Question

Zirconia is present in _________ crystal structure in the mineral baddeleyite.

• A. Monoclinic
• B. Triclinic
• C. Tetragonal
• D. Cubic

Hint:

Zirconia (ZrO\(_2\)) exists in monoclinic, tetragonal, and cubic phases depending on temperature. The monoclinic phase is stable at room temperature and occurs naturally as baddeleyite.

Answer 1

The Correct Option is A

Zirconia (ZrO\(_2\)) is a polymorphic material, meaning it can exist in different crystal structures depending on temperature.
Step 1: Understanding the Crystal Structures of Zirconia - Monoclinic Zirconia: Found in baddeleyite, it is the most stable phase at room temperature. - Tetragonal Zirconia: Stable at high temperatures (~1200°C - 2370°C) and is used in ceramics. - Cubic Zirconia: Exists at very high temperatures (~2370°C - melting point). - Triclinic Structure: Not associated with zirconia.


Step 2: Evaluating the Options - Option (A) - Correct: Baddeleyite naturally occurs in the monoclinic phase of zirconia.
- Option (B) - Incorrect: Triclinic structure is not a phase of zirconia.
- Option (C) - Incorrect: Tetragonal zirconia is stable at high temperatures but not in baddeleyite.
- Option (D) - Incorrect: Cubic zirconia occurs only at extreme temperatures or in synthetic forms.


Step 3: Conclusion Since baddeleyite exists in the monoclinic phase, the correct answer is option (A).