The role of Eu++ aggregation on optical absorption, emission, luminescence time decay, and ITC plots in NaCl:Eu++

Capelletti, R.; Manfredi, M.

doi:10.1002/pssa.2210860138

Cited by 22 publications

(2 citation statements)

References 25 publications

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“…This would surely be wrong, since every center luminesces in a broad band extending over some tens of nanometers, due to the electron-phonon interaction. On the contrary, it is well known that usually, in the presence of a continuous distribution of lifetimes, a single exponential decay is observed and v given by the fit is a weighted average of the actual lifetimes (25). Therefore the actual meaning of the results in Fig.…”

Section: Discussionmentioning

confidence: 92%

Spectroscopical Analysis of Laser‐Excited Eu2+ β″‐Alumina Crystals

Bicchi¹,

Meucci²,

Tonelli³

et al. 1991

J. Electrochem. Soc.

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Optical spectroscopy of Eu 2 § ions in the conduction region of ~"-alumina is carried out following excitation with different wavelengths. The analysis of both the time-resolved spectra and the luminescence lifetimes suggests the occupation of two different manifolds of sites for Eu 2 § ions inside the crystal lattice. The defective nature of the conduction plane of 13"-alumina is reflected by the strongly disordered distribution of the crystal fields.Sodium {3"-alumina is a solid electrolyte with a highly anisotropic structure consisting of spinel-like blocks of AP + and 02-ions alternating with relatively loosely packed layers occupied by Na + and O 2-ions (1). Sodium cations easily diffuse within these loosely packed, nearly empty regions, usually referred to as conduction planes, while they do not migrate across the compact spinel blocks. Therefore the material is a two-dimensional ionic conductor and is essentially an insulator in the third dimension, parallel to the c-axis of the crystal. The characteristics of 13"-alumina are extensively dealt with in Ref.(2). The extraordinary ion transport properties of this material are exploited in the ion exchange processes used to introduce in the conduction regions, besides monovalent cations, a large variety of divalent (3) and trivalent (4, 5) ions.The unique ability of sodium 13"-alumina to exhibit fast ion transport for multivalent cations prompted an immediate interest in the study of the optical properties of its exchanged isomorphs with rare earth and transition metal ions, since they could be used as solid-state laser materials (6). As a matter of fact, laser action, in both pulsed and continuous operations, has already been observed in Nd s+ I3"-alumina crystals (7). More recently, spectroscopic studies of Cu+-doped 13"-alumina have suggested that it is a very promising candidate for solid-state tunable lasers over almost the entire visible spectrum (8). With this aim, Eu 2 § I3"-alumina also could constitute another interesting material, due to the strong broad-band emission resulting from 5d-4f transitions, usually exhibited by the divalent europium ions in aluminum oxides (9).In this paper we report on the spectroscopic properties of the fluorescence of a nearly fully Eu2+-exchanged Na + 13"-alumina crystal we have investigated with the help of different laser excitations. Eu 2 ~ ions are found to occupy a large variety of sites with quite different crystal fields. The results are in general agreement with the model of site occupation of rare earth ions as deduced from x-ray experiments and spectroscopic studies on Eu 3+ and Nd 3+ 13"-aluminas (10, 1I). ExperimentalSodium ~"-alumina crystals are usually grown by a flux evaporation method in which a mixture of Na2CO3, MgO, and A1203 is heated in a Pt crucible in air at 1700-1710~ for 14-21 days (12). The crystals, in form of thin platelets (typical thickness 0.1 ram) with sizes ranging from a few square millimeters to about 1 cm 2, are generally well formed and optically clear. Their composition is given ...

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Section: Discussionmentioning

confidence: 92%

Spectroscopical Analysis of Laser‐Excited Eu2+ β″‐Alumina Crystals

Bicchi¹,

Meucci²,

Tonelli³

et al. 1991

J. Electrochem. Soc.

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“…The EuZ+ concentration was determined by means of the optical absorption measurements according to [8]. The emission and time resolved spectroscopy measurements were performed with a single-photon counting technique as described for example in a previous paper [6].…”

Section: Methodsmentioning

confidence: 99%

Influence of temperature on the aggregation processes of the NaCl:Eu2+ system

Capelletti

Cywiński

Manfredi

et al. 1988

Phys. Stat. Sol. (a)

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Results are given of optical measurements (optical emission and time decay spectra) on NaCl:Eu2+ samples annealed in the temperature range 20 to 130 °C. By annealing the samples, new emission bands are detected, besides the band that is measured for quenched samples. The time decay constants, measured along the emission bands, are rather independent of the emission wavelength and show a value that at LNT is shorter than at RT, as happens for isolated Eu2+ dipoles in quenched samples. This fact seems to suggest that the aggregates responsible for the above mentioned bands are formed chiefly by weakly interacting Eu2+ dipoles.

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Low‐temperature precipitation in NaCl: Eu⁺⁺ monocrystals

Suszynska

Gubański

Opyrchal

1987

Cryst. Res. Technol.

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Tt has bcrn shoum that the macroscopic featurcs of the as grown NaCI crystals containing ~i p t o about 140 111 pprn of Eu++ ions agree well with tlie main cliaracteristics o f tlie Nn,EuCI, phase present in these crystals.Thermal decomposition of the NaCl:Eu++ solid solution leads to the formation of the nwntioned Na,EuCJ, phase at temperatiires not very much higher t,han 279 K. The kinetics of t,his procrss is governed by the pipe diffusion which leads to the growth of the small impurity aggregates already present in quenched samples.

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The role of Eu++ aggregation on optical absorption, emission, luminescence time decay, and ITC plots in NaCl:Eu++

Cited by 22 publications

References 25 publications

Spectroscopical Analysis of Laser‐Excited Eu2+ β″‐Alumina Crystals

Spectroscopical Analysis of Laser‐Excited Eu2+ β″‐Alumina Crystals

Influence of temperature on the aggregation processes of the NaCl:Eu2+ system

Low‐temperature precipitation in NaCl: Eu⁺⁺ monocrystals

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The role of Eu++ aggregation on optical absorption, emission, luminescence time decay, and ITC plots in NaCl:Eu++

Cited by 22 publications

References 25 publications

Spectroscopical Analysis of Laser‐Excited Eu2+ β″‐Alumina Crystals

Spectroscopical Analysis of Laser‐Excited Eu2+ β″‐Alumina Crystals

Influence of temperature on the aggregation processes of the NaCl:Eu2+ system

Low‐temperature precipitation in NaCl: Eu++ monocrystals

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Product

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Low‐temperature precipitation in NaCl: Eu⁺⁺ monocrystals