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1.
《Journal of Non》2007,353(13-15):1341-1345
PbOx[(Na2O)0.25(SiO2)0.75]1−x glasses (with x = 0.1–0.30) were prepared by a conventional melt-quench method and characterized by UV–visible optical absorption, photoluminescence and 29Si magic angle spinning nuclear magnetic resonance (MAS NMR) studies. It has been confirmed that the increased number of non-bridging oxygen atoms brought about by the increase in Q2 structural units of silicon is responsible for the shifting of the wavelength corresponding to the onset of absorption, as PbO concentration increases in the glass. Emission in the visible region (400–450 nm), from these glasses has been attributed to the presence of L-centers, whose the peak maxima and line widths systematically shift to higher values by incorporating Pb2+ along with Na+ in the network modifying positions. All the Pb2+ ions in these glasses occupy only the network modifying positions, as revealed by the identical chemical shift values of Qn structural units of silicon with increase in PbO concentration. In contrast to binary lead silicate glasses, no luminescence has been observed for comparable concentration of PbO, possibly due to the significant quenching of Pb2+ ions in the excited state. 相似文献
2.
Reflection spectra of silicate, borate, phosphate, fluorophosphate and fluoride glasses are studied in the spectral region of 2–13 eV in order to understand their dispersion behaviors in the visible region from the point of view of atomic structures.The absorption bands due to bridging oxygen ions or fluorine ions are found at 11.6 eV and 10.4–9.5 eV in silicate glasses, at 10.2 and 8.8 eV in borate glasses, at 9.5 eV in phosphate glasses, at 11.2 eV in fluorophosphate glasses and at 11 eV in fluorozirconate glasses.In silicate glasses, the bands due to nonbridging oxygen ions are found in the region 8.8-4.9 eV. They shift to lower energies with increasing ionic radius, in the order of Ca2+, Sr2+ and Ba2+, for the glasses containing low valency cations, while they shift to higher energies with increasing ionic radius, in the order of Ti4+, Zr4+ and Th4+ or in the order of Nb5+ and Ta5+, for the glasses containing high valency cations.In glasses containing large amounts of PbO, strong bands due to PB2+ ions appear in the lower energy regions of 6.3–5.6 eV and 5.2–4.7 eV. 相似文献
3.
ESR and optical absorption spectra of Cu2+ in xNa2O(100?x)SiO2 glasses were measured, where x ranges from 12 to 70 mol% Na2O. This glass system was divided into three composition regions, 12 ? x ? 37, 37 ? x ? 55 and 55 ? x, from the composition dependence of the ligand field transition energy and spin hamiltonian parameters of Cu2+. Two boundary compositions (37 and 55 mol%) between the two adjacent regions agreed with the eutectics in the equilibrium phase diagram. Two types of Cu2+-complexes, with less basic ligands (HFS-1) and much more basic ones (HFS-2), were detected in ESR for ultra-high soda glasses (x ? 55). The distribution of the ESR parameters due to the fluctuation of ligand fields was negligible for HFS-2 compared with that for other glasses. The Cu2+ ion responsible for HFS-2 was considered to distribute in the microphase of orthosilicate. Imagawa's basicity, the covalency of the bondings between Cu2+ and ligands, was calculated by using Maki and McGarvey's analysis. The basicity of σ-type symmetry remained constant, irrespective of the glass composition, and the value was identical with those for other oxyanionic glasses. The π-type basicity was also constant for the glasses of x ? 55. Two different basicities, each corresponding to HFS-1 or 2, were obtained for the glasses of x ? 55. The value derived from HFS-1 was identical with those for x < 55 glasses, whereas that derived from HFS-2 suggested the formation of much more basic ligands. 相似文献
4.
