Topotactic Oxidation of Ramsdellite-Type Li0.5TiO2, a New Polymorph of Titanium Dioxide: TiO2(R)

• Published in: Journal of solid state chemistry 1994-11, Vol.113 (1), p.27-36
• Main Authors: Akimoto, J., Gotoh, Y., Oosawa, Y., Nonose, N., Kumagai, T., Aoki, K., Takei, H.
• Format: Article
• Language: English
• Subjects: Chemistry; Condensed matter: structure, mechanical and thermal properties; Elements and non-metal compounds (oxides, hydroxides, hydrides, sulfides, carbides, ...); Exact sciences and technology; Inorganic chemistry and origins of life; Inorganic compounds; Physics; Preparations and properties; Solid surfaces and solid-solid interfaces; Structure of solids and liquids; crystallography; Structure of specific crystalline solids; Surfaces and interfaces; thin films and whiskers (structure and nonelectronic properties); Water, oxides, hydroxides, peroxides; X-ray absorption spectroscopy: exafs, nexafs, xanes, etc; X-ray diffraction and scattering
• ISSN: 0022-4596; 1095-726X
• DOI: 10.1006/jssc.1994.1337

The topotactic oxidation in air at room temperature of the lithium titanate bronze LixTiO2 (x = 0.5) crystals with the ramsdellite-type structure leads to lower x values and decreased unit-cell-volumes. The crystal structures of the three specimens, Li0.41TiO2, Li0.16TiO2, and Li0.14TiO2, have been determined by the single-crystal X-ray diffraction method. The deintercalation of lithium in LixTiO2 with 0 ≤ x < 0.5 has been investigated by difference-Fourier maps at z = 1/4 sections. The complete oxidation of parent bronze crystals using an acidic solution obtained colorless crystals of a new polymorph of titanium dioxide, TiO2(R). It crystallizes in the orthorhombic ramsdellite-type structure, in the same space group Pbnm with a = 4.9022(14) Å, b = 9.4590(12) Å, c = 2.9585(14) Å, V = 137.18(7) Å3, Dx = 3.87 g/cm3, Dm = 3.80 g/cm3, and Z = 4. The TiO2(R) structure was also refined from the single-crystal X-ray study to the conventional values R = 0.049 and wR = 0.044 for 596 independent reflections. When heated above 640 K, TiO2(R) transforms into brookite-type TiO2. DTA and IR data of TiO2(R) are measured.