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1.
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
2.
A detailed study on a novel TeO2-BaO-SrO-Ta2O5 glass system developed for photonic device applications is reported in this paper. The glass transition and crystallization temperatures could be selected by varying the Ta2O5 content in this glass system. This glass system is found to have good thermal stability among tellurite glasses. Raman spectroscopy has been used as a tool to analyze the structural details of this technologically important glass system. In addition to the TeO4 trigonal bipyramid and TeO3 trigonal pyramid structural units, glasses in this system revealed the presence of an additional Raman band attributed to TaO6 octahedra. The Raman bandwidth of the present glasses are broader compared to the conventional tellurite glasses by 35%. The influence of a gradual addition of the modifier oxides on the coordination geometry of tellurium atoms has been elucidated. Unlike the other tellurite glasses, even at higher modifier concentrations the TeO4 structural units dominate in the glass network compared to TeO3 trigonal pyramids. The ratio of TeO4/TeO3 structural units was discussed for different series of glass compositions. 相似文献
3.
Temperature-assisted electrical poling of TeO2-Bi2O3-ZnO glasses for non-linear optical applications
The suitability for effective thermal poling of the ternary tellurite glasses with the compositions (100 − 2x)TeO2-xBi2O3-xZnO (x = 5, 10 and 15, in molar percentage) for the second harmonic generation (SHG) was analyzed. The glass transitions and crystallization temperatures were studied via differential thermal analysis. The structural properties of the annealed glasses and furtherly heat-treated samples were probed by extended X-ray absorption fine structure (EXAFS) spectroscopy. Thermal poling of the glasses was undertaken conventionally at various temperatures close to the glass transition temperature under high vacuum and the second harmonic generated signals were compared. A new technique of two stage poling was tested for comparison. The non-linear second harmonic signal of the poled glasses was analyzed using the Maker-fringe technique and it was found that the two stage poling enhanced the non-linear efficiency when compared to the conventionally poled samples. 相似文献
4.
Calcium phosphate based bioactive quaternary glass systems P2O5-CaO-Na2O-K2O were prepared by melt growth technique. Glasses were prepared in five different compositions by fixing P2O5 at 47 mol% and CaO at 30.5 mol% and by varying the K2O and Na2O concentrations. The structural properties of the glasses are analyzed using X-ray diffraction (XRD) studies and scanning electron microscopy (SEM) studies; and the composition of the glasses are studied using energy dispersive X-ray spectrum (EDS). The microhardness of the glass systems are studied by Vickers hardness measurements and the bioactivity of the glasses are studied using in vitro study. The thermal properties have been examined by means of thermogravimetric analysis (TGA) and differential thermal analysis (DTA). The ultrasonic velocity measurements show that the addition of K2O contents produces non-bridging oxygen ion and hence weaken of the glass structure. The weakening of the glass structure reduces the ultrasonic velocity and hence an increase in attenuation. 相似文献
5.
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 Li2OAl2O3 system and two in the Li2OBi2O3 system. The latter system also showed evidence for the occurrence of two glasses at almost all compositions. 相似文献
6.
Glass of composition 40SiO2-30BaO-20ZnO-10B2O3 (mol%) was made by conventional melting and casting process. Crystallization kinetics of above glass has been investigated under non-isothermal conditions, using the formal theory of transformations for heterogeneous nucleation. The procedure is applied to the experimental data obtained by differential thermal analysis (DTA), using continuous-heating techniques. The crystallization results are analyzed, and both the activation energy of crystallization process as well as the crystallization mechanism is characterized. Dilatometric measurement of this glass was also done and data obtained was used to calculate the viscosity of the formed glass. Development of crystalline phases on thermal treatments of the glass at various temperatures has been analyzed by X-ray diffraction. Microstructure of the crystalline phases was investigated by scanning electron microscopy (SEM) and the development of various structural features with variation in heat treatment cycle was observed. The nucleation and growth of these phases in the matrix of glass has been described and discussed. 相似文献
7.
