Gd substitution for Ca in Bi 2212 superconductors via liquid phase epitaxy

Abstract

Samples of Bi₂Sr₂Ca_1-xGd_xCu₂O_y were prepared and grown from stoichiometric melts on MgO (100) substrates using the Liquid Phase Epitaxial method (LPE), for x from 0 to 1. Single phase samples were prepared in the range of x_L, where is the Gd concentration in the melt, between 0 and 0.8. The samples were c-oriented with the c-axis perpendicular to the substrate surface. The incorporation of Gd in the film, x_s, differ significantly from the composition in the melt, first being incorporated 3 times as much as in the melt then shows a tendency of saturating and finally getting incorporated in the film at about the same composition as in the melt. As expected, the lattice c-parameter decreases with the increase in x_s. T_c drops rapidly at around x_s = 0.2 with a corresponding decrease in the carrier concentration. As in the case of LPE prepared Y and Nd substituted Bi 2212, the decrease in T_c correlates well with the decrease in the carrier concentration. From the comparison with the Y and Nd substituted films the substitution behavior of the rare earth in the Bi 2212 system depends on the kind of rare earth substituted.