Influence of modifier oxide on spectroscopic and thermoluminescence characteristics of Sm ion in antimony borate glass system

Sb₂O₃-B₂O₃:Sm³⁺ glasses mixed with three different modifier oxides viz., PbO, CaO and ZnO were prepared. Optical absorption, photoluminescence and thermoluminescence (TL) spectra of these glasses have been recorded at room temperature. From the measured intensities of various absorption bands of these glasses, the Judd-Ofelt parameters Ω₂, Ω₄ and Ω₆ have been evaluated. The Judd-Ofelt theory could successfully be applied to characterize the absorption and luminescence spectra of these glasses. From this theory, various radiative properties like transition probability A, branching ratio β_r, the radiative lifetime τ_r, and the emission cross-section σ^E for various emission levels of these glasses have been determined and reported. An attempt has also been made to throw some light on the relationship between the structural modifications and luminescence efficiencies of all the three glasses. The analysis of TL data indicates high non-radiative losses in ZnO mixed glasses.     

Thermoluminescence properties of rare earth doped lithium magnesium borate phosphors

This paper reports the thermoluminescence (TL) properties of rare earth doped lithium magnesium borate (LMB) polycrystalline phosphor. LMB phosphor has been prepared by high temperature solid state diffusion method. Among all the rare earth doped LMB phosphors, terbium doped material has shown maximum TL sensitivity with a broad dosimetric glow peak at 240 °C. near the tissue equivalent TL phosphor with terbium dopant has about four times the TL sensitivity of TLD-100. The main dosimetric properties such as glow curve stability, TL response versus absorbed dose, post-irradiation storage stability, and reusability are investigated. This TL material has a linear dose response up to 10³ Gy, negligible storage fading and a simple annealing procedure for reuse. The TL emission spectra of LMB:Tb³⁺ showed broad green emission at 544 nm, which merged with host emission. The characteristic Tb³⁺ emissions are seen in the photoluminescence (PL) spectra.     

Luminescence studies of rare earth doped yttrium gadolinium mixed oxide phosphor

This paper reports the photoluminescence and thermoluminescence properties of gamma ray induced rare earth doped yttrium gadolinium mixed oxide phosphor. The europium (Eu³⁺) was used as rare earth dopant. The phosphor was prepared by chemical co-precipitation method according to the formula (Y_2−x−yGd_x) O₃: Eu_y³⁺ (x=0.5; y=0.05). The photoluminescence emission spectrum of the prepared phosphor shows intense peaks in the red region at 615 nm for ⁵D₀→⁷F₂ transitions and the photoluminescence excitation spectra show a broad band located around 220–270 nm for the emission wavelength fixed at 615 nm. The thermoluminescence studies were carried out after irradiating the phosphor by gamma rays in the dose range from 100 Gy to 1 KGy. In the thermoluminescence glow curves, one single peak was observed at about 300 °C of which the intensity increases linearly in the studied dose range of gamma rays. The glow peak was deconvoluted by GlowFit program and the kinetic parameters associated with the deconvoluted peaks were calculated. The kinetic parameters were also calculated by various glow curve shape and heating rate methods.     

Structure study of rare earth doped vitreous silica by molecular dynamics simulation

A series of erbium doped vitreous silica, with erbium concentration as low as 0.25 per cent up to 5 per cent, has been modeled, using molecular dynamics. It has been found that as the Er content decreases, the percentage of erbium ions in pairs remains almost constant until very low concentration, when pairing is the only clustering mechanism and those that are not in pairs are isolated.     

Combined Optical/MCD/ODMR investigations of photochromism in doubly-doped Bi 12 GeO 20

Electron paramagnetic resonance is detected optically via the change of magnetic circular dichroism under microwaves at 35 v GHz. The technique is applied to Bi 12 GeO 20 samples co-doped with vanadium and a second transition metal (Cr, Mn, Co, Cu). The optical and magnetic properties of several paramagnetic defects (V Ge 4+ and Cr Ge 4+ ) are directly correlated. The basic photochromic processes occuring in samples doped with V, Mn, and Mn+V are explained. The V Ge 4+/5+ level is positioned roughly 2.2 v eV above the valence band.     

Structure and properties of soda lime silicate glass doped with rare earth

Soda-lime-silicate glasses doped with different rare-earth oxides (La₂O₃, CeO₂, Nd₂O₃, Gd₂O₃ and Y₂O₃) of 1 mol% content were prepared with the traditional melting-quenching methods. In order to reveal the effects of rare-earth elements on the behavior of soda-lime-silicate glass, the structure of soda-lime-silicate glasses doped with different rare-earth oxides were determined with Fourier transform infrared spectrometer using the KBr method, and viscosity of glass melts were measured by the rotating crucible viscometer, the melting temperature of the studied glasses were derived on the basis of Arrhenius Equation, moreover the density, bending strength and molar volume were measured and calculated. The effect of rare-earth dopants on the structure of soda-lime-silicate was analyzed by a shift of peak position and variation in the full-width at half-maximum. The effect of doping rare-earth oxides into glass on the viscosity, density and bending strength was interpreted by changing in structure of soda-lime-silicate glasses doped with rare-earth oxides.     

