ENHANCEMENT OF MICROSTRUCTURAL AND MAGNETIC-PROPERTIES BY LI-DOPING IN TL,PB-1223 SUPERCONDUCTORS

Polycrystalline Tl0.5Pb0.5Sr2Ca2Cu3LiyOx samples were synthesized. Aft er processing under the same conditions, the Li-doped samples (y = 0.2 ) showed an average grain size three times larger than that of a typic al undoped Tl,Pb-1223 sample (y = 0), and a 30% increase in sample den sity. The irreversibility line has significantly shifted to higher fie ld with B-irr (77K) congruent to 12 tesla. The intragranular critical current densities, estimated through the Bean model, are higher in Li- doped samples in temperatures below 77K and external magnetic fields g reater than 2 tesla. The T-c,T-onset of the Li-doped samples are lower ed by typically 2-5 K compared with the undoped samples.