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Structural analysis of x[(100−y)Ag2O·yMnO]·(100−x)[2B2O3·As2O3] glasses, with x=10 mol% and 0≤y≤10 mol%, was performed by means of FT-IR and FT-Raman spectroscopies. The purpose of this work is to investigate the structural changes that appear in the xAg2O·(100−x)·[2B2O3·As2O3] glasses with the addition and increase in manganese ions content. FT-IR measurements revealed the presence of pyro-, ortho-, di-, tri-, tetra- and penta-borate groups and structural units characteristic to As2O3 in the structure of the studied glasses. FT-IR spectroscopy measurements also show that BO3 units are the main structural units of the glass system. The presence of structural units characteristic to Ag2O were not directly evidenced by FT-IR spectroscopy. In addtition, the FT-Raman analysis evidenced the presence of boroxol rings in the structure of the studied glasses. 相似文献
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Sm3+-doped calcium fluoride bismuth borate glasses were prepared and characterized optically and the oscillator strengths and Judd–Ofelt parameters for the glass containing 1.5 mol% of Sm2O3 were calculated. Density and optical absorption, transmission and the emission spectra were measured. The values of Judd–Ofelt parameters suggested an increase in the degree of asymmetry the local ligand field at Sm3+ sites. The optical band gap energy, band tailing parameter and Urbach's energy were calculated for all glass samples. It was found that with increasing the concentration of Sm2O3 content the values of the optical band gap energy decrease whereas Urbach's energy increases. Absorption and excitation spectra indicate that commercial UV and blue laser diodes, blue and bluish-green LEDs and Ar+ optical laser are powerful excitation sources for Sm3+ visible fluorescence in the glass. 相似文献
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Essam R. Shaaban 《Physica B: Condensed Matter》2011,406(3):406-411
Glasses with compositions 70B2O3-30Bi2O3 and 70B2O3-30PbO have been prepared and studied by differential thermal analysis (DTA). The crystallization kinetics of the glasses were investigated under non-isothermal conditions. From the dependence of glass-transition temperature (Tg) on heating rate, the activation energy for the glass transition was derived. Similarly the activation energy of the crystallization process was determined. Thermal stability of these glasses were achieved in terms of the characteristic temperatures, such as glass-transition temperature, Tg, onset temperature of crystallization, Tin, temperature corresponding to the maximum crystallization rate, Tp, beside the kinetic parameters, K(Tg) and K(Tp). The results revealed that 70B2O3-30PbO is more stable than 70B2O3-30Bi2O3. The crystallization mechanism is characterized for both 70B2O3-30Bi2O3 and 70B2O3-30PbO glasses (kinetic exponent n=2.06 for 70B2O3-30Bi2O3, and n=3.03 for 70B2O3-30PbO). The phases at which the glass crystallizes after the thermal process were identified by X-ray diffraction. 相似文献
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木文研究了Al2O3对B2O3-0.7Li2O-0.7LiCl非晶态的形成和电学性能的影响,我们发现:加入适量的Al2O3后,无需借助液氮骤冷技术,直接将熔体倾倒在室温下的紫铜板上就很容易形成大块非晶锂离子导体B2O3-0.7Li2O-0.7LiCl-xAl2O3。Al2O3的加入使B2O3-0.7Li2O-0.7LiCl的电导率有所降低,但在高温下不太明显,电导激活能略微升高,实验发现:Al2O3含量x=0.03是较合适的剂量,较容易形成大块非晶态,对电导率的影响也不大。
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Li2O-Nb2O5-ZrO2-SiO2 glasses mixed with different concentrations of V2O5 were crystallized. The samples were characterized by XRD, SEM and DTA techniques. The SEM pictures indicated that the samples contain well defined and randomly distributed crystal grains. The X-ray diffraction studies have revealed the presence of several crystalline phases in these samples. Optical absorption, ESR and photoluminescence spectral studies on these samples have indicated that a considerable proportion of vanadium ions do exist in V4+ state in addition to V5+ state and the redox ratio seems to be increasing with increase in the concentration of crystallizing agent V2O5. The infrared spectral studies have pointed out the existence of conventional SiO4, ZrO4, NbO6, VO structural units in the glass ceramic network. The study of dielectric properties suggested a decrease in the insulating character of the glass ceramics with increase in the crystallizing agent. A.C. conductivity in the high temperature region seems to be connected mainly with the polarons involved in the process of transfer from V4+↔V5+ ions. 相似文献
