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1.
The linewidth-broadening of the EPR spectra of Cu 2+ in silicate, borate and phosphate glasses was analyzed in terms of the distribution of g| and A| (δ | and δ A|) and related to the distribution of the rigidity of the network structure. X- and K-band spectra were measured for the glasses doped with 63Cu 2+ (93% abundance). The linewidth of the HFS shoulders with parallel orientation to H increased linearly with increasing m or microwave frequency. δ g| and δ A| showed a marked dependence on glass composition. For example, in Na 2O---B 2O 3 glasses, on going from x (mol% of Na 2O) being small through intermediate to large, δ g| varied from small through large to negligibly small. In contrast to these glasses δ g| was extremely large for 75PbO · 25B 2O 3 glass. The large δ g| for the Na 2O---B 2O 3 glassesof intermediate x was attributed to the coexistence of various borate groups competitively coordinating to Cu 2+. Negligibly small δ g| for 70Na 2O · 30B 2O 3 glass and extremely large δ g| for 75PbO ·25B 2O 3 glass, both with a narrower structural distribution, reflect regidity of the glass network. The Pb---O bonding is strong enough to distort the coordination of Cu 2+-complex. The situation is the reverse in Na 2O---B 2O 3 glasses. 相似文献
2.
Gallate glasses containing no conventional glass formers were obtained in the systems (Na 2O, K 2O or Cs 2O)-Ta 2O 5---Ga 2O 3 and (Sr or BaO)-Ta 2O 5---Ga 2O 3 by an ordinary crucible-melting technique. The glasses showed high optical transmission in the infrared as well as in the visible region. Infrared spectroscopic analysis suggested that the Ga 3+ ions are tetrahedrally coordinated in the glasses. The glass-forming tendency of the melt and the infrared transmission of the glasses are discussed in terms of the glass structure. 相似文献
3.
Previously optical basicity was always measured using s-p absorption spectra of Tl +, Pb 2+ and Bi 3+, but since these spectra are in the UV region, media containing oxides of transition metal aons have been excluded from such measurements. The present work shows that for VO 2+ the d-d transition 2B 2 → 2E red-shifts with increasing optical basicity, and a study in the Na 2O---P 2O 5 glass system allows comparison with results obtained previously with Tl + and other probe ions. It is shown that under controlled conditions determination of optical basicity with VO 2+ is viable, and since the 2B 2 → 2E spectral band occurs in the visible / near-IR region, UV transparency of the medium is no longer necessary. The VO 2+ probe therefore offers a means of obtaining optical basicities of glasses containing e.g. PbO, or of metallurgica slags containing e.g. Fe 2O 3 or MnO. 相似文献
4.
The properties and structure of (45 - x)RO · xNa 2O · 2.5Al 2O 3 · 52.5P 2O 5 (R = Mg, Ca, Sr, Ba, 0 x 31 mol%) glasses were investigated. The variation in the molar volumes of glasses in the MgO series is closely related to the formation of the end groups in the glasses with the substitution of Na + ions for Mg 2+ ions, resulting in a variation of the density and refractive index of the glasses. The properties of glasses containing CaO in terms of Na 2O substitution depend mainly on the low field strength of Na + ions substituting for CaO even though the end groups occurring in the glasses increased. The variation in properties of the glasses containing SrO and BaO, some of which were substituted by Na 2O, could be explained by differences in masses, field strength and polarizability between the Na + ions and the alkaline-earth ions due to a small variation in the structure of the glasses despite Na 2O substitution. 相似文献
5.
The 11B, 27Al, 29Si and 31P magic angle spinning (MAS) NMR spectra of MO–P 2O 5, MO–SiO 2–P 2O 5 and MO(M ′2O)–SiO 2–Al 2O 3–B 2O 3 (M=Mg, Ca, Sr and Ba, M ′=Na) glasses were examined. In binary MO–P 2O 5 (M=Ca and Mg) glasses, the distributions of the phosphate sites, P(Q n), can be expressed by a theoretical prediction that P 2O 5 reacts quantitatively with MO. In the ternary 0.30MO–0.05SiO 2–0.65P 2O 5 glasses, the 6-coordinated silicon sites were detected, whose population increases in the order of MgO xCaO–0.05SiO2–(0.95−x)P2O5 glasses, its population increases with an increase in f (=([P2O5]−[MO]−[B2O3]−[Na2O])/[SiO2]) and has maximum at f=9. The signal due to the 5-coordinated silicon atoms is also observed when x is smaller than 0.45. When three network-forming oxides such as SiO2, Al2O3 and B2O3 coexist, Al2O3 reacts preferably with MO. The populations of 4-coordinated boron atoms, N4, are expressed well with r/(1−r), where r=([Na2O]−[Al2O3])/([Na2O]−[Al2O3]+[B2O3]). The correlation of the Raman signal at 1210 and 1350 cm−1 with the NMR signal of Si(Q6) at −215 ppm is also seen. 相似文献
6.