Saswati Ghosh 《Journal of Non》2008,354(34):4081-4088
Several compositions based on BaO-CaO-Al2O3-SiO2 (BCAS) glass system have been studied in this investigation to see their applicability as sealant for solid oxide fuel cell (SOFC). The glasses as well as the corresponding glass-ceramics have been systematically characterized by differential thermal analysis, dilatometry, X-ray diffractometry, electron microscopy and impedance analysis to examine their suitability as sealant. While the glass transition temperature (Tg) determined from DTA are within 600-665 °C, the coefficient of thermal expansion (CTE) can be tailored between 9.5 and 13.0 × 10−6 K−1. These glasses are found to be well adhered with metallic interconnects, such as commercial ferritic steel (Crofer22APU), at an optimum sealing temperature of 850 °C. The shrinkage behavior of the developed glasses in their pellet form has also been investigated. The resistivities of the glass-ceramics, as obtained from impedance analysis, are found to be within 104-106 Ω cm at 800 °C. Under sandwiched condition between two metals, some of the developed compositions are found to maintain this high resistivity even after 100 h of operation. One of the glass compositions has shown a low leak-rate of the order of ∼10−7 Pa m2 s−1. 相似文献
8.
Bismuth based glasses containing LiF, Li2O and SrO were investigated by different physical, spectroscopic and transport techniques. The results show that density of the glass system increases whereas glass transition temperature decreases with increase in LiF content. The decrease in glass transition temperature is attributed to the entry of the fluoride ions into the glass network mainly substitutionally in place of oxygen ion. The increase in dc electrical conductivity in the present glasses with increase in the fluorine ions is due to the mixed contribution of the positively charged lithium cations throughout the glass network and the negatively charged fluorine, which may act as impurity and/or as terminal non-bridging halide ion. Infrared and Raman spectroscopic results indicate that the glass network consists of BiO6 octahedral and BiO3 pyramidal units. 相似文献
9.
H. Doweidar 《Journal of Non》2011,357(7):1665-1670
Data of density, refractive index and thermal expansion coefficient for B2O3-SiO2 and GeO2-SiO2 glasses have been analyzed. The volumes of the structural units are the same found for the vitreous B2O3, GeO2 and SiO2. The volume of any structural unit is constant over the entire composition region of the glass system. The same has been found for the differential refraction and unit refraction of the structural units in these glasses. Different features are observed for the differential expansion of the structural units. There is a considerable change with composition in the differential expansion of BO3, GeO4 and SiO4 units. The effect is attributed to a change in the asymmetry of vibrations with the number of Si-O-B or Si-O-Ge linkages in the matrix. The thermal expansion coefficient is mainly determined by the contribution of B2O3 or GeO2 in the concerned glasses. 相似文献
10.
The conductivity of glazes consisting of SnO2 in Sb-doped BaAl-borate and BaAl-borosilicate glasses has been studied for fields in the range 102–105 V/cm at temperatures 4.2 K ? T ? 470 K. The glazes were free of mobile ions such as K, Na, Li and Pb. Conduction takes place between Sb-doped SnO2 particles concentrated in the fused contact region between the much larger glass particles. At high temperatures (300–470 K), the conductivity is thermally activated of the Frenkel-Poole type. At 77 K, both tunneling and thermally activated conductivity appear to be present. 相似文献
11.
As an approach to the mixed alkali effect in glass, the self-diffusion coefficients of sodium and cesium ions in Na2OCs2OSiO2 glasses were measured at temperatures 350–550°C. Electrical conductivity of the glasses and the transport number for sodium ions were also measured. The substitution of the alkali ions in the glass by different alkali ions caused the mobility of each alkali ion to decrease pronouncedly and the activation energy for migration to increase rapidly. The increase of activation energy was attributed to an increase in alkali-oxygen bond strength resulting from the presence of two kinds of alkali ions. This is related to the expectation that the activity of the alkali ions decreases when two alkali ions are mixed. 相似文献
12.
《Journal of Non》2007,353(52-54):4702-4706
The crystallization of glasses in the GeSe2–Sb2Se3–RbI system has been studied by using differential scanning calorimeter. Thermodynamic study has permitted to determine the best nucleation time and temperature for the 60GeSe2–30Sb2Se3–10RbI glass composition. RbI crystals with controllable size were reproducibly and homogeneously generated in the glassy matrix with appropriate annealing times and temperatures. Mechanical properties and resistance to thermal shocks of glasses and transparent glass–ceramics were investigated. 相似文献
13.
