Enhanced superconducting properties of Cu_(1-x)Tl_xBa_2Ca_(2-y)Mg_yCu_3O_(10-σ) (y = 0, 0.5, 1.0, and 1.5)

摘要

In the present studies, the interplane couplings in Cu_(0.5)Tl_(0.5)Ba_2Ca_2Cu_3O_(10-σ) superconductor have been enhanced by Mg doping. With the improved interplane coupling a- and c-axis lengths are decreased while critical current density [J_C(H = 0)] is enhanced by two orders of magnitude and the zero resistivity critical temperature [T_C(R = 0)] is increased by 10 K. Predominant single phase of Cu_(1-x)Tl_xBa_2Ca_(2-y)Mg_yCu_3O_(10-σ) (y=0, 0.5, 1.0, and 1.5) was prepared by the solid state reaction of Ba(NO_3)_2, Ca(NO_3)_2, MgO, and Cu(CN). The material was checked by x-ray diffraction for crystallinity and was found to be the predominant single phase of Cu_(1-x)Tl_xBa_2Ca_(2-y)Mg_yCu_3O_(10-σ) ( y=0, 0.5, 1.0, and 1.5) with a- and c-axes lengths 3.840 and 14.20 A, respectively. The c-axis length decreases with the increased concentration of Mg in the compound. Fourier transform infrared absorption measurements have shown softening of apical oxygen modes with increased Mg doping and improved interplane coupling.