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Paramjeet Singh Ashish Agarwal Sujata Sanghi Navneet Singh Satish Khasa 《Physica B: Condensed Matter》2012,407(24):4752-4759
Solid solutions of bismuth layered (Bi2O3)(BaxMo1−xO3) (0.2≤x≤0.8, x is in step of 0.2) ceramics were prepared by conventional solid-state reaction of the constitutive oxides at optimized temperatures with a view to study its electrical properties. Powder X-ray diffraction has been employed for physical characterization and an average grain size of ∼16 to 22 nm was obtained. XRD study reveals the single phase structure of the samples. Dielectric properties such as dielectric constant (ε′), dielectric loss (tanδ) and ac electrical conductivity (σac) of the prepared ceramics sintered at various temperatures in the frequency range 101–107 Hz have been studied. A strong dispersion observed in the dielectric properties shows the relaxor type behavior of the ceramic. The presence of maxima in the dielectric permittivity spectra indicates the ferroelectric behavior of the samples. Impedance plots (Cole–Cole plots) at different frequencies and temperatures were used to analyze the electric behavior. The value of grain resistance increases with the increase in Ba ion concentration. The conductivity mechanism shows a frequency dependence, which can be ascribed to the space charge mainly due to the oxygen vacancies. The relaxation observed for the M″ (ω) or Z″ (ω) curves is correlated to both localized and long range conduction. A single ‘master curve’ for the normalized plots of all the modulus isotherms observed for a given composition indicates that the conductivity relaxation is temperature independent. 相似文献
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The effect of heat treatment on the optical and electrical properties of Ge15Sb10Se75 and Ge25Sb10Se65 thin films in the range of annealing temperature 373-723 K has been investigated. Analysis of the optical absorption data indicates that Tauc's relation for the allowed non-direct transition successfully describes the optical processes in these films. The optical band gap (Egopt.) as well as the activation energy for the electrical conduction (ΔE) increase with the increase of annealing temperature (Ta) up to the glass transition temperature (Tg). Then a remarkable decrease in both the Egopt. and ΔE values occurred with a further increase of the annealing temperature (Ta>Tg). The obtained results were explained in terms of the Mott and Davis model for amorphous materials and amorphous to crystalline structure transformations. Furthermore, the deduced value of Egopt. for the Ge25Sb10Se65 thin film is higher than that observed for the Ge15Sb10Se75 thin film. This behavior was discussed on the basis of the chemical ordered network model (CONM) and the average value for the overall mean bond energy 〈E〉 of the amorphous system GexSb10Se90−x with x=15 and 25 at%. The annealing process at Ta>Tg results in the formation of some crystalline phases GeSe, GeSe2 and Sb2Se3 as revealed in XRD patterns, which confirms our discussion of the obtained results. 相似文献
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For optical basicity and electronic polarizability, the previous studies basically concentrate on the wavelength range of the visible light region. However, heavy metal oxides glasses have a reputation of being good materials for infrared region. In this study, new data of the average electronic polarizability of the oxide ion O2-, optical basicity Λ and Yamashita–Kurosawa's interaction parameter A of Bi2O3–B2O3 glasses have been calculated in a wavelength range from 404.66 to 1083.03 nm. The present investigation suggests that both O2- and Λ increase gradually with increasing wave number, and A decreases with increasing wave number. Furthermore, close correlations are studied among O2-, Λ, A and refractive index n in this paper. Particularly, it has been found that a quantitative relationship between electronic polarizability and optical basicity is observed in a wavelength range from 404.66 to 1083.03 nm. Our present study extends over a wide range of O2-, Λ and A values. 相似文献