The a.c. and d.c. conductivities of PbOSiO2 glass with 0–10 mole% Fe2O3 additions were measured in the temperature range 77–700 K. Two relaxation processes were noted. The relaxation mechanism at lower temperatures is due to polaron hopping between ferric-ferrous ion pairs with a distribution of relaxation times which is energy independent. The second relaxation phenomenon, at higher temperatures is polaron hopping along iron ion chains in the glass of which the pairs responsible for the first process are a part. A theoreticalmodel is proposed and additional evidence for this model is presented in the form of magnetic susceptibility and electron spin resonance (esr) data. 相似文献
14.
Glasses in the BaO-ZnO-B2O3 system were examined as potential replacement for PbO glass frits with low firing temperature (500-600 °C) for the dielectric layer of a plasma display panel (PDP). The glasses were evaluated for glass transition temperature (Tg), thermal expansion coefficient (α) and dielectric constant ε. The electrical and the thermal properties were also compared with theoretical data calculated by a known empirical equation. Tg of the glasses varied between 480 and 560 °C, and α was in the range of 7-9×10−6 K−1. The dielectric constant ranges from 14 to 19 and the theoretical data showed lower α and ε than the experimental data. The results suggest that BaO-ZnO-B2O3 glasses would be suitable as an alternative to Pb-based dielectric layer in PDPs. 相似文献
15.
Gurbinder Kaur 《Journal of Non》2011,357(3):858-863
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
16.
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
17.
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
18.
A sol-gel method was used to prepare CaO-B2O3-SiO2 (CBS) glass powder for making low-temperature cofired ceramics. This paper was focused on the mechanism of hydrolysis and polymerization and also on the structural evolution of xerogel at various temperatures. The xerogel was transformed into glass ceramics containing CaSiO3 and CaB2O4 crystalline phases through nucleation and crystallization processes. The results indicated that the xerogel exhibits [BO4] or [SiO4] based three-dimensional network structure whose interstices Ca ions fill in, which becomes more orderly and stable after heat treatments. The CBS glass ceramics through controlled crystallization have a potential as electronic packaging materials. 相似文献
19.
Manabu Ichikawa 《Journal of Non》2010,356(43):2235-2240
We prepared sulfide glasses based on a Ga2S3-GeS2-Sb2S3 system and investigated the compositional dependences of their physico-chemical properties and structure. Additivities were observed for density and refractive index; i.e., these properties were presented by the summation of the contribution from each component. With the increase of Sb2S3 content, the density, refractive index, and thermal expansion coefficient increased while the glass transition and softening temperatures decreased, and the short-wavelength absorption edge shifted to the longer wavelength side. These variations are expected from the incorporation of a heavy element (Sb) into the glasses. On the other hand, the replacement of GeS2 by Ga2S3 increased the density and refractive index, and shifted the short-wavelength absorption edge to the longer wavelength side. These variations were explained by the increase of the number densities of the cations with the replacement and the formation of metal-metal bonds. The latter was confirmed from the Raman spectra. We also investigated the effects of Ag2S incorporation on the optical properties. The incorporation of Ag2S increased the density and refractive index whereas the position of the short-wavelength absorption edge varied little. These results show the possibility of fabricating an optical waveguide by Ag incorporation into the glasses. 相似文献
20.
A. Dutta 《Journal of Non》2005,351(3):203-208
Dc and ac conductivities of Li2O-BaO-Bi2O3 glasses have been studied in a temperature range of 263-523 K and a frequency range of 10 Hz-2 MHz and have been compared with those of binary Li2O-Bi2O3 glasses. The frequency dependent conductivity has been studied employing both the modulus and conductivity formalisms. We have observed small changes in the dc conductivity and its activation energy from those of the binary glass when content of BaO is small. However we have observed noticeable changes in the conductivity and the activation energy when BaO content is large. The significant changes in the values of the non-exponential parameter and the power-law exponent of the ac electrical properties have been observed due to introduction of BaO in the lithium bismuthate glasses. The existing relation between the power-law exponent and the non-exponential parameter was also violated in the present glass compositions. 相似文献