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The luminescence properties of ceramic phosphors based on two spinel hosts MgAl2O4 and ZnAl2O4 doped with manganese ions have been studied. It has been found that the spectral properties of these phosphors can be strongly varied by changing synthesis conditions. Both types of doped ceramic spinel can serve as efficient Mn2+ green-emitting phosphors having peak emissions at 525 and 510 nm, respectively. Mn-doped MgAl2O4 spinel can also be prepared as an efficient Mn4+ red-emitting phosphor having peak emission at ~651 nm by using specific temperatures of heat treatment in air. It has also been shown that the conversion of Mn2+ to Mn4+ and viсe versa, as well as the coexistence of Mn2+ green and Mn4+ red emissions, can be accomplished by properly chosen annealing conditions of the same initially synthesized MgAl2O4:Mn sample. Manganese doped MgAl2O4 spinel with an optimal intensity ratio of green and red emissions can be a promising single-phase bicolor phosphor suitable for the development of warm white phosphor-converted LED lamps. On the other hand, it has been determined that perfectly normal ZnAl2O4 spinel cannot be doped with Mn4+ ions in contrast to partially inverse MgAl2O4 spinel. However, ZnAl2O4 samples unintentionally doped with impurity Cr3+ ions show emission spectra in the far-red region with well pronounced R, N and vibronic lines of Cr3+ luminescence due to the perfect normal spinel structure of synthesized ZnAl2O4 ceramics. Also, by partially substituting Al3+ cations for Mg2+ in ZnAl2O4 there is an opportunity to obtain Mn4+ doped or Mn4+/Cr3+ codoped far-red emitting phosphors which can be suitable for indoor plant growth lighting sources.

A method to synthesize spinel (MgAl2O4)–based compounds doped with magnesium ions was developed, which makes it possible to create red-emitting phosphors (band peak at 651 nm) or green-emitting phosphors (band peak at 525 nm) due to the luminescence of Mn4+ or Mn2+, respectively, and also phosphors that have both (red and green) emission bands. Both types of luminescence exhibit quite high thermal stability; particularly, the green luminescence does. Namely, the temperature at which the luminescence intensity halves in comparison with the maximum intensity is T0.5 = 448 and 737 K for the red (Mn4+) and green (Mn2+) luminescence, respectively. On the other hand, for the phosphors that have both emission bands, the temperature dependences of the intensities of the red and green luminescence more closely resemble each other because of the energy transfer from Mn4+ ions to Mn2+ ions. Both emission bands are efficiently excited in the blue spectral region, which enables the use of the conventional three-color RGB (red–green–blue) method to create LED white-light sources based on a combination of a blue light-emitting diode and a phosphor containing manganese ions with an optimally chosen ratio between the intensities of the green and red emission bands.

Spectroscopic properties and energy transfer mechanisms for isostructural fluoride K2YF5 and K2GdF5 crystals singly and doubly doped with different concentrations of Tb3+ and Sm3+ ions have been investigated under excitation in the deep ultraviolet (DUV) and vacuum UV (VUV) spectral regions. In these hosts luminescence of Sm3+ ions is enhanced under DUV excitation by doping with Tb3+ ions, namely, the Sm3+ excitation spectra show additional intense excitation in the region of Tb3+ spin-allowed 4f – 5d transitions at 200–220 nm due to energy transfer from Tb3+ to Sm3+. The decay curves of Tb3+ ion luminescence have been measured at room temperature for the series of samples containing different concentration of Sm3+ and have been fitted by the Inokuti-Hirayama model. The results have revealed that the dipole-dipole interaction is the dominant interaction mechanism in the energy transfer process from Tb3+ to Sm3+ ions. The probability (WET) and the efficiency (EET) of energy transfer from Tb3+ to Sm3+ increase depending on the Sm3+ concentration in these crystals.

At present, searching for new efficient red light-emitting phosphors remains extremely relevant for obtaining warm white light from phosphor-converted white LEDs (pc-WLEDs). Appropriate phosphors should have significant absorption in the blue spectral range and emit in the red range of 620 ÷ 650 nm. Mn 4+ -doped luminescent materials with narrow-band emission due to the Mn 4+ d-d electronic transition have been subjected to intensive studies in the last years as promising red-emitting phosphors efficiently excited with blue LEDs.

Samples of magnesium aluminum spinel ceramics doped with manganese ions were prepared by a high-temperature solid-state reaction method, their potential as red-emitting phosphors was analyzed using a time-resolved luminescence spectroscopy technique, from room temperature to 10 K. It was found that in the red spectral range, the luminescence spectra of manganese ions in the MgAl2O4 spinel showed a narrow band peaking at 651 nm due to the emission of Mn4+ and a broader emission band in the region of 675 &divide, 720 nm, the ratio of intensities for these bands depends on the synthesis conditions. By applying a special multi-step annealing procedure, the MgAl2O4:Mn4+ phosphor containing only tetravalent manganese ions, Mn4+, was synthesized. Broad-band far-red emission observed from MgAl2O4:Mn and Mg1.25Al1.75O3.75F0.25:Mn phosphors, prepared by a conventional method of a solid-state reaction, was interpreted as coming from Mn3+ ions.

