5d Transitions Research Articles

Judd-Ofelt analysis and luminescence characteristics of Eu3+ doped Nepheline (NaAlSiO4)-based glass ceramics for solid-state lighting applications

The present work addresses on the optical and spectroscopic properties of glass ceramics containing a hexagonal NaAlSiO4 crystalline phase (Nepheline) and Eu3+ dopant, prepared by melt-quenching technique followed by subsequent heat treatment. The precipitation of NaAlSiO4 crystals in the glass system with increasing heating temperature was determined by XRD analysis. The existing vibrational bands such as BO3, BO4, SiO2 and O-H groups in the glass network and the increase in the amount of non-bridging oxygens with increasing heating temperature of the precursor glasses were evaluated through FTIR spectroscopy. Morphological changes in the glass surface induced with the growth of NaAlSiO4 crystals is recorded by field emission scanning electron microscopy at resolutions of 1 µm and 200 nm. The impact of heating temperature and Eu3+ ions embedded in the NaAlSiO4 crystalline phase on the optical properties was studied using absorption spectra, excitation, emission spectra, and decay curves. The glass ceramics exhibited a decrease in their bandgap energy values and an increase in their Urbach energy values with heat treatment at higher temperatures. The Judd-Ofelt (J-O) intensity parameters evaluated from the emission spectra showed the trend Ω2>Ω4. The emission bands with intense electric dipole transition 5D0→7F2, long decay lifetimes, and improved quantum efficiency of Eu3+ ions evidenced the partitioning of Eu3+ ions into the NaAlSiO4 crystalline phase. Radiative calculations from the emission spectra showed a higher stimulated emission cross-section for glass ceramics. The CIE-1931 color coordinates, correlated color temperature (CCT, K), and color purity measurements favoured red emission from Eu3+ ions with better quality. Therefore, the prepared glass ceramics can favour the need for LED applications and laser devices.

Study of Eu3+–Gd3+ co-doped Ba–Bi–B glasses for red-laser applications: Physical, structural, photoluminescence and time-resolved spectral characteristics

A series of Eu3+ and Eu3+/Gd3+ co-doped barium-bismuth-borate (Ba–Bi–B) glasses were prepared by melt-quench technique. And deliberated the physical, structural, and spectroscopic properties of all glasses and explored the energy transfer process from Gd3+ to Eu3+ ions. The density of glasses increased with increasing of Gd3+ concentration in co-doped glasses. Characteristics of steady-state and time-resolved photoluminescence (PL) of Eu-doped and Eu3+-Gd3+ co-doped glasses under different excitation wavelengths suggested the prospects of the investigated glass system for display device applications. PL spectrum displays a strong red emission peak centered at 612 nm due to the Eu3+: 5D0→ 7F2 transition. Less intense emissions centered at 577 nm (7F0), 590 nm (7F1), 651 nm (7F3) and 700 nm (7F4) are also observed from the radiative transitions of the excited state 5D0 of Eu3+ions. The values of radiative parameters such as transition probability, branching ratios, and stimulated emission cross-sections were obtained from Judd–Ofelt theory analysis and indicated the aptness of the Ba–Bi–B glasses for optical devices. A 5-fold enhancement in the PL intensity was observed in 1.0 mol% Eu3+ and 3.0 mol% Gd3+ co-doped glass under λExci. = 394 nm excitation. The calculated commission Internationale de l'eclairage color coordinates and correlated color temperature values show that the Ba–Bi–B glasses are useful for red-laser and display device applications.

Photoluminescence properties of Eu3+-doped Na2CaSiO4 phosphor prepared by wet-chemical synthesis route

