Influence of the Crystal Structure on the Energy Transfer Tb3+ → Eu3+ in Oxyorthosilicates Ln2SiO5: TbxEUy

In the system X1–GdTbSiO5:Eu an energy transfer between the hole trap Tb3+ and the electron trap Eu3+ is working in cathodoluminescence. That energy transfer is less effective than in the corresponding series with X2 structure X2–YTbSiO5: Eu, due to the marked differences between the two crystallographic positions for the Ln3+ ions in the X1 structure. In photoluminescence for X1–GdTbSiO5:Eu an energy transfer Tb3+ → Eu3+ is working as well. Interestingly Gd3+ does not participate, despite the fact that the Gd3+ -Gd3+ distance is below the critical value for an energy migration within the Gd3+ sublattice.