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1.
G. Paramesh 《Journal of Non》2011,357(5):1479-1484
Transparent glasses in the system 0.5Li2O-0.5M2O-2B2O3 (M = Li, Na and K) were fabricated via the conventional melt quenching technique. The amorphous and glassy nature of the samples was confirmed via the X-ray powder diffraction and the differential scanning calorimetry, respectively. The frequency and temperature dependent characteristics of the dielectric relaxation and the electrical conductivity were investigated in the 100 Hz-10 MHz frequency range. The imaginary part of the electric modulus spectra was modeled using an approximate solution of Kohrausch-Williams-Watts relation. The stretching exponent, β, was found to be temperature independent for 0.5Li2O-0.5Na2O-2B2O3 (LNBO) glasses. The activation energy associated with DC conduction was found to be higher (1.25 eV) for 0.5Li2O-0.5K2O-2B2O3 (LKBO) glasses than that of the other glass systems under study. This is attributed to the mixed cation effect.  相似文献   

2.
E. Mansour 《Journal of Non》2011,357(5):1364-3380
Fourier transformation infrared spectra, density and DC electrical conductivity of 30Li2O · xCeO2⋅(70 − x)B2O3 glasses, where x ranged between 0 and 15 mol%, have been investigated. The results suggested that CeO2 plays the role of network modifier up to 7.5 mol%. At higher concentrations it plays a dual role; where most of ceria plays the role of network former. The density was observed to increase with increasing CeO2 content. The effect on density of the oxides in the glasses investigated is in the succession: B2O3 < Li2O < CeO2. Most of CeO2 content was found to be associated with B2O3 network to convert BO3 into B O4 units. The contribution of Li+ ions in the conduction process is much more than that due to small polarons. The conductivity of the glasses is mostly controlled by the Li+ ions concentration rather than the activation energy for CeO2 > 5 mol%. Lower than 5 mol% CeO2 the conductivity is controlled by both factors. The dependence of W on BO4 content supports the idea of ionic conduction in these glasses.  相似文献   

3.
Lead chloroantimonite glasses form stable binary glasses that may accommodate numerous oxides or halides as a third component. Molybdenum trioxide is a glass progenitor leading to molybdate glasses. Ternary glasses have been synthesized and studied in the Sb2O3-PbCl2-MoO3 system. Compositional limits of glass formation are reported and two series of glass samples have been prepared corresponding to the general formulas: (90 − x)Sb2O3-xPbCl2-10MoO3 and (90 − x)Sb2O3-xMoO3-10PbCl2. Glass transition temperature is close to 290 °C at high Sb2O3 content and decreases as antimony oxide is substituted by MoO3 or PbCl2. Position, width and intensity of crystallization peak suggest that devitrification rate is small in some composition ranges. The evolution of density, thermal expansion, refractive index and microhardness has been studied as a function of composition parameter x. Deviations from linearity are observed. They suggest structural changes in the case of the MoO3/Sb2O3 substitution while it appears that molar volume increases linearly versus lead content in the other series of glasses. Refractive index is close to 2.04. Optical transmission ranges from 550 nm in the visible spectrum to 5.5 μm in the infrared. It is limited by extrinsic absorption bands arising from hydroxyls and silicon impurities. Young's, bulk and shear moduli have been measured for the two series of samples.  相似文献   

4.
Eun-Sub Lim 《Journal of Non》2006,352(8):821-826
A BaO-B2O3-SiO2 glass system was chosen as a candidate composition for the application to Pb-free low temperature sinterable glass. The effect of BaO content on the crystallization, sintering behavior, and properties of the glasses was examined. Both the glass transition temperature and crystallization temperature decreased as the BaO content increased. Crystallization easily occurred during sintering with a BaO content of more than 50 mol%, which effectively inhibited the over-firing phenomenon. The dielectric characteristics and thermal expansion coefficient of the glasses were examined and the results were explained on the basis of the crystallization and densification of the specimens.  相似文献   

