Hideji Kuwajima

MAGNETIZATION OF CERAMIC Y-BA-CU-O AND BI-SR-CA-CU-O AFTER NEUTRON IRRADIATION

Magnetization of ceramic Y-Ba-Cu-O and Bi-Sr-Ca-Cu-O superconductors was studied after neutron irradiation in the fluence from 2.4×1021/m2 to 1.8×1022/m2 at 60°C. The area of hysteresis loops was enhanced at low neutron fluence, followed by saturation and then a decrease at high fluence. In Bi-Sr-Ca-Cu-O, the degree of enhancement was smaller than in Y-Ba-Cu-O and the enhancement reached saturation at lower neutron fluence.

Variation of Composition in a Bi(Pb)-Sr-Ca-Cu-O Grain and the Influence of Mg and Ba Doping on Its Superconductivity

The 110 K phase (2223) and (Sr, Ca)-Cu-O phase exist in the Bi(Pb)-Sr-Ca-Cu-O ceramics. The Cu content varies in the perpendicular direction of platelike 2223 grains, but little variation is observed on the planer surface of the grains along their length. Only the 110 K phase was found in the X-ray diffraction pattern of Bi(Pb)-Sr(Ba, Mg)-Ca-Cu-O. Its electrical resistivity became zero at 110 K. By the partial substitution of Mg and Ba for Sr, the range of sintering temperatures in which we obtained a higher Tczero was much larger than that for Bi(Pb)-Sr-Ca-Cu-O.

Formation of 2223 Phase and Variation in Composition of Bi(Pb)-Sr-Ca-Cu-O Superconductors

Sintering of Bi1.6Pb0.4Sr2Ca2Cu3.6Ox for long time resulted in an increase of the volume fraction of the 2223 phase to 53%. The 2223 phase appears to take the form of flaky grains. The chemical composition of the constituents of the flaky grains are not exact stoichiometric proportions. Substances in the calcined powder start to react around 832°C, then change to (Sr,Ca)-Cu-O and an unknown phase at 862°C. Growth of the 2223 phase is enhanced between these two temperatures.

Superconducting Properties of Y-Ba-Cu-O Sheet by a Tape Casting Method

YBa2CuO3O7-δ (YBCO) superconducting sheets were successfully fabricated by a tape casting method. Critical temperature (Tczero) was 92.IK with a tape sintered at 940°C for 10 hours in oxygen. The (001) planes of YBCO particles were oriented parallel to the casting plane of the 9 green sheet. The highest Jc was 1,510A/cm2 at 77K in zero magnetic field. It is supposed that the grain orientation contributed principally to the enhancement of Jc of the YBCO sheet.