Titanium dioxide has three crystal forms in nature: rutile, anatase and brookite
Author: sainuoTime: 2020-08-05 14:21:14
Titanium dioxide has three crystal forms in nature: rutile, anatase and brookite.
1. The brookite type belongs to the orthorhombic crystal system and is an unstable crystal type. It is transformed into a rutile type above 650°C, so it has no practical value in industry. The anatase type is stable at room temperature, but will transform to rutile type at high temperature. The conversion strength depends on the manufacturing method and whether there are inhibitors or accelerators added during the calcination process.
2. The rutile type is the most stable crystalline form of titanium dioxide with a compact structure. Compared with the anatase type, it has higher hardness, density, dielectric constant and refractive index. Both the rutile type and the anatase type belong to the tetragonal crystal system, but have different crystal lattices, so the X-ray images are also different. The diffraction angle of the anatase type titanium dioxide is at 25.5°, and the diffraction angle of the rutile type is at 27.5°.
3. The rutile type crystals are slender and prismatic, usually twin crystals; while the anatase type generally approximates a regular octahedron.Compared with the anatase type, the unit lattice of the rutile type is composed of two titanium dioxide molecules, while the anatase type is composed of four titanium dioxide molecules, so its unit lattice is smaller and compact, so it has greater stability. It has high refractive index and dielectric constant and low thermal conductivity.