K2GdF5 single crystals doped with 5.0 at.% of Nd3+ ions (K2GdF5:Nd3+) have been synthesized by the hydrothermal technique. The identification and control of the phase purity of synthesized crystals were performed using powder X-ray diffraction analysis. The spectroscopic characteristics of Nd3+ ions in K2GdF5 were analyzed through the absorption and luminescence spectra as well as decay curves. Upconversion luminescence spectra of K2GdF5:Nd3+ in the visible region were recorded under excitation by laser radiation with a wavelength of 785 nm. The nature of the Nd3+- ligand bonding and Judd-Ofelt intensity parameters were estimated using the absorption spectrum. The Ω4/Ω6 ratio was used to predict the structure of the emission spectrum of the K2GdF5:Nd3+ crystal. The application capability of the 4F3/2 → 4I9/2 emission band (864 nm) for laser action in K2GdF5:Nd3+ is proposed based on the radiative parameters such as the experimental branching ratio (βexp), integrated emission cross-section (ΣJJ’) and stimulated emission cross-sections (σλp). The nonradiative energy transfer process between Nd3+ ions in K2GdF5:Nd3+ is also discussed in detail using the Inokuti-Hirayama and Yokota-Tamimoto models.

The work is dedicated to the growth and investigation of the luminescent and scintillation properties of single crystalline films (SCFs) of Ca2−xR1+xMg1+xSc1−xSi3O12:Ce (R = Y, Lu) mixed garnets with x = 0–0.25, grown using the liquid phase epitaxy method onto Y3Al5O12 substrates from PbO-B2O3 based flux. The absorption, luminescent and scintillation properties of Ca2−xY1+x Mg1+xSc1−xSi3O12:Ce and Ca2−xLu1+xMg1+xSc1−xSi3O12:Ce SCFs with x = 0 and 0.25 were investigated and compared with the reference YAG:Ce and LuAG:Ce SCFs. Using the Ca2+, Mg2+ and Si4+ alloying, the Ce3+ emission spectra in Ca2−xR1+xMg1+xSc1−xSi3O12:Ce (R = Y, Lu; x = 0–0.25) SCFs can be notably extended in the red range in comparison with YAG:Ce and LuAG:Ce SCFs due to the increase of crystal field strength and Ce3+ multicenter creation in the dodecahedral positions of the lattices of these mixed garnet compounds. Due to the formation of Ce4+ ions, the as-grown Ca2−x R1+xMg1+xSc1−xSi3O12:Ce (R = Y, Lu) SCFs at x = 0 and 0.25 show relatively low light yield. However, after annealing in reducing atmosphere (95% N2 + 5% H2) at T > 1000 °C, a recharging Ce4+→Ce3+ takes place. After that, these SCFs possess the light yield about of 30% and 31% in comparison with the reference YAG:Ce and LuAG:Ce SCFs, respectively, and a fast scintillation response with the decay times in the ns range under α–particles excitation by 239Pu (5.15 MeV) source.

Microsize powder of Mn-doped potassium hexaflourosilicate (PFS, K2SiF6) phosphor has been synthesized using the microwave-hydrothermal (MWHT) method, a new approach for obtaining this material. Special attention has been paid to the identification of the valence states for Mn doping ions using EPR and XANES techniques. Although photoluminescence results reveal luminescence properties typical for Mn4+ ions, the XANES spectra show the presence of Mn ions in various valence states (+2 to +4). The analysis of the temperature dependence for the Mn4+ integrated luminescence intensity and luminescence decay time has shown that the MWHT synthesis provides better performance of the PFS phosphor compared to that of commercially available PFS phosphors in respect of higher thermal stability because of improved crystallinity and lower concentration of defects. It has been revealed that above 500 K, Mn4+ luminescence decay becomes non-exponential due to the energy transfer to defect quenching centers. Repeated thermal treatment of microparticles up to 700 K results in considerably changed thermal quenching parameters due to the transformation of K2SiF6 into the K3SiF7 phase. The latter compound doped with Mn4+ shows spectral properties very similar to those of K2SiF6:Mn4+ but demonstrates better thermal stability and shorter decay time of Mn4+ luminescence at normal conditions which can make the red-emitting K3SiF7:Mn4+ phosphor a promising candidate for application in wLEDs.

K2YF5 single crystals doped with Sm3+ ions (K2YF5:Sm3+) have been synthesized by the hydrothermal method at a temperature of 750 K and pressure of 100 MPa. The absorption and luminescence spectra of the K2YF5:Sm3+ samples have been measured at room temperature. Sm3+ luminescence quenching occurs in K2YF5:Sm3+ single crystals at Sm3+ concentrations higher than 2.0 at%. This phenomenon relates to the energy transfer process through cross-relaxation between Sm3+ ions. Dynamics of the energy transfer process has been analyzed by the Inokuti-Hirayama model and the dipole–quadrupole interaction has been found to be a dominant mechanism in this process. Under excitation by 785 nm laser radiation, K2YF5:Sm3+ single crystals show the upconversion luminescence bands in the visible spectral region as well as some sharp and strong emission lines in the near infrared region. The excited state absorption has been defined to be the main mechanism for upconversion luminescence in K2YF5:Sm3+ crystals.

