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SUMMARY In reservoir and environmental studies, the geological material characterization is often done by measuring its electrical conductivity. Its main interest is due to its sensitivity to physical properties of porous media (i.e. structure, water content, or fluid composition). Its quantitative use therefore depends on the efficiency of the theoretical models to link them. In this study, we develop a new physically based model that takes into account the surface conductivity for estimating electrical conductivity of porous media under partially saturated conditions. The proposed model is expressed in terms of electrical conductivity of the pore fluid, water saturation, critical water saturation and microstructural parameters such as the minimum and maximum pore/capillary radii, the pore fractal dimension, the tortuosity fractal dimension and the porosity. Factors influencing the electrical conductivity in porous media are also analysed. From the proposed model, we obtain an expression for the relative electrical conductivity that is consistent with other models in literature. The model predictions are successfully compared with published experimental data for different types of porous media. The new physically based model for electrical conductivity opens up new possibilities to characterize porous media under partially saturated conditions with geoelectrical and electromagnetic techniques.

Eu-doped CdS quantum dots (QDs) with the Eu dopant concentration in the range of 0.5–10% and zinc blende (ZB) structure were successfully synthesized by a wet chemical method. The fabricated Eu-doped CdS QDs exhibited emissions in the visible window approximately at 465, 590, 618 and 696 nm, which correspond to the excitonic emission of CdS QDs and the electronic transitions of the intra 4f6 configuration from the 5D0 level to 7F1, 7F2 and 7F4 levels of Eu3+ dopant ions, respectively. Judd–Ofelt theory was used to estimate the properties of ligand field and luminescence quantum efficiency of the material. The interaction mechanism and the efficiency of the energy transfer process from CdS QDs to Eu3+ ions were found by using Reisfeld's approximation formulas. The luminescence quenching of Eu3+-doped CdS QDs was studied through analysis of emission spectra and decay curves. The dominant interaction mechanism between Eu3+ ions and energy transfer parameters have been found by fitting the decay curves to the Inokuti–Hirayama model. The cross-relaxation channels leading to the luminescence quenching of Eu3+ have also been predicted.

Dy3+-doped glasses with compositions of (69-x)B2O3 + 10TeO2 + 10Al2O3 + 10Li2O + xDy2O3 (x = 0.1; 0.5; 1.0 and 2.0 mol%) were prepared by a melt–quenching technique. An in-depth Judd-Ofelt analysis has been carried out to estimate the influence of the hypersensitive transitions (HST) of Dy3+on the validity of the obtained intensity parameters Ωλ (λ = 2, 4, 6). The thermalization effect of the three-levels system of 6H13/2 (level 0), 4F9/2 (level 1) and 4I15/2 (level 2) was taken into account to evaluate its radiative transition probabilities, life times and energy levels. The obtained results were compared with the experimental data to estimate the validity of the Judd-Ofelt analysis. The Inokuti-Hirayama model was used to analyze the luminescence decay curves. The dipole-dipole interaction was shown to be the dominant mechanism in energy transfer process through cross-relaxation between Dy3+ ions. The possibility to produce the light with chromaticity coordinates in the white-light region by mixing intense blue (484 nm, 4F9/2 → 6H15/2) and yellow (575 nm, 4F9/2 → 6H13/2) emissions of the single Dy3+doped alumino-lithium-telluroborate glass was observed and estimated.