Polarized Raman spectra of x NaAlO2·(100 ? x) GeO2 glasses (x = 0, 5, 10, 15, 20, 25, 33, 42, and 50) are presented. Analyses of the Raman data indicate that the aluminogermanate glasses have three-dimensional network structures consisting of interconnected AlO4 and GeO4 tetrahedra; Na+ ions are present in cavities and charge balance the Al3+ ions. Systematic changes are observed in the frequencies, intensities and polarization characteristics of spectral bands with variations in the NaAlO2 content of these glasses. The antisymmetric stretching mode [νas (TOT), where T = Al, Ge] in the high-frequency region of the spectra (800–1000 cm?1) appears as a doublet consisting of well-defined bands in the spectra of glasses along the entire join. Both components of the high-frequency doublet shift to a lower frequency with increasing NaAlO2 content, indicating that the νas (GeO4) and νas(AlO4) stretching modes are coupled. The variations in the TO force constants and TOT bond angles with change in composition most likely cause the bands to shift. The frequencies of the Raman bands of sodium aluminogermanate glasses are compared with those of the corresponding bands in isostructural sodium gallogermanate glasses. On the basis of this comparison, the origin and delocalization of the vibrational modes producing characteristic Raman bands in the spectra of these glasses are discussed. The changes observed in the Raman spectra of aluminogermanate glasses with variation in NaAlO2 content are analogous to those observed in the spectra of glasses along the NaAlO2SiO2 join. 相似文献
5.
A. Klonkowski 《Journal of Non》1983,57(2):339-353
The mixed alkali glass system Na2OK2OAl2O3SiO2 was investigated. Density, transformation temperature, refractive index, and chemical durability were studied. Optical absorption and ESR spectra of the CuO-doped glasses were determined.Calculations of the polarizability of O2?, bonding parameters of the Cu2+ complex, and the packing density are presented. It was found that for the mixed alkali glasses, the oxygen- alkali bond has a more ionic character than expected from additivity. This fact enables the non-linear changes of the refractive index, of the shift of the Cu2+ absorption band, and of the covalency to be interpreted as the Na mole fraction is varied. It is also possible to explain qualitatively the density, Tg and chemical durability non-linear variations with change of the Na content by the ionicity deviations of the bond character and the postulated pairs of Na+ and K+ ions in the mixed alkali glasses. 相似文献
6.
ESR and optical absorption of Cu2+ were measured in xNa2O(100?x)B2O3 (1 ≤ x ≤ 75), x ZnO(100?x)B2O3 (46 ≤ x ≤ 64) and x Pb(100?x)b2O3 (20 ≤ x ≤ 75) glasses, where x is expressed in mol.%. Spin hamiltonian parameters and ligand field absorption energy changed abruptly in the regions of 15 ≤ x ≤ 23 and 37 ≤ x ≤ 55 in the soda system, while both parameters were hardly dependent upon the glass composition in zinc and lead systems. The magnitude of micro-environmental fluctuation of Cu2+-complexes in the glasses was estimated qualitatively and correlated with the distribution of the strength of π-bonding between cupric ion and oxygen in the glass. Typical network modifiers and intermediates behaved differently, especially in the composition region of invert glass; the large deformation of the coordination sphere of Cu2+ in lead glasses due to the stronger PbO bond resulted in the large distribution of . The situation was reverse in the case of soda glasses. 相似文献
7.
45S5 Bioglasses of the composition 46.1 SiO2–2.6 P2O5–26.9 CaO–(24.4 ? x) Na2O–xMe2O (Me = Li or K) have been investigated using MAS NMR and MQ–MAS NMR methods. The analysis of the 29Si MAS NMR spectrum revealed two lineshapes whose chemical shift is consistent with two silica Qn=2,3 species. The 31P MAS NMR spectrum reveals the effect of both Na and Ca ions. The chemical shift of the observed 31P signal is intermediate between those of Na3PO4 (near 10 ppm) and Ca3(PO4)2 (near 3–0 ppm) species. The 23Na MAS NMR spectra were observed in the alkali oxide composition: 24.4 Na2O, 12.2 Na2O–12.2 K2O and 12.2 Na2O–12.2 Li2O. The substitution of Na with Li or K was done to determine the extend of alteration of the glass structure. This goal was best accomplished by 23Na MQ–MAS NMR. The two-dimensional spectra revealed three sites in the 24.4 mol% Na2O glass. These sites were not resolved in the 1D MAS NMR spectroscopy. In the mixed glasses, only two sites were obtained. 相似文献
8.