The results on crystallization and investigation of the luminescent properties of prospective ceramic phosphors based on the Ce3+ doped {Ca2R}[ScB](CSi2)O12 (R = Lu, Y, Gd; B = Sc, Ga, C = Ga, Al) silicate garnets are presented for the first time in this work. We have observed the variations of the spectroscopic properties of Ce3+ ions in the mentioned Ca2+-Si4+ garnet hosts depending on the cation content at the dodecahedral {}, octahedral [] and tetrahedral () sites of garnet lattice. These results can be useful for the development of new generation of ceramic phosphor converters for white LEDs based on the garnet compounds under study.

Optical materials 107, 110049 (2020). doi:10.1016/j.optmat.2020.110049, K$_2$Y$_{0.99}$Ln$_{0.01}$F$_5$ (Ln = Ce, Eu and Sm) single crystals have been synthesized by the hydrothermal technology. The optical properties of Ce$^{3+}$ and Eu$^{3+}$ ions doped into K$_2$YF$_5$ matrix have been studied under excitation in the deep UV and vacuum UV (VUV) region. The obtained data from excitation spectra and Dorenbos models have been used to predict the energies of the f-d and charge transfer transitions as well as the energy levels location of divalent (Ln$^{2+}$) and trivalent (Ln$^{3+}$) lanthanide ions within the band gap of K$_2$YF$_5$. In particular, the f-d and charge-transfer transitions of Sm$^{3+}$ in the luminescence excitation spectrum of K$_2$YF$_5$:Sm$^{3+}$ have been identified. The host referred binding energy (HRBE) and vacuum referred binding energy (VRBE) schemes have been constructed for Ln$^{2+}$ and Ln$^{3+}$ ions doped K$_2$YF$_5$ crystal which were used for the analysis of possible applications of K$_2$YF$_5$ doped with Ln$^{3+}$ ions as thermoluminescence materials., Published by Elsevier Science, Amsterdam [u.a.]

The Raman, absorption, luminescence spectra and lifetimes curves of Sm 3+ -doped K 2 GdF 5 were measured. Based on the Judd-Ofelt analysis, the values of radiative transition probabilities, branching ratios, integrated emission cross-sections and radiative lifetimes of excited states of Sm 3+ in K 2 GdF 5 crystal were calculated. The migration of excitation energy between the Gd 3+ ions and the trapping processes of Gd 3+ excitation energy by Sm 3+ and Tb 3+ ions in K 2 GdF 5 crystal are reported. The role of the overlapping between the broad, allowed absorption bands of the RE 3+ ions and the narrow absorption lines 6 I J and 6 P J of Gd 3+ ions on the trapping rates of the RE 3+ was discussed. The energy transfer between the Sm 3+ ions was studied by the decay measurement, which has been fitted by Inokuti-Hirayama energy transfer model and revealed that electric dipole–quadrupole interaction is responsible for the energy transfer process in Sm 3+ ions doped K 2 GdF 5 crystal.

In the present paper a complementary investigation about the mechanisms behind the thermoluminescence of LaAlO 3 :Ce,Dy crystals have been performed. The aim of this study is to present a model that, by using as guess values the parameters obtained by employing the GOK model, explain the role of Ce 3+ and Dy 3+ in the huge increase of the thermoluminescence signal of undoped LaAlO 3 crystals. In the first section of this paper, the previous recorded TL glow peaks were further analyzed and their corresponding kinetic parameters such as order of kinetics (b), trap depth ( E ) and frequency factor ( s ) were determined; in this approach, the GCD analysis is mainly used to find the individual glow-peaks of a composite TL glow-curve and further to evaluate the sets of trapping parameters of each glow-peak.

K2GdF5:Dy crystals show excellent TL output for fast and thermal neutrons. An additional thermoluminescent peak, as yet unidentified, is revealed in TL of K2GdF5 doped with different dysprosium Dy3+ concentrations, after exposing to 12.1 mSv of gamma radiation. In 2013, Silva et al., have studied the thermoluminescent responses of K2GdF5: Dy3+ exposed to photon and neutron radiation fields. The results presented in this paper show that the introduction of the dysprosium Dy3+ induced the appearing of an additional TL peak at 234 °C (507 K). Particularly, for K2GdF5 crystals doped exactly with 5.0 at.% Dy3+, the TL output reaches its maximum. In the first part of this paper, the glow curves of the pure and doped K2GdF5 after gamma radiation were analyzed and the kinetics parameters (trap depth (E) and frequency factor (s)) were determined by using the Chen's peak shape method. The appearance of the additional peak has been explained and attributed to the energy transfer that occurs from Gd3+ to Dy3+. The mechanisms of the charge transfer have been studied carefully based on the excitation spectra of the Dy3+ doped K2GdF5 crystal at the wavelengths 575 nm and 485 nm, respectively. In the second part of this paper; the thermoluminescence properties of both the pure K2GdF5 and Dy3+ doped K2GdF5 have been investigated using the 3T1R and 4T1R models, respectively.

