Synthesis,Structure, and Photoluminescence Properties of Novel KBaSc2(PO4)3:Ce3+/Eu2+/Tb3+ Phosphors for White‐Light‐Emitting Diodes

A series of novel KBaSc₂(PO₄)₃:Ce³⁺/Eu²⁺/Tb³⁺phosphors are prepared using a solid‐state reaction. X‐ray diffraction analysis and Rietveld structure refinement are used to check the phase purity and crystal structure of the prepared samples. Ce³⁺‐ and Eu²⁺‐doped phosphors both have broad excitation and emission bands, owing to the spin‐ and orbital‐allowed electron transition between the 4f and 5d energy levels. By co‐doping the KBaSc₂(PO₄)₃:Eu²⁺ and KBaSc₂(PO₄)₃:Ce³⁺ phosphors with Tb³⁺ ions, tunable colors from blue to green can be obtained. The critical distance between the Eu²⁺ and Tb³⁺ ions is calculated by a concentration quenching method and the energy‐transfer mechanism for Eu²⁺→Tb³⁺ is studied by utilizing the Inokuti–Hirayama model. In addition, the quantum efficiencies of the prepared samples are measured. The results indicate that KBaSc₂(PO₄)₃:Eu²⁺,Tb³⁺ and KBaSc₂(PO₄)₃:Ce³⁺,Tb³⁺ phosphors might have potential applications in UV‐excited white‐light‐emitting diodes.     

Research on Molecular Structure and Electronic Properties of Ln3+ (Ce3+, Tb3+, Pr3+)/Li+ and Eu2+ Co-Doped Sr2Si5N8 via DFT Calculation

We use density functional theory (DFT) to study the molecular structure and electronic band structure of Sr₂Si₅N₈:Eu²⁺ doped with trivalent lanthanides (Ln³⁺ = Ce³⁺, Tb³⁺, Pr³⁺). Li⁺ was used as a charge compensator for the charge imbalance caused by the partial replacement of Sr²⁺ by Ln³⁺. The doping of Ln lanthanide atom causes the structure of Sr₂Si₅N₈ lattice to shrink due to the smaller atomic radius of Ln³⁺ and Li⁺ compared to Sr²⁺. The doped structure’s formation energy indicates that the formation energy of Li⁺, which is used to compensate for the charge imbalance, is the lowest when the Sr2 site is doped. Thus, a suitable Li⁺ doping site for double-doped lanthanide ions can be provided. In Sr₂Si₅N₈:Eu²⁺, the doped Ce³⁺ can occupy partly the site of Sr₁²⁺ ([SrN₈]), while Eu²⁺ accounts for Sr₁²⁺ and Sr₂²⁺ ([SrN₁₀]). When the Pr³⁺ ion is selected as the dopant in Sr₂Si₅N₈:Eu²⁺, Pr³⁺ and Eu²⁺ would replace Sr₂²⁺ simultaneously. In this theoretical model, the replacement of Sr²⁺ by Tb³⁺ cannot exist reasonably. For the electronic structure, the energy level of Sr₂Si₅N₈:Eu²⁺/Li⁺ doped with Ce³⁺ and Pr³⁺ appears at the bottom of the conduction band or in the forbidden band, which reduces the energy bandgap of Sr₂Si₅N₈. We use DFT+U to adjust the lanthanide ion 4f energy level. The adjusted 4f-CBM of Ce_Sr1Li_Sr1-Sr₂Si₅N₈ is from 2.42 to 2.85 eV. The energy range of 4f-CBM in Pr_Sr1Li_Sr1-Sr₂Si₅N₈ is 2.75–2.99 eV and its peak is 2.90 eV; the addition of Ce³⁺ in Eu_Sr1Ce_Sr1Li_Sr1 made the 4f energy level of Eu²⁺ blue shift. The addition of Pr³⁺ in Eu_Sr2Pr_Sr2Li_Sr1 makes part of the Eu²⁺ 4f energy level blue shift. Eu²⁺ 4f energy level in Eu_Sr2Ce_Sr1Li_Sr1 is not in the forbidden band, so Eu²⁺ is not used as the emission center.     

