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1.
This article presents the optical absorption and emission properties of Pr3+ and Er3+ in mixed alkali borate glasses of the type 68B2O3·xLi2O·(32-x)Cs2O (where x=8, 12, 16, 20 and 24). The variation of Judd-Ofelt intensity parameters (Ωλ), the peak wavelength of the hypersensitive transitions, radiative transition probabilities (Arad) and peak emission cross-sections (σp) with x in the glass matrix have been discussed in detail. The changes in position of hypersensitive transition and intensity parameters with x are correlated to the structural changes in the host matrix. The estimated radiative lifetimes (τR) of certain excited states of both Pr3+ and Er3+ in lithium cesium mixed alkali borate glasses are reported. Branching ratios (β) and integrated absorption cross-sections (Σ) for certain important transitions are presented. Peak stimulated emission cross-sections (σp) are calculated for the observed emission peaks of Pr3+ and Er3+ ions in this glass matrix. 相似文献
2.
El Sayed Moustafa Yasser B. Saddeek Essam R. Shaaban 《Journal of Physics and Chemistry of Solids》2008,69(9):2281-2287
Glasses with compositions 25Li2O-(75−x)Bi2O3-x B2O3, with 0?x?30 mol%, have been prepared using the melt quenching technique. The density and the molar volume have been determined. IR spectroscopy is used as a structural probe of the nearest neighbor environment in the glass network. The optical transmittance and reflectance spectrum of the glasses have been recorded in the wavelength range 400-1100 nm. The values of the optical band gap Egopt for indirect transition and refractive index have been determined for 0?x?30 mol%. The average electronic polarizability of the oxide ion αo2− and the optical basicity have been estimated from the calculated values of the refractive indices. Variations in the different physical parameters such as the density, molar volume, optical band gap, refractive index, average electronic polarizability of the oxide ion and optical basicity with B2O3 content have been analyzed and discussed in terms of the changes in the glass structure. 相似文献
3.
Glass transition temperatures (Tg), crystallization temperatures (Tx), and 113Cd magic-angle spinning (MAS) NMR spectra of the chlorocadmate, bromocadmate, and bromochlorocadmate glasses and the CdCl2, CdBrCl, and CdBr2 crystals have been measured. The Tg and Tx, and thermal stabilities (Tx−Tg) decreased with increasing Br-content. No enhancement of (Tx−Tg) of bromochlorocadmate glasses by anion-mixing was observed. The CdCl2 and CdBr2 crystals gave the isotropic chemical shifts of 183 and −24 ppm, which are assigned to the CdCl6 and CdBr6 octahedra, respectively. The isotropic chemical shifts of CdBrCl crystal (186, 166, 135, 101, 63, 25 and −21 ppm) were assigned to CdBrnCl(6−n) (n=0-6) octahedra, respectively. It was found that the Br and Cl atoms in CdBrCl randomly occupy chlorine sites in the CdCl2 structure. The 113Cd MAS NMR spectra revealed that the chlorocadmate, bromocadmate, and bromochlorocadmate glasses are composed of the CdCl6, CdBr6 and CdBrnCl(6−n) octahedra (n=0-6), respectively, and that the Cd2+ in all the bromochlorocadmate glasses was more preferentially bonded to Br− than Cl−. The relationship between the thermal properties and the anion coordination environments around Cd2+ in these glasses is discussed. 相似文献
4.
Local atomic structures of Zr100−xNix (x=33.3, 36, 50 at%) binary metallic glasses were investigated by means of extended X-ray absorption fine structure (EXAFS) probe. Structural parameters show that the Zr-Ni bond length, RZr-Ni, keeps a constant value of 2.62 Å, regardless of alloy compositions. This result implies that there is a strongly chemical interaction between Zr and Ni atoms, leading to significant chemical short-range orders (CSROs) in the present metallic glasses. Further analysis indicates that the SRO structures in these metallic glasses are extremely similar with those in their crystalline counterparts. It is interesting to note that the CSROs in the eutectic Zr64Ni36 metallic glass consist of Zr2Ni-like and ZrNi-like CSROs. 相似文献
5.
