3d Levels Research Articles

Enhanced Quantum Efficiency via Co-Substitution in Red-Emitting Phosphor Sr2[MgAl5N7] : Eu2+ for Advanced Spectroscopic Applications Including Laser Displays with Ultra-High Luminescence Saturation Threshold.

In order to obtain novel and more efficient red light-emitting materials, a series of Sr2[Mg1-xLixAl5-xSixN7] : 0.01Eu2+ (SMAN-xLS, 0≤x≤0.5) red phosphors were devised and successfully synthesized via the high temperature solid state reaction and the effects of the co-substitution of [Mg-Al]5+ by [Li-Si]5+ on structural and luminescence properties is investigated in detail. A series of powder XRD data and Rietveld refinement indicate that [Li-Si]5+ co-substitution can successfully enter the Sr2[MgAl5N7] : 0.01Eu2+ (SMAN) lattice. With the entry of [Li-Si]5+ into the lattice, the substitution of Al3+ by Si4+ leads to the weakening of the nephelauxetic effect of the 5d level of Eu2+, which shifts the emission peak from 657 nm to 647 nm and reduces the excitation in the green region, i.e., lowers the absorption of green light. When the amount of [Li-Si]5+ co-substitution is x=0.1, the luminescence intensity and thermal stability of the sample are enhanced, in which the external quantum efficiency (EQE), reflecting the luminescence intensity, is elevated by 49.6 %. The increase in lattice rigidity gives rise to higher luminescence intensity, and the introduced trap levels for the compensation of luminescence enhances the thermal stability. Under blue laser excitation, the SMAN-0.1LS can achieve an ultra-high luminescence saturation threshold of 52.22 W/mm2, which is remarkably superior to other existing red phosphors, a breakthrough performance that has enormous potential for application in high-power laser display light sources. Cathodoluminescence (CL) characterization and measurements attest to the favorable CL properties of SMAN-0.1LS. By measuring the pressure-dependent luminescence of SMAN-0.1LS, the emission peak can be shifted from 650 nm to 702 nm with the increase of pressure, and the sensitivity dλ/dP is 5.07 nm/GPa, which is indicative of the potential application of this system as an optical pressure sensor.

Enhanced Quantum Efficiency via Co‐Substitution in Red‐Emitting Phosphor Sr2[MgAl5N7] : Eu2+ for Advanced Spectroscopic Applications Including Laser Displays with Ultra‐High Luminescence Saturation Threshold

AbstractIn order to obtain novel and more efficient red light‐emitting materials, a series of Sr2[Mg1−xLixAl5−xSixN7] : 0.01Eu2+ (SMAN‐xLS, 0≤x≤0.5) red phosphors were devised and successfully synthesized via the high temperature solid state reaction and the effects of the co‐substitution of [Mg−Al]5+ by [Li−Si]5+ on structural and luminescence properties is investigated in detail. A series of powder XRD data and Rietveld refinement indicate that [Li−Si]5+ co‐substitution can successfully enter the Sr2[MgAl5N7] : 0.01Eu2+ (SMAN) lattice. With the entry of [Li−Si]5+ into the lattice, the substitution of Al3+ by Si4+ leads to the weakening of the nephelauxetic effect of the 5d level of Eu2+, which shifts the emission peak from 657 nm to 647 nm and reduces the excitation in the green region, i.e., lowers the absorption of green light. When the amount of [Li−Si]5+ co‐substitution is x=0.1, the luminescence intensity and thermal stability of the sample are enhanced, in which the external quantum efficiency (EQE), reflecting the luminescence intensity, is elevated by 49.6 %. The increase in lattice rigidity gives rise to higher luminescence intensity, and the introduced trap levels for the compensation of luminescence enhances the thermal stability. Under blue laser excitation, the SMAN‐0.1LS can achieve an ultra‐high luminescence saturation threshold of 52.22 W/mm2, which is remarkably superior to other existing red phosphors, a breakthrough performance that has enormous potential for application in high‐power laser display light sources. Cathodoluminescence (CL) characterization and measurements attest to the favorable CL properties of SMAN‐0.1LS. By measuring the pressure‐dependent luminescence of SMAN‐0.1LS, the emission peak can be shifted from 650 nm to 702 nm with the increase of pressure, and the sensitivity dλ/dP is 5.07 nm/GPa, which is indicative of the potential application of this system as an optical pressure sensor.