The present investigation focuses on the development of Eu3+ activated phosphors for near ultraviolet (NUV) excited light emitting diode (LED) applications. In this investigation, we have synthesized a series of Na2CaSiO4:Eu3+phosphors via wet-chemical method and characteristic of synthesized phosphors have been analyzed by X-ray diffraction (XRD), Scanning electron microscopy (SEM), Thermo gravimetric analysis– Differential thermal analysis (TGA–DTA) and photoluminescence (PL) techniques. The recorded excitation band indicates a broad excitation band centered at 262 nm due to charge transfer (CT) band and sharp peaks at 395 nm and 466 nm due to 7F0→5L6 and 7F0→5D2 transition of Eu3+ ions. The highest excitation intensity was observed at 396 nm wavelength. Therefore under 396 nm excitation, the emission spectrum showed characteristics peaks located at 595 nm and 615 nm, which are attributed due to the 5D0→7F1 and 5D0→7F2 transition of Eu3+ ions. Emission spectra shows dominant emission peak at orange region around 595 nm due to the magnetic dipole transition of5D0→7F1. In addition, the effects of the Eu3+ ions on the emission intensity were investigated, it was found that the emission intensity increases as the concentration of Eu3+ ions increases up to 0.5 mol%. Thereafter, PL emission intensity was decreased due to concentration quenching. The CIE Chromaticity coordinate of the prepared phosphor was located in the orange region around (0.584, 0.421) with high color purity. As per the investigation of prepared Na2CaSiO4:Eu3+phosphors, it was concluded that it is a promising candidate for lighting and display applications.

Impact of Tb doping on luminescence properties of LiCaAlF6 phosphor prepared in argon atmosphere and charge transfer mechanism

This work focuses on the synthesis and characterization of Tb doped LiCaAlF6 phosphor for its OSL dosimetry properties. The phosphor has been prepared by melting method. XRD shows the formation of LiCaAlF6 with enrichment of CaF2. The excess availability of Ca2+ions are advantageous in incorporation of Tb dopant. The photoluminescence studies show the increase in the luminescence intensity after Tb doping by showing strong emission corresponding to 5D4 → 7FJ (J = 6, 5, 4, 3) transitions with a prominent green emission transition 5D4 → 7F5 at 540 nm. Further, Tb ion exist in Tb3+ and Tb4+ state as observed from XPS. The incorporation of Tb4+ ion is difficult to achieve and its presence in the host might also increase the of number of trapping states. The OSL studies of LiCaAlF6: Tb show high intensity under blue light stimulation for beta irradiation in the dose range 0.05–10Gy. The OSL sensitivity of LiCaAlF6: Tb phosphor is found to be ∼8 times higher to that of commercially available Al2O3: C. The phosphor has shown dose linearity in the range of 0.05–10Gy and minimum detectable dose (MDD)∼6.95 μGy. The enhanced sensitivity may be attributed to the additional defect centers due to excess CaF2 with mixed oxidation state of Tb3+ and Tb4+ ions. The enhancement of OSL signal of LiCaAlF6: Tb in comparison to Al2O3:C has been discussed based on charge compensation mechanism. These results indicate that LiCaAlF6: Tb phosphor prepared via melting method in Ar gas atmosphere shows good OSL properties and has potential application in radiation dosimetry.

Photoluminescence and Judd-Ofelt analysis of Eu3+ doped akermanite silicate phosphors for solid state lighting

After aluminates, alkaline-earth silicates are the most researched category of luminescent inorganic phosphors. Eu3+ doped Ca2MgSi2O7 and Sr2MgSi2O7 phosphors synthesized by the combustion process. For the as-prepared phosphors, XRD and Rietveld refinement revealed a single phase with akermanite type structure belonging to tetragonal crystallography. UV–Vis spectroscopy was used to calculate the optical bandgap. Ca2MgSi2O7:x%Eu and Sr2MgSi2O7:x%Eu (x = 0.5 - 2.5) phosphors produced orange-red light with emission peaks at 590 nm, 614 nm, and 702 nm, which corresponded to the Eu3+ transitions 5D0 → 7F1, 5D0 → 7F2, and 5D0 → 7F4, respectively. Using a modified Judd-Ofelt technique based on the emission spectrum, the key spectroscopic properties (transition probabilities, radiative lifetimes, and branching ratios) associated with the 5D0 orange-red emitting level were found. Ω2 < Ω4 reveals that Eu3+ ions occupy high symmetry locations in the generated sample under the doping level studied in this work. There has also been a decrease in the Ω4 parameter. It implies that the 5D0 → 7F2 transition is more efficient than the 5D0 → 7F4. This indicates that the red color emission has been improved. The estimated CIE coordinates corroborated the PL emission in the orange-red region.

