EFFECT OF SINTERING TEMPERATURE ON TC AND PHASE-STABILITY OF ND2-XCEXCUO4 AND EU2-XCEXCUO4

The impurity phases appeared in T' -phase Nd2-xCexCuO4 and Eu2-xCexCuO4 (0.1 less-than-or-equal-to x less-than-or-equal-to 0.2) prepared by solid-state reaction were examined and determined to be Ce-contained Ln2O3 and Ce-contained LnCuO2 (Ln = Eu,Ce) by XRD and EPMA. The impurity phases and the c-axis lattice parameter of T' -phase decreased with increasing sintering temperature. Although Ce can dissolve in Nd2CuO4 by the increase of sintering temperature, solubility limit exists near x = 0.16 in Eu2-xCexCuO4 system. If suitable amount of Ce dissolves in T' -phase, the sample shows superconductivity after heat treatment under flowing argon gas or under vacuum.