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Upconversion luminescence modulated by alkali metal (Li, Na, and K) induced crystallization in Er3+/Yb3+ co-doped β-PbF2 oxyfluoride glass ceramics

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Abstract

Alkali metal ions (Li+, Na+ and K+) are introduced into oxyfluoride glass ceramics (GCs) by a traditional melt-quenching and thermal treatment method to regulate crystallization behavior and upconversion luminescence (UCL) of β-PbF2:Er3+/Yb3+ nanocrystals (NCs). The crystallization behavior of β-PbF2:Er3+/Yb3+ NCs in GCs is characterized by X-ray diffraction (XRD), high-resolution transmission electron microscopy (HRTEM), EDX analysis, Raman spectroscopy and photoluminescence (PL) spectroscopy with Eu3+ ions as structural probes. Li+, Na+ and K+ ions are inserted into a glass matrix to destroy its glass network structure, which results in fluoride crystallization even without thermal treatment. Compared with alkali metal ion-free doped GCs, crystallization behavior and UCL properties of β-PbF2:Er3+/Yb3+ NCs in Li+ doped GCs are almost unchanged because Li+ ions are too small to incorporate into the β-PbF2:Er3+/Yb3+ NCs. Na+ and K+ ions are believed to enter the β-PbF2 lattice by substituting Pb2+ ions due to their similar ionic radii. Na+ ions as charge compensation ions doped into the β-PbF2:Er3+/Yb3+ NCs result in sharp lattice shrinkage due to their smaller ionic radius than Pb2+ ions. β-PbF2:Er3+/Yb3+ NCs doped with Na+ ions become more crowded because of a tight network structure limited by a Si–O layer. The crowded growth of β-PbF2:Er3+/Yb3+ NCs results in a very small distance between Er3+ and Yb3+ ions, which leads to a strong EBT process between Er3+ and Yb3+ ions, then a nearly pure red UCL emission (the maximum intensity ratio of red to green (RRG)) was obtained. Meanwhile, K+ ions as charge compensation ions doped into the β-PbF2:Er3+/Yb3+ NCs result in slight lattice expansion of the β-PbF2:Er3+/Yb3+ NCs due to the larger ionic radius of K+ ions than that of Pb2+ ions. K+ ions could act as a self-promoting agent for the enhanced crystallization of the β-PbF2:Er3+/Yb3+ NCs. UCL intensity of β-PbF2:Er3+/Yb3+ NCs doped with K+ ions increases by about 30 times due to high crystallinity and lattice distortion around Er3+ ions. The results show that simultaneous co-doping of alkali metal ions (Li+, Na+ and K+) in oxyfluoride GCs is a very effective way to integrate this material for advanced photonic applications.

Graphical abstract: Upconversion luminescence modulated by alkali metal (Li, Na, and K) induced crystallization in Er3+/Yb3+ co-doped β-PbF2 oxyfluoride glass ceramics

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Article information


Submitted
22 Oct 2019
Accepted
26 Nov 2019
First published
27 Nov 2019

CrystEngComm, 2020, Advance Article
Article type
Paper

Upconversion luminescence modulated by alkali metal (Li, Na, and K) induced crystallization in Er3+/Yb3+ co-doped β-PbF2 oxyfluoride glass ceramics

Y. Guo, L. Zhao, Y. Fu, H. Dong and H. Yu, CrystEngComm, 2020, Advance Article , DOI: 10.1039/C9CE01667H

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