Yoshinobu Sasaki

The Effect of Pb Addition on Superconductivity in Bi–Sr–Ca–Cu–O

The effect of Pb addition on superconductivity was studied on the systems with nominal compositions (BiPbx)2Sr2Ca2Cu3Oy, (Bi1-xPbx)2Sr2Ca2Cu3Oy and (Bi1-xPbx)2Sr2Ca2Cu3.6Oy. The melting point decreases monotonically from ~880 to ~860°C as x increases from 0 to 0.45 in the systems, while the volume fraction of the high-Tc phase (HTP) and the offset value of Tc show a peak around x=0.2~0.3. Further increase in x produces the Ca2PbO4, leading to the suppression of the HTP. The amount of Pb suitable for the formation of the HTP is limited by the competition between the reaction to form the HTP by the catalytic effect of Pb and the one to form the Ca2PbO4.

Superconductivity at 100 K in Bi-Pb-Sr-Ca-Cu-O

The superconductivity with an onset temperature of ?110 K and a zero resistance at Tc(offset) ?100 K was observed under measuring current I?1 mA in the oxide with nominal composition Bi0.7Pb0.3SrCaCu1.8Ox. The sharp decrease in susceptibility around 110 K due to the Meissner effect and the magnetic levitation on a magnet at 77 K were also observed in the sample. The superconducting and magnetic properties are compared with the ones for the oxides with nominal composition BiSrCaCu1.8Ox and BiSrCaCu2Ox.

Superconducting and magnetic properties of the high-Tc and high-density superconductor Y1△xLuxBa2Cu3O7−δ

Superconducting and magnetic properties have been studied in high-density samples of Y1-xLuxBa2Cu3O7-δ (0≤x≤0.88) with the porosity of 3~7% through X-ray, resistivity, magnetization and susceptibility measurements. The results suggest that the disorder appearing on the Y plane due to the Lu substitution for Y in YBa2Cu3O7-δ would have an effect on the two-dimentional Cu(2)-O plane, which causes the enhancement of the effective moment of Cu on the plane.

Electrical, magnetic and superconducting properties of the high-Tc superconductor Er1−xYbxBa2Cu3O7−δ

Structure, resistivity, magnetization and susceptibility have been studied on the Er1-xYbxBa2Cu3O7-δ system. The results indicate that both Er and Yb atoms order at x = 0.50 on the basal plane with missing oxygen in a unit cell. The results also show that they are present as nearly-free trivalent ions in this system on the basal plane in a unit cell.

Superconducting and Magnetic Properties in Metamorphic Phases of GdBa2Cu3O7-δ

Superconducting and magnetic properties were studied on samples of GdBa2Cu3O7-δ in the ortho-I, ortho-II and tetra-II phases, where ortho-I is typical of the 90 K-superconductor. The ortho-I sample shows a value of Tc=92.7±0.3 K and the Meissner flux expulsion near 100% at T=79.0 K. Ortho-II has a value of Tc=49.0±5.0 K, while tetra-II shows no superconductivity until 4.2 K. The susceptibility data for ortho-I between 100 and 700 K provides the effective magnetic moment 7.38µB, which is slightly smaller than 7.94µB for a free trivalent ion of Gd.