5.
Crystallization processes of Li2O-Ga2O3-SiO2-NiO system glasses have been studied by X-ray diffraction, differential calorimetry and optical absorption. Transparent glass-ceramic containing LiGa5O8:Ni2+ as the sole crystalline phase has been obtained from glass with the composition of 13Li2O-23Ga2O3-64SiO2-0.1NiO (in mol%) by the heat treatment in the temperature range from 923 to 953 K. It was revealed that the specific surface area of samples enhances crystallization of LiGaSi2O6 but obstructed that of LiGa5O8. LiGa5O8 grew to nano-sized crystallites dispersed in the glass matrices and did not affect the transparency seriously. In contrast, LiGaSi2O6 grew to crystallites with diameters more than 100 nm on the surface and made the glasses opaque. Optical absorption measurements revealed that doped Ni2+ occupied five-folded trigonal bipyramidal sites in the as-quenched glass matrices but six-folded octahedral sites of precipitated LiGa5O8 in the glass-ceramics. It was confirmed that transparent glass-ceramic containing Ni2+:LiGa5O8 was effectively obtained by the heat treatment at a temperature of 953 K for 10 h.  相似文献   

6.
New phosphate glasses of the quaternary system A2O-Nb2O5-WO3-P2O5, where X = Li and Na were prepared by the melt-quenching method. The introduction of WO3 in the glass composition was based on the proposal of analysing the effect of the diminishing of the molar amount of the alkaline oxide and thus decreasing the molar ratio between network modifiers and network formers (M/F).In the present work we present the preparation of 20A2O-30WO3-10Nb2O5-40P2O5 (A = Li, Na) transparent glasses. These glasses were heat-treated in air, at 550 °C and 650 °C for 4 h. The structure of the obtained samples was studied by X-ray powder diffraction (XRD) and Raman spectroscopy and the morphology by scanning electron microscopy (SEM). The dc (σdc), ac (σac) conductivity and dielectric spectroscopy measurements were performed in the function of the temperature and were related with the structural changes of the glass structures.  相似文献   

7.
Glasses having compositions 40Bi2O3-20GeO2-(40−x)PbO-xMoO3 (where x = 3, 6, 9, 12 and 15 mol%) were prepared by normal melt quenching technique. The density (d) decreases gradually with the increase of the MoO3 content in such glasses. This may be due to the lower molecular weight MoO3 is substituted by a higher molecular weight PbO. The dc conductivity decreases while the activation energy increases with the increase of the MoO3 content. The dc conductivity in the present glasses is electronic depends strongly upon the average distance, R, between the Mo 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. Dielectric properties (constant ε, loss tan δ, ac conductivity σac, over a range of frequency 0.12-100 kHz and temperature 325-650 K and frequency exponent s) of these glasses have been studied.  相似文献   

8.
By rapid quenching in a twin roller apparatus, glass was found to occur widely in the systems of Li2O with Al2O3, Ga2O3, Bi2O3 and in mixed systems. Examination of the resulting flakes by X-ray powder diffraction, differential thermal analysis, and capacitance data revealed the occurrence of glass, glass transitions, crystallization exotherms and the nature of some of the crystallization paths.The log ionic conductivity of the glasses was found to follow a linear relationship with the Li concentration. Evidence was observed for three new metastable crystalline phases, one in the Li2OAl2O3 system and two in the Li2OBi2O3 system. The latter system also showed evidence for the occurrence of two glasses at almost all compositions.  相似文献   

9.
Specimens of the glassy system: (70 − x)TeO2 + 15B2O3 + 15P2O5 + xLi2O, where x = 5, 10, 15, 20, 25 and 30 mol% were prepared by the melt-quenching. An ultrasonic pulse-echo technique was employed, at 5 MHz, for measuring: the ultrasonic attenuation, longitudinal and shear wave velocities, elastic moduli, Poisson ratio, Debye temperature and hardness of the present glasses. It is found that the gradual replacement of TeO2 by Li2O in the glass matrix up to 30 mol% leads to decrease the average crosslink density and rigidity of prepared samples which affects the properties, i.e., the hardness, ultrasonic wave velocities and elastic moduli are decreased, while the Poisson ratio and the ultrasonic attenuation are increased. Also, optical absorption spectra were recorded in the range, 200-800 nm for these glasses. The obtained results showed that a gradual shift in the fundamental absorption edge toward longer wavelengths occurred. Values of both of the optical energy gap, Eopt, and width tails, ΔE, are determined. It is observed that Eopt is decreased and ΔE increased with the increase of Li2O in the glass matrix up to 30 mol%. The compositional dependences of the above properties are discussed and correlated to the structure of tested glasses.  相似文献   

