Preparation and Crystal Structure of a New Reduced Calcium Niobium Oxide: CaNb2O4

Single crystals of a new reduced calcium niobium oxide, CaNb2O4, were prepared in an evacuated quartz tube at 1100°C. The calcium niobium oxide crystallizes in the orthorhombic space group Pbcm with a=5.054(1), b=11.904(1), and c=5.839(1) ?, Z=4, and the final R factors are R= 0.027 and Rw=0.029 for 799 unique reflections. The crystal structure has the layer built up by edge-sharing of NbO6 trigonal prisms to form infinite metal–metal bondings as seen in ANbO2 (A=Li,Na). The Ca2+ ion is located at the trigonal prism site in the interlayer. No evidence for superconductivity was found down to 2.0 K.