Emission lifetimes of europium-doped pyrochlores for phosphor thermometry

Hansel, Rachael A.; Desai, Sanket; Allison, S. W.; Heyes, Andrew; Walker, D. G.

doi:10.1063/1.3275871

Cited by 23 publications

(19 citation statements)

References 13 publications

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“…The low phonon energy of LHO (745 cm −1 ) compared to LZO (785 cm −1 ) is responsible for low A NR value and higher quantum efficiency of LHOE over LZOE. 49 Higher Judd-Ofelt parameter Ω 2 value of the LHOE NPs suggests that the environment around Eu 3+ ions in the LHO lattice is more polarizable and highly covalent compared with that in the LZO lattice. Due to the more polarizable nature of the Eu-O bond in the LHOE NPs, there is more distortion in electronic environment around the Eu 3+ ions at the La 3+ sites of the LHOE NPs compared with that of the LZOE NPs.…”

Section: Corroborate the Different Optical Properties Of Lzoe And Lmentioning

confidence: 95%

“…Phonon energy is one of the most important selection criteria for a luminescence host as it dictates the quanta of nonradiative pathways directly affecting the quantum efficiency of phosphors. The maximum optical phonon frequency ( op ) is inversely proportional to square root of mass of A and B atom according to equation: 49 (1) where m A and m B are the atomic mass of La and Zr/Hf, and g is the interatomic potential. The fact that atomic mass of Hf (178.49) is much larger than that of Zr (91.22) reducing the optical phonon frequency of LHO compared to LZO.…”

Section: Corroborate the Different Optical Properties Of Lzoe And Lmentioning

confidence: 99%

“…26 For example, Hansel et al have explored the variation in luminescence lifetime of Eu 3+ ions in La 2 Zr 2 O 7 and La 2 Hf 2 O 7 hosts as a function of temperature for possible applications in non-contact thermometry. 27 However, the literature pertaining to photoluminescence study in undoped La 2 B 2 O 7 (B = Zr and Hf) and their comparison is completely missing, though there have been reports for Nd 2 Zr 2 O 7 , Gd 2 Zr 2 O 7 , Y 2 Zr 2 O 7 , and Eu 2 Zr 2 O 7 . [28][29][30] Eagleman et al observed blue emission in bulk La 2 Hf 2 O 7 powder induced by oxygen vacancies but could not assign the exact types of oxygen vacancies involved.…”

Section: Introductionmentioning

confidence: 99%

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On comparison of luminescence properties of La₂Zr₂O₇ and La₂Hf₂O₇ nanoparticles

et al. 2019

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Unveiling the underlying mechanisms of properties of functional materials, including the luminescence differences among similar pyrochlores A2B2O7, opens new gateways to select proper hosts for various optoelectronic applications by scientists and engineers. For example, although La2Zr2O7 (LZO) and La2Hf2O7 (LHO) pyrochlores have similar chemical compositional and crystallographic structural features, they demonstrate different luminescence properties both before and after doped with Eu3+ ions. Based on our earlier work, LHO‐based nanophosphors display higher photo‐ and radioluminescence intensity, higher quantum efficiency, and longer excited state lifetime compared to LZO‐based nanophosphors. Moreover, under electronic O2−→Zr4+/Hf4+ transition excitation at 306 nm, undoped LHO nanoparticles (NPs) have only violet blue emission, whereas LZO NPs show violet blue and red emissions. In this study, we have combined experimental and density functional theory (DFT) based theoretical calculation to explain the observed results. First, we calculated the density of state (DOS) based on DFT and studied the energetics of ionized oxygen vacancies in the band gaps of LZO and LHO theoretically, which explain their underlying luminescence difference. For Eu3+‐doped NPs, we performed emission intensity and lifetime calculations and found that the LHOE NPs have higher host to dopant energy transfer efficiency than the LZOE NPs (59.3% vs 24.6%), which accounts for the optical performance superiority of the former over the latter. Moreover, by corroborating our experimental data with the DFT calculations, we suggest that the Eu3+ doping states in LHO present at exact energy position (both in majority and minority spin components) where oxygen defect states are located unlike those in LZO. Lastly, both the NPs show negligible photobleaching highlighting their potential for bioimaging applications. This current report provides a deeper understanding of the advantages of LHO over LZO as an advanced host for phosphors, scintillators, and fluoroimmunoassays.