Orange-red luminescence features of Eu3+ doped CaAl4O7 phosphors

A series of orange-red emitting Eu3+ doped CaAl4O7 phosphors was synthesized by the citric acid sol gel process using the metal nitrates as precursors. A study of the phosphors according to their X-ray diffraction patterns confirmed the desired phase without any intermediate or precursor compounds. The SEM imaging does not reveal the crystal structure, but it shows a variation of crystalline size within a few micrometers. In the excitation spectrum of CaAl4O7:xEu3+ (x = 0.01–0.11 mol), sharp multiple peaks at 293 nm, 464 nm, and 533 nm which are characteristics of Eu3+ transitions from 7F → 5D were observed. The photoluminescence emission spectra with an excitation wavelength of 464 nm showed characteristic peaks corresponding to the transition of 5D0 → 7F2 at 612 nm and expressed orange-red region of the electromagnetic field. The emission intensity increased as the concentration of Eu3+ increased to 0.05 mol, where it exhibited the highest emission intensity in the series. The intensity ratio results also indicate an intensity drop after a 0.05 concentration of the Eu3+ ion. The full width at half maximum (FWHM) of the synthesized phosphors is expressed as the concentration increase, which leads to a drop in sharpness. The chromaticity properties indicate high color purity of the synthesized phosphor in the orange-red region by the position of the color coordinates at the edge of the CIE color chromaticity diagram.

Photoluminescence and electrochemical performance evaluation of Eu3+ doped MgAl2O4 phosphors for LED and energy storage applications

Crystal structure of Eu3+ doped MgAl2O4 (MAO) phosphors synthesised by solid state reaction method was investigated using X-ray diffraction. Raman peaks appeared at 307 cm−1, 408 cm−1, 668 cm−1 and 767 cm−1 were assigned to F2g (1), F2g (2), Eg and A1g respectively. Spherical morphology and microstructural analysis of synthesised phosphors was analysed by Field emission scanning electron microscope (FESEM) high resolution transmission electron microscope (HRTEM) and energy dispersive X-ray analysis (EDAX) was used to establish the chemical composition of the phosphors. Optical properties were analysed by photoexcitation (394 nm) and photoluminescence (PL) spectra displayed all the characteristic emission of Eu3+ related to transition 5D0 to 7Fj (j = 0, 1, 2, 3, 4). The emission color was observed in red region and it was confirmed by the Commission Internationale de l’Eclairage (CIE) chromatic coordinate graph. The color purity and quality (correlated color temperature- CCT value) of red light was observed in 0.9% Eu3+ doped MAO to be 90.76% and 2097K respectively. Electrochemical evaluation of Eu3+ doped MAO was performed through cyclic voltammetry (CV) studies.

Synthesis and Characterization of Coordination Compound [Eu(µ2-OC2H5)(btfa)(NO3)(phen)]2phen with High Luminescence Efficiency.

A high-luminescent, blue-light excitable europium(III) coordination complex, [Eu(µ2-OC2H5)(btfa)(NO3)(phen)]2phen (1) {btfa = benzoyl trifluoroacetone, phen = 1,10-phenantroline}, has been synthesized and investigated. The complex was characterized by infrared (IR) and photoluminescence (PL) spectroscopy. The PL emission spectra of powder samples registered in a range of 10.7–300 K exhibit characteristic metal-centered luminescence bands, assigned to internal radiative transitions of the Eu3+ ion, 5D1→7Fj and 5D0→7Fj (j = 0–4). The high-resolution spectrum of the transition 5D0→7F0 shows that it consists of two narrow components, separated by 0.96 meV, which indicates the presence in the matrix of two different sites of the Eu3+ ion. The splitting pattern of 5D0→7Fj (j = 0–4) transitions indicates that europium ions are located in a low-symmetry environment. The absolute quantum yield and the sensitization efficiency were determined to be 49.2% and 89.3%, respectively. The complex can be excited with low-cost lasers at around 405 nm and is attractive for potential applications in optoelectronics and biochemistry.

Synthesis and properties of novel Pb/La/WO4: Eu3+ red phosphors for white light emitting diodes (WLEDs)

A novel red emitting phosphor PbLa2–2xEu2xW4O16(0 ≤ x ≤ 1) was successfully synthesized via solid-state method. Structure and crystallite size were investigated by X-ray diffraction (XRD) and scanning electron microscope (SEM). Excitation transmission and photoluminescence (PL) properties of the samples have been studied. The prepared red phosphor of PbLa1.13Eu0.88W4O16 demonstrated the highest red luminescence compatible with electronic transition 5D0→7F2 at 615 nm during the excitation by Light-emitting diode (LED) with a wavelength of 460 nm which corresponds to the excitation band 7F0→5D2. Moreover, the intensity parameters Ω2,4 and the quantum efficiency of the PbLa1.13Eu0.88W4O16 were calculated based on the Judd-Ofelt’s theory. We compared the PL properties of our prepared red phosphors with the compound of BaGd1.3Eu0.7(MoO4)4. Such comparison is a clear evidence of the superior efficiency of our prepared red phosphors for several applications related to the White Light Emitting Diodes (WLEDs).

