Title
Controllable Eu valence based on linear structural evolution in single-phased Sr3-xLa1+x(PO4)3-x(SiO4)x phosphors to realize tunable/white light emissions
Author
Yue Guo, Yeqing Chen, Qingguang Zeng, Sung Heum Park, Byung Chun Choi, Jung Hyun Jeong
Year
2019
Journal
Journal of Alloys and Compounds
Abstract
A series of Sr3-xLa1+x(PO4)3-x(SiO4)x phosphors based on the elemental co-substitution scheme of [La3++SiO44−] for [Sr2++PO43−] units has been successfully synthesized by solid-state method. X-ray diffraction and Rietveld refinement analysis confirmed that the well synthesized single-phase structure obeys excellent Vegard’s rule in structural parameters, and it has a cubic structure with space group I4‾3d (220). Detailed photoluminescence spectra and XPS analysis confirmed that Eu ions present in both the Eu2+ and Eu3+ oxidation states. The Eu2+ ions occupied two types of Sr luminescent centers with peaking at 420 nm exhibited blue emission and peaking at about 510 nm exhibited green emission, while the Eu3+ ions resided one type of Sr/La luminescent centers exhibited typical red emission. Interestingly, it is feasible to control the valence of Eu from Eu3+ to Eu2+ by substituting [La3++SiO44−] for [Sr2++PO43−] unit in Sr2.9-xLa1+x(PO4)3-x(SiO4)x matrix. In addition, a discussion for explaining the valence transformation from Eu2+ to Eu3+ in the Sr2.9-xLa1+x(PO4)3-x(SiO4)x matrix was also given. Our work can also encourage the study of the complicated luminous behavior among multi-oxidation states in single Wyckoff site with huge potential applications.
Instrument
V-670, FP-8500
Keywords
Fluorescence, Quantum yield, Diffuse reflectance, Absorption, Coordination chemistry, Materials