Novel reddish-orange emitting BaBPO5:Eu3+ phosphor for n-UV warm white-LEDs: Synthesis and study of structural and spectroscopic investigations

A novel reddish-orange emitting 2Ba2-xO-B2O3-P2O5:xEu3+ (x= 0.04, 0.06, 0.08, 0.10, 0.12 and 0.14 mol%) phosphor with different concentrations of Eu3+ ions were synthesized through high temperature solid-state reaction technique. The crystal structure has been studied by X-ray diffraction technique for all the concentrations of Eu3+ ions. The morphology and elemental analysis of the optimal ∼0.1 mol% concentration was examined by the SEM-EDS images. The functional groups were analysed by the FTIR characterization technique. The thermal properties were studied by the TGA-DSC analysis. The energy band gap of all the samples were analysed by using UV–VIS DRS technique. The photoluminescence properties of BaBPO5:Eu3+ phosphor with different concentrations of Eu3+ ions were investigated at λem = 611 nm and λex = 394 nm. Variation in emission intensity with Eu3+ ion concentrations, phonon side bands, multi-phonon relaxation rate and energy transfer mechanisms were studied. The BaBPO5:Eu3+ phosphors exhibit characteristic emission peaks corresponding to 5D0 → 7FJ (J = 0, 1, 2, 3, 4) transitions of Eu3+ ions under n-UV excitation. Among all the transitions, 5D0 → 7F1 (593 nm) transition shows higher intensity and asymmetric ratio (R21) for all concentrations of Eu3+ ions were calculated. The lifetimes of 5D0 level of Eu3+ ions in BaBPO5: Eu3+ phosphor were calculated by using fluorescent decay curve analysis. The CIE color coordinates reveal, reddish-orange emission in the low CCT range. These findings imply that BaBPO5: 0.1Eu3+ phosphor is a promising candidate for solid-state lighting applications as well as phosphor-converted warm w-LEDs.

Photoluminescence optical and thermal quenching in heavily doped Gd3(Ga,Al)5O12:Ce, Mg single crystals: Dependence on the Ga3+, Ce3+, and Mg2+ concentration

Heavily doped single crystals of Gd3GaxAl5-xO12:Ce, Mg (x = 2.46–2.95) with different concentrations of Ce (0.016–0.188 at.%) and Mg (0–0.083 at.%) are investigated by the X-ray diffraction, photoluminescence, and thermoluminescence methods. Dependences of the luminescence characteristics, as well as crystal lattice parameters and distances between the Ce3+ and Mg2+ ions, on the Ga, Ce, and Mg concentration are studied. Mechanisms of the processes, resulting in the photoluminescence optical and thermal quenching and acceleration of decay kinetics, and the influence of the crystal composition on these processes are discussed. The role of close {Ce3+ - Mg2+Ga} pairs in these processes is considered. At T > 400 K, the luminescence thermal quenching is caused by the crossover process, while in the 200–350 K temperature range, by the electron transfer from the 5d1 excited state of Ce3+ to nearby defect levels (electron traps) located between the 5d1 level and the conduction band. The latter process results also in the appearance of thermally stimulated luminescence, and its efficiency depends on the Ga3+ content and concentration of intrinsic defects. The optimum concentrations of Ga3+ and Mg2+ ions in the investigated crystals are determined.

