Synthesis and thermal stability of the new copper oxide carbonate Ba4ScCu2O7–xCO3 and other members of the series Ba4ScxCu2Oy(CO3)2–x

Abstract

We report the synthesis of a new perovskite-type oxide carbonate, Ba ₄ ScCu ₂ O _7–x CO ₃ . This phase has a tetragonal cell (a=b≈7.99 Å, c≈4.10 Å) based on a doubling of the basic perovskite subcell in the a and b directions. A possible structural model based on an ordering of Sc, Cu and C in the small cation sites is proposed. Experiments on the thermal stability of this phase have shown that raising the synthesis temperature from 940 to 1000 °C results in partial carbonate loss and a change in cell to a √2a _p ×√2a _p ×2c _p cell as previously observed for Ba ₄ YCu _2.27 O _7.08 (CO ₃ ) _0.53 . In addition we show that Ba ₄ ScCu ₂ O _7–x CO ₃ may be classed as the x=1 member of the series, Ba ₄ Sc _x Cu ₂ O _y (CO ₃ ) _2–x and we also report the synthesis of other new phases in this series.