Effect of ZnO as modifier on up and downconversion properties of Ho/Yb doped tellurite glasses

Optical absorption and photoluminescent properties of Ho³⁺/Yb³⁺ co-doped tellurite and zinc tellurite glasses are investigated. The effect of zinc oxide as a modifier on the luminescence properties of above mentioned samples has been explored. Two intense upconversion emission bands centered at 546 (⁵F₄ + ⁵S₂ → ⁵I₈) and 660 nm (⁵F₅ → ⁵I₈) are observed on excitation with 976 nm diode laser. Zinc oxide acts as a quencher for 976 nm excited upconversion emission. The up and downconversion emission spectra are recorded with 532 nm excitation source also. In this case zinc oxide improves the up and downconversion emissions. A large enhancement in upconversion intensity has been observed when Ho³⁺ ion is co-doped with Yb³⁺ ion. The dependence of upconversion intensities on excitation power and on temperature has also been studied. The power dependence study shows a quadratic dependence of the fluorescence intensity on the excitation power while a decrement in emission intensity of all the transitions at different rates with increase in temperature is observed in temperature dependence study. The possible mechanisms are also discussed in order to understand the upconversion and energy transfer processes.     

Raman spectroscopic investigation of pure and ytterbium‐doped rare earth silicate crystals

Raman spectroscopy was used to study the molecular structure of a series of selected rare earth (RE) silicate crystals including Y₂SiO₅ (YSO), Lu₂SiO₅ (LSO), (Lu_0.5Y_0.5)₂SiO₅ (LYSO) and their ytterbium‐doped samples. Raman spectra show resolved bands below 500 cm⁻¹ region assigned to the modes of SiO₄ and oxygen vibrations. Multiple bands indicate the nonequivalence of the RE O bonds and the lifting of the degeneracy of the RE ion vibration. Low intensity bands below 500 cm⁻¹ are an indication of impurities. The (SiO₄)⁴⁻ tetrahedra are characterized by bands near 200 cm⁻¹ which show a separation of the components of ν₄ and ν₂, in the 500–700 cm⁻¹ region which are attributed to the distorting bending vibration and in the 880–1000 cm⁻¹ region which are attributed to the symmetric and antisymmetric stretching vibrational modes. The majority of the bands in the 300–610 cm⁻¹ region of Re₂SiO₅ were found to arise from vibrations involving both Si and RE ions, indicating that there is considerable mixing of Si displacements with Si O bending modes and RE O stretching modes. The Raman spectra of RE silicate crystals were analyzed in terms of the molecular structure of the crystals, which enabled separation of the bands attributed to distinct vibrational units. Copyright © 2007 John Wiley & Sons, Ltd.     

Photoluminescence spectra of rare earth doped CaGa2S4 single crystals

Six kind CaGa₂S₄ single crystals doped with different rare earth (RE) elements are grown by the horizontal Bridgman method, and their photoluminescence (PL) spectra are measured in the temperature range from 10 to 300 K. The PL spectra of Ce or Eu doped crystals have broad line shapes due to the phonon assisted 4f-5d transitions. On the other hand, those of Pr³⁺, Tb³⁺, Er³⁺ or Tm³⁺ doped samples show narrow ones owing to the 4f-4f transitions. The assignments of the electronic levels are made in reference to the reported data of RE 4f multiplets observed in same materials.     

Protonic conducting properties of sol-gel derived organic/inorganic nanocomposite membranes doped with acidic functional molecules

High temperature protonic conducting polymer membranes provide new technological applications in electrochemical devices including electrochromic displays, chemical sensors, fuel cells and others. Organic/inorganic nanocomposite membranes consisting of SiO₂/PEO (polyethylene oxides) hybrids are a remarkable family of isotropic, flexible, amorphous polymer materials, which have been synthesized through sol-gel processes. The hybrid membrane doped with acidic moieties such as monododecylphosphate or phosphotungstic acid shows good protonic conductivities at high temperatures above 100°C. The protonic conducting membrane was found to be thermally stable at high temperatures because of the inorganic SiO₂ framework in the nanocomposite matrix.     

Spectroscopic and optical properties of Nd doped fluorine containing alkali and alkaline earth zinc-aluminophosphate optical glasses

Nd³⁺ doped fluorine containing zinc-aluminophosphate glasses have been prepared with alkali and alkaline earth content to understand the effect of network modifiers on radiative process. The physical and optical properties of these glasses have been evaluated. The Judd-Ofelt model for the intensity analysis of induced electric dipole transitions has been applied to the measured oscillator strengths of the absorption bands to determine the three phenomenological intensity parameters Ω₂, Ω₄ and Ω₆ for each glass. Using these parameters, transition probability (A), total transition probability (A_T), branching ratios (β_R) radiative life times (τ_R) and integrated cross-section (σ_a) for the stimulated emission have been theoretically calculated for certain excited Nd³⁺ fluorescent levels. From the obtained results the conclusion is made about the possibility of using these glasses as laser material.     