KGdF4:Tb3+, KGdF4:Sm3+ and KGdF4:Tb3+,Sm3+ polycrystalline were synthesized under hydrothermal conditions. The XRD and TEM patterns as well as excitation, luminescence spectra and luminescence decay curves of Sm3+, Tb3+ and Gd3+ have been measured at room temperature. For KGdF4:Tb3+(Sm3+), energy transfer processes from Gd3+ ions to Tb3+ (or Sm3+) ions are related to energy migration through Gd3+ ions and energy trapping by Tb3+ (or Sm3+) ions. The energy trapping rate strongly depends on the nature of RE3+ (Tb3+ or Sm3+) ions and it influences to the luminescence efficiency of RE3+ ion. For KGdF4:Tb3+,Sm3+, the characteristic emission bands of Tb3+ ion (blue and green) and Sm3+ ion (orange-red) are obtained simultaneously upon excitation by 375 nm. The chromaticity coordinates and correlated color temperature (CCT) are used to estimate the emission feature of prepared material. The quenching of the luminescence and lifetime of 5D4 (Tb3+) level are relate to the energy transfer process from Tb3+ to Sm3+ ions. It is shown that, by fitting the decay curves of 5D4 (Tb3+) to the Inokuti and Hirayama model, the dominant interaction mechanism between Tb3+ and Sm3+ is dipole-quadrupole interaction. The probability (WET) and the efficiency (ηET) of energy transfer from Tb3+ ions to Sm3+ ions increase with the increase of Sm3+ concentration.

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.

International audience; Electrokinetics methods have attracted increasing interest to characterize hydrogeological processes in geological media, especially in complex hydrosystems such as fractured formations. In this work, we conceptualize fractured media as a bunch of parallel capillary fractures following the fractal size distribution. This conceptualization permits to obtain analytical models for both the electrical conductivity and the electrokinetic coupling in water saturated fractured media. We explore two different approaches to express the electrokinetic coupling. First, we express the streaming potential coupling coefficient as a function of the zeta potential and then we obtain the effective charge density in terms of macroscopic hydraulic and electrokinetic parameters of porous media. We show that when the surface electrical conductivity is negligible, the proposed models reduces to the previously proposed one based on a bundle of cylindrical capillaries. This model opens up a wide range of applications to monitor the water flow in fractured media.

Pressure reducing valves (PRVs) are commonly used for pressure control in water distribution systems (WDSs) by means of dissipating the pressure excess. The use of pumps as turbines (PATs) is an alternative and more favorable system since they not only control the system pressure to decrease water leakage, but also utilize the pressure excess to generate electrical energy. The optimal localization of PATs can be casted into a mixed-integer nonlinear program (MINLP) where binary variables are used to represent the presence of PATs on links. Most of the available MINLP models for optimal PAT localization adopted the optimization approaches for PRV localization without considering the bound constraints on flow rates and heads of PATs. As a result, such an optimization model may make PATs delivering a non-desired output. In this paper, we propose a new MINLP model for optimal PAT localization. Instead of using a constraint on the maximum number of PATs to be placed in a WDS, new constraints relating to the minimum power generated by PAT are introduced to find links having adequate flows and head drops for placing PATs. Moreover, constraints are used to restrict flows and heads of PATs to their feasible operating range, so that the problem can be efficiently solved. The proposed MINLP model is applied to the optimal localization of PATs for a WDS benchmark and a real-world WDS in Vietnam. The results demonstrate that the new MINLP model can efficiently identify optimal locations for PAT placement where the specified working range and minimum power generated by the PATs are ensured.

Photocatalysis under low energy light is of great importance for study of environmental pollution impact. There is an increasing demand for preparing integrated photocatalysts to show their potential in persistent organic compound degradation under visible and near-infrared light. In this work, we have reported the structural combination of three functional components of NaYF4:Yb,Er, TiO2, Cu into photocatalytic nanocomposites for near-infrared light (NIR) photocatalysis. Uniform and monodisperse NaYF4:Yb,Er nanocubes prepared by hydrothermolysis were used as a photon converter and they were combined with TiO2 semiconductor and Cu co-catalysts by sequential deposition to fabricate NIR-active photocatalysts. The Cu/TiO2/NaYF4:Yb,Er nanocomposites were investigated for the organic degradation under NIR light. The Cu/TiO2/NaYF4:Yb,Er photocatalysts were photoactive with NIR light and full decomposition of methylene blue was reached for 90 min. These nanocomposites exhibit the NIR photocatalytic response caused by the NIR light absorption and photon electron transfer over NaYF4:Yb,Er, TiO2, and Cu components.