Tb3+ doped K2YF5 single crystal was synthesized by the hydrothermal technique. Structure of material was analyzed by X-ray diffraction pattern and Raman spectra. The optical properties were studied through absorption, luminescence spectra and decay curves. Absorption spectra were used to calculate the bonding parameter (δ) and Judd-Ofelt intensity parameters (Ω2,4,6). The JO parameters and emission spectra have been used to estimate radiative properties such as transition probability (AR), branching ratios (βcal, βexp), lifetime (τcal) stimulated emission cross-sections (σλp, 10−22 cm2) and optical gain (σλp × τcal, 10−25 cm2 s) for 5D3→7FJ and 5D4→7FJ (J = 0 ÷ 6) transitions. The dominant interaction mechanism and energy transfer parameters between Tb3+ ions have been found by fitting the decay curves of 5D3 level to the Inokuti-Hirayama model. In addition, the quantum cutting process based on energy transfer between Tb3+ ions has also been studied for K2YF5:Tb3+ crystal.

Ceramic samples of LiAl4O6F phosphors doped with 1.0 mol. % manganese ions have been synthesized by high-temperature solid-state reaction technique and investigated as possible red-emitting light converters. It has been found that the emission spectrum of LiAl4O6F:Mn phosphors consists of a narrow band peaked at 661 nm and a broader band peaked in the region of 675 ÷ 720 nm depending on synthesis conditions. The intensity of the latter band increases and the peak of this band shifts to longer wavelengths with increasing the fraction of MgF2 used as a flux material. Besides that, these two emission bands have strongly different decay times, namely τ1 ~ 240 μs and τ2 ~ several ms, respectively. The decay kinetics and time-resolved spectra of these two emission components have been studied in the temperature range of 10 ÷ 290 K under pulsed laser excitation at 262 nm. The observed luminescence properties have been analyzed within a model which considers the presence of manganese ions having different valence states (Mn4+ and Mn2+) in the specific spinel-type crystal structure of the LiAl4O6F host matrix, which provides many possibilities for different local environment near the doping manganese ions.

In this work we simulated the concentration quenching (CQ) of the thermoluminescence glow peaks of K 2 YF 5 single crystals doped with different concentrations of Tb 3+ ions, for samples irradiated with a 137 Cs gamma source. A physical model used in this study, consisting of three trapping states and one kind of recombination center, has been assumed and the set of differential equations have been integrated without additional approximations. The parameters employed in the simulation have been estimated by previous glow curve deconvolution employing the general order kinetic (GOK) model. The model succeeds to predict the behavior of the areas under glow peaks as function of Tb 3+ ions concentrations, confirming that the proposed model provides a good explanation of the concentration quenching phenomena.

Photoluminescence, radioluminescence and thermoluminescence properties of K2YF5 crystals containing different concentrations of samarium and terbium ions have been investigated for the first time. It has been found that the emission peaks observed in ranges from 300 to 550 nm and from 550 to 750 nm can be attributed to the 4f–4f transitions of the Tb3+ ions and the Sm3+ ions, respectively, for both photoluminescence and radioluminescence. The maximum of light output for radioluminescence under beta irradiation has been obtained for K2YF5 crystals doped with 1.0 at% Sm3+ ions and the prospects for using such dosimeters in fiber optic dosimetry have been evaluated. On the other hand, it has been found that the glow curves of doubly doped fluoride crystals are made up of at least four overlapping glow peaks and that K2YF5:1.0 at% Tb3+; 0.5 at% Sm3+ crystals show the most intense thermoluminescence emission. Fil: Marcazzo, Salvador Julian. Universidad Nacional del Centro de la Provincia de Bs.as.. Facultad de Ciencias Exactas. Instituto de Fisica Arroyo Seco; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil; Argentina Fil: Santiago, Martin Alejo. Universidad Nacional del Centro de la Provincia de Bs.as.. Facultad de Ciencias Exactas. Instituto de Fisica Arroyo Seco; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil; Argentina Fil: Makhov, V. N.. Lebedev Physical Institute; Rusia Fil: Tuyen, Vu Phi. Institute of Materials Science; Vietnam Fil: Khaidukov, N. M.. Kurnakov Institute of General and Inorganic Chemistry; Rusia Fil: Caselli, Eduardo Eladio. Universidad Nacional del Centro de la Provincia de Bs.as.. Facultad de Ciencias Exactas. Instituto de Fisica Arroyo Seco; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil; Argentina. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina

