FLUX GROWTH AND CHARACTERIZATION OF YBA2CU3O7 DELTA SINGLE-CRYSTALS

Two different flux techniques have been used to grow crystals of YBCO. Large crystals have been grown using a flux of mixed alkali halides and the typical size for these crystals is 4x4x4mm. Smaller crystals have been grown from a CuO:BaO flux and these vary in morphology and size depending upon the cooling rate and proportion of flux used. The superconducting properties of both types of crystals have been measured in the as grown state and after post growth high pressure oxygen annealing using a.c. susceptibility. The crystals have also been characterised using x-ray diffraction, optical metallography and SEM. X-ray rocking curves have been used to examine the mosaic spread of the crystals. The results show that the crystals grown by the alkali halide flux are larger but have a greater number of inclusions and microcracks, than those grown from a CuO:BaO flux and also have poorer crystallinity. © 1990.