Energy Transfer in Li6Gd(BO3)3
In the new material Li6Gd(BO3)3 Gd3+ ions belong to parallel chains separated by about 7A for an intrachain distance of about 4A, so that the energy transfer among Gd3+ ions is expected to be mostly one-dimensional. The Gd3+ 6P7/2→8S7/2 fluorescence has been studied from 300K to 1.5K. Above 40K the fast exponential fluorescence decay indicates fast diffusion of the energy among the Gd3+ ions and trapping by impurities. Below 40K the energy transfer takes place predominantly toward perturbed Gd3+ ions and is diffusion-limited. The nonexponential intrinsic fluorescence decay consists in a short-time component corresponding to diffusion and a longtime component coming from thermal back-transfers from,the traps. The cross-over from a fast diffusion regime to a diffusion-limited regime is discussed in relation to the one-dimensional crystal structure.