Tunable color and energy transfer of Y2Mg3Ge3O12: Tb3+, Tm3+, Eu3+ phosphors with excellent thermal stability

Y2Mg3Ge3O12: RE3+ (RE ​= ​Tb, Eu, Tm) phosphors were prepared by solid phase method. XRD and EDS show that the samples were pure phases. The ET efficiency of Y2Mg3Ge3O12: Tb3+, Eu3+ can reach up to 96.63%, and the mechanism is d-d interaction. In Y2Mg3Ge3O12: Tb3+, Eu3+, Tm3+, the intensity of Tb3+ decreases with the increase of Eu3+ concentrations, and the intensity of Tm3+ is basically unchanged, the intensity of Eu3+ increased first and then decreased. Meanwhile, the ET efficiency can reach up to 77.53%. Moreover, the luminescence intensity at 423 ​K can still be maintained at 87–96.58% of that at the initial temperature. The value of CCT which shows a decreasing trend with increasing Eu3+ concentrations also indicates that warm white light can be obtained by triple doping of Tb3+-Eu3+-Tm3+. The above findings show that these samples are likely to be used in warm w-LEDs.