Abstract
Specimens of (M2.1) Sr2.0Ca2.0Cu3.15Oy [(M2.1)=(Bi2.1-m-xPbmSbz) : O.1≤m≤0.5, O≤z≤0.4)] were sintered at 830, 840 or 850°C for 20hr after pre-treatment (20hr) and heating processes [I (20hr) and II (40hr) using envelope method] at the same temperature in air atmosphere. XRD patterns of specimens in each process and the resistance curves of sintered specimens were compared in order to find effects of Sb2O3 addition on the formation of high-Tc phase. The optimum heat treatment temperature was 840°C, which was a little lower than that of specimens without Sb3+(z=0). And the range of treatment temperature forming high-Tc phase becomes narrower. In reaction diagram at 840 °C, it was found that high-Tc phase amounted to 70-80% for 20-40hr at the small content of Sb3+:z≤0.2, although any single phase of high-Tc was not obtained. For specimen with Sb3+ addition, the formation time of high-Tc phase was reduced very much in such composition range. A special case was observed in the specimens with Bi content of 1.75-1.80mol. In the case, Sb3+ content incorporated with the ratio of Pb2+: Sb3+ larger than 8:2 brought a little increase of Tc rather than the decrease of Tc. The composition of the case, for example, is (M2.1)=(Bi1.8Pb0.3-zSb2) with z=0.05.