《Journal of Non》2006,352(23-25):2444-2447
In this work, we report the optical properties of Yb3+ ions in halogeno-sulfide glasses of composition (75 − x)GeS2–25Ga2S3–xCsCl (x = 5%, 10%, 15%, 20%, and 25% CsCl). This study includes an analysis of the influence of halide concentration on the absorption and emission cross-sections and lifetimes of Yb3+ ions. A blue shift of the absorption and emission bands and a decrease of the absorption and emission cross-sections and transition probability are observed as the halide concentration increases in the glass. 相似文献
9.
《Journal of Non》1986,79(3):325-332
The magnetic properties and microstructure of x%V2O5·(100−x)%As2O3 glasses with x varying in the range 40 to 90 mol% were investigated in order to elucidate their magnetic ordering. Weak antiferromagnetic interactions between V4+ ions were observed. Glasses with x ⩾ 60 separated into two glassy phases. The effect of microstructure on magnetic properties of these glasses was investigated. Phase separation increases with increasing V2O5 content and produces a broadening of the EPR line width of glasses with high vanadium content (x > 70). The c = V4+/Vtotal ratio of x%V2O5·(100−x)%As2O3 glasses, determined from EPR and chemical analysis, are considerably greater than those usually reported for x%V2O5·(100−x)%P2O5 glasses. 相似文献
10.
A.V. Ravi Kumar Ch. Srinivasa Rao N. Narasimha Rao V. Ravi Kumar I.V. Kityk N. Veeraiah 《Journal of Non》2012,358(10):1278-1286
Sodiumsulpho borophosphate glasses with composition (40 ? x)Na2SO4–30B2O3–30P2O5: xMnO with x ranging from 0 to 5.0 mol% were manufactures. Dielectric spectra have been studied over a wide frequency range of 102–105 Hz and in the temperature range within 30–250 °C. The valance states of manganese ions and their ligand coordination in the glass network have been investigated using optical absorption, luminescence and ESR spectroscopy. The analysis of the these results has indicated that the manganese ions exist both in Mn2+ as well as in Mn3+ states and occupy prevailingly octahedral positions and serve as modifiers similarly to Na+ ions The values of dielectric parameters (dielectric constant, ε′(ω), loss tan δ and ac conductivity, σac) were found to increase with increasing MnO content. They play a role of modifiers similarly to Na+ ions, create bonding defects and free ions viz., [SO4]2?, [POO1/2O2]2?, [POO0/2O3]3–, Na+ and (NaSO4)?. The migration of these charge carriers would build up space charge polarization and may be responsible for the enhanced dielectric parameters. The ac conductivity also is enhanced with increasing MnO content. The mechanism responsible for such increase is well explained based on the modifying action of Mn2+ ions. 相似文献
11.
151Eu Mössbauer spectra of fluorozirconate glasses of nominal composition 0.61 ZrF4 · (0.32 ? x) BaF2 · x EuF2 · 0.07 ThF4 with x = 0.10 and 0.20 show that Eu2+ is present in sites with isomer shifts in the range ?15.5 to ?12.9 mm/s, corresponding to EuF bond lengths of 2.3–2.8 Å and a coordination number ranging from 8 to 12. The glasses contain a minor amount (~10%) of Eu3+ in well-defined sites. Effective Debye temperatures deduced from the recoilless fractions for the two ions are θD2+ = 145 K and θD3+ = 261 K. The differences in coordination and bonding indicate that trivalent eurpoium is a network former, whereas the divalent ions are network modifiers. 相似文献
12.