M.S. Al-Assiri 《Physica B: Condensed Matter》2008,403(17):2684-2689
Characterization and electrical properties of vanadium-copper-phosphate glasses of compositions xV2O5-(40−x)CuO-60P2O5 have been reported. X-ray diffraction (XRD) confirms the amorphous nature of these glasses. It was observed that, the density (d) decreases gradually while the molar volume (Vm) increases with the increase of the vanadium oxide content in such glasses. This may be due to the effect of the polarizing power strength, PPS, which is a measure of ratio of the cation valance to its diameter. The dc conductivity increases while the activation energy decreases with the increase of the V2O5 content. The dc conductivity in the present glasses is electronic and depends strongly upon the average distance, R, between the vanadium ions. Analysis of the electrical properties has been made in the light of small polaron hopping model. The parameters obtained from the fits of the experimental data to this model are reasonable and consistent with glass composition. The conduction is attributed to non-adiabatic hopping of small polaron. 相似文献
6.
Molecular dynamics simulation of binary glass 52Li2O-48P2O5 and ternary glasses 45Li2O-42P2O5-13LiCl and 39Li2O-36P2O5-25LiCl was undertaken to study the effects of the addition of LiCl to the binary phosphate glass. The results show that addition of LiCl in the glass creates more non-bridging oxygens and reduces P-O-P chain lengths and branches in these chains, leading to a weakening of the glass matrix and consequent lowering of Tg. Interchain linkages mediated by Li in the binary structure diminish, and consequently better channels are created for Li+ movement, enhancing the ionic conductivity σ. Structure parameters also indicate the absence of LiCl clusters in the glass matrix. 相似文献
7.
Optical absorption, thermoluminescence, infrared spectra and differential thermal analysis of three different tellurite glass systems viz., ZnF2-As2O3-TeO2, ZnF2-Bi2O3-TeO2 and ZnF2-P2O5-TeO2 containing 0.4% of Cr2O3, have been investigated. Results have been analysed in the light of different oxidation states of chromium ion and the most suitable host for lasing Cr3+ ions has been identified and reported. 相似文献
8.
M. Suszynska L. Krajczyk R. Capelletti 《Applied Physics A: Materials Science & Processing》1999,68(4):471-473
2 O-rich droplets dispersed throughout the SiO2-rich matrix and nanoparticles of metallic silver. In exchanged specimens the joint effect of colloidal silver and electric
field results in partial transformation of the amorphous droplets into crystalline Na2O particles.
Received: 11 February 1998 / Accepted: 20 November 1998 / Published online: 24 February 1999 相似文献
9.
Yong Gyu Choi 《Journal of luminescence》2009,129(6):620-623
It has been experimentally confirmed that the addition of very small amount, tantamount to ∼1 mol%, of the group III elements (Ga or In) in combination with alkali halides (CsBr or RbBr) into chalcogenide Ge-As-S glass significantly improves the emission properties of Dy3+ dopant. Preferential location of Br in the first coordination shell of Dy3+, which occurs spontaneously during the vitrification process, is proposed to make Dy3+ experience different crystal fields, reduced phonon energy and modified local refractive index. This restructuring effect as a result of such minute compositional adjustments thus enhances the optical properties of rare earth elements embedded in chalcogenide glasses, while keeping their thermal properties unaltered. 相似文献
10.
R. S. De Oliveira J. A. C. De Paiva M. A. B. De Araujo A. S. B. Sombra 《Il Nuovo Cimento D》1998,20(2):209-220
Summary Iron molybdenum phosphate glasses [xMoO3 · (0.6 -x)P2O5 · 0.4Li2O] :yFe2O3 with 0 ≤x ≤ 0.6 andy = 0.03 (mol%) prepared in ambient atmosphere using the melt quenching technique were studied by using DC electrical conductivity,57Fe M?ssbauer and infrared spectroscopies. The DC conductivity depends on the MoO3 concentrationx. It was observed that, with increasingx, the ratio Fe2+ /(Fe3+ + Fe2+) and the DC conductivity increase. Infrared spectroscopy and X-ray powder diffraction indicate that a Li2 MoO4 crystalline phase is present for high MoO3 content samples (x = 0.5, 0.6).
This work was partly sponsored by FINEP, CNPq (Brazilian agencies) and UECE (Universidade Estadual do Cearà). 相似文献
11.
Molar volumes, V, and compactness values, α, of 34 glassy compositions of the GeSeFe system have been obtained using their
measured densities. The property–composition dependences are examined in light of the models proposed for the structure of
these network glasses.
Received: 28 August 2000 / Accepted: 9 January 2001 / Published online: 23 March 2001 相似文献
12.
