ALD Applied to Conformal Coating of Nanoporous γ-Alumina: Spinel Formation and Luminescence Induced by Europium Doping

We report on conversion of nanoporous γ-alumina particles into the spinel type ZnAl2O4 without deteriorating porosity of the host material notably. The material was converted by depositing thin layers of ZnO by the atomic layer deposition (ALD) technique and annealing the sample at 800°C to facilitate a solid state reaction for formation of the spinel phase. Such particles represent robust and inert structures most suitable as host materials for catalysis and other processes where large surface area is desired. These samples were used as host materials for a red-emitting phosphor by depositing a thin layer of europium on the surface of the particles, also by the ALD technique. The europium coating was limited to the particle surface due to reaction kinetics, however a strong luminescence at 620 nm was observed. The synthesis and characterization of all these structures will be described.