10.
The well known and characterized fast ion conducting (FIC) LiI + Li2S + GeS2 glass-forming system has been further optimized for higher ionic conductivity and improved thermal and chemical stability required for next generation solid electrolyte applications by doping with Ga2S3 and La2S3. These trivalent dopants are expected to eliminate terminal and non-bridging sulfur (NBS) anions thereby increasing the network connectivity while at the same time increasing the Li+ ion conductivity by creating lower basicity [(Ga or La)S4/2] anion sites. Consistent with the finding that the glass-forming range for the Ga2S3 doped compositions is larger than that for the La2S3 compositions, the addition of Ga2S3 is found to eliminate NBS units to create bridging sulfur (BS) units that not only gives an improvement to the thermal stability, but also maintains and in some cases increases the ionic conductivity. The compositions with the highest Ga2S3 content showed the highest Tgs of ∼325 °C. The addition of La2S3 to the base glasses, by comparison, is found to create NBS by forming high coordination octahedral LaS63− sites, but yet still improved the chemical stability of the glass in dry air and retained its high ionic conductivity and thermal stability. Significantly, at comparable concentrations of Li2S and Ga2S3 or La2S3, the La2S3-doped glasses showed the higher conductivities. The addition of the LiI to the glass compositions not only improved the glass-forming ability of the compositions, but also increased the ionic conductivity glasses. LiI concentrations from 0 to 40 mol% improved the conductivities of the Ga2S3 glasses from ∼10−5 to ∼10−3 (Ω cm)−1 and of the La2S3 glasses from ∼10−4 to ∼10−3 (Ω cm)−1 at room temperature. A maximum conductivity of ∼10−3 (Ω cm)−1 at room temperature was observed for all of the glasses and this value is comparable to some of the best Li ion conductors in a sulfide glass system. Yet these new compositions are markedly more thermally and chemically stable than most Li+ ion conducting sulfide glasses. LiI additions decreased the Tgs and Tcs of the glasses, but increased the stability towards crystallization (Tc − Tg).  相似文献   

11.
The influences of different alkali and alkali-earth oxide substitutions on the properties of lithium-iron-phosphate (LIP) glasses have been studied. Na2O, K2O, MgO, CaO and BaO were used to substitute Li2O to prepare LIP glasses with molar compositions of (20 − x)Li2O − xR2O(RO) − 30Fe2O3 − 50P2O5 (x = 2.4, 4, 5.6 and 7.2). The glass transition temperature (Tg) was determined by the differential thermal analysis technique. The density and chemical durability of the prepared glasses were measured based on the Archimedes principle and the weight losses after the glasses were boiled in water. The results show that Tg decreases with the initial substitutions, whereas the density and chemical durability increase. The diminution of the aggregation effect of Li+ ions on the glass structure due to the decrease in Li+ concentration, the larger molecule weights of the substitutes, the mixed-alkali and depressing effects as well the slower mobility of substitute ions mainly contribute to the initial changes in Tg, density and chemical durability of the LIP glasses, respectively. Further increasing the amounts of substitutes brings about increasing diminution of the aggregation effect of Li+ ions and breakage of the glass network on the one hand and increasing amounts of substitutes with larger molecule weights and ion radii on the other hand. Both aspects influence the glass properties oppositely and consequently non-monotonic variations in the properties of LIP glasses with the substitutions are observed.  相似文献   

12.
Glasses of the system: (70−x) TeO2 + 15B2O3 + 15P2O5 + xLi2O, where x = 5, 10, 15, 20, 25 and 30 mol% were prepared by melt quench technique. Dependencies of their glass transition temperatures (Tg) and infrared (IR) absorption spectra on composition were investigated. It is found that the gradual replacement of oxides, TeO2 by Li2O, decreases the glass transition temperature and increases the fragility of the glasses. Also, IR spectra revealed broad weak and strong absorption bands in the investigated range of wave numbers from 4000 to 400 cm−1. These bands were assigned to their corresponding bond modes of vibration with relation to the glass structure.  相似文献   