Tagging of avidin immobilized beads with biotinylated YAG:Ce3+ nanocrystal phosphor

YAG:Ce³⁺ nanoparticles 9.5 ± 1.2 nm in diameter have been synthesized from aluminium isopropoxide and acetates of yttrium and cerium in 1,4-butanediol (1,4-BD) by autoclave treatment at 300 °C for 2 h. After replacing 1,4-BD by ultrapure water, NH₂ groups were introduced on the surface of YAG:Ce³⁺ nanoparticles by addition of 3-aminopropyltrimethoxysilane then biotinylation with sulfo-NHS-LC-biotin. We demonstrated that avidin immobilized beads are tagged by biotinylated YAG:Ce³⁺ nanoparticles by the selective avidin-biotin interaction, furnishing a green fluorescent image on excitation with blue light. This result indicates that YAG:Ce³⁺ nanoparticle phosphors have much potential in biological applications.     

Separation of cerium and europium by extraction with tributyl phosphate and di(2-ethylhexyl)phosphoric acid in n-alkane from nitrate solutions

The following extraction systems have been studied: (Ce³⁺+Eu³⁺) (NO₃)-(EDTA, DCTA, DTPA)/TBP in n-alkane and (Ce³⁺+Eu³⁺)(NO₃)/DEHPA in n-alkane at concentration ratios as follows: [Ce³⁺]=trace –1 mol·dm^–3, [Eu³⁺]=trace –0.1 mol·dm^–3. [TBP]=(0.183–1.83) mol·dm^–3, [DEHPA]=(5·10^–3–0.1) mol·dm^–3, [(H, Na)NO₃]=(0.1–6) mol·dm^–3, [Eu³⁺]: [EDTA, DCTA, DTPA]=11–110. The initial concentration of Eu³⁺ in aqueous phase in the extraction system containing a mixture of Ce³⁺ and Eu³⁺ was trace, 1% and 10% compared with the Ce³⁺ concentration. The distribution of the elements between the phases was observed radiometrically using¹⁴¹Ce,¹⁵²Eu and¹⁵⁴Eu. The results are documented by the distribution ratios D_Ce, D_Eu and separation factor =D_Eu/D_Ce as functions of variable parameters of the systems.     

Luminescence Quenching between Ce and Eu in LAB3O6

The Ce³⁺ and Eu³⁺ ions in LaB₃O₆ quench each other's luminescence. However, Ce³⁺ quenches Eu³⁺ more effectively than Eu³⁺ quenches Ce³⁺. The critical distances for this quenching are about 15 and 6 Å respectively.     

A new BaB2Si2O8:Eu/Eu, Tb phosphor - Synthesis and photoluminescence properties

In the present work, we have synthesized maleevite mineral phase BaB₂Si₂O₈ for the first time, which is isostructural with the pekovite mineral SrB₂Si₂O₈. In these europium doped host lattices, we observed the partial reduction of Eu³⁺ to Eu²⁺ at high temperature during the synthesis in air. Tb³⁺ co-doping in MB₂Si₂O₈:0.01(Eu³⁺/Eu²⁺) [M=Sr, Ba] improves the emission properties towards white light. The emission color varies from bluish white to greenish white under UV lamp excitation when the host cation changes from Sr to Ba.     

CaWO4:xEu3+,ySm3+,zLi+红色荧光粉的制备及光学性能

采用微波固相法制备了CaWO₄：xEu³⁺,ySm³⁺,zLi⁺红色荧光粉。测量样品的XRD图、激发谱、发射谱及发光衰减曲线,研究并分析了Eu³⁺、Sm³⁺、Li⁺的掺杂浓度,对样品微结构、光致发光特性、能量传递及能级寿命的影响。结果表明,Eu³⁺、Sm³⁺、Li⁺掺杂并未引起合成粉体改变晶相,仍为CaWO₄单一四方晶系结构。Eu³⁺、Sm³⁺共掺样品中,Sm³⁺掺杂为3%时,Sm³⁺对Eu³⁺的能量传递最有效。Li⁺掺杂起到了助熔剂和敏化剂的作用,使样品发光更强。在394 nm激发下,与CaWO₄：3%Eu³⁺样品比较,3%Eu³⁺、3%Sm³⁺共掺CaWO₄及3%Eu³⁺、3%Sm³⁺、1%Li⁺共掺CaWO₄样品的发光分别增强2倍及2.4倍。同一激发波长下,单掺Eu³⁺样品寿命最短,Sm³⁺、Eu³⁺共掺样品随Sm³⁺浓度增加,寿命先减小后增加,且掺杂了Li⁺的样品比不掺Li⁺的样品⁵D₀能级寿命有所增加。     

