7F2 Transition Research Articles

Effect of Gd-codoping on photoluminescence properties of Eu-doped natural fluorapatite

This study investigated the photoluminescence properties of Eu, Gd, and Eu-Gd co-doped natural fluorapatite (FAP) particles. Ca10(PO4)6F2:EuxGd0.2−x powders were synthesized by the solid-state powder synthesis method at 1150 ⁰C. X-Ray Diffraction (XRD), Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscopy (SEM) with Energy-Dispersive X-Ray Spectroscopy, and Photoluminescence Spectroscopy (PL) were used to characterize the structural, morphological, chemical, and optical properties, respectively. XRD and FTIR analysis demonstrated the presence of mainly FAP while CaO and larnite as minor phases. Approximately 1–2 µm equiaxed FAP particles were seen in SEM microstructure images. Regardless of Gd3+, in the presence of Eu3+, under 253 nm excitation, the FAP samples showed characteristic emission bands of Eu3+ at 600 nm and 625 nm originating from 5D0→7F1 and 5D0→7F2 transitions, respectively. In addition, a noticeable increase was observed in the emission intensity of Eu3+ with the addition of Gd3+. On the other hand, the Gd-doped FAP sample showed an emission band at 320 nm originating from the Gd3+ 6P7/2→8S7/2 transition under excitation at 205 nm. As a result, the emissions of Eu-FAPs were improved with the Gd-codoping, and materials with high color purity and excellent chromaticity coordinate characteristics were obtained.

A new Na2BaCa(PO4)2: Eu3+ red-emitting phosphor with excellent thermal stability and high quantum efficiency for WLEDs

A series of new red phosphors Na2BaCa(PO4)2: xEu3+ was synthesized by the high temperature solid phase reaction method. Through employing X-ray diffraction, scanning electron microscope, photoluminescence spectroscopy, quantum efficiency curves and high-precision rapid spectrometers, a systematic investigation was conducted on the microstructure and optical characteristics of the material. The XRD analysis of Na2BaCa(PO4)2: xEu3+ shows the sample to be a pure phase. The spectroscopic results show the presence of a red emission peak originated from 5D0 → 7F2 transition, and the quenching mechanism is attributed to interaction between nearest neighboring ions. Under 423 K, the fluorescence intensity of Na2BaCa(PO4)2: 0.2Eu3+ phosphor can still maintain 94.82 % of the value observed at 298 K, and the thermal activation energy ΔE reaches up to 0.3543 eV. The CCT of the LED packaged with Na2BaCa(PO4)2: 0.2Eu3+ was measured to be 4314 K, with the CIE coordinates (0.3658, 0.3600), which is very close to the point of standard white light source. The quantum efficiency of Na2BaCa(PO4)2: 0.2Eu3+ was measured to be 82.92 %. All results indicate that Na2BaCa(PO4)2: 0.2Eu3+ is suitable for WLED applications.

Detecting and shielding properties of Ce3+-doped zinc–gadolinium-fluoroborate glasses for X-ray and proton radiation

Zinc-gadolinium-fluoroborate glasses doped with cerium fluoride (CeF3) were successfully fabricated to detect and shield X-ray and proton radiation. The doped glasses were studied at varying ZnO concentrations to investigate their properties, including density, transmittance, photoluminescence, and the oxidation states of dopants The glasses were tested for their sensitivity to detect X-ray and proton radiation, and calculations of the half-value layer and proton range were used to investigate their shielding properties. The results showed that an increase in ZnO concentrations induced a higher glass density and shifted the absorption edge to a longer wavelength (redshift) in the optical transmittance spectra. The cerium dopant mainly formed the Ce3+ oxidation state, resulting in a single broad band emission due to the 5d→4f transition of Ce3+ ions. The luminescence behavior of the doped glasses under x-ray irradiation showed a single broad emission at 375 nm. In contrast, under proton irradiation, the single broad emission shifted to a longer wavelength at 400 nm. The increase in ZnO concentration decreased light emission when exposed to x-rays and protons. The results also demonstrated that increasing ZnO concentrations improved the shielding properties of the glasses. We found that the glass with a 25 mol% ZnO concentration revealed a half-value layer of the 100 keV photon energy equal to 0.116 ± 0.001 cm, and a 70 MeV proton energy penetrated the maximum range in the glass at 1.308 ± 0.019 cm. We concluded that ZnO could be used to control the fraction between Ce3+ and Ce4+ ions in the cerium ions of the CeF3-doped glasses.

