GROWTH FROM SOLUTION-MELT IN KCL AND PROPERTIES OF HIGH-QUALITY LOW-T(C) PHASE (2201) SINGLE-CRYSTALS

High Sr-deficient Bi2+xSr2-(x+y)CuyOz (2201)-phase) single crystals from solution-melt in KCl keeping constant both growth temperature and temperature gradient were obtained. Superconducting crystals were produced in the temperature range 830-845-degrees-C up to Bi/Sr ratio of 1.7 provided the Cu concentration was increased. The T(c) values measured by d.c. resistive and a.c. susceptibility methods are equal to 3-13 K. The best single crystals with T(c0) = 3-5 K, DELTAT(c) = 1 K have size up to 2 x 2 X 0.01 mm3 and consist of blocks with a relative misorientation in the ab-plane no larger than three tenths of a degree. Measurements of supercell structure parameters have revealed that the in-plane and out-of-plane components of the modulation vector vary with opposite manner. The superlattice monoclinic angle of the superconducting crystals ranges from 123.5-degrees to 129-degrees whereas that of nonsuperconducting ones from 110-degrees to 121-degrees. It was found that the parameters of modulated structure can be successfully used to assess the crystal inhomogeneity.