This work is devoted to a new family of highly emissive white phosphors for solid-state lighting (SSL) applications. The phosphors, based on yttrium aluminoborates (g-YAB) compositions, were prepared from solutions by the polymeric precursor (PP) method (modified Pechini process), involving non-toxic and low cost precursors. The resulting resins were then dried at moderate temperatures. Then, a two-step annealing treatment with controlled atmospheres (pyrolysis under nitrogen and calcination under oxygen) favored the gradual oxidation of organic moieties coming from the starting materials. This allowed avoiding the formation of impurities, which are detrimental to photoluminescence (PL) emission such as pyrolytic carbon (visible light absorber) or carbonates (PL quenchers). Thus, we have synthesized glassy yttrium aluminoborate powders exhibiting intense PL emissions extended in the whole visible range leading to warm light emissions. These PL properties arise from structural defects (non-bridging oxygen or carbon impurities such as carbonyl radicals), whose energy levels are widely extended within the large bandgap of these g-YAB powders. Moreover, these samples exhibit good thermal and chemical stabilities. We determined their internal quantum yields using near ultraviolet excitations, which reached high promising values, around 80 - 90%. This new family of lanthanide-free phosphors exhibiting intense warm white emissions, with high Color Rendering Indexes (CRI), is promising for SSL through the development of phosphor coated -LED devices.

Date Published: 27 February 2016
PDF: 8 pages
Proc. SPIE 9749, Oxide-based Materials and Devices VII, 97490B (27 February 2016); doi: 10.1117/12.2220397

Published in SPIE Proceedings Vol. 9749:
Oxide-based Materials and Devices VII
Ferechteh H. Teherani; David C. Look; David J. Rogers, Editor(s)