Nano-YAG:Ce Mechanisms of Growth and Epoxy-Encapsulation

We have investigated the mechanism of nano-YAG:Ce growth in butanediol and glycol solvents. The static autoclave and low synthesis temperature (225 degrees C) that we employed provided conditions of slow growth in which we were able to observe an intermediate phase, a butanediol-intercalated layered alumina. This phase serves to passivate the surface in nano-YAG:Ce precipitates and thus contributes to increasing the quantum yield of YAG:Ce by diminishing surface effects such as Ce oxidation. While neat 1,4-butanediol results in precipitation of the nano-YAG:Ce, a mixture of 1,4-butanediol and diethylene glycol stabilizes a transparent colloid. We attribute this to higher solubility of the layered alumina intermediate in the solvent mixture and, thus, more homogeneous nucleation of the nano-YAG:Ce compared to heterogeneous nucleation in the neat 1,4-butanediol. However, the trade-off is slightly lower quantum yield in the transparent colloid, since the nano-YAG:Ce is not as thoroughly surface-passivated. With the transparent colloid, we were able to encapsulate the nano-YAG:Ce into a transparent epoxy dome that may be utilized in solid-state devices.