EzzEldin Metwalli 《Journal of Non》2003,317(3):221-230
Copper oxidation states, structure and properties of xCuO · (50-x)PbO · 50B2O3 glasses were investigated. Both infrared (IR) and 11B magic angle spinning nuclear magnetic resonance (MAS NMR) spectroscopies were employed to determine the tetrahedral BO4 fraction in the glasses as a function of CuO content. IR study indicates that the replacement of Pb2+ by Cu2+ ions increases the BO3 units by converting BO4- containing groups into ring type metaborate groups. The oxidation states of copper ions in the glasses have been studied using both X-ray photoelectron spectroscopy (XPS) and the wet chemical method. For high CuO containing (?30 mol%) glasses, high Cu+ ion concentrations (Cu+/Cutot.>0.3) result in a relatively slow disproportionation of B4-containing groups because of the small coordination number of Cu+ compared to Cu2+ ions. Effects of both glass structure and redox states of copper ions on glass properties including density, Vickers’ hardness, coefficient of thermal expansion, and chemical durability have been discussed. 相似文献
13.
《Journal of Non》2005,351(49-51):3730-3737
Ternary sodium–cobalt–phosphate glasses of the composition (50 − x)Na2O–50P2O5–xCoCl2 with x varying between 0 and 15 mol% prepared by melt quenching have been characterized by Fourier transform infrared (FT-IR) spectroscopy and X-ray diffraction (XRD) techniques. Thermal (Tg, Tc) and electrical properties have been investigated. Infrared spectra reveal the formation of metaphosphate glasses (Q2 tetrahedral units) with symmetric bridging oxygen (P–O–P) and non-bridging oxygen (P–O−). The spectra also indicate the formation of P–O–Co bonds in the metaphosphate glasses that replace P–O−–Na+ bonds. The results of thermal studies correlate with these FT-IR findings and support the formation of P–O–Co bonds and an increased cross-link density with increasing CoCl2. This results in enhanced chemical durability and increased Tg and Tc of the glasses. The electrical conductivity parameters upon changing the composition have been correlated with structural changes in the glass matrix. 相似文献
14.
Molar volumes and optical absorption spectra of Ni2+ ions were measured for sodium and potassium borosilicate glasses of the compositions xR2O·B2O3·rSiO2 (0.01 < x < 2.0; r = 1 and 2), where parameters x and r represent respectively the molar ratios R2O/B2O3andSiO2/B2O3. The presence of structural groups was discussed from the results. It was confirmed that addition of an alkali oxide changed BO3 units to RBO4 units in the range x < 0.55 for r=1 and x < 0.6 for r=2, while it created ROSiO3 units in the range . In the range x > 0.8 for r=1 and x > 9 for r=2, ROSiO3 and ROBO2 units were created by the alkali addition. Here ROBO2 units were also formed as a result of self-decomposition of RBO4 units. The volume of void associated with a BO4 unit was calculated and compared with the size of sodium and potassium ions. It was shown that sodium ions were small enough to be accommodated in the void whereas potassium ions were too large. This could explain the composition dependence of the molar volume of the sodium and potassium borosilicate glasses in the composition range x < 0.55 for r = 1 and x < 0.6 for r =2. 相似文献
15.
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
16.
《Journal of Non》2006,352(26-27):2778-2782
10Al2O3–5B2O3–85SiO2–xSm2O3 glasses were prepared by the sol–gel method. The emission spectra of the glasses indicate that the quench concentration of the Sm3+ ions is about 0.2 mol%. The emission spectra of the glasses after high-temperature treatment with H2 gas exhibit the coexistence of the Sm3+ and Sm2+ ions. We observed the strong emission line of the Sm2+ ions and the emission band of the non-bridging oxygen hole center when the glasses were exposed to a femtosecond laser. It indicates that some Sm3+ ions were reduced to Sm2+ ions by femtosecond laser pulses and non-bridging oxygen hole centers were formed. The 5D0–7F0 emission line of the Sm2+ ions by femtosecond laser irradiation shows a red shift, compared with the emission of the Sm2+ ions by reduction with H2 gas. The strong absorption band and weak, sharp absorption lines in the range from the UV to IR come from charge transfer and the transition from the 6H5/2 state to the various excited states of the Sm3+ ions. The reduction mechanism of Sm3+ ions is discussed. 相似文献
17.
