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With a conventional X-ray rotating-anode diffractometer, structure characterization of a pure and highly oriented Bi 2 Sr 2 CaCu 2 O y single crystal sheet with large dimensions of 5×1.8×0.03 mm 3 has been conducted. Incommensurate satellites corresponding to a modulation 0.21 b ∗ + c ∗ have been observed up to second order. Apart from the asymmetry in intensities of the symmetrically located satellites, we revealed one more characteristic of the modulated structure, that the satellites are stretched along the c ∗ direction to form poles in reciprocal space. The technique used is suggested to be convenient and practical for studies concerning especially the modulations for large crystals.

High-quality Bi 2 Sr 2 CaCu 2 O 8 single crystals with dimensions up to 15x4x0.05 mm 3 were grown from the starting composition Bi 2+ x Sr 2 CaCu 2 O y , where x =0, 0.1, 0.2, 0.3, 0.4, 0.5, 0.6 and 0.7. Different amounts of Bi 2 O 3 in excess are included in each crystal growth run to act as flux for the growth and the optimum concentrations of the flux amount have been found. Structure characterization of a high-quality 2212 free crystal of 5x1.8x0.02 mm 3 was conducted by the (00 l ), ( h 00) and (0 k 0) X-ray diffractions, using a rotating anode diffractometer, and the back-reflection Laue photograph. It is found that melting incongruency is the main problem encountered in the growth of large and pure-phase single crystals from Bi 2 O 3 -rich melts and we have shown that, for x =0.8, crystals of 2212 phase and crystals of 2201 phase coexisting with CuO are obtained from the two segregated parts of the Bi-rich melts.