Subsolidus Phase Relations of the CoOx-CuO-SrO System

The subsolidus phase relations of the CoOx-CuO-SrO system were investigated in air. The samples were equilibrated at 900 A degrees C. The pseudo-ternary section contains three stoichiometric binary oxide phases (Sr2CuO3, SrCuO2 and Sr14Cu24O41-delta) and a binary oxide solid solution: Sr6+xCo5O15+delta (0 <= x <= 0.36). Two binary phases extend into the ternary system forming solid solutions, i.e., Sr14Cu24-xCoxO41-delta (0 <= x <= 5) and Sr6+xCo5-yCuyO15+delta (0 <= x <= 0.36, 0 <= y <= 1.0). The Sr6+xCo5O15+delta solid solution was found to undergo a phase separation into a mixture of Sr6Co5O15-delta and Sr14Co11O33 upon annealing at 600 A degrees C. This transformation is reversible.