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1.
Cobalt sodium silicate glasses with the chemical composition (0.70 - x)SiO 2-(0.30)Na 2O- xCoO, where 0.0 ≤ x ≤ 0.20, have been investigated by means of X-ray photoelectron spectroscopy (XPS) and magnetization techniques. The Co 2p spectra show intense satellite structures 6 eV above the photoelectron peak and the Co
separation was 15.9 eV for all the samples studied. These observations indicate the presence of high spin Co 2+ ions in the glasses. The Co 3p spectra have been fitted with contributions from octahedral and tetrahedral Co 2+ and the ratio [Co 2+(oct)]/[Co Total2+] increases with increasing CoO content. The O Is spectra also show composition-dependent changes. The fraction of non-bridging oxygen atoms was determined from these spectra and was found to increase with increasing cobalt oxide. Co(II) ions are found to be incorporated in the glass as network modifiers but the contribution from SiOCo(II) to the non-bridging part of the O Is signal could be separated from that from SiONa by simulating the spectrum. DC magnetic susceptibility measurements were performed on the same samples but these suggest that Co 2+ exists mainly in octahedral coordination. The magnetic data indicate that the exchange interaction is antiferromagnetic and increases with increasing CoO in the glass. 相似文献
2.
The Ge 25Ga 5Se 70 and Ge 30Ga 5Se 65 pure and Pr 3+-doped glasses were prepared by direct synthesis from elements and PrCl 3. It was found that up to 1 mol% PrCl 3 can be introduced in the Ge 25Ga 5Se 70 and Ge 30Ga 5Se 65 glasses. Both types of glasses with overstoichiometric and substoichiometric content of Se were homogeneous and of black color. The optical energy gap is Eoptg=2.10 eV, and the glass transition temperature is Tg=543 K for Ge 25Ga 5Se 70 and Tg=633 K for Ge 30Ga 5Se 65. The long-wavelength absorption edge is near 14 μm and it corresponds to multiphonon processes. Doping by Pr 3+ ions creates absorption bands in transmission spectra, which can be assigned to the electron transitions from the ground 3H 4 level to the higher energy levels of Pr 3+ ions 3H 5, 3H 6, 3F 2, 3F 3 and 3F 4, respectively. By excitation with YAG:Nd laser line (1064 nm), two intense luminescence bands (1343 and 1601 nm) were excited. The first band can be ascribed to electron transitions between 1G 4 and 3H 5 energy levels of Pr 3+ ions. Full width at half of maximum (FWHM) of the intensity of luminescence was found to be 70 nm for (Ge 25Ga 5Se 70) 1 − x(PrCl 3) x and (Ge 30Ga 5Se 65) 1 − x(PrCl 3) x glasses. The FWHM in selenide glasses is lower than in halide and sulphide glasses. The second luminescence band (1601 nm) can be probably ascribed to the transitions between 3F 3 and 3H 4 energy levels of Pr 3+ ions. The absorption and luminescence spectra of Pr 3+ ions in studied glasses are slightly influenced by stoichiometry of glassy matrix. The Raman spectra of studied glasses were deconvoluted and assignment of Raman bands to individual vibration modes of basic structural units was suggested. The structure of studied glasses is mainly formed by corner-sharing and edge-sharing GeSe 4 tetrahedra. The vibration modes of Ga-containing structural units were not found, they are apparently overlapping with Ge-containing structural units due to small difference between atomic weights of Ge and Ga. In the glasses with substoichiometry of Se, the Ge–Ge bonds of Ge 2Se 6 structural units were found. In Se-rich glasses the Se–Se vibration modes were found. In all studied glasses also ‘wrong' bonds between like atoms were found in small amounts. Maximum phonon energy of studied glasses is 320 cm −1. 相似文献
3.
Absorption spectra of Cr ions in multi-component oxide glasses melted in Ar were measured. The integrated extinction coefficient is used as a parameter to analyze the redox reaction of Cr 3+ and Cr 6+ in glass samples. The relative content of Cr 6+ increased and that of Cr 3+ decreased with increasing basicity in silicate and borate glasses; this result is consistent with previous studies. On the contrary, only Cr 3+ exist in phosphate glasses. Cr 4+ ions were found only in aluminate, gallate and alumino-silicate glasses with modifier contents ≥ 60 mol%. The relationship between point defects and Cr 4+ formation is examined on the basis of electron spin resonance measurements. We concluded that the superoxide ion radical (O 2−) and the peroxy bonding (-O-O-) oxidize Cr 3+ to Cr 4+ in aluminate, gallate, and alumino-silicate glasses. 相似文献
4.
