Bibliographies thématiques / Dielectric Spectra - Glass Network Structure

Littérature scientifique sur le sujet « Dielectric Spectra - Glass Network Structure »

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Publié le 7 septembre 2023

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Articles de revues sur le sujet "Dielectric Spectra - Glass Network Structure"

Xu, Xing Jun, Yun Long Yue, Hai Tao Zhang et Zhao Du. « Effect of MgO on Structure and Properties of CaO-Al₂O₃-SiO₂ Glass System ». Advanced Materials Research 306-307 (août 2011) : 531–34. http://dx.doi.org/10.4028/www.scientific.net/amr.306-307.531.

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CaO-Al2O3-SiO2system glasses with MgO were prepared by melt quenching. The glass structure was characterized by Infrared spectra (IR) and Differential Thermal Analysis (DTA). Dielectric properties, devitrification and chemical durability have been studied. IR spectra and DTA indicated that glass network structure change by doping MgO. The glass chemical improved and dielectric constant decreased after doping with MgO. The glass shows a severe tendency of phase separation.

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Rani, S., S. Sanghi, A. Agarwal et N. Kishore. « Study of Structure and Li⁺ Ions Dynamics in Presence of Fe₂O₃ in Bi₂O₃∙B₂O₃ Glasses ». Solid State Phenomena 161 (juin 2010) : 51–61. http://dx.doi.org/10.4028/www.scientific.net/ssp.161.51.

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Glasses having composition xLi2O∙(30-x)Fe2O3∙20Bi2O3∙50B2O3 (0 ≤ x ≤ 30, in mol%) have been prepared using normal melt-quench technique. The variation in density and molar volume with composition has been investigated in terms of the structural modification that takes place in the glass matrix on decreasing Fe2O3. Infrared spectra of these glasses were recorded over continuous spectral range (400-4000 cm-1) in an attempt to study their structure systematically. IR spectra show that with increase in Li2O/Fe2O3 ratio there is formation of more structural units (e.g. [FeO4/2]-Li+) in the glass network. Bi3+ cations are present as [BiO6] octahedral units and acts as modifier in this glass system. Further, the effect of transition metal ions (iron) on the dynamics of lithium bismuth borate glasses has been studied in the frequency range of 20 Hz - 1 MHz and in the temperature range 240 – 350 °C using impedance spectroscopy. Possible conduction mechanisms are discussed. Various AC and DC electrical and dielectric parameters have been calculated and analyzed. The results show that the contribution of electronic conduction towards conductivity decreases with decreasing iron concentration, which is understood to be due to hopping of electrons from Fe2+→Fe3+. The frequency dependent conductivity has been studied using both conductivity and modulus formalism. The absence of maximum observed in dielectric permittivity in the temperature and frequency range studied, indicate the non-ferroelectric behavior of the glasses.

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Modak, D. K., G. Banerjee, M. Karar, M. Sadhukhan, A. K. Bera, B. K. Chaudhuri et P. K. Pal. « Nonlinear physical properties of some nonconventional semiconducting Bi–Pb–Ba–O glasses ». Journal of Materials Research 13, n^o 8 (août 1998) : 2328–33. http://dx.doi.org/10.1557/jmr.1998.0325.

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Semiconducting Bi1−xPbxBaO3−δ (or BPB) glasses with x = 0 to 0.8 have been prepared by fast quenching from the melt. Interesting anomalies in the temperature-dependent polaronic conductivity and dielectric constant have been observed in all these glass compositions at temperatures, Tp, varying from 310 to 330 K (depending on Pb concentration). This nonlinear behavior is considered to be associated with the local ordering or the displacements of the BiO3 type pyramidal structural units present in the glass matrix (observed from the infrared spectra of these glasses). This type of ordering/displacement gives rise to a local instability in the glass network structure which is also supported by the observed heat capacity anomaly around the same temperatures Tp.

