Fabrication of single crystalline Bi-2212 whiskers from Ga added Bi_2Sr_2Ca_2Cu_3O_x composition and their thermal, structural, electrical and magnetic properties

摘要

In this study, Bi-2212 superconducting whiskers have been fabricated by annealing a melt quenched Bi_2GaSr_2Ca_2Cu_3O_x precursor. Whiskers with 6-15 μm thickness, 60-95 μm width and 3-9mm length were obtained. Crystallization activation energy, E_a. was calculated to be 362 kJ mol~(-1) by using Kissinger method. Structural and/or microstructural changes as a result of different heat treatments were investigated with SEM, EDX and XRD analyses. It was found that Ga ions in the starting composition did not diffuse to the structure of whiskers and they enhanced mass transport and accelerated the whisker growth. XRD analysis showed that whiskers consisted of highly c-axis oriented single crystalline Bi_2Sr_2CaCu_2O_x phase. From SEM analysis, it was seen that whiskers had very smooth surface without cracks and dislocations. T_c and T_o values of the whiskers were found to be 93.1 K and 88.2 K, respectively. Applied magnetic field dependence of the magnetization (M-H) was investigated at 10,20 and 30 K. J_c of whiskers were calculated by using Beans' equation and found to be 2.27 × 10~6 A cm_(-2),1.99 × 10~6 A cm~(-2) and 0.81 × 10~6 A cm~(-2) at 10K, 20 K and 30 K, respectively.