Influences of Sintering Time on the T_C of Bi_(2-x)Cu_xPb_(0.3)Sr2Ca2Cu30_(10+δ) High Temperature Superconductors

摘要

Solid state thermodynamical reaction method involving mixing, calcinations and sintering were used to prepare a high temperature superconductor with a nominal composition Bi_(2-x)Cu_xPb_(0.3)Sr2Ca2Cu30_(10+δ) for Cu (0 < x < 0.5). The effect of sintering time and substituting Cu on Bi sites have been investigated by X-ray diffraction, resistance measurements and oxygen content to obtain the optimum conditions for the formation and stabilization of the high Tc phase (2223-phase). The results showed that the optimum sintering time for the composition Bi_(2-x)Cu_xPb_(0.3)Sr2Ca2Cu30_(10+δ) is 140 hr at sintering temperature 860 °C. Substitution for Cu equals to 0.2 and 0.3 led to increase the transition temperature to T_C=127 K and 130 K respectively but for 0.4, T_C decreased to 125 K. The X-ray diffraction (XRD) analysis showed that all samples have almost two phases: high-T_C phase (2223-phase) and low-T_C phase (2212-phase) in addition to the existing of very low phase in the sample x=0.4. It was found that the all samples having an orthorhombic.