Multi-color luminescence properties and energy transfer behaviour in host-sensitized CaWO4:Tb3+,Eu3+ phosphors

摘要

A series of host-sensitized and color-tunable CaWO4:Tb3+,Eu3+ phosphors were prepared via a high-temperature solid-state reaction route, and the crystal structure and luminescence properties, especially the energy transfer behavior, were investigated in detail. Under UV radiation, the CaWO4 host presents a broad emission band from about 320 to 600 nm centered around 415 nm, ascribed to the charge transfer in WO42- groups; while Eu3+ and Tb3+ ion doped CaWO4 samples show both host emission and respective emission lines derived from the characteristic f-f transitions of activators, which present abundant emission colors owing to an efficient energy transfer from the host to Eu3+/Tb3+ ions. The energy transfer from the host to Eu3+ and Tb3+ was evidenced by directly observing appreciable overlap between the excitation spectrum of the host and the emission spectrum of Eu3+/Tb3+, as well as by the decreased decay time of host emission with increasing Eu3+/Tb3+ concentration. The energy transfer mechanisms in CaWO4:Eu3+/Tb3+ phosphors have been determined to be a resonant type via dipole-dipole interaction. In the Eu3+ and Tb3+ co-doped system, CaWO4:Eu3+,Tb3+, the energy transfer phenomenon not only occurs from host to activators, but also from Tb3+ to Eu3+, resulting in color-tunable emission including white light by simply adjusting the doping concentration of Eu3+ and Tb3+ ions. The PL properties of the as-prepared materials indicate their promising application in solid-state lighting fields.