Crystal growth of high-T-c superconductors Pr2-xCexCuO4+delta with substitutions of Ni and Co for Cu

We report the crystal growth of the electron-doped high-T-C superconducting Pr2-xCexCuO4+delta by a modified CuO self-flux flow method. We found that for the crystal growth process at different Ce concentrations the maximum growth temperature is the most important parameter and report about optimized crystal growth procedures for the Ce-concentration range x=0-0.18. Using this flux growth method only Ni and Co atoms can be substituted for Cu in the Pr2-xCex(Cu(1-y)M(y))O-4+delta crystals, the other substitutional elements that we have tested (M = Fe, Zn, Ga, and Sn) do not dissolve in the T' phase. We introduce a new reduction treatment for single crystalline samples which ensures a homogeneous and variable oxygen stoichiometry over the whole crystal.