The influence of the mixed alkali effect on the chemical durability of Na 2O---TiO 2---SiO 2 glasses during substitution of K 2O for Na 2O in 21Na 2O---26TiO 2---53SiO 2 glasses was investigated. The best chemical durability was found at K 2O/Na 2O = 2.5 where the minimum was close to K + ions of larger size. It was shown that the water corrosion process of the system was predominantly controlled by both the mobility and the exchange function of K + ions resulting in the generation of a titanium-rich and silicon-rich layer at the surface. The mixed alkali effect can therefore be applied to lower the rate of water corrosion and increase chemical durability so that optical glasses with higher chemical durability can be obtained. 相似文献
7.
The infrared absorption spectra of sodium-disilicate glasses containing various amounts of Fe 2O 3 ([Na 2O · 2 SiO 2] 1−x [Fe 2O 3] x, where X = 0.05, 0.1 and 0.2) were investigated in the wavenumber range from 200–2000 cm −1. The addition of Fe 2O 3 to the sodium-disilicate glass does not seem to introduce any new absorption band as compared with the spectrum of a pure sodium-disilicate glass; nevertheless, a general shift of the existing absorption bands toward lower wavenumbers is observed. The amount of shift is, in fact, proportional to the content of Fe 2O 3 in the glass. This observation is consistent with the recently proposed structural model for the bonding of Fe 3+ ions in the iron-sodium-silicate glass system. Annealing of 20 mol% iron oxide glasses at 550 and 580°C produced an extra sharp infrared absorption peak at about 610 cm−1 wavenumber. This new peak is believed to be related to the crystallized particles of the glass as concluded from both a scanning electron micrograph and an electron diffraction pattern. 相似文献
8.
Alkoxide derived gels were prepared in the system Na 2O---B 2O 3---SiO 2. The gel compositions were situated in the liquid-liquid immiscibility area of the phase equilibrium diagram. Hydrolytic resistance tests were performed on the gels heat-treated at temperatures ranging between 120 to 850 °C. The Na2O, B2O3 and SiO2 extracted from the attack gels were analyzed. The experimental results indicate that the amount of B2O3 has a significant influence on the chemical durability of the heat-treated gels. At temperatures of 850 °C the greater the B2O3 mol% the greater are the amounts of Na2O and B2O3 extracted. Different behaviour was observed for gels heat-treated at 600 °C where the amounts of B2O3 and Na2O extracted slightly increases as the B2O3 mol% increases. Small amounts of extracted SiO2 were always observed. These results are complemented with other measurements so that an explanation of the controlling mechanism is given. 相似文献
9.
11B ( I=3/2) MAS NMR in the binary glass system xV 2O 5–B 2O 3 ( x=0.053, 0.43) and the ternary glass system xV 2O 5–B 2O 3–PbO (0.1 x1.5) has been investigated at room temperature. In the xV 2O 5–B 2O 3 glasses, one NMR line due to BO 3 unit was observed. Meanwhile in the xV 2O 5–B 2O 3–PbO, two NMR lines which arise from BO 3 and BO 4 units were detected, where the appearance of BO 4 units is produced by the presence of PbO. From the computer-simulation of the 11B NMR central transition line ( m=−1/2↔1/2), the quadrupole parameters ( e2qQ/ h and η) for BO 3 units in xV 2O 5–B 2O 3, and those for BO 3 and BO 4 units in xV 2O 5–B 2O 3–PbO were obtained as a function of x. As the V 2O 5 content increases in xV 2O 5–B 2O 3–PbO, the e2qQ/ h and η values of the BO 3− associated resonance are found to slightly decrease and increase, respectively. Meanwhile, the e2qQ/ h and η values of BO 4− associated resonance in xV 2O 5–B 2O 3–PbO are found to slightly increase and decrease, respectively. By comparing the intensities of the total transitions ( m=−3/2↔−1/2, m=−1/2↔1/2, and 1/2↔3/2) for the 11B NMR line of BO 3 and BO 4 units contained in xV 2O 5–B 2O 3–PbO with those of respective standard samples of 0.053V 2O 5–B 2O 3 and NaBH 4, the quantitative fractions of BO 3 and BO 4 in xV 2O 5–B 2O 3–PbO were obtained as a function of x. 相似文献
10.
