Glass forming regions and dielectric properties of Na2O-Bi2O3-TiO2-P2O5 glasses

The glass forming regions have been determined in the quaternary systems Na₂O-Bi₂O₃-0.05TiO₂-P₂O₅ and Na₂O-0.05Bi₂O₃-TiO₂-P₂O₅. The largest vitreous do main has been found in the diagram with 5mol% of titanium oxide TiO₂- The variation of dielectric constant has been followed along two lines inside the glass regions. e'_r increases with increasing amount of sodium oxide Na₂O and diminishes with increasing percentage of either Bi₂O₃ or TiO₂.     

Glass transition (Tg) and dielectric loss in Na3PO4–Pb3(PO4)2–BiPO4 phosphate glasses

Thermal and dielectric loss properties of Na₃PO₄-Pb₃(PO₄BiPO₄ (Na₂O-PbO-Bi₂O₃-P₂O₅) phosphate glasses, have been studied by the differential scanning calorimetry (DSC) and electrical factor loss (tgδ) measurements. Experiments have been carried out from ambient temperature to 500°C and show a strong influence of sodium ions on T_g and tgδ.     

Spectroscopic studies on Li2O–MgO–Bi2O3–B2O3 glasses

MgO-Li₂O-Bi₂O₃-B₂O₃ glasses were prepared by melt quench technique and analyzed with the help of refractive index, optical, IR, and Raman spectroscopy studies. The present glasses exhibited the mixed modifier effect (MME) through refractive index change non-linearly. The variation in the indirect optical band gap and band tailing in MgO content have been discussed with the glass structure. Based on the obtained values of α_o2-, optical basicity, and interaction parameters, the present glasses were termed as very semi covalent acidic oxide glasses. Raman and Infrared spectra reveal that these glasses are built up of BO₃, BO₄ units of B₂O₃ and octahedral [BiO₆], pyramidal [BiO₃] units of Bi₂O₃ were observed.     

Na2O-Al2O3-P2O5系统玻璃中的[Al-O-P]-基团

本文报道Na₂O-Al₂O₃-P₇O₅系统玻璃中[Al-O-P]^-基团的Raman谱。我们把高频峰有规律地移向低波数归结为由[Al-O-P]^-基团构成的玻璃网络聚合度下降造成。 关键词：     

Study of the electronic structure of sodium-vanadium bronze (Na x V2O5) single crystals at x = 0.23, 0.28, and 0.33

The photoelectron spectra and electron energy loss spectra in reflection geometry have been measured for the clean (010) surface of Na _x V₂O₅ compounds with x = 0.23, 0.28 and 0.33. The investigations made it possible to reveal some specific features of the electronic structure of such compounds. Ionization parameters of trinitrotoluene molecules have been measured at the surface of polycrystalline Na_0.33V₂O₅ and the (010) surface of the single crystals Na_0.28V₂O₅ and Na_0.33V₂O₅. The results of investigations can be successfully used in a construction of the model of electronic structure of alkaline oxide bronzes and also in the development of materials for selective surface ionization sources of organic nitro-compounds.     

A mössbauer investigation of non-bridging oxygens in Na2O-Fe2O3-B2O3 glasses

Mössbauer measurements of sodium borate glasses 4 Fe₂O₃· x Na₂O· (96-x) B₂O₃ (x=6, 10, 15, 20, 25, 30) have been carried out. It was found that Fe³⁺ is present in both octahedral and tetrahedral sites, whereby the tetrahedral sites are preferred. In the range of Na₂O contents higher than about 15 mol%, the isomer shifts and quadrupole splittings for Fe³⁺ decrease continuously with increasing Na₂O concentration. These changes could be attributed to the formation of non-bridging oxygens (NBO) in the neighborhood of ferric ions. Increasing Na₂O content thus gives rise to more NBO increasing the symmetry of the iron polyhedra.     

