Intrinsic- and Rare Earth Ion-Activated Luminescence in NbAlO<sub>4</sub> with Wide Structure Channels
Donglei Wei, Xifeng Yang, Yushen Liu, Joo Hyun Kim, Sung Heum Park, Hyo Jin Seo, Bo Ram Lee
Abstract
Compounds with ordered and interconnected channels have versatile multifunctional applications in technological fields. In this work, we report the intrinsic- and Eu 3+ -activated luminescence in NbAlO 4 with a wide channel structure. NbAlO 4 is an n-type semiconductor with an indirect allowed transition and a band-gap energy of 3.26 eV. The conduction band and valence band are composed of Nb 3d and O 2p states, respectively. Unlike the common niobate oxide Nb 2 O 5, NbAlO 4 exhibits efficient self-activated luminescence with good thermal stability even at room temperature. The AlO 4 tetrahedron effectively blocks the transfer/dispersion of excitation energy between NbO 6 chains in NbAlO 4, allowing for effective self-activated luminescence from NbO 6 activation centers. Moreover, Eu 3+ -doped NbAlO 4 displayed a bright red luminescence of 5 D 0 → 7 F 2 transition at 610 nm. The site-selective excitation and luminescence of Eu 3+ ions in a spectroscopic probe were utilized to investigate the doping mechanism. It is evidenced that Eu 3+ is doped in the structure channel in NbAlO 4 lattices, not in the normal cation sites of Nb 5+ or Al 3+ . The experimental findings are valuable in developing new luminescent materials and improving the understanding of the material’s channel structure.