Synthesis and luminescent properties of a novel long-afterglow phosphor BaGd2Al2Ga2SiO12: Ce3+

With the widespread adoption of blue light chips, the demand for long afterglow phosphors excited by blue light is increasing. The current long afterglow phosphors excited by blue light exhibit relatively low afterglow brightness. However, the afterglow brightness can be effectively enhanced by regulating the activation energy of the host materials. In this study, a novel long afterglow phosphor with photoluminescence, BaY1.95-xGdxAl2Ga2SiO12: 0.05Ce3+(0≤ x ≤1.95), was prepared using a high-temperature solid-state method. The activation energy between the 5d1 level and the conduction band (CB) in the material was regulated through the single substitution of Y With Gd (When x = 1.95, Y is completely substituted by Gd, forming BaGd2Al2Ga2SiO12: Ce3+). As the concentration of Gd increases, the Stokes shift of the emission spectrum increases, and the activation energy between the 5d1 level and the CB decreases from 0.38 eV to 0.32 eV, making it easier for electrons to enter the conduction band, thereby enhancing the afterglow intensity. Furthermore, it was found that the substitution of Gd leads to a strengthening of the crystal field splitting of Ce3+ and a weakening of the centroid shift, which in turn causes a red shift in the spectrum. The AC-LED fabricated by combining BaGd1.95Al2Ga2SiO12: 0.05Ce3+ long afterglow phosphor with a blue light chip effectively reduces flicker to 68.80 %.

The interplay between structural features and the efficiency of the energy transfer process in terbium complexes with triarylcyclopentadienyl ligands

Terbium and gadolinium complexes with triarylcyclopentadienyl ligands having electron-donating methoxy substituents in the ortho- (CpPh2Ar−o) and para- (CpPh2Ar−p) positions of one of the phenyl rings have been synthesized. Different structural types, including tetranuclear [{CpPh2Ar−oTb (THF)}2 (μ2-Cl)2(μ3-Cl)3K (THF)]2 (Tb1), [{CpPh2Ar−oTb}2 (μ2-Cl)2 (μ3-Cl)3K]2 (Tb3), [{(CpPh2Ar−oTb)2 (μ2-Cl)3}2 (μ2-Cl)2] (Tb5), [{CpPh2Ar−pTb (THF)}2 (μ2-Cl)2 (μ3-Cl)3K (THF)]2 (Tb6), binuclear [{CpPh2Ar−oTb (THF)Cl}2 (μ2-Cl)2] (Tb4), [{CpPh2Ar−pTb (THF)}2 (μ2-Cl)2 (μ3-Cl)3K (THF)]2 (Tb7), [CpPh2Ar−p2Tb (μ2-Cl) (μ3-Cl)K]2 (Tb8) and mononuclear [CpPh2Ar−o2TbCl] (Tb2) complexes have been obtained and confirmed by single crystal X-ray diffraction analysis. All designed terbium complexes exhibit high quantum yields of the photoluminescence (up to 65 %). The introduction of a methoxy group into one of the phenyl rings of the triarylcyclopentadienyl ligand leads to a more than twofold increase in the quantum yield of the terbium ion luminescence. The estimated values of radiative rate krad of the terbium ion vary in the range of 0.23–0.69 ms. The presence of the methoxy group as well as the mutual disposition of the phenyl rings promotes the appearance of an intraligand charge transfer states involved in the energy transfer process. Due to a lowering of the energy of the interconfigurational 4f −5d transitions caused by the relatively strong crystal field of the Cp ligand in bis(cyclopentadienyl) terbium complexes, the quantum yield of the photoluminescence is high at the short lifetimes of the 5D4 level of the terbium ion.

Novel Eu3+-Doped Glasses in the MoO3-WO3-La2O3-B2O3 System: Preparation, Structure and Photoluminescent Properties.