Dy3+-doped K2GdF5 single crystals with 10.0 mol% have been prepared by hydrothermal condition. The spectra are analyzed in term of the Judd?Ofelt theory, the intensity parameters (Xk, k = 2, 4, 6) have been evaluated for Dy3+-doped K2GdF5 sample. The electric (Sed), magnetic (Smd) dipole line strength, radiative (A), and total radiative (AT) transition probabilities, lifetime (sR), branching ratios (bR) for the excited levels of Dy3+ doped K2GdF5 crystals were investigated by using the intensity parameters. In addition, the stimulated emission cross-sections (rkp) and integrated emission cross-section (Rif) have been predicted for the transitions from excited level, 4F9/2, to the 6H15/2, 6H13/2 and 6H11/2 levels. The energy transfer occurs from Gd3+ to Dy3+, resulting in the additional intense excitation UV-narrow bands for the luminescence of the Dy3+ ions. Fil: Do, Phan Van. Water Resources University; Vietnam Fil: Tuyen, Vu Phi. Vietnam Academy of Science and Technology. Institute of Materials Science; Vietnam Fil: Quang, Vu Xuan. Duy Tan University; Vietnam Fil: Thanh, Nguyen Trong. Vietnam Academy of Science and Technology. Institute of Materials Science; Vietnam Fil: Thai Ha, Vu Thi. Vietnam Academy of Science and Technology. Institute of Materials Science; Vietnam Fil: Tuyen, Ho Van . Duy Tan University; Vietnam Fil: Khaidukov, Nicholas M.. Kurnakov Institute of General and Inorganic Chemistry; Rusia Fil: Marcazzo, Salvador Julian. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Fí­sica Arroyo Seco; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Tandil; Argentina Fil: Lee, Yong Ill . Changwon National University. Department of Chemistry; Corea del Sur Fil: Huy, Bui The . Changwon National University. Department of Chemistry; Corea del Sur

A novel Y 3 Si 3 O 10 F:Eu 3+ phosphor was synthesized under hydrothermal conditions. Luminescence properties and crystallographic sites for Eu 3+ ions in Y 3 Si 3 O 10 F:Eu 3+ are investigated by site-selective laser-excitation spectroscopy. The three Eu 3+ centers are identified in the 7 F 0 → 5 D 0 excitation spectra. The luminescence due to the 5 D 0 → 7 F J ( J = 1, 2) transitions under excitation at each center exhibits its own spectral features and temporal behavior. The crystal-field splitting of the 7 F 1 and 7 F 2 multiplets and intensity ratio of the 5 D 0 → 7 F 2 to 5 D 0 → 7 F 1 emission depend strongly on the crystallographic sites in Y 3 Si 3 O 10 F. The decay time of the 5 D 0 level is shorter for the site with higher energy. The results are discussed in relation to the site symmetry and the crystal-field strength on Eu 3+ in the Y 3 Si 3 O 10 F lattice.

K2YF5 crystals doped Sm3+ ions were synthesized under hydrothermal condition. The absorption, luminescence spectra, and lifetimes of K2YF5:Sm3+ were measured at room temperature. The results were analyzed using Judd–Ofelt (JO) theory giving the values of three Ω2, Ω4, and Ω6 intensity parameters. Using these JO parameters as well as from the emission, various radiative parameters such as transition probabilities (AR), radiative lifetime (ιR), calculated branching ratios (βR), measured branching ratios (βmes), and stimulated emission cross-sections (σλp) have been calculated for 4G5/2 excited level.

Optically stimulated luminescence (OSL) properties of K2YF5 crystals singly doped with different concentrations of Tb3+ ions and doubly doped with Tb3+ and Ce3+ or Tb3+ and Dy3+ have been investigated for the first time. Radioluminescence spectra and OSL efficiency for stimulation with different wavelengths of light have been analyzed for each compound. Also, dosimetric characteristics of the most efficient composition, namely K2YF5:1 at.% Tb3+, have been studied. Finally, the OSL signal peculiarities for K2YF5:1 at.% Tb3+ have been compared to those of a commercial Al2O3:C dosimeter.

The emission and excitation spectra of Ce(3+) and Pr(3+) doped into the cubic host Cs(2)NaYF(6) have been recorded at room temperature and ∼10 K using synchrotron radiation. The two 5d(1) T(2g) states of Ce(3+) have been located from the excitation spectra, whereas the E(g) state is placed above the host band gap. Decay measurements of the 5d(1) → 4f(1) Ce(3+) emission, and spectra collected using selective excitation, indicate the occupation of more than one type of site by Ce(3+) in this host lattice. By contrast, the location of features in the 4f(1)5d(1) → 4f(2) emission of Pr(3+) is independent of the excitation wavelength. Assignments are presented for some of the 4f(1)5d(1) levels and for the Pr(3+)-F(-) charge transfer band. The 5d emission lifetimes for Ce(3+) and Pr(3+) in the Cs(2)NaYF(6) host are 42 and 29 ± 1 ns, respectively, and are not temperature-dependent.

