Measurement of host-to-activator transfer efficiency in nano-crystalline Y2O3:Eu3+ under VUV excitation

Waite, Christopher B.; Mann, Rusty; Diaz, Anthony L.

doi:10.1016/j.jssc.2012.10.023

Cited by 17 publications

(16 citation statements)

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“…In our work on nano-crystalline materials we found that the decrease in efficiency in YBO 3 :Eu 3+ is due primarily to surface losses, with about 40% of e-h pairs being lost to the surface at particle sizes < 100 nm [3]. In nano-Y 2 O 3 :Eu 3+ prepared by a combustion process, the loss of efficiency appears to correlate more with poor bulk crystallinity than with surface losses [4].We are now pursuing a comprehensive study of e-h migration and trapping by doping YBO 3 with elements across the entire lanthanide series. We seek to identify how or if the activator capture cross section is related to the relative energies of host and dopant electronic states.…”

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confidence: 67%

19.2: Distinguished Paper: Characterization of Electron‐Hole Pair Migration and Trapping in Rare Earth Doped YBO₃ under Vacuum Ultraviolet Excitation

Wallace

Diaz

2013

Symp Digest of Tech Papers

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We have measured host-to-activator energy transfer efficiencies in rare-earth doped YBO 3 under vacuum ultraviolet excitation. From these data, relative electron-hole (e-h) pair trapping rate constants can be estimated. Our analysis suggests a correlation between e-h trapping efficiency and the energy of activator electronic states relative to the host conduction band. IntroductionDeveloping a detailed understanding of electron transport processes in solids is important to a wide variety of fields within materials science, including the study of scintillators, two-photon phosphors, dye-sensitized solar cells and transparent conductors. Functioning devices based on these technologies often require the transport of electrons through an oxide insulator. Although a fairly large number of useful materials have been developed for these applications, relatively little is known about the fundamental factors governing these processes. Our research focuses on the electron transport and trapping processes associated with vacuum ultraviolet (VUV) excitation of luminescent materials, such as are found in plasma display panels (PDP) and xenon-based mercuryfree lamps. Our goal is to establish the basic structure/property relationships that govern efficient VUV excitation.Absorption of a VUV photon by a doped luminescent material results in the formation of an electron-hole (e-h) pair in the host. For luminescence to occur, this e-h pair must be trapped by the activator. Thus, a critical factor dictating the overall VUV efficiency of a phosphor will be the efficiency of e-h pair migration and trapping, which we refer to here as the energy transfer efficiency,  t . Over the last several years we have developed spectroscopic methods for evaluating host-to-activator transfer efficiency in doped luminescent materials under vacuum ultraviolet (VUV) excitation. Previously we applied these tools to the study of [3,4]. By evaluating our data using accepted kinetic models [5,6] we are able to characterize e-h migration, capture and surface trapping in these materials. In our study of (Y,Gd)BO 3 :Eu 3+ we quantified the effect of energy migration along the Gd sublattice as the Gd concentration was increased. We observed a three-fold increase in the rate constant of capture in going from 0 -10% Gd, while at 30% Gd the migration and trapping was so efficient that we were unable to quantify it using our methods [2]. In our work on nano-crystalline materials we found that the decrease in efficiency in YBO 3 :Eu 3+ is due primarily to surface losses, with about 40% of e-h pairs being lost to the surface at particle sizes < 100 nm [3]. In nano-Y 2 O 3 :Eu 3+ prepared by a combustion process, the loss of efficiency appears to correlate more with poor bulk crystallinity than with surface losses [4].We are now pursuing a comprehensive study of e-h migration and trapping by doping YBO 3 with elements across the entire lanthanide series. We seek to identify how or if the activator capture cross section is related to the relative energies o...

