Persistent luminescence in rare-earth codoped Ca2Si5N8:Eu2+

The luminescence properties of Ca2Si5N8:Eu, M (with M = Nd, Sm, Dy, Ho or Tm) are reported. Ca2Si5N8:Eu without codopants shows a relatively weak afterglow. Ca2Si5N8:Eu,Tm shows the highest persistent emission intensity, with an orange emission color due to a broad emission band peaking at 620 nm. The persistence emission spectrum is red-shifted by about 10 nm compared to the steady state photoluminescence. Based on thermoluminescence measurements, it is shown that the addition of Nd, Dy and Ho to Ca2Si5N8:Eu introduces trap states which are too shallow for considerable enhancement of the persistent luminescence. The persistent luminescence in Ca2Si5N8:Eu,Tm is efficiently excited in the visible part of the spectrum. (C) 2009 Elsevier B.V. All rights reserved.