High concentration quenching, improved PLQY and high color purity of novel Gd2TiO5:Eu3+ triggered by complete solubility of dopant

In the surge of new inorganic luminescent host for lanthanide ion for efficient solid-state lighting, Ln2TiO5 comes as a new class of materials with all optically suited properties. Triggered by very high solubility of Eu3+ ion in Gd2TiO5 with minimal lattice strain, negligible doping induced structural distortion and no charge compensating defects; Gd2TiO5:Eu3+ (GTOE) delivered an extraordinary credentials as novel phosphor material. GTOE demonstrated no concentration quenching up to 10 mol % doping; monotonic rise in emission intensity, higher excited state lifetime, high red color purity∼99% and PLQY∼ 14%. Luminescence lifetime spectroscopy suggested stabilization of Eu3+ in both GdO7 with distorted pentagonal bipyramid (DPB) and distorted hexagonal bipyramid (DHB) geometry having similar coordination and symmetry and is well supported by two stark components in 5D0→7F0 transitions. Positron annhilation lifetime spectroscopy (PALS) suggested that average positron lifetime remained constant in all the samples indicating no charge compensating defects formation further justifying occupancy of Eu3+ in isovalent Gd3+ site. Judd-Ofelt analysis suggested that local symmetry around Eu3+ ion and polarizability of Eu–O bonds in GTO host doesn't change throughout the concentration range. This work proposed an excellent candidate for red emitting materials towards phosphor converted white light emitting diodes (pcLEDs) having high dopant solubility, PLQY and color purity.

A novel scheelite‐type LiCaGd(WO4)3:Eu3+ red phosphors with prominent thermal stability and high quantum efficiency

AbstractA series of LiCaGd(WO4)3: xEu3+ (0 ≤ x ≤ 1.0) red phosphors with tetragonal scheelite structure were synthesized via the conventional solid‐state reaction. Their crystal structure, photoluminescence excitation (PLE), and photoluminescence (PL) spectra, thermal stability and quantum efficiency were investigated. The phosphors exhibit a typical red light upon 395 nm near ultraviolet excitation, and the strongest emission peak at 617 nm is dominated by the 5D0→7F2 transition of Eu3+ ions. The PL intensity of the phosphors gradually increases with the increase of Eu3+ doping concentration, and the concentration quenching phenomenon is hardly observed. The quantum efficiency and the color purity of the phosphor reach maximum values of about 94.2 and 96.6% at x = 1.0, respectively. More importantly, LiCaGd(WO4)3:xEu3+ phosphors have prominent thermal stability. The temperature‐dependent PL intensity of the phosphors at 423 K is only reduced to 89.1% of the PL intensity at 303 K, which is superior to that of commercial red phosphors Y2O3:Eu3+. Finally, LiCaGd(WO4)3:Eu3+ phosphor is packaged with near ultraviolet InGaN chips to fabricate white light emitting diodes, which has a low color temperature (CCT = 4622 K) and a high color rendering index (CRI= 89.6).

