Enlargement effect of the crucible size on Bi2Sr2CaCu2Oy single crystals grown by a modified vertical Bridgman method

Bi2Sr2CaCu2Oy (Bi-2212) superconducting single crystals were prepared by a modified vertical Bridgman method using large alumina crucibles of a 26 mm bore diameter with cone-shaped bottom. In order to obtain large and high quality single crystals, we optimized growth conditions using the large crucibles. We obtained a large plate-like single crystal with a size of 17.0 mm x 5.5 mm when the crystal growth was carried out with the rotation speed of 50 rpm and at the temperature for starting the crystal growth of 1000 degrees C. In the single crystal, the FWHM value of the (0010) x-ray diffraction peak which was assigned to a Bi-2212 superconductor was small and about 0.06 degrees. T-c of the single crystal was about 87 K, which was higher than T-c = 82 K of the single crystals grown with smaller crucibles whose bore diameter is 35% less than the large crucibles.