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SO2 adsorption capacity of K2CO3-impregnated activated carbon as a function of K2CO3 content loaded by soaking and incipient wetness 总被引:1,自引:0,他引:1
The SO2 adsorption capacity of K2CO3-impregnated activated carbons, prepared by soaking carbon in large volumes of K2CO3 in solution of various concentrations, varies linearly with respect to the loading of K2CO3 on the carbon up to about 12% K2CO3 by weight. Above 12%, the capacity for SO2 levels out and then decreases. This suggests that at high loadings the K2CO3 either aggregates and/or blocks pores of the activated carbon. In contrast, the adsorption capacity of carbons prepared by repeatedly (maximum of three times total) loading K2CO3 via incipient wetness is much larger than that of the soaked samples, up to 70% more, when the loading of K2CO3 is greater than 12%. Static and dynamic adsorption, DSC, SEM, EDX and incipient wetness studies of the samples show that the impregnant aggregates but does not block carbon pores. 相似文献
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Gurinder Pal Singh Parvinder KaurSimranpreet Kaur D.P. Singh 《Physica B: Condensed Matter》2012,407(21):4269-4273
xV2O5–xCeO2–(30−x)PbO–(70−x) B2O3 glasses are synthesized by using the melt quench technique. The number of studies such as XRD, density, molar volume, optical band gap, refractive index and FTIR spectroscopy are employed to characterize the glasses. The band gap decreases from 2.20 to 1.78 eV and density increases from 3.49 to 4.25 g/cm3. FTIR spectroscopy reveals that incorporation of V2O5 in glass network helps to convert the structural units of [BO3] into [BO4]. At higher concentration of vanadium, VO vibration of [VO5] structural units and V–O–V vibration are present. The bond ionicity of glasses increases with incorporation of V2O5 contents. 相似文献
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G. Murali Krishna 《Journal of luminescence》2008,128(4):631-634
Li2O-CaF2-P2O5 glasses mixed with different concentrations of TiO2 (ranging from 0 to 0.8 mol%) were crystallized at 500 °C. The photo luminescence spectra of these samples excited with the wavelengths corresponding to their absorption edges have been recorded at room temperature. The spectra exhibited an emission band in the wavelength region 470-500 nm. The emission band is identified due to the charge transfer from O2− ion in to empty 3d orbital of octahedrally positioned Ti4+ ions. The analysis of the results further indicates the highest luminescence efficiency for the glass ceramic sample crystallized with 0.6 mol% of TiO2. 相似文献
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Qiuhua Nie Tiefeng Xu Xiang Shen Xudong Zhang 《Journal of Physics and Chemistry of Solids》2007,68(4):477-481
A series of Er3+-doped Bi2O3-B2O3-SiO2-Na2O glasses with different hydroxyl groups were prepared and the interaction between the Er3+ ions and OH groups was investigated. Infrared spectra were measured in order to calculate the exact content of OH groups in samples. The observed increase of the fluorescence lifetime with the oxygen bubbling time has been related to the reduction in the OH content concentration evidenced by infrared (IR) absorption spectra, which confirmed that the OH groups were dominant quenching centers of excited Er3+ and a cause of concentration quenching of 1.5 μm band emission. Various nonradiative decay rates from 4I13/2 of Er3+ with the change of OH content were determined from the fluorescence lifetimes and radiative decay rates, which were calculated on the basis of Judd-Ofelt theory. 相似文献
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以Li2CO3、Nb2O5、TiO2和Eu2O3为原料,采用固相法制备Eu3+掺杂的5Li2CO3-1Nb2O5-5TiO2(LNT)发光介质陶瓷。通过密度、XRD和荧光光谱测试,对0.2%(质量分数)Eu2O3掺杂的陶瓷片进行性能表征。结果表明:1 120℃烧结致密的陶瓷片,其晶相结构为“M-相”与Li2TiO3两相复合构成;在400 nm的近紫外光激发下,样品有较强的橙光(592 nm)和红光(615 nm)发射,分别属于Eu3+的5D0→7F1的磁偶极跃迁和5D0→7F2的电偶极跃迁。 相似文献