Structural and luminescence characterization of red-emitting Li6SrLa2Nb2O12:Eu3+ phosphors with excellent thermal stability

Eu3+ doped Li6SrLa2Nb2O12 phosphors were synthesized and XRD patterns for the representative samples revealed its single phase structure. The Rietveld refinements indicate Li6SrLa2Nb2O12:Eu3+ samples crystallized in the cubic structure with Ia-3d space group. The optical band gaps of Li6SrLa2Nb2O12 calculated by the diffuse reflectance spectra (3.75 eV) were in very good agreement with the density functional theory (3.59 eV). Monitored at 609 nm, the phosphor showed serials of sharp peaks originated from f-f transitions of Eu3+ ions from 350 nm to 500 nm. Under 394 nm excitation, the Li6SrLa2Nb2O12:Eu3+phosphor showed red photoluminescence band centered at about 609 nm because of 5D0→7F2 transition of Eu3+ ions. The Li6SrLa2Nb2O12:0.4Eu3+sample exhibits the internal quantum yield as high as 51.3% and the color coordinates of this sample were calculated to be (0.6443, 0.3554) with high color purity of 98.9%. Particularly, the phosphor has excellent luminescence thermal stability, maintaining 82.25% of the room temperature emission intensity at 423 K. All the results confirmed that Li6SrLa2Nb2O12:Eu3+ samples have strong potential for NUV w-LEDs.

Realizing full-spectrum LED lighting with a bright broadband cyan-green-emitting CaY2ZrGaAl3O12:Ce3+ garnet phosphor

Full-visible-spectrum white light-emitting diodes (LEDs) with ultrahigh color rendering index (CRI), which are capable of offering a light source that mimics natural sunlight, have great application potentials in healthy lighting, high-resolution displays, and plant growth lighting. However, cyan gap in the 480–520 nm wavelength range is commonly existed in the emission spectra of traditional phosphor-converted white LEDs, and thus it is urgent to develop high-performance cyan-emitting phosphors to close this spectral gap for realizing full-visible-spectrum LED lighting. Herein, we demonstrate a new efficient cyan-green-emitting Ce3+-activated CaY2ZrGaAl3O12 garnet phosphor for near-ultraviolet (near-UV) pumped full-visible-spectrum warm-white LEDs. The CaY2ZrGaAl3O12:Ce3+ cyan-green phosphor has a cubic structure with the space group Ia3‾d and lattice parameters of a = b = c = 12.39645(8) Å and V = 1886.08(6) Å3. Ce3+ doping concentration dependent luminescence properties have been studied, and the highest emission intensity is obtained at 1 mol%. The optimal CaY2ZrGaAl3O12:1%Ce3+ sample shows a broad excitation band in the 300–490 nm wavelength range with peak at 409 nm due to the 4f→5d transition of Ce3+ ions. Upon 409 nm excitation, CaY2ZrGaAl3O12:1%Ce3+ produces a wide cyan-green emission band in the 425–750 nm spectral range with a peak at 514 nm and a full width at half-maximum of 110 nm owing to the 5d→4f transition of Ce3+ ions, and the corresponding CIE color coordinates and internal quantum efficiency are determined to be (0.2802, 0.4856) and 56%, respectively. Furthermore, the resulting CaY2ZrGaAl3O12:1%Ce3+ phosphor exhibits good thermal stability, and its emission intensity at 423 K is about 58% of that at 303 K. Finally, a white LED device is fabricated by employing a 395 nm near-UV chip with the phosphor blend of commercial BaMgAl10O17:Eu2+ blue phosphor, as-prepared CaY2ZrGaAl3O12:1%Ce3+ cyan-green phosphor, commercial (Ba,Sr)2SiO4:Eu2+ green phosphor and commercial CaAlSiN3:Eu2+ red phosphor, which exhibits a bright full-spectrum warm-white light with low color correlated temperature of 3334 K and ultrahigh CRI values (Ra = 97, R9 = 95.3, R12 = 90.1) for 20 mA driving current. This work provides a new perspective in designing luminescent materials for high-color-quality full-visible-spectrum LED lighting.

