Yttrium Aluminum Garnet (YAG, Y3Al5O12) has outstanding functional and mechanical properties, such as:
In addition polycrystalline YAG, when sintered at theoretical density, can achieve high optical transparency, and used as:
Transparent YAG, with 66% light transmission in the visible range, 2.5 mm thickness.
The fabrication of optically transparent ceramics requires the strict control of many processing parameters, such as:
1. Highly pure nanocrystalline powder
YAG powder is synthesized by a wet-chemical route. By thermal treatment at ~900°C, a highly pure and nanocrystalline powder, free from secondary phases is obtained.
2. Loosely dispersed powder
A proper dispersion route is necessary, to de-agglomerate the powder and improve its sinterability, without inducing pollution from the dispersion medium.
3. Fully dense sintered ceramics
The powder is densified by Spark Plasma Sintering (SPS), to achieve full density and high optical transparency, while keeping a fine microstructure.
Both SPS sintering and post-annealing temperatures play a key role on YAG optical transparency and mechanical properties.
Best properties for the material sintered at 1325°C, with high transmittance, ultra-fine microstructure and high hardness.
Post-annealing at 900°C maximizes the transmittance.
*Real-in-line transmission, 1 mm thickness.