More about the BaO(BaCO3)–Lu2O3–CuO system

The phase diagram of the BaO(BaCO₃)–Lu₂O₃–CuO system was built at 900 °C. It comprises of 8 single-phase, 15 two-phase, and 8 three-phase regions. The boundary oxide systems Lu₂O₃–CuO and BaO–CuO contain the phases Lu₂Cu₂O₅ (structure type Ho₂Cu₂O₅, Pearson symbol oP36, space group Pna2₁, a = 10.702(1), b = 3.412(1), c = 12.360(1) Å, R_B = 0.076) and Ba₄₄Cu₄₅O₉₀ (own structure type, cI400, Im-3m, a = 18.294(3) Å, R_B = 0.114), whereas in the Lu₂O₃–BaO(BaCO₃) system the oxide-carbonate Ba₃Lu₂[CO₃]O₅ (Ba₃Yb₂[CO₃]O₅, tP26, P4/mmm, a = 4.322(1), c = 11.862(2) Å, R_B = 0.107) was identified under the conditions of the experiment. Two quaternary oxides were observed. The structure of BaLu₂CuO₅ was confirmed (BaY₂CuO₅, oP36, Pnma), whereas the structure of the phase with approximate composition Ba₃LuCu₂O_6.5 still needs to be established. The electrochemical properties of BaLu₂CuO₅ as cathode material in Li-ion batteries were investigated. The existence of a (in part) substitutional solid solution BaLu₂CuO₅:Li was confirmed by the decrease of the unit-cell volume (−0.11 %). No traces of the formation of a phase with YBCO-type structure were detected at 900 °C.