Abstract
The effect of Al doping on the crystal growth of Bi-2212 was studiedby a floating zone method. The results show that the planar solid-liquidinterface breaks down into a cellular growth front while increasing Al doping inthe rods of Bi2.1Sr1.9Ca1.0Cu2.0AlyOx. The size of the single crystals decreases with the increase inAl doping. The solubility limit for Al or the maximum Cu-site substitution by Alin the Bi-2212 crystals is less than y = 0.01. The majority of nominal Al dopingin the rods forms an Al-rich phase in the grain boundaries of the singlecrystals. The superconductivity of as-grown Al-doped crystals decreasesprogressively with increasing Al doping in the rods, however, the Tc forannealed Al-doped crystals does not change with increasing Al doping in therods. The unchanged Tc for annealed Al-doped Bi-2212 crystals either suggeststhat a small amount of Al substitution in the Cu site does not cause Tc todrop significantly, or indicates that Al only enters the Bi-2212 crystals as animpurity, but does not substitute at the Cu site in the Bi-2212 crystals.
Published Version
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