CRYSTAL-GROWTH AND PHYSICAL-PROPERTIES OF ND2-XCEXCUO4-Y SINGLE-CRYSTALS

Single crystals of Nd2-xCexCuO4-y with dimensions up to 5 × 8 × 0.15 mm3 were grown from Cu2O flux at 1250 °C. The effects of the reduction time at 900 °C in N2 atmosphere have been investigated. For more than 20 hours we found by EDAX analysis an increase of Ce and Cu concentration at the crystal surface and we simultaneously observe, by means of X-ray diffraction, the appearance of a cubic phase (Nd0.5Ce0.5O1.75) within the crystal. The best superconducting properties are obtained for a reduction at 900 °C for 10-15 hours with Tc = 22.9 K and ΔTc = 0.4 K. The resistivity shows a metallic temperature dependence, ρ(300K) = 550μΩcm and the Hall coefficient (H//c-axis) is negative between Tc and room temperature. © 1990.