Efficient tunable photoluminescence of Dy3+/Eu3+ co-doped OFSZBS glasses for warm white LEDs

A series of oxyfluoride strontium zinc borosilicate (OFSZBS) glasses co-doped with Dy3+/Eu3+ ions was prepared via melt quench method. The structural properties were examined using XRD and scanning electron microscope (SEM) with energy dispersive X-ray analysis (EDX) on DE2.0 and undoped OFSZBS glasses, respectively. UV–Vis absorption spectroscopy was used to evaluate the direct & indirect energy band gaps. At different excitations (348, 362, 385 and 393 nm), the photoluminescence (PL) spectra were observed with tuned light. Warm white light was generated through the Dy3+ (4F9/2→6H15/2, 6H13/2) and Eu3+ (5D0→7F2) transitions. Dexter Reisfield approximation applied to PL data revealed a dipole-dipole (d-d) mechanism accountable for the energy transfer (non-radiative) between sensitizer (Dy3+) and activator (Eu3+) ions. The energy transfer efficiency in the co-doped glass samples was found between 8% to 50%, depending on the doping. The Inokuti-Hirayama (I-H) fitting of PL decay profiles also confirm the energy transfer mechanism. The CIE chromaticity color coordinates observed for OFSZBSDE2.0 glass also confirm the color tunability. The above findings reveal the applications of as-prepared Dy3+/Eu3+ co-doped OFSZBS glasses excited using n-UV light for warm white LEDs and tuned devices.

Novel Red Phosphor of Gd3+, Sm3+ co-Activated AgxGd((2-x)/3)-0.3-ySmyEu3+0.30☐(1-2x-2y)/3WO4 Scheelites for LED Lighting.

Gd3+ and Sm3+ co-activation, the effect of cation substitutions and the creation of cation vacancies in the scheelite-type framework are investigated as factors influencing luminescence properties. AgxGd((2-x)/3)-0.3-ySmyEu3+0.3☐(1-2x)/3WO4 (x = 0.50, 0.286, 0.20; y = 0.01, 0.02, 0.03, 0.3) scheelite-type phases (AxGSyE) have been synthesized by a solid-state method. A powder X-ray diffraction study of AxGSyE (x = 0.286, 0.2; y = 0.01, 0.02, 0.03) shows that the crystal structures have an incommensurately modulated character similar to other cation-deficient scheelite-related phases. Luminescence properties have been evaluated under near-ultraviolet (n-UV) light. The photoluminescence excitation spectra of AxGSyE demonstrate the strongest absorption at 395 nm, which matches well with commercially available UV-emitting GaN-based LED chips. Gd3+ and Sm3+ co-activation leads to a notable decreasing intensity of the charge transfer band in comparison with Gd3+ single-doped phases. The main absorption is the 7F0 → 5L6 transition of Eu3+ at 395 nm and the 6H5/2 → 4F7/2 transition of Sm3+ at 405 nm. The photoluminescence emission spectra of all the samples indicate intense red emission due to the 5D0 → 7F2 transition of Eu3+. The intensity of the 5D0 → 7F2 emission increases from ~2 times (x = 0.2, y = 0.01 and x = 0.286, y = 0.02) to ~4 times (x = 0.5, y = 0.01) in the Gd3+ and Sm3+ co-doped samples. The integral emission intensity of Ag0.20Gd0.29Sm0.01Eu0.30WO4 in the red visible spectral range (the 5D0 → 7F2 transition) is higher by ~20% than that of the commercially used red phosphor of Gd2O2S:Eu3+. A thermal quenching study of the luminescence of the Eu3+ emission reveals the influence of the structure of compounds and the Sm3+ concentration on the temperature dependence and behavior of the synthesized crystals. Ag0.286Gd0.252Sm0.02Eu0.30WO4 and Ag0.20Gd0.29Sm0.01Eu0.30WO4, with the incommensurately modulated (3 + 1)D monoclinic structure, are very attractive as near-UV converting phosphors applied as red-emitting phosphors for LEDs.