微弧等离子喷涂碳纳米管/纳米Al2O3-TiO2复合涂层的吸波性能研究

将碳纳米管与纳米Al₂O₃-TiO₂陶瓷粉末超声共混制备了碳纳米管/纳米Al₂O₃-TiO₂复合粉末,测试了复合粉末在2—18GHz波段的电磁参数.研究表明：随着碳纳米管质量分数的增加,碳纳米管/纳米Al₂O₃-TiO₂复合粉末的复介电常数和损耗角不断增大.当碳纳米管质量分数和厚度增加时,复合粉末对电磁波的反射率峰值先增加后减小,而谐振频率不断向低频移动.采用微弧等离子喷涂制备了7wt%碳纳米管/纳米Al₂O₃-TiO₂复合吸波涂层,当厚度为1.5mm时,涂层最小反射率为-24.0dB,当厚度为2.0mm时,涂层小于-10dB的频带宽为3.60GHz,当温度为500℃高温时,1.0mm厚的涂层最小高温反射率为-12.2dB,小于-10dB频带宽为2.0GHz.复合涂层的实际厚度D与理论厚度d呈线关系：d=0.898D+0.515. 关键词： 等离子喷涂 碳纳米管 2O₃-TiO₂')" href="#">纳米Al₂O₃-TiO₂ 吸波性能     

Preparation of photocatalytic Fe2O3-TiO2 coatings in one step by metal organic chemical vapor deposition

There are two major difficulties in the TiO₂ liquid-solid photocatalytic system: effective immobilization of the TiO₂ particles; and improving the catalytic activity under visible light. To simultaneously solve these two problems, Fe₂O₃-TiO₂ coatings supported on activated carbon fiber (ACF), have been prepared in one step by a convenient and efficient method—metal organic chemical vapor deposition (MOCVD). XRD results revealed that Fe₂O₃-TiO₂ coatings mainly composed of anatase TiO₂, α-Fe₂O₃ phases and little Fe₂Ti₃O₉. The pore structure of ACF was preserved well after loading with Fe₂O₃-TiO₂ coatings. UV-vis diffuse reflectance spectra showed a slight shift to longer wavelengths and an enhancement of the absorption in the visible region for Fe₂O₃-TiO₂ coatings, compared to the pure TiO₂ sample. A moderate Fe₂O₃-TiO₂ loading (13.7 wt%) was beneficial to mineralizing wastewater because the intermediates could be adsorbed onto the surface of photocatalyst following decomposition. The stable performance revealed that the Fe₂O₃-TiO₂ coatings were strongly adhered to the ACF surface, and the as prepared catalysts could be reused showing potential application for wastewater treatment.     

Fabrication and Li+-intercalation properties of V2O5-TiO2 composite nanorod arrays

A capillary-enforced template-based method has been applied to fabricate V₂O₅-TiO₂ composite nanorod arrays via filling mixture of VOSO₄ and TiOSO₄ solutions into the pores of polycarbonate membrane. For comparison purposes, pure V₂O₅ nanorod arrays were prepared through the similar template-based method with V₂O₅ sol and the sol was synthesized through the V₂O₅-H₂O₂ route. The nanorods covered completely a large area and projected from the surface of ITO substrate. The addition of TiO₂ to V₂O₅ has demonstrated to greatly affect the Li⁺ intercalation capacity of V₂O₅. For example, V₂O₅-TiO₂ nanorod array with molar ratio V/Ti=75/25 delivered 1.5 times discharge capacity of V₂O₅ nanorods at a current density of 92 mA/g. Such improvement in the intercalation properties was ascribed to the change of crystallinity and possible modification in lattice structure and interaction forces between adjacent layers in V₂O₅. PACS 81.05.Je; 82.45.Yz; 81.10.Dn; 81.20.Fw; 82.47.Aa     

SiO x -P2O5 films—promising components in photonic structure

We intend to prepare periodic multilayered structures for photonic applications. With this goal we have performed a study of some characteristics of SiO _x -P₂O₅ films deposited by the sol–gel method on glass and ITO (InSnO _x )-coated glass. The as prepared films were annealed to different temperatures (150 and 200°C). The chemical composition of the samples was determined by X-ray Photoelectron Spectroscopy (XPS). The XPS results revealed the presence of P in the as-deposited films. The structural an optical properties were examined by Fourier Transform Infrared Spectroscopy (FTIR), Spectroellipsometry (SE) and UV Transmission Spectroscopy. IR spectra of the deposited films attest the interaction of an amorphous SiO₂ with the H₃PO₄ used as a P-precursor. Refractive indices for individual SiO _x -P₂O₅ determined from SE measurements show a densification of the layer structure with the increasing temperature in the thermal treatment. The UV transmission spectra revealed a lower transmission for the sol-gel SiO _x -P₂O₅ films as compared to ITO/glass substrate. AFM images proved the densification of the films with annealing in agreement with the ellipsometric results. The work was originally presented at “Physics of Photonic Crystals and Metamaterials (PPCM)” Workshop, Brussels, 12–15 June, 2006.     

