Effects of Slight Non-Stoichiometry in Sm-Ba-Cu-O Systems on Superconducting Characteristics

We studied the effects of slight Sm-Ba non-stoichiometry in Sm-Ba-Cu-O superconducting compounds on their transition, structural, and magnetic properties. Two series of single-phase samples of Sm_1+xBa_2-xCu₃O_7+Δ and Sm_1+xBa_2-xCu₃O_7+Δ with composition deviation from stoichiometry x from 0 to 0.1 were synthesized by the solid-state reaction method from Sm₂O₃, BaCO₃ and CuO precursors and sintered at the temperature of ~ 1060 °C in flowing oxygen. All samples showed the values of T_c > 90 K and the volume density, p, 6.45 g cm^-3 < p ≤ 6.73 g cm^-3. The effect of the composite deviation of x on T_c, ΔT_c, and volume magnetization M was studied. For Sm_1+xBa_2-xCu₃O_7+Δ compounds, optimal values of x were determined to maximize the width of the magnetization hysteresis at higher values of the applied magnetic field, corresponding mainly to the grain contribution. We also prepared the Sm_1+xBa_2-xCu₃O_7+Δ samples with x from 0 to 0.1 using the same processing conditions as in the case of A and B series. For the Sm_1+xBa_2-xCu₃O_7+Δ samples, values of x = 0.02 - 0.03 optimize T_c, ΔT_c, H_p1 as well as M.