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

Abstract

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, RB = 0.076) and Ba44Cu45O90 (own structure type, cI400, Im-3m, a = 18.294(3) Å, RB = 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, RB = 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 Ba3LuCu2O6.5 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.