Tb3+/Yb3+ co-doped Y2O3 upconversion transparent ceramics: Fabrication and characterization for IR excited green emission

Tb³⁺/Yb³⁺ co-doped Y₂O₃ transparent ceramics were fabricated by vacuum sintering of the pellets (prepared from nanopowders by uniaxial pressing) at 1750 °C for 5 h. Zr⁴⁺ and La³⁺ ions were incorporated in Tb³⁺/Yb³⁺ co-doped Y₂O₃ nanoparticle to reduce the formation of pores which limits the transparency of ceramic. An optical transmittance of ∼80% was achieved in ∼450 to 2000 nm range for 1 mm thick pellet which is very close to the theoretical value by taking account of Fresnel’s correction. High intensity luminescence peak at 543 nm (green) was observed in these transparent ceramics under 976 and 929 nm excitations due to Yb–Tb energy transfer upconversion.     

Efficient sensitization of Tb3+ emission by Dy3+ in CaMoO4 phosphors: Energy transfer,tunable emission and optical thermometry

Dy³⁺/Tb³⁺ codoped CaMoO₄ phosphors were synthesized by a simple sol–gel method and characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM) and photoluminescence spectroscopy. The energy transfer process of Dy³⁺→Tb³⁺ was confirmed by excitation and emission spectra and luminescence decay curves, and the energy transfer efficiency was also estimated. The results verified that the efficient emission of Tb³⁺ was sensitized by Dy³⁺ under the excitation of 354 nm, realizing tunable emission in CaMoO₄ phosphors. Furthermore, optical thermometry was achieved by the fluorescence intensity ratio between Tb³⁺: ⁵D₄→⁷F₅ (~546 nm) and Dy³⁺: ⁴F_9/2→⁶H_13/2 (~575 nm). It is expected that the investigated CaMoO₄ nanograins doped with Dy³⁺/Tb³⁺ have prospective applications in display technology and optical thermometry.     

Self-crystallized Ba2LaF7:Nd3+/Eu3+ glass ceramics for optical thermometry

Eu³⁺/Nd³⁺-codoped Ba₂LaF₇ transparent bulk glass ceramics were successfully fabricated by glass self-crystallization. The structure and morphology of the sample were investigated by X-ray diffraction, transmission electron microscopy (TEM), high-resolution TEM, and selected area electron diffraction. The fluorescence intensity ratios of Nd³⁺ emission at 800 nm to the Eu³⁺ emission at 699 nm (⁵D₀ → ⁷F₄) were measured under 578.3 nm laser excitation in a wide temperature range from 290 to 740 K. A relatively good temperature sensing performance was obtained with a maximum relative sensitivity of 1.02% K⁻¹ at 420 K. Both the emission peaks for temperature sensing were located in the optical window of biological tissue, which is favorable for biomedical applications. The results indicate that Ba₂LaF₇:Nd³⁺/Eu³⁺ glass ceramics have a potential application as temperature probes.     

Near-UV light excited Eu3+, Tb3+, Bi3+ co-doped LaPO4 phosphors: Synthesis and enhancement of red emission for WLEDs

A series of single-phase Eu³⁺, Tb³⁺, Bi³⁺ co-doped LaPO₄ phosphors were synthesized by solid-state reaction at 800 °C. Crystal structures of the phosphors were investigated by X-ray diffraction (XRD). A monoclinic phase was confirmed. The excitation (PLE) and emission (PL) spectra showed that the phosphors could emit red light centered at 591 nm under the 392 nm excitation, which is in good agreement with the emission wavelength from near-ultraviolet (n-UV) LED chip (370–410 nm). The results of PLE and PL indicated that the co-doped Tb³⁺ and Bi³⁺could enhance emission of Eu³⁺ and the fluorescent intensities of the phosphors excited at 392 nm could reach to a maximum value when the doping molar concentration of Tb³⁺ and Bi³⁺ is about 2.0% and 2.0%, respectively. The co-doping Tb³⁺ and Bi³⁺ ions can strengthen the absorption of near UV region. They can also be efficient to sensitize the emission of Eu³⁺, indicating that the energy transfer occurs from Tb³⁺ and Bi³⁺ to Eu³⁺ ions. From further investigation it can be found that co-doping Tb³⁺ and Bi³⁺ ions can also induce excitation energy reassignment between ⁵D₀–⁷F₁ and ⁵D₀–⁷F₂ in these phosphors, and result in more energy assignment to ⁵D₀–⁷F₂ emission in LaPO₄:Eu³⁺, Tb³⁺, Bi³⁺. Our research results displayed that La_0.94PO₄:Eu³⁺_0.02, Tb³⁺_0.02, Bi³⁺_0.02 could be a new one and could provide a potential red-emitting phosphor for UV-based white LED.     