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Yan, Hong Qiang, Hua Qing Wang, Jie Cheng et Zheng Ping Fang. « Cure of Neat Resins and Properties of Composites for Interpenetrating Polymer Networks from the Novel Bismaleimide and Cyanate Containing Naphthalene ». Advanced Materials Research 233-235 (mai 2011) : 1636–41. http://dx.doi.org/10.4028/www.scientific.net/amr.233-235.1636.

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To obtain attractive properties, such as increased resistance to moisture absorption, low dielectric constant and low dielectric loss, the novel bismaleimide, viz. 2,7-bis(4-maleimidophenoxy) naphthalene (BMPN), and dicyanate ester, viz. 2,7-dihydroxynaphthalene dicyanate (DNCY), containing naphthalene ring and ether linkages, have been synthesized. The cure process of the blends including of 0.11mmol/mol Fe(AcAc)3 and 2% nonylphenol is characterized by in-situ FTIR. The result obtained from in-situ FTIR spectra of cured resin illuminates that the cure reaction is homo-polymerized respectively at this condition for the mixtures of B1C1. Interlaced network patterns are seen obviously and no visible phase separation could be detected in the region for IPNs BT resin by SEM. The structure of IPNs can be formed for the blends of BMPN and DNCY containing 0.11 mmol/mol Fe(AcAc)3 and 2% nonylphenol, which is tested by in-situ FTIR and SEM methods. The glass fiber reinforced composites for this blends are made and their properties are studied. This composites show good flexural property, low dielectric constants ( Dk ) and low moisture absorption.

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Basu, S., J. R. Macdonald et D. Chakravorty. « Conductivity relaxation in the interfacial phase of iron core–iron oxide shell nanocomposites ». Journal of Materials Research 21, n^o 7 (1 juillet 2006) : 1704–11. http://dx.doi.org/10.1557/jmr.2006.0231.

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The alternating current electrical conductivity of a gel-derived glass of composition 55Fe2O3⋅45SiO2 (mol%) was measured over a frequency range of 100 Hz to 6 MHz. The gel was subjected to a reduction treatment at 923 K for ½ h and subsequently heated in ordinary atmosphere at a temperature 773 K for ½ h to grow a Fe-core Fe3O4 shell nanostructure with a median diameter of 6.2 nm. This formed a percolative network within the silica gel. Mossbauer spectra confirmed the presence of Fe3O4 in the nanoshell. Electrical measurements were also carried out on these nanocomposites at different frequencies and temperatures. Isothermal electrical modulus data for both reference and treated glass systems were analyzed using both the CK0 and CK1 Kohlrausch-related frequency response models. Reference-glass shape parameter values, estimated by fitting the experimental data to the K0 model at several temperatures, were found to be ∼0.32. Here, the K0 model led to much better fits than the K1 did. However, for the treated core–shell-structured nanocomposite material, both models yielded good fits with consistent but different shape parameter estimates: very close to ½ for the K0 model and ⅓ for the K1 model. In accordance with the structural measurements and with axiomatic topological considerations that predict a shape-parameter value of ⅓ for one-dimensional motion and ½ for two-dimensional motion, it appears that the ∼0.32 value is consistent with one-dimensional motion of charge carriers along the narrow channels of the interconnected iron-rich three-dimensional phase of the reference glass. Further, although the K1-model ⅓ estimates for the treated material also indicate the presence of one-dimensional charge motion at the two-dimensional interface between the two interconnected phases of the reference glass, the ½ K0 estimates for the same material suggest an effective charge-motion dimension of 2. Importantly, comparison of the high-frequency dielectric constant estimates for the K0 reference glass and the K1 treated one clearly leads to the new but physically plausible conclusion that the bulk frequency-independent dielectric constant of about 30 is independent of the treatment.

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Singh, N. L., Chaitali Gavade et P. K. Khanna. « Swift Heavy Ion Induced Modification in Physical Properties of Poly Methylmethacrylate (PMMA)/Nickel (Ni) Nanocomposites ». Defect and Diffusion Forum 341 (juillet 2013) : 51–68. http://dx.doi.org/10.4028/www.scientific.net/ddf.341.51.

