Crystal structure and luminescence mechanism of novel Fe3+‐doped Mg0.752Al2.165O4 deep red‐emitting phosphors

Abstract

AbstractNonstoichiometric alumina‐rich spinel provides diverse and changeable local environments for transition‐metal dopants. In this contribution, novel Mg0.752Al2.165−xO4:xFe3+ deep red‐emitting phosphors were designed and prepared by the solid‐state reaction method. The red emission presents an unexpected shift from 735 to 770 nm by comparing with Fe3+‐doped MgAl2O4. The excitation spectrum of Mg0.752Al2.165−xO4:xFe3+ is broadened in the UV region with a new strong peak at 320 nm. The crystal structure refinement and NMR spectra fitting reveal that the cation vacancies and disorder increase with excess Al3+ entering the spinel crystal lattice. According to the results of EPR, NMR, and PL/PLE measurements, it was proposed that the Fe3+ ions locate at the distorted octahedral coordination. The changes of the local structure of Fe3+ ions promote the doublet state's involvement in the d−d transition. It was proposed that the new excitation peak at 320 nm in Mg0.752Al2.165−xO4:xFe3+ is associated with the transitions from the ground state 6A1g(6S) to the 4A2g(4F)/T1g(4P) and doublet states. The transition between the lower energy excited state of 2T2g(2I) and 6A1g(6S) mainly contributes to the deep red emission and the red‐shifting effect.