C. Chen et al., Relationship between growth, structure and superconductivity of single crystal YBa2Cu3O7-delta, J L TEMP PH, 117(3-4), 1999, pp. 711-715
We study the crystal growth of YBa2Cu3O7-delta with additives, using ac sus
ceptibility, X-ray diffraction and STM. One specific additive, BaF2, dramat
ically improves both the crystal growth and the superconducting properties.
A cluster growth model is proposed to describe the function of the additiv
e. F- reduces the Al contamination of Cu-O chains, and the orthorhombicity
increases. On a nanometer scale, the roughness of the chains decreases mark
edly. Superconductivity is further enhanced using noncontaminating crucible
s. Large single crystals with T-C = 93.7 K and Delta T-C = 0.1 K were grown
in Y2O3 or BaZrO3 crucibles using the BaF2 additive.