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We have These films were irradiated with 85 MeV C-ions at the fluences of 1 x 1011 and 1 x 1012 ions/cm2. Changes in the optical, structural, dielectric, magnetic and thermal properties of (PMMA)/Ni nanocomposites of different concentrations of nickel nanoparticles (5%, 10%, 15%) due to swift heavy ion irradiation were studied by means of UVvisible spectroscopy, X-ray diffraction, impedance gain phase analyzer, SQUID and differential scanning calorimetry. Optical properties like band gap were estimated for pure polymer and nanocomposite films from their optical absorption spectra in the wavelength range 200-800 nm. It was found that the band gap value shifted to lower energy on doping with metal nanoparticles. Differential scanning calorimetry analysis revealed a decrease in the glass transition temperature upon irradiation, which may be attributed to the scissioning of polymer chain due to ion beam irradiation which is also corroborated with XRD analysis. Surface morphology of the pristine and irradiated films was studied by scanning electron microscopy (SEM). The breakage of chemical bonds resulted in an increase of free radicals, unsaturation etc. as revealed from FTIR analysis. The dielectric properties were observed to enhance with an increase in metal compound concentration as well as with irradiation dose. This may be due to metal/polymer bonding and conversion of polymeric structure into hydrogen-depleted carbon network. Zero-Field-Cooled (ZFC)/Field-Cooled (FC) magnetization and magnetic hysteresis measurements were performed using a superconducting quantum interference device (SQUID) magnetometer from temperatures ranging from 5 K to 300 K, to investigate the magnetic properties of nanocomposites. The changes in topography of surfaces were also observed upon irradiation.

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Yuan, X. M., S. M. Lu, X. H. Zhang, Y. J. Cui, H. T. Wu et Y. L. Yue. « Effects of CaO Additions on the Structure and Dielectric Properties of Aluminoborosilicate Glasses ». Advanced Materials Research 710 (juin 2013) : 127–31. http://dx.doi.org/10.4028/www.scientific.net/amr.710.127.

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Glasses with compositions xCaO-(60-x)SiO2-5MgO-15Al2O3-20B2O3 (x=0, 3, 6 and 9 mol %) were prepared by conventional melting method. Fourier-transform infrared spectroscopy (FTIR) indicated that the addition of CaO converted trigonal boron ([B) to tetrahedral boron ([B). The glass transition temperatures (Tg) were determined using a differential scanning calorimetry (DSC). Tg increased with increasing CaO content. Thus, the addition of CaO instead of SiO2 strengthened the glass network. The dielectric εr and loss tanδ were measured for the MgO-B2O3-Al2O3-SiO2 glass system in the frequency range 103-105 Hz. The decrease in εr and tanδ could be attributed to the increase in the rigidity of the glass network.

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Shao, Hui, Hong Qing Zhou et Xiao Dong Shen. « The Influence of B₂O₃ on the Microstructures and Properties of CaO-B₂O₃-SiO₂-Al₂O₃ Glass-Ceramics (α-Al₂O₃) System ». Advanced Materials Research 189-193 (février 2011) : 4466–71. http://dx.doi.org/10.4028/www.scientific.net/amr.189-193.4466.

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The glass composition CaO-Al2O3-B2O3-SiO2 as an alternative glass composition, and commercial α-Al2O3 as a ceramic material was used. The structure of the glass was analyzed by infrared spectra; the glass-ceramics thermal expansion coefficient was measured by dilatometer, the phase separation of the sample was investigated by scanning electron microscope and the component of phase was analyzed by X-ray. The results show that [BO3] increases and [BO4] decreases in the glass structure with the increasing of B2O3 content added into CaO-Al2O3-B2O3-SiO2 glass. The relative density and dielectric constant (εr) are considerably decreased with the addition of amount of B2O3. Excellent microwave dielectric properties of 1MHz, εr = 8.0 and tanδ=0.003 are obtained by adding 10 wt% B2O3 to glass-ceramic and sintering at 875°Cfor 30 min.

