Thermodynamic Study of the Liquid Cu–O System

抄録

The phase relationships in the liquid Cu–O system were determined by the following three experimental techniques, (1) Water quenching of the samples in crucible, (2) Water quenching of the samples after suction into an alumina tube, (3) Emf measurements combined with the suction-water quenching.
The cells used were as follows: Pt/Ni, NiO/ZrO₂(+CaO)/O in Cu(1) or copper oxide (1)/LaCrO₃/Pt, Pt/Ni, NiO/ZrO₂(+CaO)/O in Cu(1)+copper oxide (s or 1)/LaCrO₃/Pt.
It was confirmed that the miscibility gap exists between liquid copper and liquid copper oxide and it seems to disappear at higher temperature than 1620 K.
From emf measurements, the activities of oxygen and copper were calculated at 1573 K, and the standard free energies of formation of solid and liquid Cu₂O were determined in the temperature range from 1370 to 1600 K . Relative partial molar entropy of oxygen in the liquid Cu–O system showed a minimum value at or close to the stoichiometric Cu₂O composition.
The oxygen potential-temperature-composition (P-T-X) diagram for the Cu–O binary system was determined from the results of this study.