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Baddeleyite-Type High-Pressure Phase of TiO2
Science (New York, N.Y.)
|February 15, 1991
Summary
Researchers identified a new high-pressure titanium dioxide (TiO2) phase using in situ X-ray diffraction. This phase, stable at 20 GPa and 770°C, exhibits a baddeleyite-type structure with a 9% volume reduction.
Area of Science:
- Geochemistry
- Materials Science
- Mineral Physics
Background:
- High-pressure phases of titanium dioxide (TiO2) are crucial for understanding planetary interiors and advanced materials.
- Previous shock-wave experiments indicated a distinct high-pressure TiO2 phase, but its structure remained uncharacterized.
Purpose of the Study:
- To elucidate the crystal structure of the previously unresolved high-pressure phase of TiO2.
- To determine the formation conditions and structural characteristics of this new phase.
Main Methods:
- In situ X-ray diffraction was employed to study the TiO2 phase under high-pressure and high-temperature conditions.
- Sintered-diamond multianvils were used to achieve pressures up to 20 gigapascals (GPa) and temperatures of 770 degrees C.
Main Results:
- A single-phase TiO2 was successfully synthesized at 20 GPa and 770°C.
- The high-pressure phase adopts the baddeleyite (monoclinic ZrO2) structure.
- A transition from the rutile structure to the baddeleyite-type structure was observed, involving an increase in titanium (Ti) coordination from six to seven.
- This structural transition resulted in a significant volume reduction of approximately 9%.
Conclusions:
- The high-pressure phase of TiO2 has a baddeleyite-type structure, clarifying previous experimental observations.
- The transition to this denser phase involves a change in Ti coordination and a substantial volume decrease, impacting geophysical models.
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