The selective response to Hg 2+, Cd 2+ and Cu 2+ ions was studied for HgS- and CdS---Ge 0.20Te 0.30Se 0.50 and Cu 2Se---As 0.40Se 0.60 glass electrodes. These glass electrodes, containing a suitable amount of the above heavy metals, showed the Nernstian response to the corresponding metal ions. Some metal ions, however, interfered with the selective response. The selectivity of these glass electrodes was found to be connected with the relative position of the Fermi levels of the chalcogenide glasses and redox couples for metal ions. 相似文献
5.
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
6.
By selecting carefully controlled conditions for the thermal treatment of sodium borate glasses coated with PbO films, it is possible to prevent Pb 2+ ions from penetrating deeply into the glass. For low alkali glasses, an interdiffusion layer can be formed, which sub-surface cation profiling (by ion beam induced radiation) shows is a solid solution of Na 2O and B 2O 3 in PbO which acts as solvent. Experiments with 18.0 mol-% Na 2O glass show that it is possible to transform such an interdiffusion layer into a second type in which Na 2O and B 2O 3 together act as solvent and the concentration of PbO solute varies through the layer. For both types of layer the Na 2O : B 2O 3 ratio is different from that of the glass substrate, and for the production of the second type of layer it is shown that an important factor connected with penetration of PbO into the glass surface is a “sweating” process in which thermal treatment of the glass, even in the absence of PbO, results in migration of Na + ions so that the glass surface has a Na 2O content higher than that of the bulk glass. Changes in the UV spectra of the Pb 2+ ion are correlated with the formation of the interdiffusion layers, and results show that types of layer have optical basicities significantly greater than that of the glass substrate, through either the high PbO or high Na 2O content. 相似文献
7.
The distribution functions of doped Tb 3+ and Nd 3+ in silicate, germanate, borate and phosphate glasses, in which cross-relaxation among active ions plays an important role, have been estimated by fluorescence measurements. In order to analyze both the steady state and the transient fluorescence characteristics, a non-linear model for the resonant energy transfer has recently been developed. The experimental fluorescence intensity and decay curves, measured as a function of acceptor concentration, suggested a modified distribution function, which included the effect of the segregation of donors and acceptors. The number of segregated Tb 3+ ions at the second nearest neighbor position around a Tb 3+ ion was estimated to be 0.1–3.4, depending on the host glass. 相似文献
8.
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
9.
The coordination states of Fe 3+, B 3+ and Al 3+ ions in the alkali-silicate glasses have been determined. The structural effects of these cations coexisting in the glass, and the effects of the iron and boric oxide anomaly on glass density, are also analysed. 相似文献
10.
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
11.
Glass formation in the P 2O 5---WO 3---K 2O---Al 2O 3 system was investigated and the glass-forming regions are presented. the properties of the glasses in the P2O5---WO3---K2O---Al2O3 system (Al2O3 8 mol.%) are reported. The colouration of glass was studied. It was found that W5+ ions make glass blue. Infrared spectra were measured by means of making KBr pills. Results of the investigation suggest that P---O---P, P---O---W, and W---O---W bonds form a continuous network in the phosphate glasses. So we suggest that tungsten trioxide is a glass former. 相似文献
12.
采用高温固相法制备了一系列可被紫外光有效激发的Na 1+xSr 4-2x(BO 3) 3∶ xCe 3+荧光粉,并通过X射线衍射、扫描电镜、荧光光谱等测试方法对样品的物相结构、形貌和发光特性进行了表征及分析。X 射线衍射结果显示,Ce 3+成功掺入到基质NaSr 4(BO 3) 3中;利用高斯峰拟合、多光谱对比等手段,分析并验证了发光中心Ce 3+占据了NaSr 4(BO 3) 3中Sr 2+(1)和Sr 2+(2)两个格位;研究了不同浓度Ce 3+的掺杂对发光位置和发光强度的影响,随着Ce 3+掺杂浓度的提高,发射光谱出现红移,发光强度出现增强→减弱→再增强的趋势;将荧光粉的发射光谱与植物光合色素吸收光谱进行对比,发现它不仅可以吸收300~350 nm的紫外光,发射光谱还很好地覆盖了植物光合色素所需的蓝光区吸收波段,证明其在农业生产的转光剂方面有潜在应用价值。 相似文献
13.
