화학공학소재연구정보센터
Materials Science Forum, Vol.363-3, 398-400, 2001
Positron study of negative charge states in order-disorder ferroelectrics
The positive positron charge opens the possibility for determining the changes in charge states in technologically important order-disorder ferroelectrics. Here we show that dipole polarization disordering within domains affects the positron annihilation mechanism. The positron lifetime parameters in Triglycine Sulphate (TGS) (NH(3)CH(2)COOH)(3)H(2)SO(4), Rochelle Salt (RS) NaKC(4)H(4)O(6).4H(2)O and Potassium Dihydrogen Phosphate (KDP) KH(2)PO(4), at different temperatures and gamma- irradiation doses depend on the charge point defects. The increase of the positron long lifetime component tau (2) is proportional to the temperature and gamma-irradiation dose. In gamma irradiated TGS positrons are trapped in defect electron states of oxigen ions of two radicals CH(2)COO(-) and NH(3)CHCOO(-). In RS positrons are trapped also in defect electron states of oxygen ions and OH groups.