Interfacial barrier contribution in Na2B4O7 glass system

Summary Frequency domain measurements on Na₂B₄O₇ and Na₂B₄O₇(95%)-V₂O₅(5%) glass systems have been carried out in the frequency range 10⁻² to 10⁴ Hz and temperature range 300 to 450 K. The complex capacitance has shown fractional power law dependences on frequency which obey the generalized Maxwell-Wagner relationships. The activation energy is found to increase with an increase in V₂O₅ composition.     

Glass Transition (T g) And Ftir Study Of Na2O-CuO-Bi2O3-P2O5 Glasses

(40?x)Na₂O-xCuO-10Bi₂O₃-50P₂O₅ glasses (0 h x h 40) were prepared and studied. Their density, molar volume, glass transition temperature and IR spectroscopy have been investigated in order to understand the structural role of Bi₂O₃ and CuO in these glasses. In the sodium bismo-phosphate glass, the structures consist of some phosphate chains linked together through P-O-Bi bonds. When copper oxide is added to sodium bismo-phosphate glass, phosphate chains are depolymerised by the incorporation of Cu through P-O-Cu bonds. The former bonds are the origin of the partial glass forming ability of Bi³⁺ and Cu²⁺.     

d 1 Electrons in amorphous semiconducting V2O5 and MoO3 compounds. (ESR measurements)

We have performed electron spin resonance experiments on binary amorphous V₂ O₅- and MoO₃ compounds (V₂O₅-TeO₂, V₂O₅-BaO, V₂O₅-PbO, V₂O₅-GeO₂, V₂O₅-As₂O₃, MoO₃-P₂O₅, MoO₃-TeO₂) and determined the parameters of the corresponding spin Hamiltonian by 3 cm-, 1.2 cm- and 8 mm band measurements. These measurements yielded values of the contribution to the mean energy difference of thed ¹ levels between different vanadium- or molybdenum sites caused by fluctuations of the crystal field.     

可紫外激光刻写的掺铒铋硅酸盐玻璃光谱性质研究

报道了可紫外激光刻写的掺铒Na₂O-Bi₂O₃-SiO₂和Na₂O-B₂O₃-Bi₂O₃-SiO₂玻璃的光谱特性. 测量和计算了玻璃的光谱参数，分析、讨论了Bi₂O₃和B₂O₃含量变化对光谱参数的影响.实验表明基质玻璃中Bi₂O₃和B₂O₃含量改变可有效调节掺铒铋硅酸盐玻璃光谱参数.Bi₂O₃和B₂O₃含量增加，玻璃的光吸收和荧光性质改善，但Er³⁺离子的⁴I_13/2能级寿命降低.在B₂O₃含量为40%(Bi₂O₃/SiO₂＝0.67)时，Er³⁺离子峰值发射截面、⁴I_13/2能级的荧光寿命和荧光半高宽分别为8.49×10^－21cm²，0.52ms和78nm.结果表明掺铒铋硅酸盐玻璃是有前途的紫外光敏有源玻璃材料之一.     

Availability of water glass/Bi2O3 composites in dielectric and gamma-ray screening applications

ABSTRACT

Sodium silicate (Na₂Si₃O₇) also known as water glass is a very low cost material which is used in many industrial applications such as a builder in detergents, as a binder and adhesive etc. But so far the electrical properties of sodium silicate and its ability to screen radiation have never been investigated. In the present study, the frequency dependent electrical properties and gamma-ray shielding performance of water glass based bismuth oxide composites have been studied for the first time. In accordance with this purpose, Na₂Si₃O₇/Bi₂O₃ glassy composites have been prepared for searching their possible applications in electronics and radiation screening. The surface morphology of the samples have been determined by Scanning Electron Microscope (SEM). The frequency dependent electrical properties such as complex impedance, complex dielectric function and conductivity have been analyzed at room temperature between 1 and 40?MHz. As a result of alternative current (ac) electrical analysis, it has been determined that the Na₂Si₃O₇/Bi₂O₃ composites can be utilized as a dielectric layer in capacitors. On the other hand, since bismuth oxide is an anti-radiative material, the gamma-ray screening parameters such as mass attenuation coefficient, half layer and tenth layer values along with mean free path of the composites have been defined experimentally by using NaI(Tl) scintillation detector for the Ba-133 radiation source at 81 and 356?keV. The values of these parameters have also been checked by Monte–Carlo simulation. Since a good agreement has been assigned between experimental and Monte–Carlo simulation results, the related gamma ray shielding parameters have been determined by Monte–Carlo simulation for other gamma photon energies (140?keV, 208?keV, 468?keV, and 661?keV) which are generated from Tc-99, Lu-177, Ir-132, and Cs-137 sources. Ultimately, Na₂Si₃O₇/Bi₂O₃(35%) composite has been suggested as an eco-friendly, lead-free glassy structured material for the gamma radiation shielding in medical applications.     

