Luminescence centers and valence change of Eu2+ in KCaF3

The nature of the emission centers and the valence change of Eu2+ in KCaF3:Eu2+ depends strongly on preparation conditions. Experimental results show that there are two different d→f emission bands, located at 425 and 510 nm, respectively. Their origin, relationship, and the effect of doping concentration on them are discussed. A Eu2+–Eu3+ valence change process is proposed.