Novel multicomponent glasses with nominal compositions of (50-x)MoO3:xWO3:25La2O3:25B2O3, x = 0, 10, 20, 30, 40, 50 mol% doped with 3 mol % Eu2O3 were prepared using a conventional melt-quenching method. Their structure, thermal behavior and luminescent properties were investigated by Raman spectroscopy, differential thermal analysis and photoluminescence spectroscopy. The optical properties of the glasses were investigated by UV-vis absorption spectroscopy and a determination of the refractive index. Physical parameters such as density, molar volume, oxygen molar volume and oxygen packing density were determined. The glasses are characterized by a high glass transition temperature. Raman analysis revealed that the glass structure is built up mainly from tetrahedral (MoO4)2- and (WO4)2- units providing Raman bands of around 317 cm-1, 341-352 cm-1, 832-820 cm-1 and 928-935 cm-1. At the same time, with the replacement of MoO3 with WO3 some fraction of WO6 octahedra are produced, the number of which increases with the increasing WO3 content. A strong red emission from the 5D0 level of Eu3+ ions was registered under near-UV (397 nm) excitation using the 7F0 → 5L6 transition of Eu3+. Photoluminescence (PL) emission gradually increases with increasing WO3 content, evidencing that WO3 is a more appropriate component than MoO3. The integrated fluorescence intensity ratio R (5D0 → 7F2/5D0 → 7F1) was calculated to estimate the degree of asymmetry around the active ion, suggesting a location of Eu3+ in non-centrosymmetric sites. All findings suggest that the investigated glasses are potential candidates for red light-emitting phosphors.

Thermal enhancing luminescence and thermal quenching luminescence of Sc2(MoO4)3: X mol% Eu3+

The synthesis of a series of Sc2(MoO4)3: x mol% Eu3+ red phosphors (x = 0, 1, 3, 5, 7, 10, 15, 20, 30, 50, 70 and 100) was successfully completed through the implementation of a high-temperature solid-phase synthesis methodology. The optimum 5 mol% Eu3+ doped Sc2(MoO4)3 were prepared at 900 °C, and no concentration quenching luminescence were observed in Sc2(MoO4)3: x mol% Eu3+ phosphors though crystalline phase varied. In particular, the 10 mol% Eu3+-doped Sc2(MoO4)3 exhibited thermal enhancing luminescence (TEL) when excited with 277 nm light. At 125 °C, the intensity reached 250 % of the initial value, while at 300 °C, it remained at approximately 190 % of the initial intensity. With 396 nm excitation, the phosphor presented thermal quenching luminescence (TQL). In the TEL Sc2(MoO4)3: x mol% Eu3+ phosphors, the optimal temperature of TEL enhanced with Eu3+ concentration increasing. For the Eu2(MoO4)3 phosphor, it only demonstrated TQL with 277 nm and 396 nm excitations. The mechanism of TEL can be ascribed to the enhancement in structural rigidity resulting from the negative thermal expansion (NTE), which was accompanied by efficient energy transfer from MoO42− to Eu3+. Furthermore, the fluorescence lifetime of the 5D0 level demonstrated a declining trend then a rising trend with elevated Eu3+ concentrations, whereas the color purity value exhibited an ascending trend always.

Concentration- and temperature-dependent luminescence mechanisms and fluorescence dynamic temperature sensing of NaY(MoO4)2:Tb3+ phosphors

High-temperature solid-state reaction technique was used to prepare NaY(MoO4)2:Tb3+ phosphors with different Tb3+ concentrations. XRD patterns showed that the prepared samples contained only single-phased compound NaY(MoO4)2. The concentration-dependent green luminescent intensity of Tb3+ was studied, and it was found that the concentration quenching process is in charge of Ozawa's model. The concentration-effect of luminescence decay of 5D4 level was explained by the Auzel's self-generated quenching theory. Starting from the Reisfeld's theory, the analysis on the luminescence decays also indicated exchange interaction was responsible for the concentration quenching. Temperature dependences of the green emission intensity and decay were comprehended based on the crossover mechanism. A novel temperature sensing technique rooting in the fluorescence dynamics of 5D4 level of Tb3+ in NaY(MoO4)2 was proposed, and the absolute and relative sensitivities were deduced and assessed.