Investigation of thermal decomposition of yttrium–aluminum-based precursors for YAG phosphors

Three types of precursors were prepared using the wet-chemical synthesis route, starting from yttrium?Ceuropium?Caluminum nitrate solution and different precipitating agents (urea, oxalic acid, and ammonium carbonate). The precursors were fired at 1200?°C in nitrogen atmosphere in order to obtain europium-doped yttrium aluminate Y₃Al₅O₁₂:Eu³⁺ phosphor with garnet structure (YAG:Eu). The processes involved in the thermal decomposition of precursors and their composition were put in evidence using thermal analysis (TG?CDTA) and FT-IR spectroscopy. The GA?CDTA curves possess typical features for basic-oxalate, -nitrate, and -carbonates as formed with oxalic acid, urea, and ammonium carbonate, respectively. Correlation between the thermal decomposition steps, mass loss, and composition of gases evolved during the thermal treatment was established using TG?CDTA?CFT-IR coupling. It was found that the different composition of precursors reflects on the luminescent characteristics of the corresponding phosphors. Urea and ammonium carbonate lead to the formation of YAG type phosphors, with garnet structure and specific red emission. As for the oxalic acid, this precipitating agent generates a non-homogeneous powder that contains yttrium oxide as impurity phase. This phosphor is a mixture of Y₂O₃:Eu³⁺, Y₄Al₂O₉:Eu³⁺, and Y₃Al₅O₁₂:Eu³⁺ that explain the relative higher emission intensity.     

Luminescence Properties of Ca2Ga2SiO7:RE Phosphors for UV White‐Light‐Emitting Diodes

A series of Eu²⁺‐, Ce³⁺‐, and Tb³⁺‐doped Ca₂Ga₂SiO₇ phosphors is synthesized by using a high‐temperature solid‐state reaction. The powder X‐ray diffraction and structure refinement data indicate that our prepared phosphors are single phased and the phosphor crystalizes in a tetrahedral system with the ${P\bar 42m}$ (113) space group. The Eu²⁺‐ and Ce³⁺‐doped phosphors both have broad excitation bands, which match well with the UV light‐emitting diodes chips. Under irradiation of λ=350 nm, Ca₂Ga₂SiO₇:Eu²⁺ and Ca₂Ga₂SiO₇:Ce³⁺, Li⁺ have green and blue emissions, respectively. Luminescence of Ca₂Ga₂SiO₇:Tb³⁺, Li⁺ phosphor varies with the different Tb³⁺ contents. The thermal stability and energy‐migration mechanism of Ca₂Ga₂SiO₇:Eu²⁺ are also studied. The investigation results indicate that the prepared Ca₂Ga₂SiO₇:Eu²⁺ and Ca₂Ga₂SiO₇:Ce³⁺, Li⁺ samples show potential as green and blue phosphors, respectively, for UV‐excited white‐light‐emitting diodes.     

钙钛矿结构荧光材料MZrO3:Eu3+,A (M=Ca2+, Ba2+; A=Li+, Na+, K+)的制备及其发光性质

Calcium and barium zirconate powders based upon CaZrO₃:Eu³⁺,A and BaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) were prepared by combustion synthesis method and heating to ~1000℃ to improve crystallinity.The structure and morphology of materials were examined by X-ray diffraction (XRD) and scanningelectron microscopy (SEM). XRD results showed that CaZrO₃:Eu³⁺,A and BaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) perovskites possessed orthorhombic and cubic structures, respectively. The morphologies of all powderswere very similar consisting of small, coagulated, cubical particles with narrow size distributions andsmooth and regular surfaces. The characteristic luminescences of Eu³⁺ ions in CaZrO₃:Eu³⁺,A (A=Li⁺, Na⁺, K⁺) lattices were present with strong emissions at 614 and 625 nm for ⁵D₀→⁷F₂ transitions with other weakeremissions observed at 575, 592, 655, and 701 nm corresponding to ⁵D₀→⁷F_n transitions (where n=0, 1, 3, 4 respectively). In BaZrO₃:Eu³⁺ both the ⁵D₀→⁷F₁ and ⁵D₀→⁷F₂ transitions at 595 and 613 nm were strong.Photoluminescence intensities of CaZrO₃:Eu³⁺ samples were higher than those of BaZrO₃:Eu³⁺ lattices. Thisremarkable increase of photoluminescence intensity (corresponding to ⁵D₀→⁷F_n transitions) was observedin CaZrO₃:Eu³⁺ and BaZrO₃:Eu³⁺ if co-doped with Li⁺ ions. An additional broad band composed of manypeaks between 440 to 575 nm was observed in BaZrO₃:Eu³⁺,,A samples. The intensity of this band wasgreatest in Li⁺ co-doped samples and lowest for K⁺ doped samples.     

