LUMINESCENCE OF EU2- IN SILICATE HOST LATTICES WITH ALKALINE-EARTH IONS IN A ROW()

The luminescence of Eu2+ in (Ca,Sr)(2)MgSi2O7, MSiO, (M = Ba, Sr, Ca), BaSi2O5, BaMgSiO4, CaMgSiO4 and Sr2LiSiO4F has been studied. In these structures there are chains of alkaline earth ions. In some cases the Eu2+ ion in these chains shows emission at long wavelengths. This eff ect is due to preferential orientation of a d orbital and fits a model proposed earlier. In (Ca,Sr)(2)MgSi2O7:Eu2+ it is shown that when the cell parameters are increased by replacing (part of) the calcium by s trontium ions, the effect of preferential orientation of a d orbital i n the chain direction decreases and the Eu2+ emission shifts to shorte r wavelengths. However, in SrSiO3:Eu2+ and CaSiO3:Eu2+ the chains of a lkaline earth ions are close together and a blue Eu2+ emission is obse rved. This indicates that preferential orientation of only one d orbit al is required to obtain a Eu2+ emission at low energies.