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confidence: 67%

19.2: Distinguished Paper: Characterization of Electron‐Hole Pair Migration and Trapping in Rare Earth Doped YBO₃ under Vacuum Ultraviolet Excitation

Wallace

Diaz

2013

Symp Digest of Tech Papers

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“…[15][16][17]20 Here, we are interested in comparing transfer efficiency for the two preparative methods, as well as quantifying the diversion of energy at 150 nm in the coprecipitation samples.…”

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confidence: 99%

VUV Optical Properties of Rare Earth Doped YPO₄ Prepared by Different Routes

Way

Wallace

Diaz

2017

ECS J. Solid State Sci. Technol.

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The optical properties of nanocrystalline YPO 4 :Ln 3+ (Ln = Eu, Sm, Tb) prepared via co-precipitation are compared to larger crystallites of YPO 4 :Ln 3+ prepared via traditional solid state reaction. In larger crystals (∼330 nm) a distinct peak is observed at 150 nm in the excitation spectra, the intensity of which decreases markedly in smaller crystals (∼20 nm). Using excitation and reflectance spectroscopy, host-to-activator energy transfer efficiencies were calculated for Y 1-x PO 4 :Ln x 3+ (0.01 ≤ x ≤ 0.10). From the transfer efficiency data, we estimate that trapping by Eu 3+ and Sm 3+ is at least five times more efficient than trapping by Tb 3+ for excitation at the band edge. The fraction of energy lost to the surface or grain boundaries for excitation at 150 nm and 138 nm is also estimated. We propose that in the samples prepared via co-precipitation, an amorphous phase forms at grain boundaries that is responsible for the loss of efficiency under 150 nm excitation. Rare-earth doped YPO 4 has been studied extensively, both for potential technological applications and in more fundamental investigations of electron transport and trapping processes.1-4 Nakazawa reported on the vacuum ultraviolet (VUV) spectroscopy of Ln 3+ doped microcrystalline YPO 4 , 4 and assigned excitations due to host, 4f -5d, and charge transfer transitions for all of the lanthanides (except Pm and Lu). Additional studies of YPO 4 include one by Lai et al. that described a precipitation route to ∼20 nm YPO 4 :Eu 3+ , but only the UV optical properties are discussed.5 Di et al. have compared the VUV optical properties of YPO 4 :Tb 3+ prepared via solid state reaction and co-precipitation. 6 However, unlike in the work presented here, the high calcination temperatures applied to the co-precipitated samples led to materials that were similar in size to solid state samples but with improved morphology. Van Pieterson et al. obtained high-resolution excitation spectra of YPO 4 doped with both light 7 and heavy 8 lanthanides at 6 K. They assigned spectral features and compared the experimentally observed spectra with energy level calculations for the 4f n-1 5d 1 states. Makhov et al. investigated the optical properties of YPO 4 :Nd 3+ under VUV synchrotron radiation over a temperature range of 9-300 K. Their work included the assignment of various hostsensitized excitation mechanisms that will be discussed more later. 9Several groups have also reported on the optical properties of doubledoped YPO 4 .10-12 Much of that work was interpreted in the context of the lanthanide energy level scheme for YPO 4 reported by Bos et al. 13 and Dorenbos and Bos, 14 in which the Ln 2+ and Ln 3+ ground state energies are placed relative to the host valence and conduction bands. Of interest to the current study is the observation that the excitation spectra of some lanthanides (particularly Sm, Eu, Gd and Tm) contain a distinct, intense peak for excitation right at the band edge of YPO 4 (∼150 nm). Since the focus of prior work was on assigning peaks in ...

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“…[1][2][3] When the RE ions such as Eu 3+ , Tb 3+ and Yb 3+ are incorporated into the Y 2 O 3 structures; the emission efficiency was enhanced drastically. The applicability of RE oxides can be tuned based on the physical and chemical characteristics resulting from the 4f electronic shells.…”

Section: Introductionmentioning

confidence: 99%

“…[1][2][3][4][5][6] The phosphor production through the conventional high temperature solid-state reaction technique requires high synthesis temperature, and is associated with grinding or milling procedure. [1][2][3][4][5][6] The phosphor production through the conventional high temperature solid-state reaction technique requires high synthesis temperature, and is associated with grinding or milling procedure.…”