Scintillation properties of Pr-doped CaWO4 single crystals synthesized by the floating zone method

Pr-doped CaWO4 single crystals with dopant concentrations of 0.05–1% were synthesized by the floating zone method, and the photoluminescence and scintillation properties were evaluated. Emissions due to the 4f–4f transitions of Pr3+ were observed in visible–near-infrared ranges under visible light and X-ray irradiation. The X-ray-induced scintillation decay times were typical values of the transitions of Pr3+ when monitored at 380–900 nm. The afterglow levels when 20 ms passed after X-ray irradiation were calculated to be 573–730 ppm and increased as the dopant concentrations increased. In the integration-type scintillation detector property, 0.05, 0.1, and 0.5% Pr-doped samples showed good linearity between X-ray exposure dose rate and scintillation signals from 0.05 to 5 Gy/h.

Luminescence and temperature‐sensing properties of Y4GeO8:Bi3+,Eu3+ phosphor

AbstractIn this paper, Y4GeO8:Bi3+,Eu3+ phosphor with dual emission centers was elaborated via conventional solid‐state reaction technology. Thorough research on the structure, morphology, and luminous properties of Y4GeO8:Bi3+,Eu3+ phosphor, the potential applications in optical thermometry were investigated by means of fluorescence intensity ratio and thermochromic techniques. Under 290 and 347 nm excitation, Y4GeO8:Bi3+,Eu3+ phosphor presents broadband emission from 3P1 → 1S0 transition of Bi3+ ions and characteristic emission peaks from 4f–4f transition of Eu3+ ions. Outstanding temperature‐sensing capabilities are acquired from Y4GeO8:Bi3+,Eu3+ phosphor. The maximum relative sensitivity (Sr) can attain 1.51% K−1 (λex = 290 nm). With temperature raising (303–513 K), the emitted color of Y4GeO8:Bi3+,Eu3+ phosphor (λex = 290 nm) shifts from faint yellow to red with a high chromaticity shift (0.180), which can be distinguished by the unaided eye clearly. Our results indicate that Y4GeO8:Bi3+,Eu3+ phosphor has potential applications in optical temperature measurement and high‐temperature safety marker.

Er-Doped Mg4Ta2O9 Single-Crystal Scintillators Emitting Near-Infrared Photons for High-Dose Field Monitoring

Mg4Ta2O9 single crystals doped with 0.01, 0.1, and 1% Er were grown using the floating zone method, and their photoluminescence and scintillation properties were studied. X-ray diffraction analysis confirmed that all samples had a hexagonal structure of Mg4Ta2O9. The samples showed that the emission peak at 1550 nm was due to 4f−4f transitions of Er3+ ions, with quantum yields of 32.9, 46.6, and 18.0% for 0.01, 0.1, and 1% doping concentrations, respectively. All samples showed scintillation with a broad emission band at 350 nm due to charge transfer from Ta5+ to O2− ions and emission peak at 1550 nm due to 4f−4f transition of Er3+ ions. The dose rate response functions showed that the detection limit for all samples was 0.06 Gy/h for scintillation detector applications.

Intrinsic- and Rare Earth Ion-Activated Luminescence in NbAlO4 with Wide Structure Channels.

Compounds with ordered and interconnected channels have versatile multifunctional applications in technological fields. In this work, we report the intrinsic- and Eu3+-activated luminescence in NbAlO4 with a wide channel structure. NbAlO4 is an n-type semiconductor with an indirect allowed transition and a band-gap energy of 3.26 eV. The conduction band and valence band are composed of Nb 3d and O 2p states, respectively. Unlike the common niobate oxide Nb2O5, NbAlO4 exhibits efficient self-activated luminescence with good thermal stability even at room temperature. The AlO4 tetrahedron effectively blocks the transfer/dispersion of excitation energy between NbO6 chains in NbAlO4, allowing for effective self-activated luminescence from NbO6 activation centers. Moreover, Eu3+-doped NbAlO4 displayed a bright red luminescence of 5D0 → 7F2 transition at 610 nm. The site-selective excitation and luminescence of Eu3+ ions in a spectroscopic probe were utilized to investigate the doping mechanism. It is evidenced that Eu3+ is doped in the structure channel in NbAlO4 lattices, not in the normal cation sites of Nb5+ or Al3+. The experimental findings are valuable in developing new luminescent materials and improving the understanding of the material's channel structure.

