Enthalpy of the Anatase‐Rutile Transformation

Review of the anatase to rutile phase transformation

“…7), rutile is more stable than anatase. This has been confirmed by thermodynamic studies [5,9,76,148,152], which show that negative pressures would be required for anatase to be more stable than rutile [2]. The transformation to rutile thus is irreversible.…”

“…Since the particle size and surface area depend strongly on the preparation method, it would be misleading to interpret the photocatalytic performance solely in terms of the phase composition. As an example of the importance of the effect of the processing conditions on these parameters, variations in grain size, crystallite size, surface area, morphology, and phase distribution obtained during sol-gel synthesis have been observed to be highly dependent on the precursor solutes and solvents used [36,46,54], calcining temperatures [55,110,148,149], and pH [54,73,83,114,139,150].…”

Crystallization and phase transformation of anatase under the hydrothermal conditions of controlled PO2.

“…In these phases, only anatase (or perhaps brookite) is known to be metastable with respect to rutile over the wide range of temperature and pressure (Navrotsky and Kleppa, 1967). Natural anatase occurs in an association with quartz, rutile, brookite, hematite and other minerals in vein or crevice deposits of the so-called Alpine type formed from alteration and leaching of gneisses or schists by hydrothermal solutions.…”

The Balance Between Reactivity and Stability of Modified Oxide Surfaces Illustrated by the Behavior of Sulfated Zirconia Catalysts

“…The situation is slightly different from that encountered with zirconia, because in the case of extended crystals, rutile is the stable phase at all temperatures and pressures [75], making the transformation into rutile allotropic. Like the tetragonal phase of zirconia, the brookite and anatase phases of titania become thermodynamically stable at small crystallite sizes, with anatase favored at the smallest crystallite sizes corresponding to surface areas larger than 45 m 2 g -1 [45].…”