The syntheses and structures of the complex oxide carbonates Ba₁₁Pd₁₁O₂₀(CO₃)₂and Ba₈₈Ni₈₇O₁₅₆(CO₃)₁₉)

A new palladate analog, BaPdO(CO), of the complex copper oxide carbonate, BaCu(CO)O, has been synthesized by reaction of PdO and BaCOat 810°C. The structure of this phase and the isostructural nickelate have been refined from high resolution powder neutron diffraction data. The structure consists of cagesMOandMOrings (M=Pd,Ni) separated by barium ions and carbonate groups. A section of the structure separating twoMOunits is strongly disordered and has been refined as containing either carbonate groups or isolatedMOsquare planes. The presence and symmetry of the carbonate groups in these structures has been investigated by infrared and Raman spectroscopy.