11B Fourier transform spectra have been used to study the structure of Na 2O---B 2O 3---SiO 2 glasses of mid-alkali content. Based on the measurements of the fraction N4 of four-coordinated borons, it has been found that for K = mol.% SiO 2/mol.% B 2O 3 8 and R = mol.% Na 2O/mol.% B 2O 3 = 1, N4 is obviously smaller than 1 rather than equal to 1 as assumed in the relevant literature. Only when R reaches a value appropriately greater than 1, can the case where N4 = 1 occur. A structural model suggested in this paper can satisfactorily explain the fact. 相似文献
11.
An EMF cell using a Na-β″-alumina electrolyte has been designed for the quantification of the thermodynamic activity of Na 2O ( aNa 2O) in a series of sodium-bearing silicate liquids at high temperature. Initial experiments have been performed using Na 2O–0.663WO 3 and Na 2O–0.555MoO 3 as reference liquids. Values of aNa 2O derived for Na 2O–2SiO 2 binary melt are found to be in excellent agreement with data from the literature, confirming the validity of the method. To extend use of this experimental set-up to higher temperature, the aNa 2O of industrial C-glass has been calibrated as a reference liquid at temperatures up to 1263 °C. The influence of additions of CaO, Al 2O 3 and B 2O 3 on the Na 2O activity of binary sodium-silicates has been quantified. For each glass composition, measured values of aNa 2O are a function of temperature, log( aNa 2O) varying as a function of inverse absolute temperature. Activation energies derived from these data are all generally similar with the exception of industrial E-glass, which is rich in Al and poor in Na. At constant temperature, additions of network forming Al 2O 3 and B 2O 3 to a Na 2O–SiO 2 binary melt yield a decrease of the activity of Na 2O, while addition of network modifying CaO results in an increase in ( aNa 2O). These changes are qualitatively consistent with predictions based upon expected modifications of melt structure. However, measured values of log( aNa 2O) do not correlate perfectly with theoretical models of glass basicity, suggesting that either sodium activity is decoupled from melt basicity, or that current models are insufficient to calculate that parameter, in particular for the case of liquids poor in Na and rich in Al. 相似文献
12.
X-ray photoelectron spectroscopy (XPS) has been used to obtain structural information on the xPbO · (1− x)V 2O 5 glass system where x=0.22, 0.35, 0.43, and 0.54. The binding energies from the Pb 4f 7/2 and Pb 4f 5/2 core levels decrease with increasing PbO content while the full-width at half-maximum of these peaks increase. The O 1s spectra show an asymmetry for samples having composition x<0.5, which results from oxygen atoms in the V–O–V configuration (bridging oxygens) and from oxygen atoms in the V–O–Pb and Pb–O–Pb configurations (non-bridging oxygens). The number of non-bridging oxygens was found to increase from 81% to 92% with increasing PbO content. For x=0.54, the O 1s spectrum was symmetric indicating that all three oxygen configurations have essentially the same binding energy. This behavior in addition to the decreasing binding energies of the Pb 4f levels with increasing PbO content suggest that the Pb–O bonds are becoming more covalent in nature and that eventually PbO changed its role from a glass modifier to a glass former for x>0.5. The asymmetric V 2p 3/2 peaks for the x<0.4 glasses indicate the presence of a small concentration of V 4+ ions in addition to V 5+ ions, while the symmetric V 2p 3/2 peaks for the more concentrated PbO vanadate glasses indicate only V 5+ being present. The concentration of V 4+ ions (0–4%) from the XPS data is consistent with determinations from magnetic susceptibility measurements on the same glass samples. In addition to the paramagnetic contribution (Curie–Weiss temperature-dependent behavior) from the V 4+ ions, the susceptibility for these oxide glasses consisted of a positive, constant contribution arising from the temperature-independent paramagnetic V 2O 5 exceeding the diamagnetism from the core ions. 相似文献
13.
