RESISTIVITY AND MAGNETIC-SUSCEPTIBILITY STUDIES OF TLMCAN-1BA2CUNOY BEFORE AND AFTER DOPING WITH LIF

Measurements of the superconducting resistance as a function of temper ature were performed using the conventional four-probe method. The tra nsition to complete superconductivity was recorded for samples of (Tl2 Ca2Ba2Cu3O10)100-xLiFx (2223) mixed with different LiF ratios x = 0, 2 , 4, 5, 6, 8, 1 0, and 12 wt.%. It was found that the transition tempe rature T, was increased up to 5 wt.% of LiF. Further addition of LiF d ecreases T(c). Therefore, 5 wt.% LiF is the optimum concentration givi ng a transition temperature of 130 K. Measurements of the superconduct ing resistance of all the samples except the (1111) compound show that the addition of 5 wt.% LiF increases T(c) and decreases the metastabl e phases. The real part of the a.c. magnetic susceptibility chi(a.c.) is studied using a zero-field cooled mechanism. The temperature depend ence of chi(a.c.) for the prepared TlBaCaCuO having stoichiometric com position of (1111), (2223), (2234), and (3245) and that after doping w ith 5 wt.% LiF showed a broad feature. The transition to the complete diamagnetic state takes place in a broad transition region containing many transition steps, indicating the presence of metastable phases. T he addition of LiF decreases the fluctuation in the transition region and its effect in reducing the number of multiphases.