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 °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.