Intrinsic- and Rare Earth Ion-Activated Luminescence in NbAlO4 with Wide Structure Channels

Compounds with ordered and interconnected channels haveversatilemultifunctional applications in technological fields. In this work,we report the intrinsic- and Eu3+-activated luminescencein NbAlO4 with a wide channel structure. NbAlO4 is an n-type semiconductor with an indirect allowed transition anda band-gap energy of 3.26 eV. The conduction band and valence bandare composed of Nb 3d and O 2p states, respectively. Unlike the commonniobate oxide Nb2O5, NbAlO4 exhibitsefficient self-activated luminescence with good thermal stabilityeven at room temperature. The AlO4 tetrahedron effectivelyblocks the transfer/dispersion of excitation energy between NbO6 chains in NbAlO4, allowing for effective self-activatedluminescence from NbO6 activation centers. Moreover, Eu3+-doped NbAlO4 displayed a bright red luminescenceof D-5(0) -> F-7(2) transitionat 610 nm. The site-selective excitation and luminescence of Eu3+ ions in a spectroscopic probe were utilized to investigatethe doping mechanism. It is evidenced that Eu3+ is dopedin the structure channel in NbAlO4 lattices, not in thenormal cation sites of Nb5+ or Al3+. The experimentalfindings are valuable in developing new luminescent materials andimproving the understanding of the material's channel structure. The spaced distribution between cationsNb(5+) andAl(3+) in the lattice heavily limits the dispersion and quenchingof excitation energy. Consequently, NbAlO4 exhibits efficientself-active luminescence. Eu3+-activated NbAlO4 displays bright red luminescence caused by the dominant D-5(0) -> F-7(2) transition. Eu3+ ions occupy the channels in the NbAlO4 lattice.This unique doping mechanism induces inhomogeneous broadening of theexcitation and emission spectra with extremely large FWHM.

Automated summary

In this work, we investigated NbAlO4, a compound with ordered and interconnected channels, and discovered its intrinsic- and Eu3+-activated luminescence. NbAlO4 exhibited efficient self-activated luminescence with good thermal stability even at room temperature, and Eu3+ doping resulted in bright red luminescence. The doping mechanism of Eu3+ ions in the NbAlO4 lattice was found to be in the structure channels, and this unique doping mechanism induced inhomogeneous broadening of the excitation and emission spectra.