Glass Transition (T g ) and Dielectric Constant (e'r) of Li3PO4-Pb3(PO4)2-BiPO4 (Li2O-PbO-Bi2O3-P2O5) Glasses

Thermal and dielectric properties of heavy metal oxide glasses, Li₃PO₄-Pb₃(PO₄)₂-BiPO₄ (Li₂O-PbO-Bi₂O₃-P₂O₅), were studied from ambient temperature to 500°C by differential thermal analysis (DTA) and dielectric constant (?′_r) measurements. Experiment results show a strong influence of lithium, lead and bismuth ions on T _g and ?′_r.     

Optical absorption and thermoluminescence properties of ZnF2-MO-TeO2 (MO=As2O3, Bi2O3 and P2O5) glasses doped with chromium ions

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.     

A Raman spectroscopic and TEM study on the structural evolution of Na2Ti3O7 during the transition to Na2Ti6O13

The synthesis of sodium hexatitanate from sodium trititanate was characterized by Raman spectroscopy, X‐ray diffraction (XRD) and high‐resolution transmission electron microscopy (HRTEM). The structural evolution from trititanate to hexatitanate was studied using Raman spectra, XRD and HRTEM techniques. It was found that the Raman bands at 279 cm⁻¹ corresponding to very long Ti O bonds and at 883 cm⁻¹ corresponding to the very short Ti O bonds decrease in intensity and finally disappear during the transition from sodium trititanate to sodium hexatitanate. The band at 922 cm⁻¹ corresponding to an intermediate‐length Ti O bond was observed to become stronger with the increase in temperature, indicating that there is no terminal oxygen atom in the crystal structure of Na₂Ti₆O₁₃ and that all the oxygen atoms become linearly coordinated by two titanium atoms. Furthermore, the TiO₆ octahedron in Na₂Ti₆O₁₃ are more regular because the very long (2.2 Å) or very short (1.7 Å) Ti O bonds disappear. It is revealed that the phase transition from trititanate to hexatitanate is a step‐by‐step slipping process of the TiO₆ octahedral slabs with the loss of sodium cations, and a new phase with formula Na_1.5H_0.5Ti₃O₇ has been discovered as an intermediate phase to interlink Na₂Ti₃O₇ and Na₂Ti₆O₁₃. Copyright © 2010 John Wiley & Sons, Ltd.     

Frequency domain measurements on Na2B4O7−V2O5 semiconducting glass

Summary Dielectric measurements on Na₂B₄O₇(99.5%)−V₂O₅(0.5%) glass system, in the frequency range 10⁻³ to 10⁴ Hz and temperature range 300 to 500 K, have been carried out. The normalized plots of complex capacitance have shown a single mechanism responsible for conduction for both volume and surface measurements with their close values of activation energies (0.67±0.03) eV and (0.64±0.03) eV, respectively. The low-frequency dispersion (LFD) behaviour has been observed to be perturbed by the presence of more than one competing process. The impedance plots have shown a parallel combination of a capacitor (C) and a resistor (R), with some contribution of a dispersive element due to charge accumulation in the vicinity of the electrodes. The values ofR andC were found to be of the same order of magnitude, for both surface and volume measurements. The observedR has shown a decrease with an increase in temperature due to an increase in mobility of Na⁺ ions, whereasC remains practicaly constant. The complex capacitance surface behaviour is dominated by volume, due to hygroscopy of this glass system.     

Fluorescence features of Sm ions in Na2SO4-MO-P2O5 glass system—Influence of modifier oxide

Na₂SO₄-P₂O₅:Sm³⁺ glasses mixed with three different alkaline earth modifier oxides viz., MgO, CaO and BaO were prepared. Optical absorption and photoluminescence spectra of these glasses have been recorded at room temperature; the Judd-Ofelt theory was successfully applied to characterize these spectra. From this theory, various radiative properties like transition probability A, branching ratio β_r, the radiative lifetime τ_r, for various emission levels in the spectra 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 in the change of scenario for modifying oxides in the glass network.