In this article, the feasibility of using CsTb2F7 crystals as scintillating detectors to build radioluminescent fiberoptic dosimetry (FOD) probes has been investigated for the first time. The radioluminescence (RL) efficiency of this compound has been found to be more than twice as high as that of commercial Al2O3:C detectors under excitation with gamma radiation from a 60Co source. Additionally, the intensity of the RL signal shows no dependence on the accumulated dose. Both RL and photoluminescence spectra are nearly identical, showing emission bands at 490 and 550 nm and a minor band at 600 nm, which are compatible with the characteristic emission of Tb3+. In accordance with these results, stoichiometric terbium fluoride seems to be a promising material for use as an RL sensor for FOD in radiation medicine.

The thermoluminescence (TL) properties of isostructural fluoride K2YF5 and K2GdF5 crystals doped with Tb3+ of different concentrations have been studied in the temperature range from 30 to 500 °C after α, β and X-ray irradiation. Strongly different structures of TL glow curves following α or β irradiation have been found for Tb3+ doped K2YF5 for all studied concentrations of Tb3+ whereas for K2GdF5 crystals the different TL curves after α or β irradiation are detected only for heavily doped samples. On the other hand, all the studied materials show similar TL glow curves after β or X-ray irradiation. It has been discovered that K2YF5 doped with 1 at.% Tb3+ has TL radiation sensitivity to β irradiation of the same order as that of the well known TLD-100 (LiF:Mg,Ti) phosphor and much higher sensitivity to α irradiation. The TL mechanism in K2YF5 and K2GdF5 doped with Tb3+ is discussed by taking into account the TL emission spectra from irradiated samples, which are identical to the emission spectra of the Tb3+ ions in these hosts under photo-excitation, and the kinetics parameters obtained with the method of various heating rates.

In this paper optically stimulated luminescence (OSL) properties of Pr 3 +-doped double potassium yttrium fluoride (K 2 YF 5 ) under green light stimulation at room temperature as a function of the doping concentration are reported. Besides, some characteristics concerning the possible application of this composition as a new OSL dosimeter are presented, namely, the dose-response and fading of the OSL signal. The residual thermoluminescence (TL) response of K 2 YF 5 :Pr 3+ after the OSL experiment has been investigated in order to establish whether the traps responsible for OSL are also involved in the TL process. Spectral analysis of the OSL emission has been carried out to determine the role played by Pr 3+ ions in the radiative relaxation process. Finally, the total OSL output of K 2 YF 5 :Pr 3+ is compared to that of commercial Al 2 O 3 :C.

By employing a model of interactive traps which conforms to experimental findings the glow curve of K 2 YF 5 : Pr 3 + compounds has been analysed. A novel algorithm, which allows the decoupling of the equations describing the carrier traffic among traps, recombination centres and energy bands, is reported. An important conclusion drawn from the results is that it is not always correct to think of each single peak as related only to one trap.

The luminescence properties of Tb3+-doped fluoride crystals under excitation with ionizing irradiation have been studied in order to assess the feasibility of using them as crystal detectors for in vivo radiotherapy dosimetry. In particular, it has been found that the radioluminescence intensity from both CsY2F7 and CsGd2F7 doped with 15 at% Tb3+ is almost six times that from the commercial Al2O3 : C detector. The spectral composition of emitted light has been analysed in order to determine the function of the Tb3+ activator ion during ionizing radiation-induced luminescence. The thermally stimulated luminescence of the crystals has also been investigated.

In this work the optically stimulated luminescence (OSL) properties of K2YF5 crystals doubly doped with Tb3+ and Sm3+ ions have been investigated for the first time. The OSL response of K2YF5 crystals containing different dopant concentrations under optical stimulation with different wavelengths has been analyzed. Dosimetric properties of the most efficient composition, namely, K2YF5:1.0 at% Tb3+;1.0 at% Sm3+, have been studied. Finally, the possible application of this single crystal to OSL dosimetry has been evaluated. Fil: Marcazzo, Salvador Julian. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina Fil: Camargo Jimenez, Luis Antonio. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina Fil: Khaidukov, N.M.. Kurnakov Institute of General and Inorganic Chemistry; Rusia Fil: Santiago, Martin Alejo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Tandil. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires. - Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas. Centro de Investigaciones en Física e Ingeniería del Centro de la Provincia de Buenos Aires; Argentina

Excitation of the 4f3 ion Nd3+ in hexafluoroelpasolite lattices by synchrotron radiation of wavelength approximately 185 nm leads to fast 4f(2)5d --> 4f3 emission below 52,630 cm(-1) and slower 4f3 --> 4f3 emission from the luminescent states (4)F(3/2) gamma8u (11 524 cm(-1)) and 2G2(9/2) gamma8u (approximately 47,500 cm(-1)). The near-infrared emission is well-resolved, and a clear interpretation of the 4I(9/2) crystal field levels and of the one-phonon vibronic sideband is given. The excitation spectrum of the 2G2(9/2) emission enables clarification of the structure of the 4f(2)5d configuration (which extends from approximately 52,000 to 128,000 cm(-1)). Detailed energy level and intensity calculations have been performed, which provide simulations of the d-f emission and the f-d excitation spectra in good agreement with experiment. It is interesting that although the 4f3 2G2(9/2) gamma8u --> 4f3 4I(J) transitions are very weak in intensity compared with transitions terminating upon higher multiplet terms, most of the 4f(2)5d (3H) 4I(9/2) gamma8g --> 4f3 emission intensity resides in the transitions to 4I(J).

