Energy Transfer Effects in NaEuTiO4
Energy migration among Eu3+ ions has been observed in a lot of concentrated Eu systems. Transfer at low temperatures (~1.2K) has never been observed for non-glasses. This has always been explained by the fact that at low temperatures resonant multipole-multipole transfer could only occur via 7Fo ➛ 5Do transitions. In most componds that 5Do ⇆ 7Fo transition is strictly forbidden, so that energy migration does not occur. P. Berdowski investigated the energy transfer properties of a compound, NaEuTiO4 in which this 5Do ➛ 7Fo transition is no longer strctly forbidden, due to the influence of a linear crystal field at the Eu3+ site. both the concentration dependence of the intensity and decay-time measurements show that in this system transfer occurs, even at the lowest temperature. Best decay-fits can be made by assuming a 2-dimensional diffusion process. This can be explained by the plane structure of NaEuTiO4. Diffusion increases rapidly in the temperature region between 1.2 and 40 K. This is probably due to the phonon assistance which is required for the migration.