CRYSTAL-GROWTH, SEPARATION AND CHARACTERIZATION OF SUPERCONDUCTING PB2SR2(Y1-XCAX)CU3O8+DELTA

Single crystals of Pb2Sr2(Y1-xCax)Cu3O8+delta have been grown from PbO -NaCl and PbO-KCl flux. Different temperature runs were performed to o ptimize the growth. A temperature gradient in the crucible is necessar y to get crystals of Pb2Sr2(Y1-xCax)Cu3O8+delta with reproducible size s of more than 2 x 2 x 1 mm3. Crystal growth in air yields a lot of la rge crystals but with broad transitions in magnetic susceptibility. Th e best results were obtained in an atmosphere of 3% O2 in N2. The crys tals can be extracted from the flux very effectively by a solution of acetic acid in methanol. Neutron diffraction experiments confirm a low mosaicity and well defined lattice constants. High resolution energy dispersive X-ray (EDX) measurements show a very good homogeneity of th e cations with a lateral resolution of 15 nm to 1 mum. The Y-to-Ca rat io has a stable value of 2:1. In high resolution transmission electron microscopy no crystal defects could be detected.