Growth of ${\rm Bi}_{2}{\rm Sr}_{2}{\rm Ca}_{2}{\rm Cu}_{3}{\rm O}_{10+\delta }$ (Bi-2223) Single Crystal Whiskers

We prepared Bi₂Sr₂Ca₂Cu₃O_10+delta(Bi-2223) single crystal whiskers from a precursor of Bi₂Sr₂Ca₂Cu_2middot5Te_0middot5O_x using the solid state reaction method. Te was used to enhance the growth of the whiskers. High-purity commercial powder of Bi₂O₃, SrCO₃, CaCO₃, CuO and TeO₂ were mixed and calcinated in air at 760degC to 820degC for three times. The calcinated powder was pressed into a pellet and heat treated at 880degC for 100 hours. Prior to that, the pellet was heat treated at 890degC for 15 minutes and cooled down to 880degC in 30 minutes. During the process, we used an oxygen atmosphere with a constant flow of 150 ml/min and found whiskers on the surface of the pellet. We determined that the important processing factors to grow whiskers are temperature, Te doping and the ratio of Ca and Cu. To study electrical transport characteristics, we fabricated a stack with an area of 2 mum times 2 mum and height of approximately 300 nm using focused ion beam (FIB) etching method. The stack has about two hundred of elementary junctions along the c-axis. A sharp and single phase transition in ab-plane (T_c ap 108 K) shows high crystallinity of single crystal whiskers. Critical current density of 1 times 10³ A/cm² has estimated from current (I)-voltage (V) characteristics in c-axis at 30 K. A well-defined superconducting gap (Vg ap 2 V) also exists in I-V characteristics, which corresponds to number of elementary Josephson junctions.