Fast Decay U.V. Phosphor — YAlO3 : Ce

Samples prepared to obtain u.v.‐emitting YAlO 3 : Ce (YAP:Ce) by solid‐state reactions up to 1600°C are never free of visible‐emitting Y 3 Al 5 O 12 : Ce (YAG: Ce). Furthermore, YAG cannot easily be removed from the products. By adding Ba compounds, the YAG content of the product can be minimized, and BaAl 2 O 4 and other phases formed can be eliminated by HNO 3 ‐ treatment to yield “pure” YAP:Ce. The Ba compounds‐fluxed YAP:Ce is moreover the most efficient of all trial samples. It has a radiant efficiency η ∼ 7% and a decay time τ1/e ∼ 30 nsec for CR excitation.