Competition between Energy Transfer and Energy Migration Processes in Neat and Eu3+-Doped TbPO4

The luminescence spectroscopy of various TbPO4, EuPO4, and TbPO4:Eu3+ polycrystalline materials has been systematically investigated upon near- and vacuum-UV excitation. Evidence was found for an efficient overall Tb3+ -> Eu3+ energy transfer in TbPO4:Eu3+. Upon UV excitation, this process leads to a significant change in the resulting emission color of the materials from green to red even for low europium doping levels. The efficiency of the transfer at room temperature was evaluated. Fast migration among Tb3+ ions in the Tb3+-based materials was also observed, which in the case of TbPO4 causes partial luminescence quenching due to energy transfer to killer centers