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|Title:||Dielectric constant/loss behaviour of 11.6 MeV/n U238 ion irradiated poly (p-hydroxy benzoic acid-co-ethylene terephthalate) liquid crystal polymer|
Quamara, J K
|Abstract:||Polymer liquid crystal, a copolymer or polyethylene terephthalate (PET) and poly hydroxy henzoic acid (PHB) whence referred as PET/x PHB where x represents the molar concentration or PHB, for x=0.3 and 0.7 or 165 µm nominal thickness were irradiated with 11.6 MeV /n U238 -ion at DRAMSTADT (Germany) with fluence 1×106 ions/cm2 .The dielectric constant/loss measurements for these polymer liquid crystal samples were measured in the temperature range 20-220°C by using Keithley's precision LCZ meter for frequencies 120Hz, 1 kHz, 10kHz and 100kHz. An increase in the dielectric constant at low temperature (20-60 °C) mainly ascribed to α-relaxation, which depends upon the molar concentration of PHB. This peak has been attributed to the polar nature or both PET and PHB. The α-relaxation is followed by suppression in dielectric constant or PET/0.3PHB and sharp increase in dielectric constant of -PET/0.7PHB from which one can understand that, due to irradiation, the PET rich phase has been affected drastically. The decrease in the dielectric constant at higher temperatures is due to the increase in crystallinity as annealing-like effects are also induced due to irradiation by energetic heavy ions. The peak in the dielectric loss (0.3 PHB) curve ascribed to the space charge relaxation processes, which is in accordance with the thermally-stimulated polarization current behaviour. A continuous decrease in the dielectric loss curve (0.7PHB) ascribed to the m-transition that is in conformity with the investigations on internal friction.|
|ISSN:||0975-1041 (Online); 0019-5596 (Print)|
|Appears in Collections:||IJPAP Vol.40(09) [September 2002]|
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