Assessment of the Crystallization Process of CaO-Al2O3-SiO2 Glass Probed with Tb3+ Luminescence.

The ratio of the intensity of Tb3+ fluorescence at 543 nm because of an electric dipole transition (5D4–7F5) relative to that at 437 nm due to a magnetic dipole transition (5D3–7F4) was determined to be proportional to the amount of metastable CaAl2Si2O8 crystals precipitated in CaO–Al2O3–SiO2 glass. The present results indicate that Tb3+ luminescence can be used as a probe to evaluate the crystallization of glass.

A theoretical framework for optical thermometry based on excited-state absorption and lifetimes of Eu3+ compounds

Ratiometric optical thermometers correspond to one of the most extensively studied applications of luminescent lanthanide materials in recent years. Even though several systems were studied involving the Eu3+ ion, few of them explore the absorption from the low-lying 7F1 excited state and its dependence on the ligand field (LF) splitting. This work aims to describe various absorption intensity ratios (AIR) that can be built from the excitation or absorption spectrum of the europium (III) ion by using the absorptions from the 7F0 → 5D0 transition and the different ligand field components of the magnetic-dipole allowed 7F1 → 5D0 transition and the influence of the ligand field strength on the relative thermal sensitivity of such AIR constructions. We have shown that several AIR formulas can be obtained, and they can display opposite behaviors concerning the Ligand Field strength, being suitable for different compounds of non-cubic symmetries. In addition, the ligand field influence on the relative thermal sensitivity obtained by the lifetime thermometry of the Eu3+5D0 level has also been explored.

Crystallization Mechanism and Optical Properties of Antimony-Germanate-Silicate Glass-Ceramic Doped with Europium Ions.

Glass-ceramic is semi-novel material with many applications, but it is still problematic in obtaining fibers. This paper aims to develop a new glass-ceramic material that is a compromise between crystallization, thermal stability, and optical properties required for optical fiber technology. This compromise is made possible by an alternative method with a controlled crystallization process and a suitable choice of the chemical composition of the core material. In this way, the annealing process is eliminated, and the core material adopts a glass-ceramic character with high transparency directly in the drawing process. In the experiment, low phonon antimony-germanate-silicate glass (SGS) doped with Eu3+ ions and different concentrations of P2O5 were fabricated. The glass material crystallized during the cooling process under conditions similar to the drawing processes’. Thermal stability (DSC), X-ray photo analysis (XRD), and spectroscopic were measured. Eu3+ ions were used as spectral probes to determine the effect of P2O5 on the asymmetry ratio for the selected transitions (5D0 → 7F1 and 5D0 → 7F2). From the measurements, it was observed that the material produced exhibited amorphous or glass-ceramic properties, strongly dependent on the nucleator concentration. In addition, the conducted study confirmed that europium ions co-form the EuPO4 structure during the cooling process from 730 °C to room temperature. Moreover, the asymmetry ratio was changed from over 4 to under 1. The result obtained confirms that the developed material has properties typical of transparent glass-ceramic while maintaining high thermal stability, which will enable the fabrication of fibers with the glass-ceramic core.

Mechanisms and dynamics of energy transfer sensitization in the Eu3+, Cr3+ and Fe3+ ions in the LiAl5O8 phosphors

A mechanism of energy transfer sensitization in Eu-doped LiAl5O8 produced by the modified sol-gel method is proposed. The XRD results show the formation of the desired crystalline phase and the solubility limit of Eu dopant. Based in the PL results, a mechanisms of energy transfer (ET) and simultaneous excitation (SE) between the doping ion (Eu3+) and contaminating ions (Cr3+ and Fe3+) were elaborated based in the five possible dynamics. The first attributed to SE between Eu3+- Fe3+ characterized by direct excitation of Eu3+ and Fe3+ ions. The second is attributed to ET between Eu3+-Cr3+, attributed to the radiative transitions 5D0→7F1,2 and Cr3+ ion. Third mechanism is similar to the energy transfer described by the second mechanism in addition to Fe3+ sensitization. The fourth and fifth are due to the SE between Eu3+-Fe3+-Cr3+.

