Structure Solution of NaYO2 Compound Prepared by Soft Chemistry from X-Ray Diffraction Powder Data

Abstract

In this work we reveal the structure of a NaYO₂ compound solved from the X-ray diffraction powder pattern using the “ab-initio” structure solution approach. The compound turned out to be of trigonal structure, S. G. R-3m isomorphous with a-NaFeO₂ layered compound. The lattice parameters are a = 3.404 and c = 16.602 Å, respectively, the atoms being located in Wickoff sites (cba) for O, Na and Y, respectively, leading to a calculated density of 4.31 g/cm³. The ordering of sodium and yttrium atoms into alternate (111) planes of the cubic close-packed oxygen lattice of NaYO₂ is very regular. The octahedra are slightly distorted, the positive deviation of the O_z parameter from 0.25 elongates the NaO₆ octahedra while compressing the YO₆ octahedra. Actually the Na-O and Y-O bond distances are 2.58 (1) and 2.25 (1) Å, respectively, as it is expected from their ionic radii values reported (1.16 vs 1.04 radii for both ion-species octahedral coordination). Finally, the Na-Y, Y-Y, and Na-Na next neighbor distances are close to 3.40 Å.