A Study of the Sensitization of Gd3+ Luminescence by Pb2+ Ions

The possibilities of the sensitization of the Gd 3+ luminescence by Pb 2+ ions has been studied in Tb 3+ ‐activated gadolinium compounds ( and ) and alkaline‐earth gadolinium compounds with , and . Incomplete or even absence of Pb 2+ to Gd 3+ energy transfer was observed for , , and . In these compounds, the Pb 2+ luminescence has a large Stokes shift. The result is that Pb 2+ ions are out of resonance with the Gd 3+ ions for energy transfer. This can be partly compensated by direct Pb 2+ to Tb 3+ energy transfer. This transfer has a critical distance of about 6Å. Efficient energy transfer from Pb 2+ to Tb 3+ was observed only for , but even there this holds only for Pb 2+ ions on the crystallographic 4f site of the apatite structure. The luminescence of Pb 2+ ions on the other cation site (6h) has a large Stokes shift. This ion is coordinated to an O 2− ion, whose bonding strength is not saturated. This type of coordination results in large Stokes shifts. Evidence from the literature is presented.