Particle Atomic Layer Deposition on Long-Afterglow Phosphors
Extending the Lifetime of a Zero-Energy Lighting Technology for Outdoor Applications
Strontium aluminate (SrAl2O4) phosphors activated with Eu2+ and co-doped with RE3+ elements (RE: Nd, Dy, etc) are long-afterglow phosphors (>12 hrs of persistent luminescence) of significant commercial relevance. These phosphors have been widely used as luminescent additives in many commercial products including plastics and textiles. Today, these phosphors are of interest for zero-energy safety lighting both in residential markets and on roadways. However, these phosphors are prone to degradation in moist or humid conditions. This talk will discuss our work to use ALD to protect these phosphors from degradation in aggressive aqueous environments. Powders that are ALD coated with < 10 nm of Al2O3 or TiO2 show good resistance to degradation after being directly immersed in water for over 2 weeks. Achieving good conformality over all powder surfaces appears to be an important requirement to powder stability.