Fabrication and properties of transparent Tb:YAG fluorescent ceramics with different doping concentrations

Terbium doped yttrium aluminum garnet (Tb:YAG) transparent ceramics with different doping concentrations were fabricated by the solid-state reaction method using commercial Y₂O₃, α-Al₂O₃ and Tb₄O₇ powders as raw materials. Samples sintered at 1750 °C for 20 h were utilized to observe the optical transmittance, microstructure and fluorescence characteristics. It is found that all the Tb: YAG ceramics with different doping concentrations exhibit homogeneous structures with grain size distributions around 22–29 µm. For the 5 at% Tb:YAG transparent ceramics, the grain boundaries are clean with no secondary phases. The photoluminescence spectra show that Tb:YAG ceramics emit predominantly at 544 nm originated from the energy levels transition of ⁵D₄→⁷F₅ of Tb³⁺ ions, and the intensity of the emission peak reaches a maximum value when the Tb³⁺ concentration is 5 at%. The in-line transmittance of the 5 at% Tb:YAG ceramics is 73.4% at the wavelength of 544 nm, which needs to be further enhanced by optimizing the fabrication process. We think that Tb:YAG transparent ceramics may have potential applications in the high-power white LEDs.     

Study on luminescence properties of co-doped nanoparticles Gd2O3:Tb3+, Eu3+ synthesized by polyol route

Spherical-like Tb³⁺ and Eu³⁺ co-doped Gd₂O₃ nanoparticles with a particle size around 5.5 nm were synthesized by a polyol route. The optimized luminescence property was obtained when 5 mol% Tb³⁺ and 2 mol% Eu³⁺ were co-doped. The influence of different polyalcohol solvents (DEG/PEG) on particle size and luminescence properties was investigated. The results show that the nanoparticles Gd₂O₃:5%Tb³⁺ prepared in PEG presented greater particle size (around 79 nm) and higher luminescence intensity.     

Near-infrared long-lasting phosphorescence in transparent glass ceramics embedding Cr3+-doped LiGa5O8 nanocrystals

Cr³⁺ doped transparent glass ceramics of SiO₂–Ga₂O₃–Li₂O were fabricated by melt-quenching and subsequent crystallization. X-ray diffraction and transmission electron microscopy analyses evidenced that cubic LiGa₅O₈ nanocrystals were homogeneously precipitated among the silicate glass matrix. The incorporation of Cr³⁺ ions into LiGa₅O₈ nanocrystals was evidenced by absorption, emission and time-resolved luminescence spectra. Impressively, the present Cr³⁺ doped glass ceramics were demonstrated to be a new near-infrared (∼720 nm) long-lasting bulk phosphor whose luminescence can last for more than 2 h after stoppage of UV (250–350 nm) irradiation. The occurring of Cr³⁺ long-lasting phosphorescence in the glass ceramics was confirmed to be mainly due to the precipitation of Cr³⁺:LiGa₅O₈ nanocrystals from glass matrix. The filling/releasing of electrons into/from the intrinsic traps of LiGa₅O₈ nanocrystals through the conduction band of host were proposed to be responsible for the realization of the long-lasting phosphorescence of the investigated Cr³⁺ doped glass ceramics.     

Structure and luminescence properties of Eu3+ doped TiO2 nanocrystals and prolate nanospheroids synthesized by the hydrothermal processing