Thermoluminescence dosimetric characteristics of K2YF5 crystals doped with Pr3+ are reported for the first time. The efficiency of the 0.5 at.% Pr3+ doped K2YF5 crystal has been found to be maximum for this concentration series and three times higher than that of the commercial dosimeter TLD-700. The thermoluminescence glow curve of this novel phosphor has no appreciable fading. Furthermore, it bears linear dose response and good stability after reutilization. According to these results, K2YF5:Pr3+ appears to be a promising base for developing effective phosphors for TL solid state dosimetry. In this context, the spectral composition of the TL emission is also mentioned along with the values obtained by glow curve deconvolution for the trap parameters characterising electron trap centres involved in thermoluminescence.

Luminescence properties of Eu 3+ ions (0.1,1.0 and 6.0 mol%) in K 2 YF 5 crystals are investigated by the site-selective laser-excitation spectroscopy. The excitation spectrum of the 5 Do emission exhibits two strong 7 F o → 5 D o excitation lines together with four weaker lines. Six different emission spectra are obtained under the excitation at each excitation line indicating that there existed at least six different sites for Eu 3+ . The relative intensity of the excitation lines is dependent on the Eu 3+ concentrations. The 5 D o emissions of Eu 3+ show two types of decay behavior with lifetimes of 0.5 and 5.0 ms at 15 K. It is suggested that the fast and slow decays correspond to isolated and paired Eu 3+ ions in K 2 YF 5 . The results are discussed in relation with one dimensional chain structure of the K 2 YF 5 lattice.

We present polarized two-photon excitation (TPE) spectra, including Zeeman data, for europium(III) in the elpasolites Cs2NaEuCl6 and Cs2NaYF6:Eu3+. Approximately 80 and 60 levels of unambiguous symmetry have been assigned respectively in each compound up to 32 000 cm-1 with the aid of a one-electron crystal field Hamiltonian. This represents the most complete and extensive data set so far reported for Eu(III) at a cubic site. Comparisons are made between comparable data sets for Eu(III) f6 and Tb(III) f8. Deviations from the predictions of the one-electron crystal field model are discussed in terms of the spin correlation crystal field.

Single crystals of doped with molar concentrations of between 0.1 and 20% have been synthesized by the hydrothermal method, and studied by absorption, excitation and luminescence spectroscopy at temperatures down to 4 K. The observed spectral features were consistently assigned with reference to those of the corresponding europium hexachloroelpasolite. No distortion from octahedral symmetry was evident for the site in the 0.1 mol%-doped crystal, but small splittings of magnetic dipole zero-phonon lines in the spectra of the 20%-doped crystals are observed below 20 K. The vibrational behaviour of has been interpreted, and the energy-level scheme of the ion was deduced from the observed and inferred zero-phonon-line positions in the optical spectra. A parametrized Hamiltonian was fitted to 21 crystal-field levels of in . The fourth- and sixth-degree crystal-field parameters were about 1.6 times larger than for . The temperature shifts of the crystal-field levels were found to be negative, in contrast to the mostly positive shifts previously reported for actinide systems in octahedral symmetry, and were largely determined by the changes in the Slater parameters rather than the crystal-field parameters. A preliminary study has been made of the decay kinetics of the levels. is quenched by a cross-relaxation mechanism, and also by a thermally activated mechanism. The lifetime of does not exhibit a noticeable temperature or concentration dependence.

Optical bleaching of the thermoluminescence (TL) curve of K 2YF 5:Pr 3+ has been observed after optically stimulated luminescence (OSL) readout of pre-irradiated crystals. The traps being responsible for the TL signal are not emptied completely by the optical stimulation. Furthermore, if the illumination time is increased a constant intensity level of the residual TL glow curve is eventually achieved. On the other hand, if the low temperature peak of the glow curve is thermally cleaned, no subsequent OSL is measured. This behavior has been successfully explained by assuming that part of the electrons in the trap being responsible for the low temperature glow peak of K 2YF 5:Pr 3+ recombine with holes via localized transitions during optical stimulation. During TL all trapped electrons recombine via delocalized transitions. Simulations have been carried out in order to demonstrate the feasibility of the model. Fil: Marcazzo, Salvador Julian. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Fisica Arroyo Seco; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Santiago, Martin Alejo. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Fisica Arroyo Seco; Argentina Fil: Khaidukov, N.. Russian Academy Of Sciences; Rusia Fil: Caselli, Eduardo Eladio. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Fisica Arroyo Seco; Argentina

The new Y3Si3O10F:Eu3+ phosphor is hydrothermally synthesized from aqueous mixtures of Y2O3, Eu2O3, SiO2, and HF (autoclave, 250 °C, 120 h).

