共查询到20条相似文献,搜索用时 31 毫秒
1.
M.M. Elkholy 《Journal of luminescence》2010,130(10):1880-1892
Lithium borate (LiB) glasses in the system (100−x)B2O3-xLi2O with x=20, 30, 40, 50, 60 and 70 mol% were prepared. The glasses were doped with different concentrations of the order of 10−1, 10−2, 10−3, 10−4 and 10−5 of MgO and their thermoluminescent (TL) response was investigated. The irradiations were performed using γ rays from a 60Co source in the dose range from 0.1 to 25 kGy. The material displayed good sensitivity for γ-rays and intensity of TL signals is dependent on γ-ray dose and Li2O content. For each dose level and investigated temperature range (50-350 °C), exactly single isolated glow peak appears in the temperature range of 165-205 °C depending on both Li2O concentrations and time of exposure. The shape of the glow peak has altered significantly with increase in the gamma ray dose or Li2O concentrations. The glass composition with x=50 mol% doped with 10−3 mol% of MgO presented the best TL response. The results of the present study indicated that the recorded single and isolated high temperature peak is a good candidate for TL dosimetric investigations. This indicates that 50 B2O3-50Li2O-doped with 10−3 mol% of MgO is possibly used as materials for radiation dosimetry in the dose range of 0.1-20 kGy. 相似文献
2.
Rajendra Kumar Singh 《Journal of magnetism and magnetic materials》2010,322(14):2018-4319
Room temperature electron paramagnetic resonance (EPR) spectra and temperature dependent magnetic susceptibility data have been obtained on bulk x(ZnO,Fe2O3)(65−x)SiO220(CaO, P2O5)15Na2O (6≤x≤21 mole%) glasses prepared by melt quenching method. EPR spectra of the glasses revealed absorptions centered at g≈2.1 and 4.3. The variations of the intensity and line width of these absorption lines with composition have been interpreted in terms of the variation in the concentration of the Fe2+ and Fe3+ ions in the glass and the interaction between the iron ions. EPR and magnetic susceptibility data of the glasses reveal that both Fe2+ and Fe3+ ions are present in the glasses, with their relative concentration being dependent on the glass composition. The studies reveal superexchange type interactions in these glasses, which are strongly dependent on their iron content. 相似文献
3.
N.M. Shash F.E. Salman M.K. El-Mansy H.A. Ghodair 《Journal of Physics and Chemistry of Solids》2004,65(5):891-900
Characterization of the (76V2O5-24P2O5)1−X (Li3PO5)X, where X=0.0,0.01,0.02,0.10 and 0.15, glass has been done using X-ray diffraction and differential thermal analysis (DTA). The dc conductivity of the glass samples was studied over a temperature range from 300 to 593 K. The temperature dependence of dc conductivity shows two regions. One at relatively high temperature range, above θD/2, and the other at relatively low temperature range, below θD/2. The I-V characteristics of the glasses have been studied as a function of both temperature and Li3PO4 content. The I-V characteristics exhibits threshold switching with differential negative resistance. It's found that both the threshold voltage (Vth) and threshold current (Ith) are dependent on the temperature and lithium phosphate concentration. 相似文献
4.
Thermal evaporation, flash evaporation and rf-sputtering techniques were applied to the preparation of amorphous films of superionic conducting glasses in the systems AgIAg2MoO4 and AgIAg2OB2O3. The flash-evaporated films were amorphous and showed very high conductivities, about 2 × 10?2S/cm for the AgIAg2MoO4 and about 5 × 10?3S/cm for the AgIAg2OB2O3 at room temperature, and gave a Ag+ transport number of unity. The thermal evaporation method produced crystalline-phase included films. The rf-sputtered films were amorphous by X-ray diffraction and the transport number of Ag+ ions was smaller than unity (about 0.9). Thus flash evaporation was concluded to be the most suitable method for preparing amorphous films of superionic conducting glasses. 相似文献
5.
