Powder X-ray diffraction study of the rhombohedral to cubic phase transition in TiF3

Synchrotron powder diffraction has been used to examine the crystal structure of the TiF3 between 20 and 450 K with emphasis on the cubic to rhombohedral structural phase transition near 370 K. This transition involves an apparently continuous reduction in the tilts of the TiF6 octahedra. A remarkable difference in the thermal expansion coefficients in the two phases is observed.