The radioluminescence (RL) properties of K2YF5 crystals doped with Ce3+, Tb3+ and Dy3+ under ionizing irradiation excitation have been studied for the first time. The main objective of this work has been to assess the feasibility of using these crystals as detectors for fiberoptic radioluminescent dosimetry. In particular, it has been found that the RL intensity from both K2YF5:Tb (10%) and K2TbF5 is comparable to that from a commercial Al2O3:C crystal. Longer wavelength emission from these fluorides makes simple optical filtering technique possible to use in order to avoid the stem effect. Afterglow decay times for these fluorides have been found to be similar to that for Al2O3:C and, in particular, K2TbF5 does not show longer afterglow decay time compared to Al2O3:C. Fil: Molina, Pablo Fernando. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Fisica Arroyo Seco; Argentina Fil: Santiago, Martin Alejo. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Fisica Arroyo Seco; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Marcazzo, Salvador Julian. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Fisica Arroyo Seco; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentina Fil: Spano, F.. Autoridad Regulatoria Nuclear; Argentina Fil: Khaidukov, N.. Russian Academy of Sciences; Rusia Fil: Caselli, Eduardo Eladio. Provincia de Buenos Aires. Gobernación. Comisión de Investigaciones Científicas; Argentina. Universidad Nacional del Centro de la Provincia de Buenos Aires. Facultad de Ciencias Exactas. Instituto de Fisica Arroyo Seco; Argentina

In this work we have investigated the radioluminescence (RL) characteristics of three materials (Mg2SiO4:Tb, CsY2F7:Tb and KMgF3:Sm) in order to determine whether they can be used as real time dosimeters in the the framework the fiberoptic dosimetry (FOD) technique. This technique is based on the use of scintillating materials coupled to the end of an optical fiber, which collects the light emitted by the scintillator during irradiation. Since usually the intensity of the emitted light is proportional to the dose-rate, the technique provides a reliable measuring method, which can be employed in radiotherapy treatments. 17th Biennial Congress of the Argentinean-Bioengineering-Society/6th Clinical Engineering Conference, Oct 14-16, 2009, Rosario, Argentina

Emission spectra at 10 K employing synchrotron radiation have been recorded for the tripositive lanthanide ions, Ln = Sm, Gd, Tb, Ho, and Er situated at octahedral (or nearly octahedral) site symmetry in hexafluoroelpasolite Cs2NaMF6 (M = Y, Sc, or Ga) lattices. Interconfigurational 5d → 4f transitions are only observed for Er3+, and the intensity ratio of 4f105d → 4f11 emission, compared with 4f11 → 4f11 emission, with excitation into 5d levels, is greater for M = Ga than M = Sc. The highest energy intraconfigurational emission is from 4G5/2 (Sm3+), 6P7/2 (Gd3+), 5D3 (Tb3+), 5G4 (Ho3+), and 2F(2)7/2 (Er3+). Detailed energy level assignments have been given for Ln = Sm, Gd, and the remaining spectra are assigned as multiplet–multiplet transitions.

Fe(3+) ions in hexagonal and cubic fluoroelpasolite crystals (A(1)(2)B(I)M(III)F(6)) have been investigated in a combined Electron Paramagnetic Resonance (EPR) and Electron Nuclear Double Resonance (ENDOR) study. A detailed analysis of the ENDOR spectra for the nearest (19)F and (23)Na shells in X (9.5 GHz) and Q band (34 GHz) allowed the complex EPR spectra to be disentangled and to determine the spin Hamiltonian parameters for the various S = 5/2 Fe(3+) centres. W-band (95 GHz) EPR measurements as a function of temperature were performed to provide unambiguous evidence about the absolute signs of the Zero Field Splitting (ZFS) and SuperHyperFine (SHF) parameters for Fe(3+) in Cs(2)NaAlF(6) as already determined from the ENDOR work. It could be concluded that all principal (19)F hyperfine values were positive, in agreement with earlier assignments in the literature for related systems. A comparative analysis of the (19)F SHF data for Fe(3+) at a perfectly octahedral site in the cubic crystal, and at two slightly trigonally distorted environments in the hexagonal crystals, indicates that the metal-to-ligand distance changes upon doping. The obtained set of parameters concerning one defect in various analogous environments can furthermore be used to test different methods of theoretical calculations for ZFS and SHF values.

X-Ray irradiation at room temperature produces several paramagnetic centres in rare-earth activated K2YF5 crystals, whose thermal annealing behaviour can be linked with the occurrence of thermoluminescence (TL) glow peaks. In this paper, continuous wave (CW) and pulsed paramagnetic resonance techniques are used to study the structure of a very stable radiation-induced centre, which may be involved in the TL peak at approximately 390 degrees C reported for Ce- and Tb-activated crystals. From the spectra the centre's g tensor and hyperfine (nuclear quadrupole) tensors for several 19F and 39K neighbouring nuclei are extracted, but no self-hyperfine interaction could be detected. Based on the analysis of the interaction tensors, a model is constructed consisting of an oxygen-related radical (e.g. O(-) or O2(-)) on a substitutional F(-) position in the mirror plane of the YF7 polyhedra. Such a centre most probably corresponds to a trapped-hole state.