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DU, ZHAO, XUEHONG ZHANG, YUNLONG YUE et HAITAO WU. « EFFECT OF MgO ON STRUCTURE AND DIELECTRIC PROPERTIES OF CaO–Al2O3–B2O3–SiO2 GLASSES ». Surface Review and Letters 19, n^o 06 (27 novembre 2012) : 1250063. http://dx.doi.org/10.1142/s0218625x12500631.

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The effect of MgO on structure and dielectric properties of aluminoborosilicate glasses was investigated. FTIR data indicated that glass network was mainly built by tetrahedral [ SiO4 ], [ BO4 ], [ AlO4 ] and trigonal [ BO3 ]. A small amount of AlO5 or AlO6 units also existed. The glass system was characterized with lower dielectric constant (4.17 ~ 4.6) and dielectric loss (12.3 × 10-4 ~ 14.77 × 10-4) at 1 MHz. With the increase of MgO content, the quantity of AlO5 or AlO6 units decreased. The variation of density showed a decreasing tendency. The dielectric constant and loss were all found to decrease.

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Herrmann, Andreas, Mohamed Zekri, Ramzi Maalej et Christian Rüssel. « The Effect of Glass Structure on the Luminescence Spectra of Sm3+-Doped Aluminosilicate Glasses ». Materials 16, n^o 2 (6 janvier 2023) : 564. http://dx.doi.org/10.3390/ma16020564.

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Peralkaline Sm3+-doped aluminosilicate glasses with different network modifier ions (Mg2+, Ca2+, Sr2+, Ba2+, Zn2+) were investigated to clarify the effect of glass composition and glass structure on the optical properties of the doped Sm3+ ions. For this purpose, the Sm3+ luminescence emission spectra were correlated with the molecular structure of the glasses derived by molecular dynamics (MD) simulations. The different network modifier ions have a clear and systematic effect on the peak area ratio of the Sm3+ emission peaks which correlates with the average rare earth site symmetry in the glasses. The highest site symmetry is found for the calcium aluminosilicate glass. Glasses with network modifier ions of lower and higher ionic radii show a notably lower average site symmetry. The symmetry could be correlated to the rare earth coordination number with oxygen atoms derived by MD simulations. A coordination number of 6 seems to offer the highest average site symmetry. Higher rare earth coordination probabilities with non-bridging oxygen result in an increased splitting of the emission peaks and a notable broadening of the peaks. The zinc containing glass seems to play a special role. The Zn2+ ions notably modify the glass structure and especially the rare earth coordination in comparison to the other network modifier ions in the other investigated glasses. The knowledge on how glass structure affects the optical properties of doped rare earth ions can be used to tailor the rare earth absorption and emission spectra for specific applications.

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Thèses sur le sujet "Dielectric Spectra - Glass Network Structure"

Chen, Ping. « Intermediate phases, boson and floppy modes, and demixing of network structures of binary As-S and As-Se glasses ». University of Cincinnati / OhioLINK, 2009. http://rave.ohiolink.edu/etdc/view?acc_num=ucin1250689099.

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Actes de conférences sur le sujet "Dielectric Spectra - Glass Network Structure"

Seeber, W., D. Ehrt, T. Danger, E. Heumann, E. Mix et G. Huber. « Improved Yb-doped fluoride phosphate laser glasses with optimized local structure ». Dans The European Conference on Lasers and Electro-Optics. Washington, D.C. : Optica Publishing Group, 1996. http://dx.doi.org/10.1364/cleo_europe.1996.cml2.

