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

• Published in: Journal of the American Ceramic Society Vol. 105; no. 9; pp. 5783 - 5792
• Main Authors: Qi, Fei, Tu, Guangsheng, Tu, Bingtian, Wang, Hao, Zhang, Jian, Wang, Weimin, Fu, Zhengyi
• Format: Journal Article
• Language: English
• Published: Columbus Wiley Subscription Services, Inc 01.09.2022
• Subjects: Aluminum oxide; Crystal lattices; Crystal structure; Emission spectra; Excitation spectra; Fe3+‐doped alumina‐rich spinel; Ferric ions; Lattice vacancies; NMR; Nuclear magnetic resonance; Phosphors; photoluminescence; Spinel; structure
• ISSN: 0002-7820; 1551-2916
• DOI: 10.1111/jace.18538

Nonstoichiometric 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.