The first silver palladium oxide, Ag2PdO2, was synthesised from a co-precip
itated oxide precursor by annealing at 423-823 K, applying an oxygen pressu
re of 73 MPa. The crystal structure has been determined from X-ray and neut
ron powder diffraction data. The new compound crystallises in space group I
mmm. The lattice constants as determined from X-ray powder diffraction are
a = 4.55523(5) Angstrom, b = 3.00803(3) Angstrom and c = 9.8977(1) Angstrom
. The crystal structure constitutes a new structure type showing some featu
res in common with the Li2CuO2-type. Palladium is found in a nearly square
planar arrangement while silver has an almost linear co-ordination. The ove
rall structure can be considered as a rocksalt defect structure. Ag2PdO2 is
diamagnetic and semiconducting. The band gap, estimated from conductivity
measurements in the temperature range of 240-300 K, is 0.18(2) eV. (C) 2001
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