Structural Evolution of TiO2 Precipitates in Ti-DopedSapphire (α-Al2O3)
A time-dependent phase stability diagram has been developed describing the structural evolution of TiO2 precipitates in Ti-doped sapphire (α-Al2O3). A high-pressure TiO2 phase with the α-PbO2 structure (α-TiO2) forms as a coherent precipitate in Ti-doped sapphire annealed at 1200°–1300°C; extended annealing times at these temperatures result in twinned particles, the twinning minimizing the precipitate–matrix misfit strain energy. Twinned α-TiO2 eventually transforms to the rutile structure, coincident with the loss of coherency with the sapphire matrix. Rutile nucleates directly in sapphire annealed at temperatures at 1350°C and above. Rutile is present mainly as semicoherent and twinned precipitates, the twinning occurring relatively early in the precipitation sequence.
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Document Type: Research Article
Affiliations: Department of Materials Science and Engineering, Case Western Reserve University, Cleveland, Ohio 44106
Publication date: 2011-04-01