We report on a new approach to the synthesis of Eu³⁺ doped TiO₂ nanocrystals and prolate nanospheroids. They were synthesized by shape transformation of hydrothermally treated titania nanotubes at different pH and in the presence of Eu³⁺ ions. The use of nanotubes as a precursor to the synthesis of Eu³⁺ doped TiO₂ nanocrystals and prolate nanospheroids opens the possibility of overcoming the problems related to molecular precursors. The shapes and sizes of the nanotubes, Eu³⁺ doped TiO₂ nanocrystals and prolate nanospheroids were characterized by transmission electron microscopy (TEM) technique. Crystal structures of the resultant powders were investigated by X-ray diffraction (XRD) analysis. The percentage ratio of Eu³⁺ to Ti⁴⁺ ions in doped nanocrystals was determined using inductively coupled plasma atomic emission spectroscopy. The optical characterization was done by using fluorescence and ultraviolet-visible reflection spectroscopies. An average size of faceted Eu³⁺ doped TiO₂ nanocrystals was 13 nm. The lateral dimensions of Eu³⁺ doped TiO₂ prolate nanospheroids varied from 14 to 20 nm, while the length varied from 40 to 80 nm, depending on precursor concentrations. The XRD patterns revealed the homogeneous anatase crystal phase of Eu³⁺ doped TiO₂ nanocrystals and prolate nanospheroids independently of the amount of dopant. A postsynthetic treatment (filtration or dialysis) was applied on the dispersions of the doped nanoparticles in order to study the influence of the dopant position on photoluminescence (PL) spectra. In the red spectral region, room temperature PL signals associated with ⁵D₀ → ⁷F_J (J = 1–4) transitions of Eu³⁺ were observed in all samples. The increased contribution of dopants from the interior region of dialyzed nanocrystals to photoluminescence was confirmed by the increase of R value.     

Translucent and persistent luminescent SrAl2O4:Eu2+Dy3+ ceramics

Ceramics that exhibit persistent luminescence are usually opaque, which limits their utility. In this work, a laser-sintering technique is employed to produce persistent luminescent SrAl₂O₄:Eu²⁺Dy³⁺ ceramics that has enhanced translucency in the visible spectral range. In this technique, a CO₂ laser was used as the main heating source for sintering with no atmosphere control employed. The ceramics sintered at a power density of 3.1 W/mm² yielded homogeneous grain size distributions and transmittance up to 40% in the range of 600–800 nm. Upon sintering in air, the ceramics exhibited the characteristic green emission from the Eu²⁺ ion, corresponding to the 5d→4f transition (514 nm) and a weak emission from the Eu³⁺ ion at 614 nm, corresponding to the ⁵D₀→⁷F₂ transition. The valence of europium ions was further studied by the X-ray absorption spectroscopy in the XANES region and those details are reported herein.     

Lead fluoride β-PbF2 nanocrystals containing Eu3+ and Tb3+ ions embedded in sol-gel materials: Thermal,structural and optical investigations

Nanocrystalline β-PbF₂ phase singly-doped with Eu³⁺ and Tb³⁺ ions have been successfully synthesized using sol-gel technique and subsequent heat-treatment of xerogels at 350 °C. Thermal behavior and structural properties of obtained materials were studied using thermogravimetric analysis (TG), differential scanning calorimetry (DSC) as well as FT-IR and Raman techniques. XRD results confirmed formation of β-PbF₂ nanocrystals embedded in silica amorphous hosts after annealing at 350 °C. Moreover, the photoluminescence properties have been investigated based on excitation and emission spectra as well as decay analysis from the ⁵D₀ (Eu³⁺) and the ⁵D₄ (Tb³⁺) excited states. The sharp intraconfigurational 4f⁶−4f⁶ and 4f⁸−4f⁸ emission transitions assigned as the ⁵D₀→⁷F_J (J=0–4) of Eu³⁺ and the ⁵D₄→⁷F_J (J=6-3) of Tb³⁺ bands, respectively, were registered. The most prominent bands in studied xerogels and glass-ceramic materials are related to the following electronic transitions: ⁵D₀→⁷F₁ (orange) and ⁵D₀→⁷F₂ (red) (Eu³⁺) as well as ⁵D₄→⁷F₅ (green) and ⁵D₄→⁷F₆ (blue) (Tb³⁺). Thus, the R/O (Eu³⁺) and G/B (Tb³⁺) luminescence intensity ratios were calculated and analyzed. Luminescence decay kinetic clearly indicated a presence of two different surroundings around Eu³⁺ and Tb³⁺ dopants in β-PbF₂-based glass-ceramic samples. In such singly-doped with Eu³⁺ and Tb³⁺ materials, the longer luminescence lifetimes (Eu³⁺: τ₁(⁵D₀)=0.90 ms, τ₂(⁵D₀)=5.15 ms; Tb³⁺: τ₁(⁵D₄)=0.48 ms, τ₂(⁵D₄)=4.01 ms) of an appropriate excited states were achieved in comparison to xerogel hosts (Eu³⁺: τ(⁵D₀)=0.38 ms; Tb³⁺: τ(⁵D₄)=0.49 ms). The obtained results indicate the incorporation of Eu³⁺ and Tb³⁺ ions into nanocrystalline phase during ceramization process.     

