Abstract

Single crystals of Nd 2− x Ce x CuO y (0< x<0.17) from a family of the electron-type superconductors have been grown using platinum crucibles by the top seeded solution growth technique. The structural quality of the crystals was examined by X-ray diffraction. The FWHM of the Bragg reflections for the best samples varies from 8 to 20 angular seconds. Full neutron activation analysis was carried out to determine the chemical composition of the as-grown crystals. Small cation stoichiometry deviations from ideal (NdCe)/Cu ratio are found as well as Pt substitution on the copper sublattice at a level up to 2 at% exists depending on growth conditions. The results of thermogravimetric measurements and further annealing of samples show that the problem of an oxygen reduction of large Nd 2− x Ce x CuO y crystals is closely connected with inhomogeneity of anion distribution in the lattice possibly caused by non-optimal parameters for the reduction process and the level of impurities contamination. A three step reduction process which produces superconductivity with T c∼19 K in single crystals thicker than 1 mm has been developed.

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