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Magnetoelectric (ME) nanocomposites containing Ni0.75Co0.25Fe2O4-BiFeO3 phases were prepared by citrate sol-gel process. X-ray diffraction (XRD) analysis showed phase formation of xNi0.75Co0.25Fe2O4-(1−x)BiFeO3 (x=0.1, 0.2, 0.3 and 0.4) composites on heating at 700 °C. Transmission electron microscopy revealed the formation of powders of nano order size and the crystal size was found to vary from 30 to 85 nm. Dispersion in dielectric constant (ε) and dielectric loss (tan δ) in the low-frequency range have been observed. It is seen that nanocomposites exhibit strong magnetic properties and a large ME effect. On increasing Ni0.75Co0.25Fe2O4 contents in the nanocomposites, the saturation magnetization (MS) and coercivity (HC) increased after annealing at 700 °C. The large ME output in the nanocomposites exhibits strong dependence on magnetic bias and magnetic field frequency. The large value of ME output can be attributed to small grain size of ferrite phase of nanocomposite being prepared by citrate precursor process. 相似文献
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R.H. ChenS.C. Shern 《Journal of Physics and Chemistry of Solids》2002,63(11):2069-2077
Optical observation under the polarizing microscope and DSC measurements on K3H(SeO4)2 single crystal have been carried out in the temperature range 25-200 °C. It reveals a high-temperature structural phase transition at around 110 °C. The crystal system transformed from monoclinic to trigonal. Electrical impedance measurements of K3H(SeO4)2 were performed as a function of both temperature and frequency. The electrical conduction and dielectric relaxation have been studied. The temperature dependence of electrical conductivity indicates that the sample crystal became a fast ionic conductor in the high-temperature phase. The frequency dependence of conductivity follows the Jonscher's universal dynamic law with the relation σ(ω)=σ(0)+Aωn, where ω is the frequency of the AC field, and n is the exponent. The obtained n values decrease from 1.2 to 0.1 from the room temperature phase to fast ionic phase. The high ionic conductivity in the high-temperature phase is explained by the dynamical disordering of protons between the neighboring SeO4 groups, which provide more vacant sites in the crystal. 相似文献
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R.T. Karunakaran K. Marimuthu S. Surendra Babu S. Arumugam 《Physica B: Condensed Matter》2009,404(21):3995-4000
Structural, optical and thermal properties of Dy3+ doped lithium fluoroborate glasses have been studied for various concentrations of Dy3+ from 0.5 to 5 wt%. The XRD studies confirm the amorphous nature of the glasses while the FTIR spectra reveal the presence of BO3 and BO4 local structural units. The UV–VIS–NIR absorption studies were carried out to calculate the bonding parameters ( and δ), to identify the ionic/covalent nature of the glasses. The JO parameters, experimental and theoretical oscillator strengths were also determined and reported. The luminescence spectra have been studied to determine the radiative transition probability (A), stimulated emission cross section () and the experimental and calculated branching ratios (βR) for the excited levels that include 4F9/2→6H11/2, 6H13/2, and 6H15/2 transitions. The variation of optical properties with varying concentrations of dysprosium oxide content in the glasses are reported and discussed. The thermal behavior of Dy3+ doped lithium fluoroborate glasses have been reported by recording DSC thermograms. 相似文献
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通过真空密封热处理、避免了样品晶化后吸水引起的误差,采用脉冲法在293K和77K测量了晶化过程初期三种非晶锂离子导体B2O3-0.7Li2O-0.7LiCl-xAl2O3(x=0.15,0.10和0.05)的7Li核磁共振谱。发现在低温(77K)只有固相锂离子对应的自旋-自旋弛豫时间T2=87μs,严格按高斯函数衰减。在室温下固相锂离子对应的T2s=127μs,仍是高斯型;但液相锂离子对应的T2却按洛仑兹函数衰减。这反映出锂离子导体的固-液二相性。三种非晶B2O3-0.7Li2O-0.7LiCl-xAl2O3(x=0.15,0.10和0.05)分别在热处理温度401,388和381℃附近,其液相锂离子对应的T2l都剧增,其吸收谱线宽都变窄。由此再次验证了非晶母体与微晶之间的两相界面效应的物理图象。
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