ELECTRICAL PROPERTIES OF Hg_(0.8)Tl_(0.2)Ba2Ca_(n-1)Cu_nO_(2n+2+δ) FOR (n=1-5) HTSC SYSTEM

摘要

Samples of high temperature superconductor Hg_(0.8)Tl_(0.2)Ba2Ca_(n-1)Cu_nO_(2n+2+δ) for (n=l-5) system has been prepared using solid state thermochemical reaction method by two steps. The present work has studied the influences of preparation method and the effect of n on the transition temperature (T_c). The value of T_c enhanced with the increase of n up to 3, after that there was a reduction of T_c for n = 4 and 5. The highest transition temperature was 125 K for (Hg-Tl)-1223 samples sintered at 860°C in capsule for 13 h under 0.5 GPa. Annealing the samples in the flow of oxygen exhibited an enhancement of the crystallites improving superconducting behavior and thus increasing the T_c of the doped samples, but decreasing T_c above optimum doped.