Fabrication and Luminescence Properties of Transparent Glass‐Ceramics Containing Eu3+‐Doped TbPO4 Nanocrystals

Eu³⁺‐doped transparent phosphate precursor glasses and glass‐ceramics containing TbPO₄ nanocrystals were successfully fabricated by a conventional high‐temperature melt‐quenching technique for the first time. The formation of TbPO₄ nanocrystals was identified through X‐ray diffraction, transmission electron microscopy, high‐resolution transmission electron microscopy, selected‐area electron diffraction, and photoluminescence emission spectra. The obvious Stark splitting of ⁵D₀‐⁷F_J (J = 1, 2, 4) transitions of Eu³⁺and the increase of internal quantum efficiency indicate the incorporation of Eu³⁺ into TbPO₄ nanocrystals. Energy transfer from Tb³⁺ ions to Eu³⁺ ions was investigated using excitation and emission spectra at room temperature. The glass‐ceramics obtained have more efficient Tb³⁺ to Eu³⁺ energy transfer than the glass, and so serve as good hosts for luminescent materials.     

Energy transfer and multicolor tunable emission in single-phase Tb3+, Eu3+ co-doped Sr3La(PO4)3 phosphors

A series of green-to-red color-tunable Sr₃La(PO₄)₃:Tb³⁺, Eu³⁺ phosphors were prepared by high temperature solid-state method. The crystal structures, photoluminescence properties, fluorescence lifetimes, and energy transfer of Sr₃La(PO₄)₃:Tb³⁺, Eu³⁺ were systematically investigated in detail. The obtained phosphors show both a green emission from Tb³⁺ and a red emission from Eu³⁺ with considerable intensity under ultraviolet (UV) excitation (~377 nm). The emission colors of the phosphors can be tuned from green (0.304, 0.589) through yellow (0.401, 0.505) and eventually to red (0.557, 0.392) due to efficient Tb³⁺-Eu³⁺ energy transfer (ET). The Tb³⁺→Eu³⁺ energy transfer process was demonstrated to be quadrupole-quadrupole mechanism by Inokuti-Hirayama model, with maximum ET efficiency of 86.3%. The results indicate that the Sr₃La(PO₄)₃:Tb³⁺, Eu³⁺ phosphors might find potential applications in the field of lighting and displays.     

Synthesis and photoluminescence properties of the high-brightness Eu3+-doped Sr3Y(PO4)3 red phosphors

A series of red-emitting phosphors Eu³⁺-doped Sr₃Y(PO₄)₃ have been successfully synthesized by conventional solid-state reaction, and its photoluminescence properties have been investigated. The excitation spectra reveal strong excitation bands at 392 nm, which match well with the popular emissions from near-UV light-emitting diode chips. The emission spectra of Sr₃Y(PO₄)₃:Eu³⁺ phosphors exhibit peaks associated with the ⁵D₀ → ⁷F_J (J = 0, 1, 2, 3, 4) transitions of Eu³⁺ and have dominating emission peak at 612 nm under 392 nm excitation. The integral intensity of the emission spectra of Sr₃Y_0.94(PO₄)₃:0.06Eu³⁺ phosphors excited at 392 nm is about 3.4 times higher than that of Y₂O₃:Eu³⁺ commercial red phosphor. The Commission Internationale de l’Eclairage chromaticity coordinates, the quantum efficiencies and decay times of the phosphors excited under 392 nm are also investigated. The experimental results indicate that the Eu³⁺-doped Sr₃Y(PO₄)₃ phosphors are promising red-emitting phosphors pumped by near-UV light.     

