Defect study on polyaniline by positron annihilation spectrometry

Fast coincidence system was constructed and applied to positron annihilation spectrometry (PAS). We studied on the factors that affected the time resolution of the system. Time resolutions were obtained and mutually compared with respect to several factors such as sizes, kinds of scintillators, length dependence of delay lines on the CFD583, and width variations of the windows for 511 keV and 1.27 MeV. Monoenergetic positron acceleration system was used to measure the lifetime components for the polyaniline, which have variable electric conductivity. We obtained 360-380ps as bulk lifetime for polyaniline, which intended to show that the higher the conductivity, the longer the bulk lifetime. The reasons were discussed in the context of the protonate H+. The defect in the sample was discussed in the relation of positron lifetime corresponding to the variation of conductivity. (c) 2009 Elsevier Ltd. All rights reserved.