Resistivity And Magnetic-Susceptibility Studies Of Tlmcan-1ba2cunoy Before And After Doping With Lif

Measurements of the superconducting resistance as a function of temperature were performed using the conventional four-probe method. The transition to complete superconductivity was recorded for samples of (Tl2Ca2Ba2Cu3O10)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 temperature T, was increased up to 5 wt.% of LiF. Further addition of LiF decreases T(c). Therefore, 5 wt.% LiF is the optimum concentration giving a transition temperature of 130 K. Measurements of the superconducting resistance of all the samples except the (1111) compound show that the addition of 5 wt.% LiF increases T(c) and decreases the metastable phases. The real part of the a.c. magnetic susceptibility chi(a.c.) is studied using a zero-field cooled mechanism. The temperature dependence of chi(a.c.) for the prepared TlBaCaCuO having stoichiometric composition of (1111), (2223), (2234), and (3245) and that after doping with 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. The addition of LiF decreases the fluctuation in the transition region and its effect in reducing the number of multiphases.