Luminescence properties of Eu- and Ce-doped CaAl2S4 and application in white LEDs

The Eu²⁺- and Ce³⁺-doped CaAl₂S₄ phosphors were comparatively synthesized by conventional solid-state reaction and the evacuated sealed quartz ampoule. The X-ray diffraction (XRD) patterns show that the sample with better crystalline quality was prepared by the evacuated sealed quartz ampoule, resulting in the enhancement of the emission intensity of Eu²⁺ ion by a factor of 1.7. The intensive green LEDs were also fabricated by combining CaAl₂S₄:Eu²⁺ with near-ultraviolet InGaN chips (λ_em=395 nm). The dependence of as-fabricated green LEDs on forward-bias currents shows that it presents good chromaticity stability and luminance saturation, indicating that CaAl₂S₄:Eu²⁺ is a promising green-emitting phosphor for a near-UV InGaN-based LED. In addition, the optical properties of CaAl₂S₄:Ce³⁺ were systematically investigated by means of diffuse reflectance, photoluminescence excitation and emission, concentrating quenching and the decay curve.     

Unique Spectral Overlap and Resonant Energy Transfer between Europium(II) and Ytterbium(III) Cations: No Quantum Cutting

Samples of the Ca₃Sc₂Si₃O₁₂ (CSS) host singly doped with Eu²⁺ or Yb³⁺, doubly doped with Eu²⁺ and Yb³⁺, and triply doped with Ce³⁺, Eu²⁺ and Yb³⁺ were synthesized by a sol–gel combustion process under reducing conditions. Unlike previous reports of Eu²⁺→Yb³⁺ energy transfer in other systems, the energy transfer is resonant in the CSS host and the transfer efficiency reaches 100 % for lightly doped samples. The transfer mechanism is multipolar rather than electron transfer for the sample compositions employed herein. The emission intensity of Yb³⁺ is further enhanced by co‐doping with Ce³⁺ in addition to Eu²⁺. The quantum efficiencies of the doped materials range between 9 % and 93 %.     

Eu3F4S2: Synthesis, crystal structure, and magnetic properties of the mixed-valent europium(II,III) fluoride sulfide EuF2·(EuFS)2

Using the method to synthesize rare-earth metal(III) fluoride sulfides MFS (M=Y, La, Ce–Lu), in some cases we were able to obtain mixed-valent compounds such as Yb₃F₄S₂ instead. With Eu₃F₄S₂ another isotypic representative has now been synthesized. Eu₃F₄S₂ (tetragonal, I4/mmm, a=400.34(2), c=1928.17(9) pm, Z=2) is obtained from the reaction of metallic europium, elemental sulfur, and europium trifluoride in a molar ratio of 5:6:4 within seven days at 850 °C in silica-jacketed gas-tightly sealed platinum ampoules. The single-phase product consists of black plate-shaped single crystals with a square cross section, which can be obtained from a flux using equimolar amounts of NaCl as fluxing agent. The crystal structure is best described as an intergrowth structure, in which one layer of CaF₂-type EuF₂ is followed by two layers of PbFCl-type EuFS when sheeted parallel to the (001) plane. Accordingly there are two chemically and crystallographically different europium cations present. One of them (Eu²⁺) is coordinated by eight fluoride anions in a cubic fashion, the other one (Eu³⁺) exhibits a monocapped square antiprismatic coordination sphere with four F⁻ and five S²⁻ anions. Although the structural ordering of the different charged europium cations is plausible, a certain amount of charge delocalization with some polaron activity has to take place, which is suggested by the black color of the title compound. Temperature dependent magnetic susceptibility measurements of Eu₃F₄S₂ show Curie–Weiss behavior with an experimental magnetic moment of 8.19(5) μ_B per formula unit and a paramagnetic Curie temperature of 0.3(2) K. No magnetic ordering is observed down to 4.2 K. In accordance with an ionic formula splitting like (Eu^II)(Eu^III)₂F₄S₂ only one third of the europium centers in Eu₃F₄S₂ carry permanent magnetic moments. ¹⁵¹Eu-Mössbauer spectroscopic experiments at 4.2 K show one signal at an isomer shift of −12.4(1) mm/s and a second one at 0.42(4) mm/s. These signals occur in a ratio of 1:2 and correspond to Eu²⁺ and Eu³⁺, respectively. The spectra at 78 and 298 K are similar, thus no change in the Eu²⁺/Eu³⁺ fraction can be detected.     