The ternary MoO3-La2O3-B2O3 glasses containing a large amount of MoO3 (10-50 mol%) are prepared, and their structure and crystallization behavior are examined from the Raman scattering spectrum measurements and X-ray diffraction analyses. It is found that the glass transition and crystallization temperatures and the thermal stability against crystallization decrease with increasing MoO3 content. It is suggested that the main coordination state of Mo6+ ions in the glasses is isolated (MoO4)2− tetrahedral units giving strong Raman bands at 830-860 and 930 cm−1. It is found that the crystalline phases in the crystallized glasses are mainly LaMoBO6 and LaB3O6, and the main crystallization mechanism in MoO3-La2O3-B2O3 glasses is surface crystallization. LaMoBO6 crystals are found to give strong Raman bands at 810-830 and ∼910 cm−1. 相似文献
6.
本文在室温到300℃的温度范围内研究了Li4SiO4-Li3VO4和Li4GeO4-Li4SiO4-Li3VO4体系中的离子导电性,发现γII相固溶体Li3+xV1-xSixO4是好的锂离子导体。所研究的成分中Li3.3V0.7Si0.3O4的离子电导率最高,室温下为1×10-5Ω-1·cm-1,在42—192℃的电导激活能为0.36eV,电子电导率可以忽略,因而这是迄今所发现的最好的锂离子导体之一。粗略确定了Li4GeO4-Li4SiO4-Li3VO4三元系中电导率高的范围,发现在Li3.5V0.5Ge0.5O4中Si部分取代Ge可以使电导率进一步提高,Li3.5V0.5Ge0.4Si0.1O4的室温电导率可达1.3×10-5Ω-1·cm-1,电导激活能为0.40eV。
关键词: 相似文献
7.
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
8.
Effect of high electric field on the dc conductivity of TeO2-V2O5-MoO3 amorphous bulk samples with different molar ratio of each component was investigated with gap-type electrode arrangement.
At low electric fields, the current-voltage (I–V) characteristics has a linear shape, while at high electric fields (>103 V/cm), bulk samples show nonlinear behavior (nonohmic conduction) and current-voltage characteristics shows increasing deviation
from Ohm’s law with increasing current density. High-field effect of Pool-Frenkel type was observed at electrical fields about
103−104 V/cm. In addition, positive deviation from Pool-Frenkel effect was observed when a field higher than about 104 V/cm was applied. 相似文献
9.
10.
Rajendra Kumar Singh 《Applied Surface Science》2010,256(6):1725-2361
Glasses with composition x(ZnO,Fe2O3)(65 − x)SiO220(CaO,P2O5)15Na2O (6 ≤ x ≤ 21 mol%) were prepared by melt-quenching technique. Bioactivity of the glasses was investigated in vitro by examining apatite formation on the surface of glasses treated in acellular simulated body fluid (SBF) with ion concentrations nearly equal to those in human blood plasma. Formation of bioactive apatite layer on the samples treated in SBF was confirmed by using Fourier transform infrared reflection (FTIR) spectroscopy, grazing incidence X-ray diffraction (GI-XRD) and scanning electron microscope (SEM) equipped with energy dispersive X-ray spectrometer. Development of an apatite structure on the surface of the SBF treated glass samples as functions of composition and time could be established using the GI-XRD data. FTIR spectra of the glasses treated in SBF show features at characteristic vibration frequencies of apatite after 1-day of immersion in SBF. SEM observations revealed that the spherical particles formed on the glass surface were made of calcium and phosphorus with the Ca/P molar ratio being close to 1.67, corresponding to the value in crystalline apatite. Increase in bioactivity with increasing zinc-iron oxide content was observed. The results have been used to understand the evolution of the apatite surface layer as a function of glass composition and immersion time in SBF. 相似文献
11.