G.A Kumar E De la Rosa-Cruz N.V Unnikrishnan 《Journal of Physics and Chemistry of Solids》2003,64(1):69-76
Spectroscopic properties of Nd3+ in barium fluoroborophosphate glassy matrix have been analyzed by fitting the experimental data with the standard Judd-Ofelt theory. Various spectroscopic parameters viz. radiative transition probabilities, radiative decay time, fluorescence branching ratios, electric dipole line strengths, stimulated emission cross-sections and optical gain of the principal fluorescence transitions from the 4F3/2 metastable level are obtained. Results show that addition of borate content to the fluorophosphate matrix will reduce the fluorescence spectral properties of Nd3+. However, the radiative properties of the present fluoroborophosphate glassy matrix are found to be well improved over that of pure borate and phosphate matrix and is attributed to the influence of fluorine content in the glassy matrix. The changes in the position and the Judd-Ofelt intensity parameters are correlated with the structural changes in the host glass matrix. The shift of the hypersensitive band shows that the covalency of the rare earth to oxygen bond increases with the increase of Na2O content. This covalency effect and the formation of the BO4 groups with the addition of Na2O content are responsible for the increase in the radiative properties of the present system. Quantitative estimation of the non-radiative processes such as multiphonon relaxation and quenching by water content was carried out and the results show that both are below the critical level for optimum laser performance. 相似文献
13.
G. Saffarini 《Applied Physics A: Materials Science & Processing》2002,74(2):283-285
The glass-transition (Tg) and crystallisation (Tx) temperatures of glassy GexSeyIn12 (7≤x≤28) have been determined from differential scanning calorimetry measurements. The variations of Tg and Tx with composition have been specified. It has been found that Tg reaches a maximum at 614 K for the composition Ge23.33 Se64.67 In12 while Tx passes through a minimum at 740 K for the same composition. The values of the cohesive energies of the studied compositions
have also been estimated using the chemical bond approach method. It is found that the composition Ge23.33Se64.67In12 possesses the maximum cohesive energy. These results are explained in terms of the structure of Ge-Se-In glasses.
Received: 12 March 2001 / Accepted: 29 March 2001 / Published online: 23 May 2001 相似文献
14.
Microexplosions in tellurite glasses 总被引:2,自引:0,他引:2
S.K. Sundaram C.B. Schaffer E. Mazur 《Applied Physics A: Materials Science & Processing》2003,76(3):379-384
Femtosecond laser pulses were used to produce localized damage in the bulk and near the surface of baseline, Al2O3-doped and La2O3-doped sodium tellurite glasses. Single or multiple laser pulses were non-linearly absorbed in the focal volume by the glass,
leading to permanent changes in the material in the focal volume. These changes were caused by an explosive expansion of the
ionized material in the focal volume into the surrounding material, i.e. a microexplosion. The writing of simple structures
(periodic array of voxels, as well as lines) was demonstrated. The regions of microexplosion and writing were subsequently
characterized using scanning electron microscopy (SEM), energy-dispersive spectrometry (EDS) and atomic force microscopy (AFM).
Fingerprints of microexplosions (concentric lines within the region and a concentric ring outside the region), due to the
shock wave generated during microexplosions, were evident. In the case of the baseline glass, no chemistry change was observed
within the region of the microexplosion. However, Al2O3-doped and La2O3-doped glasses showed depletion of the dopant from the edge to the center of the region of the microexplosions, indicating
a chemistry gradient within the regions. Interrogation of the bulk- and laser-treated regions using micro-Raman spectroscopy
revealed no structural change due to the microexplosions and writing within these glasses.
Received: 27 December 2001 / Accepted: 9 July 2002 / Published online: 25 October 2002
RID="*"
ID="*"Corresponding author. +1-509/376-3108, E-mail: sk.sundaram@pnl.gov 相似文献
15.
X-ray photoelectron spectroscopy (XPS) was used to evidence the effect of the Bi2O3 to SiO2 ratio and of partial crystallisation on the electronic charge density around the atoms entering silica-bismuthate glasses of nominal composition 0.01Fe2O3⋅0.99[xSiO2⋅(100−x)Bi2O3] with . The core level spectra show significant composition dependent changes in binding energy, and the full width at half maximum of photoelectron peaks both of cations and of oxygen atoms. The analysis reveals changes in electron density correlated with the ionic and covalent character of the samples. The shift in binding energy suggests charge transfer from silicon and oxygen atoms to bismuth atoms. Contrary to the expected behaviour in conventional silicate oxide systems, the results indicate an increase of ionicity for silicon and of covalency for bismuth atoms. The same evolution of ionicity/covalency is observed after partial crystallisation. 相似文献
16.