Section: Introductionmentioning

confidence: 99%

“…This process yields micro-sized particles with surface defects and irregular size distribution, which are prejudicial to optical performances. [1][2][3][4][5][6][7][8] Such issues affect the optical efficiency and large-scale production signicantly. [4][5][6][7][8] These methods provide different approaches to adjust the luminescence properties and tailor the homogeneity and size distribution of the obtained particles.…”

Section: Introductionmentioning

confidence: 99%

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Synthesis of strong red emitting Y₂O₃:Eu³⁺phosphor by potential chemical routes: comparative investigations on the structural evolutions, photometric properties and Judd–Ofelt analysis

et al. 2015

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In the present paper, a comparative investigation on the structural and photoluminescence properties of Y 2 O 3 :Eu 3+ phosphor prepared by different wet chemical synthesis routes such as sol-lyophilisation (SL), combustion (CR), hydrothermal (HT) and microwave assisted hydrothermal combustion (MHWC), has been reported for the first time. The MHWC derived phosphor exhibited better photoluminescence than that of the samples obtained with other adopted methods. Such outcomes were due to the increased crystallinity, well defined morphology and improved compositional homogeneity in the MWHC technique. The growth of the prepared phosphors was explained in the light of chemical kinetics.Jorgensen formula and nephelauxetic ratio was used to understand the ligand behavior of Eu-O bond and to estimate the electron phonon coupling in Y 2 O 3 :Eu 3+ phosphor. The spectroscopic behavior of Y 2 O 3 :Eu 3+ phosphor, prepared by different routes, was determined using Judd-Ofelt theory. Thermal stability, purity and efficiency of the emitted colour were checked on the basis of different synthetic approach. An efficient synthesis method for Y 2 O 3 :Eu 3+ phosphor, compatible for industrial appliances, was proposed.

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Measurement of host-to-activator transfer efficiency in nano-crystalline Y2O3:Eu3+ under VUV excitation

Cited by 17 publications

References 25 publications

19.2: Distinguished Paper: Characterization of Electron‐Hole Pair Migration and Trapping in Rare Earth Doped YBO₃ under Vacuum Ultraviolet Excitation

19.2: Distinguished Paper: Characterization of Electron‐Hole Pair Migration and Trapping in Rare Earth Doped YBO₃ under Vacuum Ultraviolet Excitation

VUV Optical Properties of Rare Earth Doped YPO₄ Prepared by Different Routes

Synthesis of strong red emitting Y₂O₃:Eu³⁺phosphor by potential chemical routes: comparative investigations on the structural evolutions, photometric properties and Judd–Ofelt analysis

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Measurement of host-to-activator transfer efficiency in nano-crystalline Y2O3:Eu3+ under VUV excitation

Cited by 17 publications

References 25 publications

19.2: Distinguished Paper: Characterization of Electron‐Hole Pair Migration and Trapping in Rare Earth Doped YBO3 under Vacuum Ultraviolet Excitation

19.2: Distinguished Paper: Characterization of Electron‐Hole Pair Migration and Trapping in Rare Earth Doped YBO3 under Vacuum Ultraviolet Excitation

VUV Optical Properties of Rare Earth Doped YPO4 Prepared by Different Routes

Synthesis of strong red emitting Y2O3:Eu3+phosphor by potential chemical routes: comparative investigations on the structural evolutions, photometric properties and Judd–Ofelt analysis

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19.2: Distinguished Paper: Characterization of Electron‐Hole Pair Migration and Trapping in Rare Earth Doped YBO₃ under Vacuum Ultraviolet Excitation

19.2: Distinguished Paper: Characterization of Electron‐Hole Pair Migration and Trapping in Rare Earth Doped YBO₃ under Vacuum Ultraviolet Excitation

VUV Optical Properties of Rare Earth Doped YPO₄ Prepared by Different Routes

Synthesis of strong red emitting Y₂O₃:Eu³⁺phosphor by potential chemical routes: comparative investigations on the structural evolutions, photometric properties and Judd–Ofelt analysis