水及水蒸气对YBa_2Cu_3O_(7-x)相结构及超导电性的影响

以热重分析(TGA)、X 射线衍射及电阻-温度关系测定等方法,研究了水及水蒸气于285-1223K 间对 YBa_2Cu_3O_(7-x)超导材料的超导电性退化、水解及热重变化等过程的影响.YBa_2Cu_3O_(7-x)试样在水及水蒸气冷凝于试样表面的水膜的作用下,将逐渐水解为 BaCO_3、CuO 及 Y_2O_3等产物.当试样或水蒸气的温度高于373K 时,水蒸气对YBa_2Cu_3O_(7-x)的晶体结构与超导电性无明显影响.在20%H_2O+80%O_2的气体介质中,YBa_2Cu_3O_(7-x)于373-1223K 问的 TGA 曲线与在常压大气中相似,其放-吸氧及相变过程是完全可逆的.自1223K 降温至373K,YBa_2Cu_3O_(7-x)恢复原来结构与性能.

Effect of Water or Vapour on Structure and Superconductivity of YBa_2Cu_3O_(7-x)

The effect of water,vapour and mixture(20%H_2O+80%O_2)on the processes of oxygen relief-absorption degradation and hydrolysis in YBa_2Cu_3O_(7-x)compounds has been studied over the tempera- ture range of 285-1223K by using systematic TGA(thermogravimetric analysis),X-ray diffraction and resist- ance measurement.Under the action of water or water film condensed on specimen,YBa_2Cu_3O_(7-x)can decom- posed progressively into BaCO_3,CuO and Y_2O_3.During the temperature of specimen or vapour above 373K,no influence of vapour upon the structure and superconductivity of YBa_2Cu_3O_(7-x),can be detected.In range from 373 to 1223K,the behaviours of TGA curve of YBa_2Cu_3O_(7-x)in 20% H_2O+80% O_2 are very similar to those in normal air,i.e.the processes of oxygen relief-absorption as well as structure transition are reversible.With the temperature lowered to 373K,the YBa_2Cu_2O_(7-x)recovers to original structure and behaviour.