Structural effects of sodium extraction on NaxFexTi2-xO4 single crystals

Sodium removal from Nax-deltaFexTi2-xO4 by means of the oxidising agent nitrosonium tetrafluoroborate (NO2BF4) leads to the formation of the solid solution Nax-deltaFexTi2-xO4. The homogeneity range of Nax-deltaFexTi2-xO4 was determined from the results of single-crystal X-ray structure analyses of several specimens. The sodium content in the as-grown crystals ranges from 0.58 up to 0.87, while the upper level of sodium extraction was delta approximate to 0.30 for a sodium content of 0.79 in the starting sample. When sodium is removed from the material a considerable change in the lattice parameters and a rearrangement of the framework are observed. No evidence was found for the splitting of the unique sodium position for low sodium content.