Spectrum regulation of YAG:Ce transparent ceramics with Pr,Cr doping for white light emitting diodes application

YAG:Ce transparent ceramics with high luminous efficiency and color render index were prepared via a solid state reaction-vacuum sintering method. Cr³⁺and Pr³⁺ were applied to expand the spectrum of YAG:Ce transparent ceramics. As prepared ceramics exhibit luminescence spectrum ranging from 500 nm to 750 nm, which almost covers full range of visible light. After the concentration optimization of Ce³⁺, Pr³⁺ and Cr³⁺, high quality white light was obtained by coupling the YAG:Ce,Pr,Cr ceramics with commercial blue LED chips. Color coordinates of the YAG:Ce,Pr,Cr ceramics under 450 nm LED excitation vary from cold white light to warm white light region. The highest luminous efficiency of WLEDs encapsulated by transparent YAG:Ce,Pr,Cr ceramic was 89.3 lm/W, while its color render index can reach nearly 80. Energy transfers between Ce³⁺ → Pr³⁺ and Ce³⁺ → Cr³⁺ were proved in co-doped ceramic system. Transparent luminescence ceramics accomplished in this work can be quite prospective for high power WLEDs application.     

Effect of crystalline fraction on upconversion luminescence in Er3+/Yb3+ Co-doped NaYF4 oxyfluoride glass-ceramics

The crystalline fraction were adjusted MgO concentration and the corresponding effect on upconversion (UC) luminescence in Er³⁺/Yb³⁺ co-doped NaYF₄ oxyfluorode glass-ceramics was investigated. With increase of MgO and the content of Na₂O reduced, the internal network structure of the glass became compact, which made the size of NaYF₄ nanocrystals unchanged, while the average distance between the nanocrystals increased significantly. Crystal growth is limited with the glass network, keeping the crystal size not changed. SNM-1 glass ceramics samples show a predominant red up-conversion emission under near infrared excitation at 980 nm, while a predominant green emission is observed in the SNM-3 samples. In this paper, it was indicated that it changed the effect of glass network modifier MgO in the glass structure. The possible mechanism responsible for the color variation of UC in Er³⁺/Yb³⁺ co-doped was discussed.     

Luminescent Eu3+-doped transparent alumina ceramics with high hardness

The Eu³⁺-doped transparent aluminas were prepared by wet shaping technique followed by pressure-less sintering and hot isostatic pressing. The effect of dopant amount on microstructure, real in-line transmission (RIT), photoluminescence (PL) properties, hardness and fracture behaviour was studied. The RIT decreased with increasing amount of the dopant. The PL emission spectra of Al₂O₃:Eu³⁺ ceramics exhibited predominant red light emission with the highest intensity (under 394 nm excitation) for material containing 0.125 at.% of Eu³⁺ and colour coordinates (0.645, 0.355) comparable with commercial red phosphors. The doping resulted in hardness increase from 26.1 GPa for undoped alumina to 27.6 GPa for Eu-doped sample. The study of fracture surfaces showed predominantly intergranular crack propagation micro-mechanism.     

Structural,optical, and spectroscopic properties of Er3+-doped TeO2–ZnO–ZnF2 glass-ceramics

Transparent fluorotellurite glass-ceramics have been obtained by heat treatment of precursor Er-doped TeO₂–ZnO–ZnF₂ glasses. ErF₃ nanocrystals nucleated in the glass-ceramics have a typical size of 45 ± 10 nm. Based on the Judd-Ofelt theory, the main radiative parameters for the ⁴I_13/2 → ⁴I_15/2 transition have been obtained. The split of the absorption and emission bands and the reduction of the Ω₂ parameter, as compared to the glass, confirm the presence of Er³⁺ ions in a crystalline environment in glass-ceramic samples. The analysis of the ⁴I_13/2 decays suggests that a fraction of Er³⁺ ions remains in a glass environment while the rest forms nanocrystals. For the glass-ceramics, intense red and green upconversion emissions were observed with an enhancement of the ⁴F_9/2 → ⁴I_15/2 red one compared to the glass sample. The temporal evolution of the red emission together with the excitation upconversion spectra suggests that energy transfer processes are responsible for the enhancement of the red emission.     

