By means of the addition of Ba into the Bi-Ca-Sr-Cu-O 2122 system, a series of Bi/sub 2/CaSr/sub 2-x/Ba/sub x/Cu/sub 2/O/sub 8+.delta./(0.ltoreq.x.ltoreq.2) quinary metal oxides were prepared by the citrate route and by the conventional powder reaction method. The samples prepared by the former method have better properties than the latter. It was found that.delta. was not equal to zero for all of them and that it increased with decreasing Tc. Two phases were identified in the oxides containing all five metal elements. One is the Bi-Ca-Sr-Cu-O 2122 phase, the other is a new insulating phase which probably contains Bi-Ca-Ba-Cu-O with undetermined stoichiometry. Superconductivity was found in those samples for which x.ltoreq.1.50 with their Tc onsets between 93-78 K by resistivity measurements. Superconductivity decreased monotonically with increasing x. However, residual resistance was found in those samples for which 1.00.ltoreq.x.ltoreq.1.50. The Meissner effect appears in the samples where x.ltoreq.1.00 with Tc onsets between 88-80 K. For x=1.75 and 2.00, the samples were semiconductors with resistivities of 6.66*10/sup 2/ and 6.96*10/sup 3/.OMEGA..bcdot.cm at 290K, and activation energies of 0.109, and 0.298eV, respectively.
關聯:
Journal of the Chinese Chemical Society=中國化學會會誌 36(3), pp.205-210
