Transparent Ceramics

 

Transparent ceramics are ceramics that can transmit visible light. Ordinary polycrystalline ceramic materials, because of their anisotropy, become opaque.

Why are traditional ceramics or specialty ceramics opaque?

1. Stomata　
   There are many micropores in ordinary ceramics. These micropores produce strong refraction and reflection of light. Consequently, all light disperse in all directions, so light cannot pass through the ceramic. Achieving ceramics that are transparent involves minimizing these micropores.
2. Impurities
   The optical properties of the second phase impurities in the ceramic and the ceramic body material are very different. This difference often causes scattering and absorption centers. These centers greatly reduce the light transmittance of the ceramics.
3. Grain boundary structure
   The composition of ordinary ceramic materials is not single-phase, but multi-phase. Light is then scatter at these different crystal phase interfaces. Transparent ceramics are single-phase. Their grain boundaries blurr, and the optical properties of the grain boundaries and the crystal itself are not much different, so it does not cause light scattering. This structure contributes to transparency in such ceramics.
4. Crystal structure
   For opaque ceramics, it generally prepares by selecting photoanisotropic crystal materials. In anisotropic crystals, when light is incident from one grain to adjacent grain, scattering will occur. This scattering is due to birefringence, resulting in opacity.
5. Surface finish　
   The light transmittance of ceramics also limit by the surface finish. The surface of opaque ceramics is rough, and the scattering of light is serious. Therefore, to improve the light transmittance of ceramics, the particle size of the raw material should reduce. It should also surface ground and polish to augment transparency.

In order to improve the transparency of ceramics, we should start from seven aspects to get the transparent ceramics:
(1) The density should be high.
(2) There can be no gaps on the grain boundaries; if there are gaps, their size should be much smaller than the wavelength.
(3) There are no impurities or glass phases on the grain boundaries, or the optical properties of the grain boundaries are very different from the crystals.

Welcome to order transparent ceramics.