Luminescence properties and energy transfer of a color-tunable Y2GeO5: Bi3+, Eu3+ phosphor

A series of Y2GeO5: Bi3+, Eu3+ phosphors were synthesized via a solid state reaction. Their crystal structures and luminescent properties were investigated. Under the 295 nm excitation of Bi3+, the Y2GeO5: Bi3+, Eu3+ phosphors presented a purplish-blue broad band at 369 nm from Bi3+ and some typical f-f characteristic emissions of Eu3+. The optimum co-dopant concentration of Eu3+ ion is 2%. Luminescence quenching of Eu3+ ions was demonstrated to be quenching interaction of Eu3+-Eu3+ and the quenching of the 5D0 state by Bi3+ ions. Energy transfer from Bi3+ to Eu3+ in Y2GeO5 efficiently occurred and the dipole-dipole interaction is the major energy transfer mechanism. With the increasing concentration of Eu3+, the luminous efficacy of the radiation increases and the luminescence colors can be tuned from purplish blue to reddish-orange. The Y2GeO5: Bi3+, Eu3+ phosphors are potential candidate materials for application in UV chip based W-LEDs with excellent thermal stability (0.2708 eV).