INVESTIGATION ON THE LUMINESCENCE OF LN(3+) (LN=EU, GD, AND DY) IN HEXAGONAL KCAR(PO4)2 PHOSPHATES (R=GD, Y)

The optical properties of Ln3+ ions (Ln = Gd, Eu and Dy) in KCaR (PO4)2 (R = Gd, Y) are studied in detail. It is found that no striking concentration quenching for Gd3+ and Eu3+ activators occurred in hexagonal KCaR(PO4)2 when exciting into their f --> f transitions, viz., via Gd3+ 274 nm and Eu3+ 394 nm, respectively. Energy transfer from Gd3+ to Eu3+ or Dy3+ ions via Gd3+ are very efficient. The concentration quenching of Dy3+ emission based on KCaGd(PO4)2 was very strong on account of its cross relaxation. The concentration dependence of Eu3+ and Dy3+ emission sensitized by Gd3+ is also reported. The interactions between Ln3+ in KCaR(PO4)2 were mainly d-d or exchange interactions.