T. SrikumarM.G. Brik Ch. Srinivasa RaoN. Venkatramaiah Y. GandhiN. Veeraiah 《Physica B: Condensed Matter》2011,406(19):3592-3598
Li2O-ZrO2-SiO2: Ho3+ glasses mixed with three interesting d-block elemental oxides, viz., Nb2O5, Ta2O5 and La2O3, were prepared. Optical absorption and photoluminescence spectra of these glasses have been recorded at room temperature. The luminescence spectra of Nb2O5 and Ta2O5 mixed Li2O-ZrO2-SiO2 glasses (free of Ho3+ ions) have also exhibited broad emission band in the blue region. This band is attributed to radiative recombination of self-trapped excitons (STEs) localized on substitutionally positioned octahedral Ta5+ and Nb5+ ions in the glass network. The Judd-Ofelt theory was successfully applied to characterize Ho3+ spectra of all the three glasses. From this theory various radiative properties, like transition probability A, branching ratio βr and the radiative lifetime τr, for 5S2 emission levels in the spectra of these glasses have been evaluated. The radiative lifetime for 5S2 level of Ho3+ ions has also been measured and quantum efficiencies were estimated. Among the three glasses studied the La2O3 mixed glass exhibited the highest quantum efficiency. The reasons for such higher value have been discussed based on the relationship between the structural modifications taking place around the Ho3+ ions. 相似文献
12.
S. Rani Anshu A. Agarwal N. Kishore V.P. Seth 《Journal of Physics and Chemistry of Solids》2008,69(7):1855-1860
Studies of structural and electrical properties have been carried out on a number of glasses with wide ranging compositions in the glass systems Li2O·MO·Bi2O3·B2O3 (where M=Zn or Cd), in order to understand the effect of transition metal (TM) ions on the structure of these glasses. The density and molar volume measurements have also been made to understand the structural changes occurring in these glasses. The dc conductivity measured in the temperature range 423-623 K obeys Arrhenius law. It increases with increase in Li2O/MO ratio. The results of infrared spectra indicate that TM ions (Zn2+ or Cd2+) behave as network former in the present system. Boron exists in both tri- and tetra-hedral units in these glasses and no boroxol ring formation takes place in the glass structure. Values of theoretical optical basicity have also been reported. 相似文献
13.
本文通过对11B核磁共振(11B-NMR)、红外光谱等实验方法,研究了LiF-LiCl-B2O3三元系统玻璃的结构和离子导电性,着重于F-离子在玻璃网络中所起的作用,以及F-,Cl-和Li+离子对导电率的影响。LiF-LiCl-B2O3三元系统玻璃,随LiF含量的增加,B由三角体向四面体变化,从而F-离子进入网络,使玻璃结构由[B2O3]三角体层状结构向三维空间延展,形成了含有[BO3F]基团的三维空间网络,Cl-离子以游离的离子存在于网络中,起着松散网络的作用,对提高电导率有利,而Li+离子作为传导离子,对电导率的贡献是主要的。本系统玻璃的电导率是随LiF,LiCl含量的增加而增大,在300℃时测得电导率σ=6.12×10-4Ω-1·cm-1。
关键词: 相似文献
14.
Mohamed Zahir Roger Olazcuaga René Berger Geneviève Vignaud 《Journal of Physics and Chemistry of Solids》1983,44(8):755-757
An EPR study of fast Na+ ion vitreous conductors of the system B2O3?Na2O?Na3PO4 has been carried out. After X-ray irradiation two types of paramagnetic centers have been observed. The first one is of boron-oxygen hole center (B.O.H.C.) type and similar to that earlier observed for other alkali borate glasses. The second one is of PO42? type. A simulation of its spectrum has been achieved and a defect model discussed. 相似文献
15.