Correlation of X-Ray Diffraction, X-Ray Absorption Spectroscopy and Optical Properties of Europium Activated Spaniel Calcium Stannate

Ca2SnO4:xEu3+ phosphors were synthesized by solid-state reaction method and characterized systematically using by XRD, XANES, EXAFS and PL spectroscopy. The XRD, XANES and EXAFS confirmed the formation of the Ca2SnO4 and the stabilization of Sn and Eu ions in 4+ and 3+ oxidation states. The PL properties of theses phosphor were investigated at room temperature. The emission spectra represent reddish-orange performance, which is due to the 5D0 → 7FJ (J = 0, 1, 2, 3, 4) transition of Eu ions. The red emission from transition 5D0 → 7F2 (red) is dominate over that of 5D0 → 7F1 (orange). The impact of doping Eu3+ and PL properties were investigated, and we propose a feasible interpretation, which this phosphor could be a good candidate as a reddish-orange component in the fabrication of white LEDs.

Synthesis, photophysical characteristics and geometry optimization of Tris(2-benzoylacetophenonate)europium complexes with 2, 2′-Bipyridine derivatives

A series based on octa coordinated tris(2-benzoylacetophenonate)europium complexes were synthesized with bidentate heteroaromatic auxiliary ligands. 2,2′-Bipyridine (Bpy) and its derivatives synthesized in the laboratory were used as auxiliary ligands. The structural analysis of synthesized materials was done by various spectroscopic techniques. Their photoluminescent characteristics specified the effective sensitization of trivalent europium ion via antenna effect. As an outcome of this sensitization, these complexes demonstrate good luminescence intensity, high quantum efficiency and long luminescence lifetime. The CIE chromaticity coordinates (x, y and u’, v’) were designed to indicate bright red emission. Luminescence decay time data were calculated by investigating the λem well-suited with the transition of the type 5D0→7F2. The molecular parameters of the geometrically optimized complexes were derived from the semi-empirical Sparkle/RM1 method. Theoretical Judd-Ofelt and photophysical parameters were estimated by LUMPAC software ascribed with experimental data, indicating the efficacy of this method. Furthermore, these luminous ternary europium complexes can be utilized as red light emitting material in designing flat panel displays and various optoelectronic devices.

Facile Preparation of YVO4: RE Films and the Investigation of Photoluminescence

Facile preparation of YVO4 films was hydrothermally achieved within 1 h by using layered yttrium hydroxide (Y2(OH)5NO3·nH2O) films as the sacrificial precursor in the presence of excess NaVO3 at pH~8, without subsequent heat treatment. Detailed structures and optical properties of the products were obtained by using a combination of XRD, FT-IR, FE-SEM, HR-TEM, and PLE/PL techniques. The phase and morphological evolution from Y2(OH)5NO3·nH2O to YVO4 was unveiled by varying the reaction time. Photoluminescence spectra showed that the Eu3+ doped YVO4 films exhibited the characteristic emission of Eu3+, with the transition 5D0–7F2 (614 nm, red) being the dominant; while Dy3+ activator doped YVO4 films exhibited the characteristic emission of Dy3+, with the transition 4F9/2–6H13/2 (575 nm, green) being the most dominant.

The effect of temperature and excitation energy of the high- and low-spin 4f→5d transitions on charging of traps in Lu2O3:Tb,M (M = Ti, Hf)

This work presents a fresh insight into the excited charges trapping in the Lu2O3:Tb,M (M= Ti, Hf) ceramics and their characteristics as storage and/or persistent luminescence phosphors. The results were obtained by applying an exceedingly versatile set of experiments based on thermoluminescence and thermoluminescence excitation spectroscopy and exposed a dual-nature of these materials. In the contrary to the previous research, here we found that at least some of these materials can generate efficient persistent luminescence due to the presence of shallow traps which can be charged only upon specific irradiation conditions – by the spin-forbidden 4f→5d transition of Tb3+ around 360 nm and, possibly, the 7F6→5D3 intra-configurational transition of the activator at just slightly longer wavelengths. Besides that, changing the sample charging temperature the efficiency of filling the traps – both deep and shallow – with the 360 nm radiation varied greatly and exposed a very broad distribution of trap energies. Charging with 360 nm radiation at room temperature fills only the shallow traps giving, never reported in Lu2O3:Tb,Ti and Lu2O3:Tb,Hf, intense persistent luminescence, while at higher temperatures the deep traps are filled. At any temperature, radiation of wavelengths < 320 nm fills almost exclusively deep traps responsible for TL at high temperatures, 230 °C in Lu2O3:Tb,Hf and 355 °C in Lu2O3:Tb,Ti.

