NaPd
3O
4, Na
2PdO
3 and K
3Pd
2O
4 have been prepared by solid-state reaction of Na
2O
2 or KO
2 and PdO in sealed silica tubes. Crystal structures of the synthesized phases were refined by the Rietveld method from X-ray powder diffraction data. NaPd
3O
4 (space group
Pm3¯
n,
a=5.64979(6) Å,
Z=2) is isostructural to NaPt
3O
4. It consists of NaO
8 cubes and PdO
4 squares, corner linked into a three-dimensional framework where the planes of neighboring PdO
4 squares are perpendicular to each other. Na
2PdO
3 (space group
C2
/c,
a=5.3857(1) Å,
b=9.3297(1) Å,
c=10.8136(2) Å,
β=99.437(2)°,
Z=8) belongs to the Li
2RuO
3-structure type, being the layered variant of the NaCl structure, where the layers of octahedral interstices filled with Na
+ and Pd
4+ cations alternate with Na
3 layers along the
c-axis. Na
2PdO
3 exhibits a stacking disorder, detected by electron diffraction and Rietveld refinement. K
3Pd
2O
4, prepared for the first time, crystallizes in the orthorhombic space group
Cmcm (
a=6.1751(6) Å,
b=9.1772(12) Å,
c=11.3402(12) Å,
Z=4). Its structure is composed of planar PdO
4 units connected via common edges to form parallel staggered PdO
2 strips, where potassium atoms are located between them. Magnetic susceptibility measurements of K
3Pd
2O
4 reveal a Curie-Weiss behavior in the temperature range above 80 K.
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