Photoluminescence Spectra Changes and Thermal Stability Improvement for Ba1.98Mg1−xAl2xSi2−xO7:0.02Eu2+ Green Phosphor with Al–Al replacing Si–Mg

Abstract

Series of Ba₂Mg_1-xAl_2xSi_2-xO₇:0.02Eu²⁺ phosphors were synthesized by the solid-state reaction method. These phosphors show efficient green emission under the near ultra violet light excitation. As Al-Al replacing Mg-Si, the changes of the structure and the morphology, the variations of the photoluminescence spectra and lifetime, and the evolutions of the thermal stability were investigated and discussed. With Mg-Si replacement by Al-Al, the crystal field splitting strength of the 5d electron of Eu²⁺ increases, which causes the red shift of the emission band. The photoluminescence intensity and lifetime of Eu²⁺ is decreased. The physical mechanisms for the variations of the photoluminescence intensity and lifetime were discussed. The thermal stability can be evidently improved with Al-Al replacing Mg-Si in the host structure. The forbidden band width has been calculated with the measurements of the reflection spectra, which is extended firstly and then narrowed. The extended forbidden band width limits the Eu²⁺ 5d electron self-ionization from the splitting levels to the conduction band, which is resulted in the improvement of the thermal stabilities. These results show Al-Al replacing Si-Mg can be a suitable route for the photoluminescence tune for Ba-Mg-(Al)-Si-O:Eu²⁺ phosphors.