An efficient red phosphor LuNb2VO9:Eu3+ with broadband excitation and abnormal thermal quenching properties for personal identification, security ink, and w-LEDs

A series of red-emitting phosphors LuNb2VO9 (LNV):xEu3+ (x = 0.5–45 mol%) were successfully obtained through the high-temperature solid-state reaction. The structure, phase purity, photoluminescence spectra, thermal stability properties, and color purity of the obtained phosphors were systematically examined. The LNV:Eu3+ phosphor exhibits broadband excitation due to the O2-→Eu3+ and O2-→V5+ charge transfer. The LNV:Eu3+ phosphor excited at 316 nm shows four emission peaks at 595, 615, 619, and 699 nm, corresponding to electron transitions from the 5D0 level to the 7F1, 7F2, 7F3 and 7F4 levels. The optimal doped concentration of LNV:xEu3+ is x = 10 mol%. The quenching mechanism is attributed to the nearest neighbor ion interaction. Furthermore, the prepared phosphor exhibits good thermal stability and remarkable activation energy Ea (0.74 eV). In addition, LNV:Eu3+@oleic acid (OA) readily exhibits the level I-III characteristics of fingerprints and the detailed characteristics of lip lines. The successful utilization of LNV:Eu3+ in anti-counterfeiting ink has yielded impressive results. The Commission International de L′ Eclairage (CIE) coordinate of the prepared white light-emitting diode (w-LED) in this study is (0.331, 0.367), accompanied by a color rendering index (Ra) of up to 95. Notably, the results of these experiments indicate that LNV:Eu3+ phosphor possesses exceptional luminescence properties and holds promising applications.

Structure and photoluminescence properties of coordination compound [Eu2(o-MBA)6(phen)2] with high quantum yield

An europium(III) coordination binuclear compound [Eu2(o-MBA)6(phen)2] (o-MBA = ortho-methylbenzoate, phen = 1,10-phenantroline) has been synthesized and investigated by X-ray diffraction method, thermogravimetric analysis (TGA), infrared (IR) and photoluminescence (PL) spectroscopy. The single crystal X-Ray diffraction measurements show that the compound crystallizes in the triclinic centrosymmetric space group P-1. The PL excitation spectrum displays a broad band between 300 and 420 nm and a number of sharp transitions between 384 and 590 nm, which can be attributed to the Eu3+ 4f6 intra-shell excitation transitions. The complex exhibits characteristic narrow, metal-centred emission bands, which are determined by the radiative transitions of the Eu3+ ion, from the first excited non-degenerate 5D0 level to the 7FJ (J = 0–4) manifold. The compound shows intense hypersensitive transition 5D0→7F2 which dominates the PL emission spectrum. The dipole strengths of the transitions were determined from the emission spectra in terms of Judd-Ofelt (JO) intensity parameters Ωλ (λ = 2, 4). The high intensity bright-red emission of the complex can be attributed to highly polarizable ligands environment and the low site symmetry (Ci) around the lanthanide ions. We suppose that the J-mixing effect in the Eu(III) ions is responsible for enhanced peak maximum of the 5D0→7F0 transition.

Boltzmann thermometry: Eu3+-doped monoclinic Y2O3 and Y2O3@SiO2 nanoparticles

During last decade optical thermometry has gained considerable attention due to the possibility to determine temperature remotely in cases when traditional contact methods fail. The most widespread type of optical temperature sensors is based on monitoring luminescence intensity ratio between transition originated from thermally coupled energy levels. Eu3+ ions own the largest energy gap between thermally coupled 5D1 and 5D0 energy levels among all lanthanides, which guarantees a high thermal sensitivity of Boltzmann-type thermometry. Here, uncoated m-Y2O3:Eu3+ and core-shell m-Y2O3:Eu3+@SiO2 nanophosphors have been successfully utilized as ratiometric thermal sensors within the 298–873 K range. It was shown that the calculation method (integral or peak intensities) only slightly affects thermal sensitivity. SiO2 coating significantly enhances emission intensity and increases lifetime, but has no noticeable effect on thermal sensitivity. m-Y2O3:Eu3+ nanophosphor has the best thermometric characteristics of Sr = 0.96 % K-1 at 373K and δT = 0.5 K.

