Study on the Valence State of Eu Ions in Sr3Al2O6:Eu Phosphor

Europium-activated strontium aluminate phosphor, Sr3Al2O6:Eu2+, was prepared by solid-state reaction. The main concerns on the formation of a stable Sr3Al2O6 phase and the complete reduction of europium ions in this crystal phase, which is considered controversial in the literature and is available for white light-emitting-diode application, were addressed. It was found that the single phase of Sr3Al2O6 could be well formed and the valence state of europium ions depended on treatment temperature, flux, reduction gas, and the resultant stiffness of the host lattice. The redshift emission of Eu2+ in the Sr3Al2O6 host was not marked in our experimental regime. However, the green emission of Sr3Al2O6:Eu2+ increased gradually with the mole fraction of Al2O3 to SrCO3 in the starting materials owing to the complete formation of the Sr3Al2O6 phase. (C) 2010 The Japan Society of Applied Physics