Subsolidus phase relations of the SrO-REOx-CuO systems (REÂ =Â Ce, Pr and Tb)

The subsolidus phase relations of the SrO-REOx-CuO (RE = Ce, Pr, Tb) systems were investigated in air. The samples were equilibrated at 1173 K. In the SrO-CeO2-CuO system, there are neither ternary oxide compounds nor ternary solid solutions. However, the slight solubility of Sr into CeO2 results in the formation of a two-phase region, where Ce1−xSrxO2−δ is in equilibrium with the Sr14Cu24O41−δ phase. The SrO-PrOx-CuO system contains four stable ternary oxide phases: Pr1.4Sr0.4CuO4−δ, Pr7Sr8Cu2Ox, Pr1.85Sr1.15Cu2O6−δ and Pr2−xSr1+xCu2O6−δ (0.8 ≤ x ≤ 0.9). Two binary oxide compounds form ternary solid solutions extending into the pseudo-ternary sections: Pr2−xSrxCuO4−δ (0.00 ≤ x ≤ 0.05) and Sr14−xPrxCu24O41−δ (0.0 ≤ x ≤ 6.0). The Sr14−xTbxCu24O41−δ solid solution (0.0 ≤ x < 6.0) is the only ternary phase formed in the SrO-TbOx-CuO system. This system is dominated by the SrTbO3 phase, which is in equilibrium with all the other compounds.