Hexagonal rod-like Eu3+doped CaMoO4 phosphors: Structural, photoluminescence and photometric properties for display device applications

A multicolored LED illumination device is a compact, durable, easy to obtain color-adjustable output illumination source. It is frequently utilized in the domains of room illumination and exterior displays. However, the advancement of multicolor LEDs has been hampered by the rise in price and the fall in luminous efficacy while changing illumination colors. In the present investigation we have prepared intense red emitting Eu3+ doped CaMoO4 phosphor nanopowders via simple solid-state reaction technique. The powder X-ray diffraction (PXRD) studies reveal the crystalline nature of the samples with scheelite–type mono phase tetragonal structure with I41/a space group. The band gap (Eg) energy values were estimated and found to range between 4.63–5.32 eV. Scanning electron microscopy (SEM) studies reveled the hexagonal rod-like structures with different Aloe Vera gel concentrations. The particle size was found to be around 40 nm. The vibrational modes of the prepared powders were evaluated by using Fourier Transform Infrared Spectroscopy (FTIR) and Raman spectroscopy. It was observed from the results that, there were 26 vibrational modes of CaMoO4 (Γ=3Ag + 5Au + 5Bg + 3Bu + 5Eg + 5Eu) 8 of which (4Au and 4Eu) were infrared active and 13 (Ag, Bg, and Eg) are Raman active. Photoluminescence (PL) emission intensity increases up to 5 mol% of Eu3+ ions load and subsequently it declines due to the concentration quenching phenomenon and effective energy transfer from Mo-O charge transfer band (CTB) to 5D0 levels of Eu3+. It was noticed from PL emission spectra that, four intense peaks located at 5D0 → 7F1 (590 nm), 5D0 → 7F2 (613 nm), 5D0 → 7F3 (654 nm), 5D0 → 7F4 (702 nm) of Eu3+ respectively. The Commission International de I'Eclairage (CIE) diagram indicates the red color emission and average correlated color temperature (CCT) value was found to be 2050 K. Further, the external quantum efficiency (QE) and color purity (CP) were calculated to check the phosphor efficiency and found to be 92% and 72% respectively. The present investigation opens up a new avenue in the fabrication of low-cost display devices with high color purity and luminous efficacy.

Structural, optical and luminescent properties of Tm3+-doped phosphate oxyfluoride glasses for blue emission solid state devices

In this work, the visible luminescence of P2O5-KF-Al2O3 glasses with Tm2O3 was studied. The Tm3+ ion can have a strong blue emission, which allows the development of LEDs in this color region. This study refers to the synthesis of oxyfluorophosphate glasses, 38P2O5+(50-x)KF+12Al2O3+xTm2O3 (PKAl:Tm), with x = 0.25, 0.50, 0.75, and 1.00 mol%, by the melt-quenching method. The prepared materials showed amorphous characteristics verified by XRD data. The absorption spectra shown six main bands characteristic of Tm3+ ions, from ground state 3H6 to excited levels 3F4, 3H4, 3H5, 3F3,2, 1G4 and 1D2, in which the intensities increased with the concentration of Tm2O3. In the FTIR spectra, it was verified that the profiles of the PKAl samples are similar to glasses based on phosphate systems. The Judd-Ofelt parameters were calculated, where for PKAl glasses the trend was Ω2>Ω4>Ω6. The excitation spectra of PKAl:Tm glasses shown an intense band centered at 358 nm (3H6→1D2). The luminescence spectra with excitation at 358 nm shown two bands at 453 nm (1D2→3F4), and 480 nm (1G4→3H6); the highest emission intensity was observed to the sample doped with 0.75 mol% of Tm2O3. The calculated CIE diagram shown that the doped samples have coordinates close to the primary blue color, which favors the application for the development of blue LEDs and wLEDs. The decay curves for the 1D2 level were fitted by single exponential with lifetime values decreasing with increasing concentration of Tm2O3. These results show that the PKAl:Tm glasses are potential candidates for applications in LEDs.