Ag +/Na + ion-exchanged R 2O–Al 2O 3–SiO 2 glasses with uniform concentration profile of Ag + and Na + were prepared by heat treatment in molten silver salt followed by holding at the same temperature in an ambient atmosphere. Their glass transition temperature ( Tg) and thermal expansion coefficient (TEC) were measured and structures were investigated using 29Si-MAS NMR, 27Al-MAS NMR, IR and Raman spectroscopies. Both Tg and TEC decreased with increase of the exchange ratio, but Tg was still above the ion-exchange temperature of 400°C even for the fully exchanged sample. The 29Si- and 27Al-MAS NMR spectra were mostly unchanged and no sign of the structural alteration of the glass network was observed. On the other hand, the vibrational spectra showed remarkable peak shifts depending on the exchange ratio. From these structural results, it was found that when the exchange ratio was low, the introduced Ag + ions were stabilized at the non-bridging oxygen (NBO) site, and then Na + ions in AlØ 4 site were exchanged by Ag + ions after full replacement of NBO sites, where Ø represents the bridging oxygen. 相似文献
14.
The glass-forming region in the BiO 1.5---BaO---CuO system was determined, and the structure and crystallization of the glasses were investigated and compared to glasses containing CaO or SrO in place of BaO. It has been found that the glass-forming region in this system is wider than those in the BiO 1.5---CaO---CuO and BiO 1.5---SrO---CuO systems. BaBiO 2.77 was preferentially formed in the first stage of crystallization at all glass compositions. It is suggested that the Ba 2+ ions may preferentially occupy the sites near BiO 6 octahedra, while the Ca 2+ ions in BiO 1.5---CaO---CuO glasses may not have a site preference with respect to the BiO 6 octahedra. 相似文献
15.
Vanadium EXAFS spectra of 50V 2O 5-50P 2O 5 glasses with different C = V +4/V tot have been measured. The V-O distances increase by Δ R1 = (0.03 ± 0.02) Å to Δ R2 = (0.07 ± 0.03) Å going from a glass with C = 0.64 to C = 0.84 and from C = 0.51 to C = 0.84, respectively. The EXAFS data show a basically similar structure of the vanadium sites for both the V 4+ and V 5+ ionic states. The density of the glasses increases with C from the value d1 = 2.81 g/cm 3 for C = 0.51 to d2 = 2.92 g/cm 3 for C = 0.84 indicating a more random packing of glass units. 相似文献
16.
The visible luminescence due to Ti 3+ ions in titanium-containing fluorophosphate glass has been observed with UV excitation. Time-resolved fluorescence and lifetime measurements have also been performed at room and low temperature, respectively. 相似文献
17.
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
18.
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
19.
氟化钡(BaF 2)晶体是已知响应最快的闪烁晶体,在高能物理、核物理及核医学等领域有着广泛的应用前景。抑制BaF 2晶体的慢发光成分对其工程应用至关重要。本文利用坩埚下降法制备了高Y 3+掺杂浓度5%、8%、10%(摩尔分数)的BaF 2晶体,并采用Y 3+与碱金属离子(Li +、Na +)共掺杂的方法形成电荷补偿阻止间隙F -的产生,制备了双掺杂型BaF 2快响应闪烁晶体,进而基于优化的5 ns和2 500 ns时间门宽测试方法,研究了Y 3+掺杂浓度以及Y 3+与碱金属离子(Li +、Na +)共掺杂浓度对BaF 2闪烁晶体快/慢成分比的影响规律。结果表明,生长的高浓度Y 3+掺杂BaF 2晶体的光学质量优异,在220 nm和300 nm处透过率分别高于90%和92%;随着Y 3+掺杂浓度由0提高至10%,BaF 2晶体的慢发光成分显著降低,快/慢成分比由0.15提高至1.21;生长的Y 3+/Li +及Y 3+/Na +共掺杂BaF 2晶体的慢发光成分较Y 3+掺杂BaF 2晶体进一步降低,快/慢成分比最高分别可达1.63和1.61。研制的双掺杂BaF 2快响应闪烁晶体有望应用于高能物理、核物理前沿实验等重要领域。 相似文献
20.
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
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