Synthesis, stoichiometry and structure of the quaternary scandium cuprate ba₃Cu₃Sc₄O₁₂ and of 334-phase solid solution members ba₃Cu₃Sc_4-xIn_xO₁₂ (0≤×≤4)

The quaternary scandium cuprate Ba₃Cu₃Sc₄O_l2 has been prepared via the high temperature solid state reaction of the respective binary oxides and BaCO₃ in air at 950 °C. The cuprate was characterised by powder X-ray diffraction (PXD) and its structure determined for the first time by Rietveld refinement of powder data. Crystallite morphology and metal stoichiometry were examined by SEM/EDAX. Oxygen stoichiometry and thermal behaviour were evaluated by TG/DTA and TPR. Ba₃Cu₃Sc₄O₁₂ crystallises with a tetragonal, perovskite-derived structure in space group I4/mcm (a= 11.9021(6) Å, c=8.3962(4) Å, V= 1189.41(10) ų, Z=4, c/a = 0.71), isostructural with Ba₃Cu₃In₄O₁₂. Ba₃Cu₃Sc₄O₁₂ is paramagnetic at room temperature consistent with Cu(II). In readily substitutes for Sc to form Ba₃Cu₃Sc_4-xIn_xO₁₂ 334-phases continuously to Ba₃Cu₃In₄O₁₂ (x=4). Structures of selected members have been determined from PXD data and correlated to the trivalent cation substituent level, x.