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The favorable laser properties of Yb-doped earth alkaline fluorapalite crystals (FAP) have been demonstrated [1]. Fluoride phosphate (FP) glasses are a kind of amorphous analogon to these both fluoride and phosphate anions containing crystals. It could be shown that Yb-doped FP-glasses have the potential for cheap diode pumped cw-lasers acting at wavelength around 1.04 μm at room temperature (2). In first experiments using laser diodes emitting at 968 nm (longitudinal pumping geometry, hemispheric resonator with an output mirror of r = −5 cm radius of curvature, T = 2 %) and not optimized FP-glasses we achieved maximum output powers Pout of about 145 mW and absorbed pump powers at thresholds Pthr,abs of about 185 mW. Recently, experiments with optimized glasses demonstrated improved laser performance (up to Pout of about 220 mW;Pthr,abs ~106 mW) [3]. Similar to DeLoach et al. [4] we trace the surprisingly good laser parameters to the special energy level structure of the 2F7/2:Yb ground manifold in the mentioned materials. The laser transition terminates at an electronic Yb-level (about 600 cm−1 above the ground state) interacting with the local vibrational modes of localized Yb-O bonds. The huge variety of FP-glass compositions provides a useful tool to tailor the local structure at the site of the Yb-ion and in this way the electron-phonon interactions itself. To optimize the host glass matrix we used the following simple structural model: Yb3− ions are mostly six co-ordinated in the investigated FP-glasses. Three PO43− (phosphate)-tetra-hedra form a cluster with D3-symmetry about the Yb ion. So-called v4-vibrations of the surrounding phosphate groups (~ 570 cm−1) can interact with the electronic Yb-transition. The addition of heavy ions (e.g. Ba) and other tetrahedral groups (e.g. SO42−) to batch composition: 95 mol-% (AlF3 earth alkaline fluorides) - 5 mol-% Sr(PO3)2 strongly improves the laser properties. This can be explained by formation of [Yb(PO4)3]-clusters which are nearly isolated from the mainparts of the network. Because of the inhomogeneous site variation in glasses no detailed structures in the absorption spectra could be observed even at low temperatures. Nevertheless, the corresponding terminal laser level (~ 600 cm−1 at high pump power densities) supports the assumption of efficient electron-phonon coupling. The intensity borrowing effect by this mechanism can be understood in terms of a electron-vibrational coupling constant [4], but the direct influence on the laser properties itself is not yet understood. We believe that the electron-phonon coupling efficiently depopulates the terminal laser level too. In conclusion, efficient cw-laser action in optimized FP-glasses can be traced to nearly isolated [Yb(PO4)3]-clusters with effective electron-phonon coupling.

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Stepanov, A. L., S. N. Abdullin, R. I. Khaibullin, Yu N. Osin et I. B. Khaibullin. « Formation Of Silver Thin Films For Nonlinear Optics By Ion Synthesis In Viscous Organic Matrix ». Dans The European Conference on Lasers and Electro-Optics. Washington, D.C. : Optica Publishing Group, 1996. http://dx.doi.org/10.1364/cleo_europe.1996.ctuk68.

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The nonlinear-optical behavior of metall nanoclusters embedded in dielectric materials have attractive properties for applications in optical devices. This paper describes the fabrication of silver particles in polymer substrate. A metal/polymer class of materials, produced by ion synthesis of metal nanoparticles in the organic matrix, has been studied from the point of view of formation mechanisms of dispersions, microstructure and optical properties Some preliminary investigations of silver/epoxy composites formed by ion implantation were presented early1. Now metal dispersions were produced by high-dose implantation of silver ions in epoxy at the different stages of polymerization process and were thus depend on metal concentration and polymer viscosity ratio The composites were characterized by transmission electron microscopy, image analysis and linear optical absorption at room temperature The average particle size can be controlled by the properties of the organic substrate, concentration of the metal and processing The silver dispersions give rise to optical absorption at the plasmon wavelength in the visible spectra and maximum of absorption is correlated with filling factor and size of particles. It is shown that 5-20 nm spherical silver particles with narrow log-normal size distribution have taken in near-surface region of viscous epoxy. It was observed the considerable increasing of size distribution width of synthesized particles at change of viscosity of substrate from similar liquid to solid state. Structure of granular silver films were be saving a constant at different quantity of dispersed metal in glass polymer.

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