13.
SiO2-BaO-ZnO-xB2O3-(10−x) Y2O3, (0 ≤ x ≤ 10) glasses are synthesized. The effect of Y2O3 on the structural and optical properties of glasses has been investigated using different characterization techniques. The results are discussed in light of non-bridging oxygens (NBO), optical basicity and heat-treatment of glasses. The band gap has been calculated for as cast and heat-treated glasses. The band gap energy is found to decrease with the increasing content of Y2O3 in the glasses and heat-treatment. The presence of the crystalline phase in the glass matrix showed remarkable effect on band gap which decreases to semiconducting range.  相似文献   

14.
Tomoharu Hasegawa 《Journal of Non》2011,357(15):2857-4499
Glasses of the Bi2O3-TeO2-B2O3 ternary system were developed and their linear and nonlinear optical properties were investigated. The absorption edges of these glasses were found to be 367-384 nm with a good transmittance in visible wavelength, although they exhibit the refractive indices as high as 1.98-2.12 at 633 nm. The absorption edges are quite steep and they are analyzed by the Urbach theory. The obtained Urbach energies of these glasses are 73-79 meV which are comparable to silica glasses. The high refractive index and its glass composition dependency are discussed according to the basics of the electronic polarizability and optical basicity. The high third order nonlinear susceptibility χ(3) = 2.0 × 10− 12 esu at 800 nm was also obtained in the 36Bi2O3-18TeO2-46B2O3 glass.  相似文献   

15.
Y. Gandhi  N. Veeraiah 《Journal of Non》2011,357(3):1193-1202
20ZnF2-30As2O3-(50 − x)TeO2:xNiO (0 ≤ x ≤ 2.0) glasses were synthesized. The glasses were characterized by X-ray diffraction, scanning electron microscopy, EDS and DSC techniques. A variety of properties, i.e. optical absorption, infrared, magnetic susceptibilities and dielectric properties (constant ?′, loss tan δ, a.c. conductivity σac over a wide range of frequency and temperature) of these glasses have been carried out. The analysis of results of all these studies has indicated that the nickel ions occupy both octahedral and tetrahedral positions and the gradual increase of NiO content in the glass matrix causes growing proportions of Ni2+ ions that occupy octahedral positions. The luminescence spectra of these glasses have exhibited a broad emission band in region 1200-1450 nm identified due to 3T2(3F) → 3A2(3F) octahedral transition of Ni2+ ions. The luminescence efficiency and cross section have been found to be the highest for the glass containing highest concentration of NiO. Finally it is concluded that the higher the concentration of octahedrally positioned Ni2+ ions, the higher is the luminescence efficiency.  相似文献   

16.
Wenlong Yao 《Journal of Non》2008,354(18):2045-2053
The structure and properties of glasses in the MI + M2S + (0.1Ga2S3 + 0.9GeS2), M = Li, Na, K and Cs, system were studied using Raman, IR spectroscopy, DSC and density measurements to help better understand the ionic transport in these glasses. The glass forming ranges of these ternary glasses were compared to those of the binary alkali sulfide and germanium sulfide systems. The more extensive glass forming range in the Na2S system was used to examine the more extensive changes of structure and properties of these glasses as a function of Na2S content. As expected, non-bridging sulfurs (NBS) form with the addition of alkali sulfide. Unlike their oxide counterparts, however, the alkali sulfide doped glasses appear to support longer-range super-structural units. For example, evidence that the adamantine-like structure exists in the K2S and Cs2S modified glasses is found in the Raman spectra of the glasses. The structural role of the alkali iodide addition was also explored since the addition of alkali iodide helps to improve the conductivity. For most of these glasses, as observed in many other oxide glasses, the added MI dissolves interstitially into the glass structure network without changing the alkali sulfide network structure. In 0.6Na2S + 0.4(0.1Ga2S3 + 0.9GeS2) glasses, however, the added NaI may affect the glass structure as it causes systematic changes in the frequency of the Ge-S network mode as seen in the Raman spectra.  相似文献   

