The Formation of Y-Ba-Cu-O Phases During Solid State Reaction

The formation of Y-Ba-Cu-O phases, including the high Tc superconducting YBa 2 Cu 3 O 7−x (Y123) phase, during solid state reaction of the mixture of Y 2 O 3 : BacO 3 : CuO, in molar ratio of 0.2:0.6:1 to conform the formula of the perovskite (Y 0.4 Ba 0.6 )CuO 3 composition was studied by means of DTA, DTG and X-ray difractometry(XRD). For continuous heating at 10 C/min, it was found that the Y123 phase exists at 790–995 C, and gradually disappears at higher temperatures. The insulating Y 2 BaCuO 5 (Y211) phase exists at 985 to 1190 C, the maximum experiment temperature. While the semiconducting YBa 3 Cu 2 O 7-y , (Y132) phase coexists with the Y123 phase. For isothermal heating, it was found that the most appropriate temperature and time for the formation of the Y123 phase is 900 C and 16 hours. Semiquantitative data on the amount of phases presented, including the above mentioned phases and other binary Ba-Y-O or Ba-Cu-O phases, during heating are also given. High temperature superconductor with a Tc of around 93 K can be synthesized reproducibly by the processes based on this study.