Vitrification and crystallization processes of high-Tc superconducting oxides in the system Bi-Ca-Sr-Cu-O

In a relatively wide region of the pseudoternary system BiO3/2-(CaO⋅SrO)1/2-CuO, CaO/SrO=1, glassy samples have been obtained by the rapid-quenching technique. The glass transition temperature in this system was found to be mainly dependent on the BiO3/2 content, with a maximum of 390°C at around 20mol% BiO3/2. The crystallization of the glasses of proper compositions such as BiCaSrCu2Ox and Bi2Ca2Sr2Cu3Ox produced superconductors consisting mainly of the low-Tc (80K) phase; this superconducting phase grew gradually with increasing heat-treatment temperature. The critical temperature Tc (zero) was 86K for Bi2Ca2Sr2Cu3Ox, whereas it can be expected to be increased by optimizing the heat-treatment conditions and/or using appropriate additives.