Photo and X˗ray induced luminescences of Eu3+˗doped sodium alumino boro˗tellurite oxyfluoride scintillating glass for X˗ray detecting material

The spectroscopy features of sodium alumino boro˗tellurite oxyfluoride glasses doped with various molar fractions of Eu2O3 ions (TBANEu) are studied through absorbance, excitation, emission, and decay curves. The excitation data are used following phonon side band spectroscopy to evaluate the phonon energy (1326 cm-1) of the glass host. The densities, molar volumes, and refractive indices, including the Ω2,4,6 parameters of fabricated glasses are studied. The magnitudes of laser properties like effective line widths, branching ratios, and emission cross˗sections obtained for the Eu3+:5D0→7F2 transition could be useful for reddish-orange lighting devices application. Additionally the quantum efficiency estimated from experimental and calculated lifetimes is about ˃ 70% for the 5D0 level luminescence of TBANEu glasses. Upon 395 nm radiation, the current glass system can exhibit color coordinates close to (0.647, 0.351) for reddish˗orange light as performed by the CIE1931 chromaticity diagram. The integral scintillation intensities of TBANEu glasses were determined using the X˗ray excitation and observed that the TBANEu20 glass showed a highest scintillation efficiency of 39%, resulting in scintillator and X˗ray sensing device applications.

Optical and radiation shielding properties of Europium doped Alkaline-Earth Boro Tellurite glasses

This research investigates the influence of Europium (Eu3+) ions concentrations on the optical, radiation shielding characteristics and photoluminescence (PL) properties of Alkaline Earth Boro Tellurite (AEBT) glasses. Absorption measurements of Eu3+ions doped AEBT glasses were used to determine the bonding parameters between the ligands and the ions. Excitation wavelength (394 nm) was used to record the PL spectra of the as prepared glasses , and analyzed for the dependent radiative characteristics and J-O parameters. The experimental lifetime (τexp) and radiative lifetimes (τR) of the as-prepared glass samples were estimated from the PL decay spectral profiles of the 5D0 level recorded at 613 nm emission under 394 nm excitation, and the quantum efficiency was then calculated. Based on its relatively higher values of the stimulated emission cross-sections and quantum efficiency, as well as its intense red luminescence at 613 nm (5D0 →7F2), the 1.0 mol% of Eu3+ ions doped AEBT glass is considered as a good optical material. In addition, the gamma-ray shielding properties have also been investigated at different photon energies ranging from 0.015 to 15 MeV using Phy-X software. From the results it is contemplated that, AEBTEu2.5 glass has the potential with better radiation absorption compared to regular concrete and other glass systems. The as prepared glasses are also suitable for optoelectronic device applications in addition to radiative shielding applications.

Structural, optical, luminescence spectroscopy and radiation shielding properties of Eu3+:borophosphotellurite glasses

Recently much effort is being paid to study the rare earth ions in multi component glass formers as they exhibit high enhancement in the efficiency of luminescence properties. In this direction, the present study focuses on the preparation and analysis of novel glass batches with composition of (in mol %) BPTCZEu: 40B2O3+20P2O5+15TeO2+ 10CaO+(15−x)ZnO + xEu2O3, x = 0.1, 0.5, 1.0, 1.5, 2.0 and 2.5. The important spectroscopic techniques such as optical absorption, luminescence, excitation and decay curves are taken to analyse the BPTCZEu glasses. Luminescence spectrum of BPTCZEu comprise of emission from excited (5D0) to the lower multiplets (7FJ (J = 0−4)), among these, 5D0 → 7F2 (red luminescence) at 612 nm found to be very intense. Judd−Ofelt characteristics, Ω2, Ω4 and Ω6, were derived from different constraints. To know the site symmetry around Eu3+, the fluorescence intensity ratio of 5D0 → 7F2 vs. 5D0 → 7F1 were analysed. Exciting 7F0 → 5L6 and monitoring 5D0 → 7F2, the lifetime of 5D0 level is determined to be 2 ms which is independent of Eu3+ content. The colour coordinates for all the Eu3+ concentrations are estimated to fall in the reddish−orange region. Theoretical radiation shielding results showed that substituting Eu2O3 for ZnO in the glasses lowers photon number that can pass via the material, enhancing the glass system's trend to shield high energy radiation. These stimulated results are compared with experimental measurements of mass attenuation coefficient with respect to energy up to 662 KeV using Cs−137 source. All these findings obtained from title glasses are compared and discussed with respect to reported Eu3+:glasses and no systematic variation has been noticed either with single, bi− or multi−component glass formers and therefore needs further systematic work to relate Eu−radiation−ligand interaction.

