Fundamental Study on the Production of Copper-Rare Earth Alloys and Oxides

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1) To understand the fundamental aspects of the preparation of copper based Cu-rare earth alloys without any inclusions, the solubilities of La, Nd, Sm, Ce, Y and Gd in the liquid copper in equilibrium with C-LaC_2, C-NdC_2, C-SmC_2, C-CeC_2, C-YC_2 and C-GdC_2 were determined.The logarithm of the solubility of the rare-earths is represented as a function of the temperature by the relations ;log(mass%La) = 0.476 + 2.17x10^<-4>T (1623-1873 K)log(mass%Nd) = 0.4924 + 2.98x10^<-4>T (1523-1775 K)log(mass%Sm) = 2.65-5.22x10^3/T + 3.89x10^6T^2(1530-1781 K)log(mass%Ce) = 0.424 + 3.59x10^<-4>T (1623-1773 K)log(mass%Y) = 1.343 + 767.2/T (1523-1723 K)log(mass%Gd) = 0.649 + 2.85x10^<-4>T (1573-1773 K)2) The isothermal phase relations of the solid Cu-La-O, Cu-Nd-O and Cu-Gd-O systems were established by powder X-ray diffractometry of the quenched samples. The formation of ternary oxides La_2CuO_4 and LaCuO_2 in the Cu-La-O system, Nd_2CuO_4 and NdCuO_2 in the Cu-Nd-O system, and only GdCuO_2 in the Cu-Gd-O system were confirmed. Equilibrium oxygen partial pressures corresponding to three-phase equilibria involving condensed phases in each Cu-RE-O system was obtained by EMF measurements using zirconia solid electrolyte. From the results, the regions of the temperature and the oxygen partial pressure where the complex oxides exist as the stable phases were determined.3) Phase diagram of the system Cu_xO-Gd_2O_3 under p_<o2> = 0.21 was determined by DTA(Differential Thermal Analysis) and TG(Thermal Gravimetry).