Synthesis of photoluminescent europium dithiocarbamate complexes with dimethyl phenanthroline and bipyridyl co-ligands

This paper reports the synthesis of photoluminescent europium diphenylamine and piperidine dithiocarbamate complexes compound containing co-ligands 2,9 dimethyl-1,10 phenanthroline and bipyridyl. Nuclear magnetic resonance analysis result indicated that the complex compound of europium diphenylamine dithiocarbamate-2,9 dimethyl-1,10 phenanthroline [(dpa-dtc)2--Eu-(Dmphen)] has an Eu metal to bind to 2 diphenylamine dithiocarbamate ligands in bidentate structure. Meanwhile, the piperidine dithiocarbamate-2,2 bipyridyl [(pip-dtc)-Eu-(Bipy)] indicates the structure to have 1 Bipy co-ligand and 1 piperidine dithiocarbamate ligand which is monodentate bonded to the Eu metal. The photoluminescence analysis results showed that the [(dpa-dtc)2-Eu-(Dmphen)] and [(pip-dtc)-Eu-(Bipy)] complexes exhibited a photoluminescent in the region of red-orange, which is associated with the electronic transition of 5D0 → 7F2. Europium dithiocarbamate complex compounds have the potential to be applied as an active material for display and others electronics devices applications.

Enhancement of green upconversion luminescence of Yb3+/Tb3+ co-doped BiOBr nanosheets and its potential applications in photocatalysis

In this work, a series of Yb3+/Tb3+ co-doped BiOBr nanosheets were synthesized by a simple solvothermal method, and the effect of Tb3+ and Yb3+ doping on the up-conversion (UC) luminescence was investigated. Under the excitation of 980 ​nm, BiOBr: Yb3+/Tb3+ nanosheets displayed emission bands at 494, 544, 584 and 622 ​nm arise from transitions 5D4 → 7FJ (J ​= ​6, 5, 4, 3) of Tb3+ ions, respectively. Furthermore, the concentration dependence of UC luminescence was comprehensively explored, and the BiOBr:15%Yb3+/3%Tb3+ nanosheets exhibited the most outstanding luminescent properties by the cooperative energy transfer. Moreover, the degradation rate of RhB by Yb3+/Tb3+ co-doped BiOBr reaches 98.9% for 30 ​min under full spectral irradiation, and 51.7% for 5 ​h under 980 ​nm irradiation, respectively. This work proves that Yb3+/Tb3+ co-doped BiOBr nanosheets have excellent green UC emission and have potential application in the field of near infrared activated photocatalysts.

Enhancing the sensitization of Ce3+ on Eu3+ by tri-doping Gd3+ in hexagonal NaYF4

Eu3+ was ideal red emitter due to its efficient red emitting transitions 5D0→7Fj and Ce3+ was most common sensitizer due to its strong parity-allowed absorption bands. However, direct sensitization of Ce3+ on Eu3+ (SCE) in hexagonal NaYF4 was very weak and unpractical. In this work, rate equations were introduced to elaborate the details of energy transfer (ET) among Ce3+, Gd3+ and Eu3+ in NaYF4, and how the SCE was much enhanced. The pure hexagonal phase of all samples were guaranteed by powder XRD patterns and SEM images, despite the morphology was influenced by rare earth components. While increasing Eu3+ concentration over 0.03, SCE was drastically dimished; on the contrary, it could be 60 folds enhanced by tri-doping Gd3+ ions. The rate equations of sensitizers were established and solved by calculating the lifetimes. It was found out that, while increasing Gd3+ concentration to 0.4, ET Ce→Gd could compete against ET Ce→Eu to capture 73.8% of energy absorped by Ce3+, which strongly favored SCE. The solution also revealed that SCE originated from ET chain Ce→Gd→Eu was much more efficient than direct SCE from ET Ce→Eu, which originated the significant enhancement.