We demonstrated an effective approach for making NdFe 11 Co alloy. We used a polyol method with ethylene glycol (EG), polyvinylpyrrolidone (PVP), NaBH 4 , FeCl 3 (and/or FeCl 2 ), NdCl 3 , and NaOH for Fe oxide with Nd element according to heat treatment. To obtain NdFe 11 Co alloy products, dried oxide products were heated for solidification, and at 900 °C in Ar gas with CaH 2 . The weight ratio of oxide/CaH 2 is 1:1, and NdFe 11 Co particles are formed by annealing at 900 °C for 1 h. The crystal structure of NdFe 11 Co was identified with the main 2–17 phase and the rich-CoFe phase inside its crystal with grain and grain boundary.

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.

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.

Dy3+-doped glasses with various compositions (35+x)B2O3+ (45−x)TeO2+9.5ZnO+10Na2O+0.5Dy2O3 (x=0; 10 and 20) were prepared by a melt–quenching technique. The Dy3+ ions are used as an optical probe, of which the Judd–Ofelt parameters, the phonon-side band, and the Raman spectra were quantitatively estimated to search the change of glass structure (the change of the ratio of [BO4] to [BO3] units, formation of the non-bridging oxygens (NBO−), the change of [TeO3] to [TeO4] units) as a function of the B2O3 content. The Ω2 and Ω6 values of Dy3+-doped boro-tellurite samples are larger than that of Dy3+-doped borate or tellurite sample. The CIE chromaticity color coordinates were calculated for the luminescence spectra of Dy3+ ions of the glasses with the different compositions and they were all located in the vicinity of white light center of the color coordination diagram.

The absorption, luminescence, Raman spectra and lifetimes of Sm-doped alkali telluroborate glasses (TB glasses) TB:Sm 3+ have been investigated. The dual energy transfers including energy transfer between Sm 3+ - Sm 3+ pairs and Sm 3+ - non-bridging oxygen (NBO) intrinsic defects were investigated. The concentration quenching of luminescence intensity was explained by the non-radiative energy transfer between the Sm 3+ ions through the cross-relaxation mechanism. The decay curves are single exponentials with low concentrations (lower 0.10 mol%) and become non-exponentials at higher concentrations. The non-exponential decay curves are fitted to the Inokuti and Hirayama model to give the energy transfer parameters between Sm 3+ ions. The dominant interaction mechanism for energy transfer process is dipole–dipole interaction. The energy transfer induced Sm 3+ photoluminescence enhancement in tellurite glass was experimentally studied and confirmed.

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.

Alkali-alumino-telluroborate glasses with the different network modifier elements were prepared by melt–quenching method. Absorption, excitation, luminescence spectra as well as decay curves of 5D4 level were measured at room temperature. A phonon side band of 7F6 → 5D4 transition has been obtained from the excitation spectra of Tb3+ ion. The role of modifier ion radius in luminescence enhancement from 5D4 level of Tb3+ ion was discussed in detail. In prepared glasses, multiphonon relaxation rate from 5D3 level to 5D4 is enhanced in the host glasses containing modifier ions with large radius. This is main reason leading to the enhancement of luminescence from 5D4 level of Tb3+ ion in alkali-alumino-telluroborate glasses under excitation at 350 nm. Additionally, the Judd-Ofelt theory was used to estimate the features of ligand field and radiative properties of Tb3+ ion. The calculated results have shown that the 5D4→7F5 transition has potential applications for laser action and optical amplifier.