制备了Tm3+(8.0mol%)掺杂(77-x)GeO2-xGa2O3-8Li2O-10BaO-5La2O3(x=4,8,12,16)系列玻璃.系统地研究了Ga2O3从4mol%变化到16mol%时,玻璃的光谱性质与热学性质的变化规律.差热分析表明,随着Ga2O3含量的增加,锗酸盐玻璃的热稳定性增加.运用Judd-Ofelt(J_O)理论计算得到了Tm3+在不同Ga2O3含量的GeO2-Ga2O3-Li2O-BaO-La2O3玻璃中的J-O强度参数(Ω2,Ω4,Ω6)及Tm3+各激发能级的自发跃迁概率、荧光分支比以及辐射寿命等光谱参量.在808nm激光二极管的激发下,测试并分析了Ga2O3对Tm3+荧光光谱特性的影响.随着Ga2O3从4mol%增加到16mol%,Tm3+在1.8μm处的荧光强度呈现先减弱后增强的特性.当Ga2O3含量大约在12mol%时,Tm3+在1.8μm处的荧光强度最弱,受激发射截面达到最小.还初步讨论了Ga2O3对玻璃结构与光谱参数的影响规律.
关键词:
3+掺杂锗酸盐玻璃')" href="#">Tm3+掺杂锗酸盐玻璃
光谱性能
Judd-Ofelt参数
热稳定性 相似文献
16.
J. Grins 《Solid State Ionics》1982,7(2):157-164
The compositional region Na2ZnSiO4-Na2ZnSi2O6 has been investigated by means of X-ray powder diffraction measurements on samples quenched from elevated temperatures. Four different phases have been observed. The powder pattern of the high and low temperature modification of Na2ZnSiO4 could thus be indexed on the basis of an orthogonal cell, while for Na1.6Zn0.8Si1.2O4 a cubic unit cell could be used. These phases are all structurally related to high-cristobalite. The powder pattern of the compound Na2ZnSi2O6 has been indexed on the basis of a monoclinic unit cell. The variation of the ionic conductivity x in NaxZn0.5xSi2-0.5xO4 (1.25 ? x ? 2) has been determined. The best conductivity, 1 × 10-2 (Ω cm)-1 at 600 K is found for the composition Na1.85Zn0.925Si1.075O4. 相似文献
17.
18.
In this paper, we present the spectral results of Dy3+ and Pr3+ (1.0 mol%) ions doped Bi2O3-ZnF2-B2O3-Li2O-Na2O glasses. Measurements of X-ray diffraction (XRD), differential scanning calorimetry (DSC) profiles of these rare-earth ions doped glasses have been carried out. From the DSC thermograms, glass transition (Tg), crystallization (Tc) and melting (Tm) temperatures have been evaluated. The direct and indirect optical band gaps have been calculated based on the glasses UV absorption spectra. The emission spectrum of Dy3+:glass has shown two emission transitions 4F7/2→6H15/2 (482 nm) and 4F7/2→6H13/2 (576 nm) with an excitation at 390 nm wavelength and Pr3+:glass has shown a strong emission transition 1D2→3H4 (610 nm) with an excitation at 445 nm. Upon exposure to UV radiation, Dy3+ and Pr3+ glasses have shown bright yellow and reddish colors, respectively, from their surfaces. 相似文献
19.
Effects of Nb2O5 on thermal stability and optical properties of Er3+-doped tellurite glasses 下载免费PDF全文
Er3+-doped tellurite glasses with molar compositions of
xNb2O5-(14.7-x)Na2O--10ZnO--5K2O--10GeO2--
60TeO2--0.3Er2O3
(x=0, 3, 5, 7 and 9) have been investigated for developing 1.5~μm
fibre and planar amplifiers. The effects of Nb2O5 on the thermal stability
and optical properties of Er3+-doped tellurite glasses have been discussed.
It is noted that the incorporation of Nb2O5 (x=5) increases the thermal
stability of tellurite glasses significantly. Er3+-doped niobium tellurite
glasses exhibit a large stimulated emission cross-section (7.2\times 10-21-
10.7×10-21~cm2 and the gain bandwidth, FWHM×\sigmae^{\rm peak} (274\times 10-28 - 480×10-28~cm3), which are
significantly higher than that of silicate and phosphate glasses. In addition, the
intensity of upconversion luminescence of the Er3+-doped niobium tellurite
glasses decreases rapidly with increasing Nb2O5 content. As a result,
Er3+-doped niobium tellurite glasses might be a potential candidate for
developing laser or optical amplifier devices. 相似文献