Complete substitution of Cu/O layers in T∗ type oxocuprates by carbonate: The new series LnKO(CO3)

A series of rare earth/alkali oxide carbonates LnKO(CO3) with Ln = La, Pr, Nd, Sm, Eu has been prepared by the low temperature synthesis from hydroxide/formate melts. The structure of these compounds corresponds with that of T∗ type oxocuprates (LnALnB)2CuO4. They are characterized by complete replacement of the transition metal/oxygen layers with carbonate layer units and represent thus the first end members of layered oxocuprate phases with partial replacement of the CuO layers by CO3 sheets.