KABxTyE (xB2O3+yTeO2 +10K2O+10Al2O3 +0.5Eu2O3) glasses with the variation of B2O3/TeO2 ratios (x/y = 30/50, 40/40 and 50/30) and KABTzEu glasses ((50-z)B2O3+30TeO2+10Al2O3+10K2O + zEu2O3, with z = 0.1, 0.5, 1.0, 2.0, 3.0, 4.0 and 5.0 mol%) were prepared by melt–quenching technique. The structure of glasses was analyzed through X-ray diffraction (XRD) patterns, Fourier-transform infrared spectroscopy (FTIR) and phonon-sideband (PSB) spectra. The Judd-Ofelt (JO) theory was used to estimate the properties of ligand and the radiative parameters of prepared glasses such as lifetime (τcal), effective line width (Δλeff), stimulated emission cross-section (σP), gain bandwidth (σP × Δλeff), optical gain (σP × τcal) and quantum efficiency (η). The influence of B2O3/TeO2 ratio and Eu3+ concentration on structure and optical properties of materials was discussed in detail. Energy transfer process between Eu3+ ions was studied by using Inokuti-Hirayama and Yokota-Tamimoto models. The energy transfer channels between Eu3+ ions were also proposed.

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.

Judd–Ofelt parameters of Eu 3+ -doped alkali and earth alkali fluoro-aluminoborate glasses are determined from the fluorescence spectra. The dependence of these parameters on the compositional changes of the materials is discussed. The glass containing sulphate component shows the larger values of Ω compared with the fluoro-aluminoborate glasses because of higher Δ CT (Eu 3+ –F − ) values. The difference of ionic radius and electronegativity between Na and Ca lead to higher Ω 2 parameter of CaF 2 –Al 2 O 3 –B 2 O 3 :Eu 3+ glass. Persistent spectral hole burning has been observed in Eu 3+ ions doped alkali-and earth alkali fluoro-aluminoborate glasses with the compositions of 16NaF·73B 2 O 3 ·8Al 2 O 3 ·3Eu 2 O 3 and 16CaF 2 ·73B 2 O 3 ·8Al 2 O 3 ·3Eu 2 O 3 , which have been prepared using conventional melting technique.

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.

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.

The dependence of luminescence intensity on Sm\(^{3 + }\) ions concentration in alkali borotellurite (ABTe) glasses has been studied. The quenching of luminescence intensity happens around 0.75 mol% concentration of Sm\(^{3 + }\) ions and it can relate the energy transfer process through cross--relaxation (CR), the CR channels in ABTe: Sm\(^{3 + }\) have been shown. The method of Van Uitert was used to find the dominant interaction mechanism for energy transfer process.

The excitation, emission spectra and and lifetime of Eu-doped borotellurite glasses (BTe) have been investigated. The sideband phonon energy and electron-phonon coupling strength (g) have been found. The intensity parameters Ωλ were calculated from the emission spectrum. These parameters were used to predict radiative properties such as transition probabilities (AR), calculated branching ratios (βR) and stimulated emission cross-sections (σλp) for 5D0→7HJHFJ transitions.

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

The environment of Eu{sup 3+} in zinc-thallium-tellurite glass of the molar composition 60TeO{sub 2}-30TlO{sub 0.5}-9.9ZnO-0.1Eu{sub 2}O{sub 3} was investigated by laser-induced fluorescence line narrowing (FLN) techniques using Eu{sup 3+} as a local site probe. From the site selective luminescence spectra of Eu{sup 3+} at 7 K, the energies of the Stark components of the {sup 7}F{sub 1} and {sup 7}F{sub 2} states were recorded and then the crystal field parameters B{sub nm} were calculated assuming a C{sub 2v} site symmetry. The ratios B{sub 22}/B{sub 20} and B{sub 44}/B{sub 40} for each excitation energy within {sup 7}F{sub 0}-{sup 5}D{sub 0} transition were obtained and compared with the values calculated for Eu{sup 3+} in other types of glasses. -- Graphical abstract: Crystal fields parameters B{sub nm} of Eu{sup 3+} ions (strength, distribution) in novel TeO{sub 2}-TlO{sub 0.5}-ZnO glass system. Display Omitted