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Section: Corroborate the Different Optical Properties Of Lzoe And Lmentioning

confidence: 95%

Section: Corroborate the Different Optical Properties Of Lzoe And Lmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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On comparison of luminescence properties of La₂Zr₂O₇ and La₂Hf₂O₇ nanoparticles

et al. 2019

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“…Some of the favorable properties include excellent dielectric properties due to its small number of defect densities, ability to accommodate large concentration of dopant both at A and B sites with a general formula of A 2 B 2 O 7 , wide bandgap, moderate phonon E = 745 cm −1 and high stopping power for X-and γ-rays with Z Hf = 72, and high density of 7.9 g/cm 3 . [19][20][21] We have done extensive work on red-emitting La 2 Hf 2 O 7 :Eu 3+ (LHOE) down-converting nanoparticle (NP) powders for several applications in the areas of phosphors, scintillators, thermographic phosphors, etc. [5,7,21].…”

Section: Introductionmentioning

confidence: 99%

Luminescent PVDF nanocomposite films and fibers encapsulated with La2Hf2O7:Eu3+ nanoparticles

et al. 2020

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Luminescent films and fibers are in high demand in display devices and optoelectronics owing to their higher flexibility and mechanical strength compared to powder samples. Keeping that in mind, we have encapsulated La 2 Hf 2 O 7 :Eu 3+ (LHOE) nanoparticles (NPs) synthesized by a molten salt method into polyvinylidene fluoride (PVDF) films and fibers. The LHOE-PVDF nanocomposite fibers were manufactured using a Forcespinning® technology while the counterpart films were fabricated by a drop-casting technique. Their photophysical properties were analyzed and compared. Specifically, the red emission with optimum lifetime, color coordinates, and branching ratio of the LHOE NPs can be reproduced even when incorporated inside the PVDF films and fibers. Our studies demonstrate that the LHOE-PVDF films have better emission output, excited-state lifetime, quantum yield, and color purity than the fibers. This is attributed to lower defect density and better surface texture of the LHOE-PVDF films compared to the fibers. Based on the Judd-Ofelt analysis, we have also elucidated that the Eu-O bond is more polarizable and has a higher degree of covalency in the LHOE-PVDF films compared to that in the fibers. The trend of the Judd-Ofelt parameters suggested that Eu 3+ has a more asymmetric environment in the films compared to the fibers which impart higher red color purity to the former.

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“…It should be noted that the hafnates of the REEs have important practical application, since they are promising materials for creating new thermal barrier coatings (TBCs) for the components of the hottest parts of gas turbine engines [8,9]; solid electrolytes for high temperature solid oxide fuel cells [10]; neu tron absorbing elements of the systems of control and protection of nuclear reactors [11]; matrices for the immobilization of the high activity nuclear wastes [12]; scintillators [13]; etc. The physicochemical properties of the compounds obtained in many respects depend on the method of their obtaining [10,14].…”

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confidence: 99%

Studying processes of crystallization and cation ordering in Eu2Hf2O7

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Zubavichus

et al. 2015

Russ. J. Inorg. Chem.

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Methods of local X ray anomalous diffraction and X ray absorption spectroscopy based on the interaction of synchrotron radiation with condensed matter have been used to study the processes of forma tion and evolution of the crystal structure in Eu 2 Hf 2 O 7 powders. It has been shown that the isothermal anneal ing of the X ray amorphous mixed hydroxide leads initially to the formation of nanocrystalline powders, which have a defect fluorite structure with a clearly pronounced nonequivalence of the local environment of the Eu 3+ and Hf 4+ cations. An increase in the temperature of heat treatment to ≥1200°C leads to the nucle ation and growth of nanodomains with a superstructural cation ordering of the pyrochlore type inside the coarse crystallites of the defect fluorite and, finally, at T ≥ 1500°C, to the complete phase transition of the flu orite-pyrochlore type in the Eu 2 Hf 2 O 7 system. In the pyrochlore Eu 2 Hf 2 O 7 structure, there was for the first time revealed a simultaneous broadening of the shape of the L 3 absorption edges of both hafnium and europium, which indicates a partial change in the symmetry of the nearest oxygen environment of both cations.

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Emission lifetimes of europium-doped pyrochlores for phosphor thermometry

Cited by 23 publications

References 13 publications

On comparison of luminescence properties of La₂Zr₂O₇ and La₂Hf₂O₇ nanoparticles

On comparison of luminescence properties of La₂Zr₂O₇ and La₂Hf₂O₇ nanoparticles

Luminescent PVDF nanocomposite films and fibers encapsulated with La2Hf2O7:Eu3+ nanoparticles

Studying processes of crystallization and cation ordering in Eu2Hf2O7

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Emission lifetimes of europium-doped pyrochlores for phosphor thermometry

Cited by 23 publications

References 13 publications

On comparison of luminescence properties of La2Zr2O7 and La2Hf2O7 nanoparticles

On comparison of luminescence properties of La2Zr2O7 and La2Hf2O7 nanoparticles

Luminescent PVDF nanocomposite films and fibers encapsulated with La2Hf2O7:Eu3+ nanoparticles

Studying processes of crystallization and cation ordering in Eu2Hf2O7

Contact Info

Product

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On comparison of luminescence properties of La₂Zr₂O₇ and La₂Hf₂O₇ nanoparticles

On comparison of luminescence properties of La₂Zr₂O₇ and La₂Hf₂O₇ nanoparticles