Excellent Color Purity and Luminescence Thermometry Performance in Germanate Tellurite Glass Doped with Eu3+ and Tb3+

Germanate tellurite glasses doped with Eu3+ and Tb3+ were synthesized by the conventional melt-quenching method. There is no indication of the energy transfer between dopant ions in this host, but the co-dopants exhibit excellent color purity of 100% for Eu3+ and 80% for Tb3+. The co-doped glass exhibits yellow luminescence. The quantum yield of the Eu3+ emission is equal to 23% under 395 nm excitation. The thermal quenching of Eu3+ and Tb3+ luminescence occurs at different temperature ranges, which enables the thermal sensing properties of the material. The relative fluorescence intensity ratio (FIR) sensitivity of 0.16% K−1 was recorded in the wide range of temperatures spanning from −193 °C up to 0 °C. The temperature dependence of the decay times was also studied. The lifetime-based temperature sensitivity was determined to be 0.95% K−1 at 250 °C for Tb3+5D3 level emission and 0.3% K−1 at 225 °C for Eu3+5D1 level emission.

Temperature dependence of photoluminescence kinetics and scintillation properties of LuY2(Al5-xScx)O12:Ce (x = 1, 1.5, 2) garnet single-crystalline films

The temperature dependence of photoluminescence (PL) kinetics and scintillation properties were investigated in LuY2(Al5-xScx)O12:Ce (x = 1, 1.5, 2) garnet single-crystalline films grown by the isothermal liquid phase epitaxy method. With the increase of Sc content, the Ce3+ 5d1 level was shifted to higher energy while the Ce3+ 5d2 level was shifted to lower energy due to the decrease in crystal field splitting of the 5d levels. Activation energy of thermal quenching, determined from temperature-dependent PL decay times, decreased with increasing Sc content. At room temperature, the decrease of light yield (LY) value with increasing Sc content is caused by the thermal ionization process. LuY2(Al4Sc)O12:Ce showed a LY value of 510 photons/MeV when excited by 5.5 MeV α-particles, which is ∼21 % larger than that of Lu2Y(Al4Sc)O12:Ce due to a smaller bandgap Eg of the former.

Insights into luminescence and energy transfer processes in Ce3+- and Tb3+ co-doped (Gd, Y)3Al2Ga3O12 garnet single crystals

Driven by the pursuit of optimizing the luminescent properties of garnet-based single crystals for X-ray imaging applications, this work reports on the successful synthesis and in-depth characterization of GYAGG crystals doped with Ce³⁺ or Tb³⁺ ions, and doubly-doped with both of them. Micro-pulling down synthesis yielded crystals with a single cubic phase confirmed by X-ray diffraction. Photoluminescence (PL) and radioluminescence (RL) measurements on Ce³⁺,Tb³⁺ co-doped GYAGG revealed bidirectional energy transfer processes. Characteristic broadband 5d1→4f emission of Ce³⁺ centers peaking at 530 nm and narrow 4f→4f emission lines of Tb³⁺ ions starting from 5D4 level within 480–630 nm were observed. At higher doping levels, cross-relaxation in Tb³⁺ pairs resulted depleted 5D3 state and only the emission from 5D4 one was observed in the spectra. Analysis of PL decay characteristics corroborated the spectral observations, confirming progressively decreasing Ce³⁺ decay time (down to 40 ns at 15 % Tb3+) due to enhanced Ce³⁺→Tb³⁺ energy transfer. Similarly, the Tb³⁺ decay time accelerated by more than 60 % after the Ce³⁺ co-doping. Notably, co-doping with 0.5 % Ce³⁺ and 10–15 % Tb³⁺ doubled the luminescence intensity of RL spectra compared to 0.5 % Ce³⁺-doping alone, attributed to the increased density of emitting centers.