Upconverting luminescence based dual-modal temperature sensing for Yb3+/Er3+/Tm3+: YF3 nanocrystals embedded glass ceramic

Yb³⁺/Er³⁺/Tm³⁺ doped transparent glass ceramic containing orthorhombic YF₃ nanoparticles was successfully synthesized by a melt-quenching method. After glass crystallization, tremendously enhanced (about 5000 times) upconversion luminescence, obvious Start-splitting of emission bands as well as long upconversion lifetimes of Er³⁺/Tm³⁺ confirmed the incorporation of lanthanide activators into precipitated YF₃ crystalline environment with low phonon energy. Furthermore, temperature-dependent upconversion luminescence behaviors of glass ceramic were systematically investigated to explore its possible application as optical thermometric medium. Impressively, both fluorescence intensity ratio of Er³⁺: ²H_11/2 → ⁴I_15/2 transition to Er³⁺: ⁴S_3/2 → ⁴I_15/2 one and fluorescence intensity ratio of Tm³⁺: ³F_2,3 → ³H₆ transition to the combined Tm³⁺: ¹G₄ → ³F₄/Er³⁺: ⁴F_9/2 → ⁴I_15/2 ones were demonstrated to be applicable as temperature probes, enabling dual-modal temperature sensing. Finally, the thermal effect induced by the irradiation of 980 nm laser was found to be negligible in the glass ceramic sample, being beneficial to gain intense and precise probing signal and detect temperature accurately.     

Gd-based oxyfluoride glass ceramics: Phase transformation,optical spectroscopy and upconverting temperature sensing

A series of precursor glasses with compositions of SiO₂-Al₂O₃-AlF₃-Na₂O- NaF-Gd₂O₃/GdF₃-YbF₃-ErF₃ were prepared and their crystallization behaviors were investigated. For the samples with high F content, meta-stable hexagonal GdF₃ nanocrystals were preferentially precipitated from glass matrix and decreasing F/O ratio induced phase transformation to cubic NaGdF₄ and finally to hexagonal NaGdF₄. Benefited from its multiple active sites, significant enhanced upconversion luminescence was achieved for Yb/Er co-doped glass ceramic containing hexagonal NaGdF₄ nanocrystals. Importantly, significant temperature-sensitive upconversion fluorescence intensity ratio between Er³⁺: ²H_11/2 → ⁴I_15/2 transition (520 nm) and ⁴S_3/2 → ⁴I_15/2 one (540 nm) was detected owing to the competitive radiation transitions from these two thermally coupled emitting-states. Furthermore, linear temperature-dependent fluorescence intensity ratio between Er³⁺: ⁴F_9/2 → ⁴I_15/2 transition (650 nm) to ⁴S_3/2 → ⁴I_15/2 one (540 nm) was achieved, showing the advantages of high sensitivity, superior signal discriminability as well as excellent thermal stability for temperature determination.     

Fabrication and Characterization of Transparent (Y0.98−xTb0.02Eux)2O3 Ceramics with Color‐Tailorable Emission

Transparent (Y_0.98?xTb_0.02Eu_x)₂O₃ (x = 0–0.04) ceramics with color‐tailorable emission have been successfully fabricated by vacuum sintering at the relatively low temperature of 1700°C for 4 h. These ceramics have the in‐line transmittances of ~73%–76% at 613 nm, the wavelength of Eu³⁺ emission (the ⁵D₀→⁷F₂ transition). Thermodynamic calculation indicates that the Tb⁴⁺ ions in the starting oxide powder can essentially be reduced to Tb³⁺ under ~10^?3 Pa (the pressure for vacuum sintering) when the temperature is above ~394°C. The photoluminescence excitation (PLE) spectra of the transparent (Y_0.98?xTb_0.02Eu_x)₂O₃ ceramics exhibit one spin‐forbidden (high‐spin, HS) band at ~323 nm and two spin‐allowed (low‐spin, LS) bands at ~303 and 281 nm. Improved emissions were observed for both Eu³⁺ and Tb³⁺ by varying the excitation wavelength from 270 to 323 nm, without notably changing the color coordinates of the whole emission. The transparent (Y_0.98Tb_0.02)₂O₃ ceramic exhibits the typical green emission of Tb³⁺ at 544 nm (the ⁵D₄→⁷F₅ transition). With increasing Eu³⁺ incorporation, the emission color of the (Y_0.98?xTb_0.02Eu_x)₂O₃ ceramics can be precisely tailored from yellowish‐green to reddish‐orange via the effective energy transfer from Tb³⁺ to Eu³⁺ under the excitation with the peak wavelength of the HS band. At the maximum Eu³⁺ emission intensity (x = 0.02), the ceramic shows a high energy‐transfer efficiency of ~85.3%. The fluorescence lifetimes of both the 544 nm Tb³⁺ and 613 nm Eu³⁺ emissions were found to decrease with increasing Eu³⁺ concentration.