Optimization results for the growth of Bi-2212 single crystals by a modified vertical Bridgman method

Bi₂Sr₂CaCu₂O_8+δ (Bi-2212) superconducting single crystals were prepared using starting materials with the compositions of Bi:Sr:Ca:Cu=x:2:1:y (x,y=2-3) by a modified vertical Bridgman method. We could obtain large plate-like single crystal with x=2 and y=2, which had a size of 18×5 mm². In the single crystal, the FWHM value of the (0010) XRD peak which corresponds to Bi-2212 superconductor was small and about 0.05°. We also found that the single crystal showed a sharp transition in resistance-temperature characteristic when it was prepared using the starting materials with the compositions of Bi:Sr:Ca:Cu=2:2:1:3.