Electron paramagnetic resonance (EPR) spectra of lithium borate glass (1 - x)(0.63B 2O 3 · 0.37Li 2O) · xFe 2O 3, with x varying from 0.001 to 0.1, were measured at different microwave frequencies and temperatures. For low Fe 3+ concentrations (Fe 2O 3 molar contents from 0.001 to 0.01), X-band EPR spectra, consisting of a gef = 4.3 peak accompanied by a shoulder continuing down to gef = 9.7, are computer simulated on the basis of a ‘rhombic’ spin-Hamiltonian with Zeeman and fine-structure terms. A good fit to the experimental spectra for various Fe 2O 3 contents is observed with the same values of the spin-Hamiltonian parameters and assuming a Lorentzian lineshape and a linewidth increasing linealry with the concentration of Fe 3+ ions. It is concluded that the spectrum is due to diluted Fe 3+ ions in a relatively strong crystal field of orthorhombic symmetry, with largely distributed fine-structure parameters. From the concentration dependence of the line width, by extending to glasses a theoretical EPR linewidth expression derived for polycrystalline systems, the minimum distance between diluted Fe 3+ ions is estimated as 4.9 Å. A diluted state of Fe 3+ ions in the glass network in this range is also confirmed by the temperature dependence of the gef = 4.3 resonance which follows a Curie law. For intermediate concentrations of Fe 3+ ions (Fe 2O 3 molar contents from 0.01 to 0.1), the width of the gef = 4.3 line is proportional to the square root of concentration, still indicating dipolar interactions. On the other hand, the microwave frequency dependence of a broad gef ≈ 2 line, which coexists at these concentrations with the gef = 4.3 line, shows that the former line is due to pairs or small clusters of exchange-coupled Fe 3+ ions. The temperature dependence of the gef ≈ 2 line intensity in 0.1 mol Fe 2O 3 glass is consistent with a more antiferromagnetic character by comparison with the 0.05 mol Fe 2O 3 glass, which is attributed to an appearance, at higher Fe 2O 3 contents, of iron-containing microclusters not incorporated in the random glass network, with smaller distances between the paramagnetic ions. These microcluster are probably the origin of a new narrow line superposed with the broad gef ≈ 2 line in the low-temperature EPR spectra. 相似文献
14.
Glasses in the system Na 2O/B 2O 3/Al 2O 3/In 2O 3 were melted and subsequently tempered in the range from 500 to 700 °C. Depending on the chemical composition, various crystalline phases were observed. From samples without Al 2O 3, In 2O 3 could not be crystallized from homogeneous glasses, because either spontaneous In 2O 3 crystallization occurred during cooling, or other phases such as NaInO 2 were formed during tempering. The addition of alumina, however, controlled the crystallization of In 2O 3. Depending on the crystallization temperature applied, the crystallite sizes were in the range from 13 to 53 nm. The glass matrix can be dissolved by soaking the powdered glass in water. This procedure can be used to prepare nano-crystalline In 2O 3-powders. 相似文献
15.
The solubility of a series of hexaferrite derivatives of BaFe 12O 19 in solvents of the system Na 2O-B 2O 3 with oxide ratios of 7:3 and 3:2 has been investigated. The temperature dependences of the saturation concentration in these solvents are determined for ferrites with the nominal compositions Ba 0.8Pb 0.2Fe 12O 19, BaFe 10Ga 2O 19, BaFe 10Al 2O 19 and BaFe 8Mn 2 Ti 2O 19. Single crystals of BaFe 12O 19, in which part of the metal ions are replaced by various amounts of Pb 2+, Ga 3+, Al 3+ and Mn 2+ + Ti 4+ ions, are g rown from the solutions by the slow cooling technique. The distribution coefficients of the substituting ions and the compositions of the crystals obtained are established by microprobe analysis (EPMA). Information on the position of substitution is obtained from the Mössbauer spectra. 相似文献
16.
