Remarkable changes in the photoluminescent properties of Y₂Ce₂O₇:Eu³⁺ red phosphors through modification of the cerium oxidation states and oxygen vacancy ordering

Abstract

A new series of red phosphors based on Eu(3+)-doped yttrium cerate [Y1.9Ce2O7:0.1Eu(3+), Y2Ce1.9O7:0.1Eu(3+) and Y2Ce2-xO7:xEu(3+) (x = 0.05, 0.10, 0.15, 0.20, 0.25 and 0.50)] was prepared via a conventional solid-state method. The influence of the substitution of Eu(3+) at the aliovalent site on the photoluminescent properties was determined by powder X-ray diffraction, FT Raman spectroscopy, X-ray photoelectron spectroscopy, transmission electron microscopy, scanning electron microscopy with energy-dispersive spectroscopy, UV-visible absorption spectroscopy, photoluminescence spectroscopy and lifetime measurements. The substitution of Eu(3+) at the Ce(4+) site induces a structural transition from a defect fluorite to a C-type structure, which increases the oxygen vacancy ordering and the distortion of the Eu(3+) environment, and decreases the formation of Ce(3+) states. In contrast, phosphors with isovalent substitution at the Y(3+) site exhibit the biphasic nature of defect fluorite and a C-type structure, thereby increasing the number of Ce(3+) oxidation states. These modifications resulted in remarkable changes in the photoluminescent properties of Y2Ce1.9O7:0.1Eu(3+) red phosphors, with emission intensities 3.8 times greater than those of the Ce0.9O2:0.1Eu(3+) and Y1.9Ce2O7:0.1Eu(3+). The photoluminescent properties of Y2Ce2-xO7:xEu(3+) were studied at different Eu(3+) concentrations under excitation with blue light. These phosphors emit intense red light due to the (5)D0-(7)F2 transition under excitation at 466 nm and no concentration quenching is observed with up to 50 mol% Eu(3+). They show increased lifetimes in the range 0.62-0.72 ms at Eu(3+) concentrations. The cation ordering linked to the oxygen vacancy ordering led to the uniform distribution of Eu(3+) ions in the lattice, thus allowing higher doping concentrations without quenching and consequently increasing the lifetime of the (5)D0 states. Our results demonstrate that significant improvements in the photoluminescence properties can be achieved by the structural alteration of a fluorite CeO2 to a C-type lattice.

Design of Efficient Noble Metal Free Copper‐Promoted Nickel‐Ceria‐Zirconia Nanocatalyst for Bio‐Fuel Upgrading

“…The high resolution deconvoluted Ce‐3d XPS spectra exhibit three characteristic BE peaks as well as their concomitant shake‐up lines of the 3d 3/2 and 3d 5/2 , for Ce 4+ and Ce 3+ species. The XPS spectra indicate the formation of fairly complex structure owing to the presence of both Ce 4+ and Ce 3+ derived modes, which deviated from their ideal stoichiometry ,,,. A notable BE shifts in Ce‐3d core‐level toward the higher region are shown in the reduced bimetallic Ni−Cu/CZ catalysts as compared to the pure CZ mixed oxide.…”

Combined Experimental and Theoretical Insights into the Synergistic Effect of Cerium Doping and Oxygen Vacancies in BaZrO3−δ Hollow Nanospheres for Efficient Photocatalytic Hydrogen Production

“…Due to very low concentration of Ce in BaZr 0.97 Ce 0.03 O 3 , the shape of the spectra is not as distinct as for pure CeO 2 . The Ce 3d XPS spectral analysis is complicated due to spin–orbit coupling between Ce 4f and O 2p electrons, leading to the structured peaks . Many reports have shown that Ce 3d spectra can consist of eight peaks with four pairs of spin–orbit coupling contributions, viz.…”

Synthesis and characterization of micro/nano-structured BaHPO4/Ba3(PO4)2/Ba5(PO4)3OH phases and their luminescence

“…Herein, the phenomenon shown in Fig. 2(b) indicates that the average crystallite sizes of as-prepared Ba 3 (PO 4 ) 2 samples produced under HT conditions are on the nanometer scale, smaller than 200 nm, which can be theoretically estimated by the Scherrer equation [23][24][25] as follows:…”