Luminescence Tuning of Sr8MgCe(PO4)7:Eu2+,Mn2+ Phosphors: Structure Refinement,Site Occupancy,and Energy Transfer

Sr₈MgCe(PO₄)₇:Eu²⁺,Mn²⁺ phosphor with whitlockite‐type structure was prepared by a combustion‐assisted solid‐state reaction. The crystal structure and luminescence properties were investigated. Under UV radiation, Sr₈MgCe(PO₄)₇ host exhibits a violet‐blue emission band from Ce³⁺ ions. When Eu²⁺/Mn²⁺ are doped into the host, the samples excited with 270 nm UV radiation present multicolor emissions due to the energy transfer (ET) from Ce³⁺ to Eu²⁺/Mn²⁺. The emitting color of Sr₈MgCe(PO₄)₇:Eu²⁺ can be tuned from violet‐blue to yellow‐green, whereas Sr₈MgCe(PO₄)₇:Mn²⁺ can emit red light. Under excitation with long wavelength at 360 nm, Sr₈MgCe(PO₄)₇:Eu²⁺ phosphor shows a broadband emission from 390 to 700 nm, which is attributed to the 4f⁶5d¹→4f⁷ transition of Eu²⁺ without the contribution from Ce³⁺ emission. Tunable full‐color emitting light can be achieved in the Eu²⁺ and Mn²⁺‐codoped Sr₈MgCe(PO₄)₇ phosphor by ET_Eu–Mn through control of the levels of doped Eu²⁺ and Mn²⁺ ions. These results suggest that Sr₈MgCe(PO₄)₇:Eu²⁺,Mn²⁺ phosphor has potential applications in NUV chip pumped white LEDs.     

Electronic properties and rare-earth ions photoluminescence behaviors in borosilicate: SrB2Si2O8

Undoped and RE ions doped SrB₂Si₂O₈ were successfully synthesized. After the application of UV and VUV spectroscopy measurements, we made a novel discovery that the emission of SrB₂Si₂O₈:Eu prepared in air can be switched between red and blue by the different excitations. The information is that quite a part of Eu³⁺ was spontaneously reduced to Eu²⁺ in air. The PL properties of Eu²⁺ in VUV and Eu³⁺, Ce³⁺ and Tb³⁺ in UV-VUV region in SrB₂Si₂O₈ were evaluated for the first time. The excitation mechanisms of the O²⁻-Eu³⁺ CT, Ce³⁺f-d and Tb³⁺f-d transitions in UV region as well as the Eu³⁺f-d, O²⁻-Ce³⁺ CT, O²⁻-Tb³⁺ CT transitions and the host lattice absorption in VUV region were established. In addition, first principles calculation within the LDA of the DFT was applied to calculate the electronic structure and linear optical properties of SrB₂Si₂O₈ and the results were compared with the experimental data.     

The Zintl Phase Eu2Si

The Zintl phase Eu₂Si was synthesized from elemental europium and silicon in a sealed tantalum tube in a high‐frequency furnace at 1270 K and subsequent annealing at 970 K. Investigation of the sample by X‐ray powder and single crystal techniques revealed: Co₂Si (anti‐PbCl₂) type, space group Pnma, a = 783.0(1), b = 504.71(9), c = 937.8(1) pm, wR2 = 0.1193, 459 F² values and 20 variables. The structure contains two europium and one silicon site. ¹⁵¹Eu Mössbauer spectroscopic data show a single signal at an isomer shift of −9.63(3) mm/s, compatible with divalent europium. Within the Zintl concept electron counting can be written as (2Eu²⁺)⁴⁺Si⁴⁻, in agreement with the absence of Si‐Si bonding. Each silicon atom has nine europium neighbors in the form of a tri‐capped trigonal prism. The silicon coordinations of the Zintl phases Eu₂Si, Eu₅Si₃, EuSi, and EuSi₂ are compared.     

