Abstract
Superconducting properties are studied for glass-ceramics which were prepared by reheating glass rods and the glass powder compacts in the BiSrCaCu2Al0.5Ox system, respectively. The glass-ceramic rod specimens obtained by reheating rod glass at 800–830 °C for 50 h have a Tc (R = 0) of 85 K, while the disk specimens obtained by reheating the powdered glass compacts in the same way do not exhibit superconductivity above 77 K. This difference in superconductivity between the specimens is discussed in terms of the crystallization process and the amount of oxygen absorption of the specimens during heating.