The energetics of the TiO2 polymorphs (rutile, anatase, and brookite) were studied by high temperature oxide melt drop solution calorimetry. Relative to bulk rutile, bulk brookite is 0.71 ± 0.38 kJ/mol (6) and bulk anatase is 2.61 ± 0.41 kJ/mol higher in enthalpy. The surface enthalpies of rutile, brookite, and anatase are 2.2 ± 0.2 J/m2, 1.0 ± 0.2 J/m2, and 0.4 ± 0.1 J/m2, respectively. The closely balanced energetics directly confirm the crossover in stability of nanophase polymorphs inferred by Zhang and Banfield (7). An amorphous sample with surface area of 34,600 m2/mol is 24.25 ± 0.88 kJ/mol higher in enthalpy than bulk rutile.
|Number of pages||6|
|Journal||Proceedings of the National Academy of Sciences of the United States of America|
|Issue number||SUPPL. 2|
|State||Published - 30 Apr 2002|