CRYSTAL-STRUCTURE OF NAXTI2O4 WITH 0.50 LESS-THAN-OR-EQUAL-TO X LESS-THAN-OR-EQUAL-TO 0.57

A new member of Ti3+ Ti4+ mixed-valence sodium titanate, NaxTi2O4 with x ≈ 0.6, was prepared by the reaction of sodium metal and titanium oxides at a high temperature of 1723 K. It crystallizes in the orthorhombic system, space group Pnam, and is isostructural with NaxFexTi2-xO4 (0.90 > x > 0.75). The framework is built up from the rutile-related type Z-shaped chains with the repeat distance of about 3.0 Å. The homogeneity range of NaxTi2O4 was determined to be 0.50 ≦ x ≦ 0.57, from the results of single-crystal X-ray structure analyses of two specimens; as-grown Na0.57Ti2O4 and Na0.50Ti2O4 derived by air oxidation at room temperature. A considerable change in the lattice parameters is observed in the NaxTi2O4 structure when the Na-content is decreased from x = 0.57 to x = 0.50. © 1991.