On the photoluminescence of the solid solution LiBaLa1-xPrxWO6 (x = 0.0–1.0)

A set of compositions belonging to the solid solution LiBaLa1-xPrxWO6 (x = 0–1) were prepared by conventional solid state synthesis. Optical spectroscopy on single phase samples revealed that this solid solution delivers the most efficient member at a Pr3+ concentration of about 7%, which is rather high for a Pr3+ activated material. The decay time of the 3P0 → 3F2 transition is at 2,1 μs at 3 K, which can be considered as the radiative decay time due to the low temperature. From temperature dependent spectroscopy a thermal quenching temperature (T1/2) of 230 K could be derived. Due to the high density of about 7.22 g/cm3 also the luminescence upon 50 kV x-ray excitation was investigated. It turned out these materials show interesting luminescent behaviour upon x-ray excitation, with the resulting emission spectra being strongly dependent on the Pr3+ concentration.

Blue-yellow emissive LaAlO<sub>3</sub>:Dy<sup>3+</sup> phosphor for high bright white light-emitting diodes

LaAlO3:Dy3+ (LAO:Dy3+) with blue-yellow emission for brilliant white light of light-emitting diodes (LEDs) was prepared using gel-combustion process. The chemical content of the created material was confirmed using energy dispersive X-ray analysis (EDX). The transmission electron microscopy was used to examine the phosphor crystal size and morphology. The luminescence analysis showed that LAO:Dy3+ phosphors exhibited peaks at 482 nm (blue) and 574 nm (yellow), attributed to the transitions 4F 9/2à6H 15/2 and 4F 9/2à6H 13/2, respectively. The investigating of correlated color temperature (CCT) and Commission International de L'Eclairage (CIE) described that the phosphor LAO:Dy3+ helped to attained good CCT coordination and bright cool-white emission under ultraviolet (UV) stimulation. However, when using in white LED fabrication, the concentration of LAO:Dy3+ should be modified to fulfill the need from manufactures. According to results from this work, the white light luminescence intensity and color rendering performance may be reduced if the LAO:Dy3+ is high (10%) because of too much scattering. On the other hand, such scattering improvements offered by LAO:Dy3+ phosphor is beneficial to reduce the color deviance for better color uniformity of light.

Orbital Hybridization and Hypersensitivity of Eu3+ in YXO4 (X=P, As, V)

A comparative study of Eu3+ ion luminescence in YXO4 (X=P, As, V) with the tetragonal zircon structure is conducted in relation to the intensity of the hypersensitivity 5D0 → 7F2 transition. Both the asymmetry ratio, and the Judd-Ofelt Ω2 intensity parameter increases in the order YPO4 < YAsO4 < YVO4. This correlation is interpreted qualitatively in terms of the covalency and polarizability of (XO4)3−, which increases in the order (PO4)3− < (AsO4)3− < (VO4)3−. The trend is supported by the results of electronic band structure calculations of the three compounds which establish the strength of hybridization between the X cation and the oxygen 2p states. The electronic structure of YAsO4 is calculated to probe the covalence of As–O bonding. The increasing oscillator strength of the Eu3+5D0 → 7F2 transition in going from YPO4 to YAsO4 to YVO4 is consistent with the expectation of ligand dipolar polarization model for hypersensitivity which states that the oscillator strength of the 5D0 → 7F2 transition is proportional to the square of the ligand dipolar polarizability. The connection between the mechanism of hypersensitivity and second harmonic generation (SHG) is presented.