双包层稀土掺杂光纤抽运吸收特性的分析

建立了复折射率纤芯结合有限差分束传播法的双包 层稀土掺杂光纤抽运吸收效率数值模型,利用该模型对几种常 用内包层外边界结构下双包层稀土掺杂光纤的抽运吸收系数进 行了详细的分析,得出相应双包层光纤的抽运吸收特性. 分析结果对双包层稀土掺杂光纤的优化设计具有重要的指导意义.     

Effect of annealing temperature on the structural, photoluminescence and magnetic properties of sol-gel derived Magnetoplumbite-type (M-type) hexagonal strontium ferrite

Magnetoplumbite-type (M-type) hexagonal strontium ferrite particles were synthesized via sol-gel technique employing ethylene glycol as the gel precursor at two different calcination temperatures (800 and 1000 °C). Structural properties were systematically investigated via X-ray diffraction (XRD), field emission scanning electron microscopy, high resolution transmission electron microscopy (HRTEM), energy dispersive spectroscopy (EDS), thermogravimetric analysis (TGA), photoluminescence spectrophotometry and superconducting quantum interference device magnetometer. XRD results showed that the sample synthesized at 1000 °C was of single-phase with a space group of P6₃/mmc and lattice cell parameter values of a=5.882 Å and c=23.048 Å. EDS confirmed the composition of strontium ferrite calcined at 1000 °C being mainly of M-type SrFe₁₂O₁₉ with HRTEM micrographs confirming the ferrites exhibiting M-type long range ordering along the c-axis of the crystal structure. The photoluminescence (PL) property of strontium ferrite was examined at excitation wavelengths of 260 and 270 nm with significant PL emission peaks centered at 350 nm being detected. Strontium ferrite annealed at higher temperature (1000 °C) was found to have grown into larger particle size, having higher content of oxygen vacancies and exhibited 83-85% more intense PL. Both the as-prepared strontium ferrites exhibited significant oxygen vacancies defect structures, which were verified via TGA. Higher calcination temperature turned strontium ferrite into a softer ferrite.     

Optical and structural characterization of KBr crystals doped cadmium bromide (CdBr2)

In this paper we demonstrate the presence of CdBr₂ and cadmium aggregates in KBr matrix during Czochralski growth of KBr crystals. The chemical decomposition of CdBr₂ due to high temperature of crystallisation and reformation of cadmium bromide seems to be responsible for this effect.     

Optical and fluorescence spectroscopy of Eu2O3-doped P2O5-K2O-KF-MO-Al2O3 (M = Mg, Sr and Ba) glasses

Fluorophosphate glasses of composition, P₂O₅ + K₂O + KF + MO + Al₂O₃ + xEu₂O₃ (M = Mg, Sr and Ba; x = 0.01, 0.05, 0.1, 1.0, 2.0, 4.0 and 6.0 mol%) were prepared and characterized their optical properties. Crystal-field (CF) analysis revealed a relatively weak CF strength around Eu³⁺ ions in the Ba based fluorophosphate glasses. The Judd-Ofelt parameters have been estimated from the oscillator strengths of ⁷F₀ → ⁵D₂, ⁷F₀ → ⁵D₄ and ⁷F₀ → ⁵L₆ absorption transitions of Eu³⁺ ions and were used to evaluate the radiative properties of the ⁵D₀ → ⁷F_J (J = 0-4) transitions. Considerable variation has been observed in the relative intensity ratio of ⁵D₀ → ⁷F₂ to ⁵D₀ → ⁷F₁ transitions of Eu³⁺ ions due to change in the alkaline earth metal ions. The decay of the ⁵D₀ level shows single exponential and less sensitive to Eu³⁺ ions concentration as well as MgO/SrO/BaO modifiers.     

Luminescence spectra and optical properties of TeO2-WO3-Li2O glasses doped with Nd, Sm and Er rare earth ions

New tellurite glass series of the form (70-x)TeO₂-20WO₃-10Li₂O-xLn₂O₃, where x=0, 1, 3 and 5 mol% and Ln=Nd, Sm and Er, were prepared. Density of the prepared glasses was measured and molar volume was calculated. Luminescence spectra of the prepared glasses were measured at room temperature using a micro-Raman spectrometer. The obtained luminescence intensity ratio was correlated with the rare earth ion concentration, the short distance between the identical rare earth ions r(Ln-Ln) and the glass density. Optical properties like refractive index, molar refractivity and optical polarizability were theoretically calculated in order to interpret the dependence of these properties on the rare earth ion content.