Aa. Elhamalawy et al., RESISTIVITY AND MAGNETIC-SUSCEPTIBILITY STUDIES OF TLMCAN-1BA2CUNOY BEFORE AND AFTER DOPING WITH LIF, Journal of superconductivity, 6(2), 1993, pp. 111-118
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.