STRUCTURAL EFFECTS OF SODIUM EXTRACTION ON NAXFEXTI2-XO4 SINGLE-CRYSTALS

Sodium removal from Nax-deltaFexTi2-xO4 by means of the oxidising agen t nitrosonium tetrafluoroborate (NO2BF4) leads to the formation of the solid solution Nax-deltaFexTi2-xO4. The homogeneity range of Nax-delt aFexTi2-xO4 was determined from the results of single-crystal X-ray st ructure analyses of several specimens. The sodium content in the as-gr own crystals ranges from 0.58 up to 0.87, while the upper level of sod ium 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.