Js. Kim et Dr. Gaskell, THE PHASE-STABILITY DIAGRAMS FOR THE SYSTEMS ND2CUO4-DELTA AND ND1.85CE0.15CUO4-DELTA, Physica. C, Superconductivity, 209(4), 1993, pp. 381-388
The dependences of the degrees of oxygen nonstoichiometry in Nd2CuO4-d
elta and Nd1.85Ce0.15CuO4-delta on temperature and oxygen pressure hav
e been determined by thermogravimetric measurements in the range of te
mperature 350-950-degrees-C and the range of oxygen pressure 10(-5)-1
atm. The nature of the decomposition of these oxides in the range of o
xygen pressure 10(-5)-1 atm has been determined by thermogravimetric a
nalysis and X-ray diffraction. In the solid state, decreasing oxygen p
ressure causes Nd2CuO4-delta to decompose to NdCuO2+Nd2O3 and then to
Nd2O3+Cu2O. The solid solution Nd1.85Ce0.15CuO4-delta decomposes to Nd
2O3+NdCeO3.5+Cu2O. The solidus line of incongruent melting has been de
termined in the range of oxygen partial pressure 10(-6)-1 atm by diffe
rential thermal analysis and the phases formed on solidification have
been identified by X-ray diffraction. The phase stability diagrams for
Nd2CuO4-delta and Nd1.85Ce0.15CuO4-delta have been constructed. The d
ependence of the onset of superconductivity in Nd1.85Ce0.15CuO4-delta
on the oxygen pressure and temperature at which the specimen was annea
led, and hence on the oxygen nonstoichiometry, has been determined.