We have investigated the temperature- and frequency-dependent ionic conductivity in (Li0.67 ? xNa0.33 Rbx)2B4O7 (LNRBO) glasses with x = 0, 0.07, 0.2, 0.33, 0.47, and 0.6. The mixed alkali effect of the ternary mixed alkali system LNRBO is compared with that of the binary mixed alkali systems (Li1 ? xNax)2B4O7 (LNBO), (Li1 ? xRbx)2B4O7 (LRBO) and the single alkali glass Rb2B4O7 (RBO). From the results of the dc conductivity and dc activation energy, we observe that the LNRBO system exhibits the combined characteristic of binary mixed alkali systems LNBO and LRBO. It is found that the power-law exponent n for binary alkali glass is the same as that for ternary alkali glass but it is lower than that for single alkali glass. This indicates that the dimensionality of conducting pathway in the mixed alkali glasses of LNBO, LRBO and LNRBO is lower than that in the single alkali RBO. We discuss the concentration dependence of the dc conductivity and dc activation energy in the framework of the bond valence technique to reverse Monte Carlo produced structural model [Phys. Rev. Lett. 90, 155507 (2003)]. 相似文献
17.
Short-range order and local atomic configuration in yttrium-aluminosilicate glasses doped with gadolinium were studied by infrared (IR) spectroscopy, 27Al magic-angle-spinning nuclear magnetic resonance (MAS-NMR) and Gd3+ electron spin resonance (EPR) on as-prepared and heat-treated samples.A small amount of yttrium was replaced by gadolinium in the host glass because Y3+ and Gd3+ cations are quite similar and gadolinium ions can be used as structural sensor in electron paramagnetic resonance measurements. The results evidence weak changes in the structure of as-prepared glasses with respect to the coordination of aluminium atoms produced by gadolinium doping (0.2 and 0.5 mol%). New IR bands recorded from heat-treated samples are associated with stretching modes of hexacoordinated aluminium in AlO6 octahedra. The effect of the heat treatment on aluminium environment is estimated by analysing the relative intensity of the component lines of simulated 27Al MAS-NMR spectra. High-coordinated AlOn species were identified in all samples. EPR results evidence the increase of the number of gadolinium sites with weak crystal field as effect of the structural relaxation. 相似文献
18.
ZnO-ZnF2-B2O3 glasses containing small concentrations of TiO2 ranging from 0 to 0.6 mol% were prepared. Dielectric properties (constant ε′, loss tan δ, ac conductivity σac over a moderately wide range of frequency and temperature at room temperature in air medium) of these glasses have been studied. The results of these studies were analyzed with the aid of data on optical absorption, ESR and IR spectra of these glasses. The analysis suggests that when the concentration of TiO2>0.2 mol%, the titanium ions, in addition to Ti4+ state, co-exist in Ti3+ state, act as modifiers and reduce the breakdown strength. 相似文献
19.
N. Mousseau D.A. Drabold 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(4):667-671
Many properties of alloyed chalcogenide glasses can be closely correlated with the average coordination of these compounds.
This is the case, for example, of the ultrasonic constants, dilatometric softening temperature and the vibrational densities
of states. What is striking, however, is that, at a given average coordination, these properties are nevertheless almost independent
of the elemental composition. Here, we report on some numerical verification of this experimental rule as applied to the vibrational
density of states. We find that this rule is not exact but holds qualitatively well over a wide range of compositions and
local chemical correlations.
Received 25 April 2000 相似文献
20.
Elastic properties of xLi2O — 20PbO — (80-x)B2O3 glasses have been measured at a frequency of 10 MHz using X-cut and Y-cut quartz transducers. The trends in the variation
of elastic moduli, Poisson’s ratio and Debye temperature have been studied. The elastic moduli namely longitudinal and young’s
modulus show strong linear dependence while bulk and shear modulus vary marginally as a function of Li2O concentration. The Poisson’s ratio is found to be almost constant and Debye temperature increases with the increase of Li2O concentration. IR, MAS-NMR and glass transition temperature studies have been also carried out. Glass transition temperature
is found to increase with increase of Li2O concentration. IR and MAS-NMR spectra show characteristic features of borate network and systematic change as a function
of Li2O concentration. The variation in the elastic properties and structural features of IR and MAS-NMR indicate that Pb2+ ions are likely to occupy network forming positions in this glass system.
Paper presented at the 2nd International Conference on Ionic Devices, Anna University, Chennai, India, Nov. 28–30, 2003. 相似文献