The crossover from a frequency independent to a frequency dependent ac response has been studied in glasses with the composition 37.2Na 2O-12.8CaO 5 · 50P 2O 5 and 30Na 2O-5CaO-7.5Al 2O 3-57.5P 2O 5 (mol%) containing 5 × 10 −3 ≤ mol% Ag 2O ≤ 5 × 10 −1. Recently, we have established that in these glasses the diffusion coefficient of guest silver ions varies in space. In this case, as a first approximation, the diffusion coefficient may be considered as a constant within regions whose size is no less than 10 nm across. We assume that the diffusion of sodium ions can be given by the D( r) coefficient with the same spatial dispersion as that of silver ions. It is demonstrated that the frequency dependence of ac response is in fair agreement with the assumption. 相似文献
17.
The thermal expansion coefficients of Cu 2O---Al 2O 3---SiO 2 glasses have been measured. These glasses have very low expansion coefficients similar to that for SiO 2 glass, but their liquids temperatures are much lower. It was possible to reduce the liquids temperature by the addition of 2 mol% of Na 2O while maintaining low expansivity. In order to explain the low expansivity, the effects of cation size, valence, the Cu 2+/Cu + ratio, bond strength and phase separation were examined. Phase separation was observed in these glasses which probably consisted of a copper-rich dispersed phase and a network former-rich matrix phase. It was concluded that the overall expansion coefficients of the glasses were governed by the low expansion matrix phase. 相似文献
18.
Mössbauer absorption measurements have been made at room temperature on 57Fe in iron sodium silicate glasses containing 3–15 mol% Fe 2O 3 and various iron alkali silicate crystals in order to study the state of iron in these glasses. The spectra of all the glasses gave one doublet with a quadrupole splitting varying from 0.73–0.78 mm s −1, while those of Na 2O · Fe 2O 3 · 4 SiO 2 and 5 Na 2O · Fe 2O 3 · 8 SiO 2 crystals showed much smaller quadrupole splitting, 0.28 mm s −1 and 0.10 mm s −1, respectively, and an asymmetrical doublet of much narrower linewidth. When sodium was replaced by other alkali metals of larger size, such as K and Cs, in MFeSi 2O 6 and MFeSi 3O 8 crystals, the quadrupole splitting became wider and approached to 0.73 mm s −1. Such a variation was not observed for glasses. These results suggest that a larger number of non-identical sites exist in iron sodium silicate glasses than in the corresponding crystals. 相似文献
19.
The short range structures of B 2O 3 (90 mol%)---Cs 2O (10 mol%) and B 2O 3 (80 mol%)---Cs 2O (20 mol%) liquids were analyzed at 973 and 1053 K, respectively, by an X-ray diffraction method, and the effects of Cs 2O addition on the boron-oxygen bonding were investigated. The existence of BO 3 triangles, which form the so-called boroxol ring structure, was confirmed in B 2O 3---Cs 2O liquids, as well as in B 2O 3 liquid, but some fraction of the BO 3 triangles was thought to be converted to BO 4 tetrahedra. Similar results have previously been observed also in B 2O 3---Cs 2O glasses. A Cs atom was found to be surrounded by six O atoms; four Cs---O interatomic distances were about 3.2 Å but the other two were at 3.8–3.9 Å. These distances indicate that distorted Cs---O octahedra may exist in these B 2O 3---Cs 2O liquids. 相似文献
20.
The electrical conductivities of (1− x) Li 2O · x BaO · 2 SiO 2, (1− x) Na 2O · x MgO ·2 SiO 2, (1− x) Na 2O · x CaO · SiO 2 and (1− x) Na 2O · x BaO · 2SiO 2 glasses were measured at temperature ranging from room temperature to 450°C. The transport numbers for Na + ion in (1− x) Na 2O · x BaO · 2 SiO 2 glasses were measured. It was found that the alkali ion carried a significant part of the current in these glasses except one that had no alkali ions, and the conductivity decreased markedly as the alkali oxide was substituted by an alkaline earth oxide. The results of conductivity measurements combined with the data hitherto reported on mixed alkali glasses led to the proposal that the so-called mixed alkali effect could be explained on the basis of the independent path model in which it is assumed that cations can move only through vacant sites left by those of the same type. 相似文献
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