17.
Crystallization was examined for glasses having chemical composition of 2(Ca,Sr,Ba)O-TiO2-2SiO2 in which the CaO/SrO/BaO molar ratio varied. Powdered glass samples were pelleted into disks and sintered at 950 °C for 2 h. The major phase precipitated in the sintered samples was (Ca,Sr,Ba)2TiSi2O8 and minor phase of perovskite such as CaTiO3 or SrTiO3 increased with CaO content in the samples containing more than 40 mol% of CaO in total CaO+SrO+BaO. Three regions having different slopes were found in linear relationships between SrO mol% and exothermal peak temperature on DSC curves or d[0 0 2] values determined by powder XRD method. These facts suggested that the major phase precipitated in each region was a solid solution containing a different amount of CaO, SrO, BaO and that these compositions varied depending on SrO content in the sample. The micro-crystalline structure, which could be useful in fabricating a dielectric dense body, was observed for samples containing 30-70 mol% of SrO.  相似文献   

18.
Glasses having compositions 20Li2O · (80 − x)Bi2O3 · xSiO2 (x = 55, 60, 65, 70 mol%) were investigated using impedance spectroscopy in the frequency range from 20 Hz to 1 MHz and in the temperature range from 543 to 663 K. The ac and dc conductivities, activation energy of the dc conductivity and relaxation frequency are extracted from the impedance spectra. The increase in conductivity with increase in SiO2 content is attributed to the change in the structural units of bismuth. Both electric modulus and the conductivity formalism have been employed to study the relaxation dynamics of charge carriers in these glasses. A single ‘master curve’ for normalized plots of all the modulus isotherms observed for a given composition indicates the temperature independence of the dynamic processes for ions in these glasses. Similar values of activation energy for dc conduction and for conductivity relaxation time indicates that the ions overcome same energy barrier while conducting and relaxing. The observed conductivity spectra follows power law with exponent ‘s’ which increases regularly with frequency and approaches unity at higher frequencies. Near constant losses (NCL) characterize this linearly dependent region of conductivity spectra. A deviation from ‘super curve’ for various isotherms of conductivity spectra was also observed in high frequency region and at low temperatures, which supports the existence of different dynamic processes like NCL in addition to the ion hopping processes in the investigated glass system.  相似文献   

19.
Glasses in the system x B2O3(1 − x) [y CaO P2O5], (x = 0, 0.1, 0.2, 0.3, y = 2, 2.6, 3, 4, 5) have been prepared by fast quenching of high temperature melts. The presence of B2O3 affected the glass forming ability, allowing the preparation of calcium phosphate glasses with y ? 2.6. The structure of glasses was analyzed by μ-Raman and infrared spectroscopy. The analysis indicated that the glass network is dominated by highly charged species from phosphate tetrahedra with 3 (pyro) or 4 (ortho) NBOs, while the boron atoms are incorporated mainly in 3 coordinated sites in the form of B∅3 or B∅2O units. A small fraction of units was also evident from the spectra analysis of glasses with high CaO content. All calcium borophosphate glasses exhibited bioactivity after soaking in SBF solution within a few days. This was observed by μ-Raman and SEM microscopy, while XRD patterns clearly revealed growth of hydroxyapatite phase. The presence of boron in the glass network has a catalytic effect at favoring bioactivity of the otherwise bioinert calcium phosphate glasses.  相似文献   

20.
Erbium-doped glasses with composition xGeO2-(80 − x)TeO2-10ZnO-10BaO were prepared by melt-quenching technique. The phonon sideband spectra and the optical absorption band edges for the host matrix were confirmed by means of the spectral measurements. Standard Judd-Ofelt calculations have been completed to these glasses. The dependence of up-conversion and infrared emission under 980 nm excitation on the glass composition was studied. The quantum efficiencies for the 4I13/2 → 4I15/2 transition of trivalent erbium in the glasses were estimated.  相似文献   

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