Combustion synthesized novel SrAlBO4:Eu3+ phosphor: Structural, luminescence, and Judd-Ofelt analysis

A series of new phosphor SrAlBO4 doped by Eu³+ was synthesized by using very known Combustion method. The structural and optical properties explored using X-ray diffraction (XRD). The XRD pattern was matched well with the standard PDF card no. 1542236.The obtained phosphor had orthorhombic structure with space group Pccn (56). The image of Scanning electron microscope shows the external morphology of SrAlBO4 phosphor material, which revails the irregular morphology and the material showed the non uniform structure with agglomerates' size was size ranging in several micrometers. The confirmation of present element and their percentage also shown in the EDX image. The luminescence properties of rare earth activated SrAlBO4 phosphor were determined by measurement of excitation and emission spectra. The PL emission spectra of Eu3+ doped SrAlBO4 phosphor show characteristics bands at 590 nm & 614 nm which corresponds due to 5D0 →7F1 and 5D0 →7F2 transition of Eu3+ ions upon 395 nm excitation. The effect of different concentration of Eu3+ on luminescence emission intensity of SrAlBO4 phosphor was also studied. Further, concentration quenching is explained using Blasse's equation and Dexter's theory. Also, Judd-Ofelt analysis was performed on photoluminescence emission spectra. On investigation synthesized rare earth activated SrAlBO4 phosphor can be suitable for all lighting application devices.

TSL, OSL and scintillation properties of Tb-doped barium fluoride translucent ceramics

We report on the fabrication of Tb-doped barium fluoride translucent ceramics, and their scintillation and dosimetric characteristics. The Tb-doped barium fluoride ceramics were fabricated by spark plasma sintering. Scintillation derived from the 4f→4f transitions of Tb3+ under X-rays was observed from the Tb-doped barium fluoride ceramics. Their decay times under X-rays were about 10 ms. Further, thermally-stimulated luminescence originating from the transitions was detected, and their dose responses were observed in the range of 0.1–100 mGy. Moreover, the Tb-doped barium fluoride ceramics exhibited optically-stimulated luminescence (OSL), and three exponential decay components were detected in the OSL decay curves.

Red luminescence from La2O3:Eu3+ nanophosphor prepared by Sol-Gel method

Pure and Eu3+ doped La2O3 nanophosphor was synthesized by sol gel process. PL spectra of undoped La2O3 samples shows broad emission peaks between 400 and 600 nm and Eu3+ doped samples show PL emission peaks at 510, 515, 531, 537, 553, 578, 585, 594, 612 and 624 nm. These peaks are attributed to 5D1 → 7F2, 5D1 → 7F2, 5D0 → 7F0, 5D0 → 7F1,5D0 → 7F2 transitions of Eu3 + ions. The electronic dipole transition corresponding to5D0 → 7F2 (624, 612 nm) is stronger than the magnetic dipole transition of 5D0 → 7F1 (585, 594 nm) of Eu3+ ions. Luminescence behavior of Eu3+ in La2O3 is analyzed by Judd–Ofelt intensity parameters.

Observation of Narrow Optical Homogeneous Linewidth and Long Nuclear Spin Lifetimes in a Prototypical [Eu(trensal)] Complex

Coherent light–matter interfaces are key elements for many quantum information processing architectures. Rare-earth ion (REI)-containing systems featuring narrow inter-configurational f–f transitions are suitable for creating such interfaces. Recently, narrow homogeneous linewidths (Γh) and long nuclear spin lifetimes (T1spin) associated with two Eu3+ complexes featuring the 5D0 → 7F0 f–f transition have been reported, elucidating that REI-molecule-based coherent light–matter interfaces can be obtained. In this study, we report a homogeneous linewidth of 2.8 MHz at 4.2 K, corresponding to an optical coherence lifetime (T2opt) of 114 ns (0.11 μs), associated with the 5D0 → 7F0 transition of the prototypical charge neutral Eu3+ complex─[Eu(trensal)]. Moreover, we have observed long nuclear spin lifetimes (T1spin) up to 460 ± 80 s at 4.2 K for the complex and efficient optical pumping of hyperfine levels of the 5D0 ground state. The results presented in this study indicate that narrow homogeneous linewidths and long nuclear spin lifetimes could be a generic property of molecular Eu3+ complexes featuring the 5D0 → 7F0 transition.