Vacuum Ultraviolet Excited Photoluminescence Properties of Y2O2S：Eu^3＋,Bi^3＋ Phosphor

As an Hg-free lamp using phosphor, the Bi^3＋ and EH^3＋ co-doped Y2O2S phosphors were prepared and their luminescence properties under vacuum ultraviolet（VUV） excitation were investigated. The VUV photoluminescent intensity of Y2O2S：Eu^3＋ was weak, however, considerably stronger red emission at 626 nm with good color purity was observed in Y2O2S：Eu^3＋,Bi^3＋ systems. Investigation on the photoluminescence reveals that the strong VUV luminescence of Y2O2S：Eu^3＋,Bi^3＋ at 147 nm is mainly because the Bi^3＋ acts as a medium and effectively performs the energy transfer process： Y^3＋-O^2-→Bi^3＋→Eu^3＋, while the intense emission band at 172 nm is attributed to the absorption of the characteristic ^1So-^1P1 transition of Bi^3＋ and the direct energy transfer from Bi^3＋ to Eu^3＋. The Y2O2S：Eu^3＋,Bi^3＋ shows excellent VUV optical properties compared with the commercial （Y,Gd）BO3：Eu^3＋. Thus, the Y2O2S：Eu^3＋,Bi^3＋ can be a potential red VUV-excited candidate applied in Hg-free lamps for backlight of liquid crystal display.     

Gamma-induced radiation polymerization of kaolin composite for sorption of lanthanum,europium and uranium ions from low-grade monazite leachate

Gamma radiation polymerization method was used for the modification of kaolin to produce (poly acrylamide-acrylic acid)-Kaolin (PAM-AA-K). Monazite ore is one of the main resources of uranium and lanthanide elements, therefore, this work focused on sorption of uranium, lanthanum and europium ions from low grade monazite leachate. The removal percent for Eu³⁺, La³⁺ and UO₂ ²⁺ are 94.6, 91.6 and 73.4%, respectively. Monolayer capacity of Eu³⁺, La³⁺ and UO₂ ²⁺ were found to be 54.64, 45.87 and 37.59 mg/g, respectively. The sorption mechanism of lanthanum and europium ions on PAM-AA-K composite mainly takes place as Ln(OH)²⁺, and for uranium as uranyl ion, UO₂ ²⁺.     

Synthesis and study of the composition and properties of chelate complexes of benzoyl acetonates of rare-earth elements and use of these in gas chromatography

Chelate complex cerium [Ce(BA)₃)] and europium [Eu(BA)₃] benzoyl acetonates were synthesized. According to IR spectroscopic data and elemental analyses, the composition of the complexes is described by the empirical formulas M(BA)₃·2H₂O. Sorbents based on a mesoporous silica gel modified with cerium and europium benzoyl acetonates were obtained. The nitrogen porosimetry demonstrated that, as the complexes are deposited onto the surface of the starting support, the specific surface area and the pore volume become smaller. The polarity of the sorbents Chromaton N-AW + SiO₂ + M(BA)₃ with respect to all classes of test compounds decreases in the order Ce^III > Eu^III. According to the data obtained for the capacity factors, the sorbent modified with cerium benzoyl acetonate selectively separates alcohols, and Chromaton N-AW + SiO₂ with deposited chelates Eu(BA)₃ shows the best separating capacity for alkanes and alcohols. It was shown that the sorbents can be used in practice for separating gaseous mixtures of light hydrocarbons.     

Luminescence study of Eu3+: KGd2F7

A spectroscopic investigation of the host matrix KGd₂F₇ is performed using Eu³⁺ as local probe. Its crystal structure derives from the fluorite-type by an ordering of the cations and anions. On powdered samples with different europium concentrations, the luminescence spectra of Eu³⁺:KGd₂F₇ allowed an identification of a multisite behaviour for the Eu³⁺ ions, leading to a lifetime distribution for the ⁵D₀ emitting level.