC) phase. In the low temperature region 30-100C, the Ɛ′ follows the Kirkwood model. Above 100C, the Ɛ′ is almost temperature independent. The radiation induced free radical cross-linking and formation of free radicals have been held responsible for this behaviour. Various relaxation processes revealed their presence in the form of loss peaks in Ɛ′′-T curves appearing around 40-50C, 120-130C and 180-220C associated to the dipolar nature of ether linkages, carbonyl groups and space charge relaxation processes, respectively.|
|Appears in Collections:||IJPAP Vol.46(09) [September 2008]|
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