Abstract
Samples prepared to obtain u.v.‐emitting 
(YAP:Ce) by solid‐state reactions up to 1600°C are never free of visible‐emitting 
(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 
and other phases formed can be eliminated by 
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.