Sezhian Annamalai Rudra P. Bhatta Ian L. Pegg Biprodas Dutta 《Journal of Non》2012,358(6-7):1019-1027
DC resistivity, thermopower and optical absorption of xV2O5–(1 ? x) As2O3 (0.58 ≤ x ≤ 0.93) glasses have been studied as a function of composition. The transport mechanism in these glasses has been identified to be a combination of hopping of small polarons between V4+ and V5+ sites and small bipolarons between As3+ and As5+ sites respectively. Electrical conductivity is found to be more of a function of vanadium content than arsenic concentration in the glasses, indicating that the contribution of bipolarons to the conductivity is negligible. Thermopower has also been found to be sensitive to the composition of the glasses. At low vanadium concentrations, the thermopower is negative, which exhibits a sign reversal as vanadium concentration is increased (at x = 0.7). An important feature of these glasses is that the thermopower is not a function of [V5+]/[V4+] ratio, as is normally observed in vanadate glasses, and such a phenomenon suggests that the arsenic ions (bipolarons) in these glasses contribute to the thermal transport phenomena in a significant way. 相似文献
18.
E. A. Sulyanova D. N. Karimov S. N. Sulyanov B. P. Sobolev 《Crystallography Reports》2014,59(1):14-21
A Sr0.7Ce0.3F2.3 crystal (CaF2 type, sp. gr. $Fm\bar 3m$ ), obtained by quenching from melt, has been studied for the first time by X-ray diffraction. Fluorine vacancies and interstitial anions are found in the 8c and 32f sites, respectively. The defect ratio in the Sr0.7Ce0.3F2.3 structure corresponds to the tetrahedral cluster configuration of defects {Sr4 ? n Ce n F26}. The defect structure of quenched (at a rate of ~25 K/min) crystal differs from that of a crystal grown from melt (cooling at a rate of ~3 K/min) by the displacement of some cations (presumably Ce3+) along the threefold axis to the 32f site and the anisotropy of thermal vibrations of ions in the cluster core (F int(32f)3). The concentration dependence of the lattice parameters of quenched Sr1 ? x Ce x F2 + x phases (x = 0–0.5) is described by a third-order polynomial: a = 5.80009 + 1.166518 × 10?3 x ? 1.124969 × 10?5 x 2 + 8.258155 × 10?8 x 3. The compositional dependence of microdistortions is also nonlinear; maximum microdistortions are observed in the SrF2 crystal. They decrease with an increase in the cerium concentration x to ~ 0.35. The minimum in the range x = 0.30–0.35 correlates with a composition corresponding to the peak (at x ~ 0.29) in the melting curves of the fluorite phase estimated from the phase diagram of the SrF2-CeF3 system (the method of thermal analysis). 相似文献
19.
S. Mizusaki Y. Toyoda K. Nakayama Y. Nagata T.C. Ozawa Y. Noro H. Samata 《Journal of Non》2009,355(16-17):960-964
The performance of phosphate glasses as a catalyst for water decomposition and a proton conductor was investigated. Glasses with a composition of 30Na2O–10BaO–30P2O5–(30?x)WO3–xNb2O5 (5 < x < 25) decompose water vapor and generate hydrogen at 500 °C. The best decomposition performance was observed on a specimen with the Nb2O5 composition of x = 15. A part of hydrogen produced on the glass surface changes to protons by reducing W6+ ions and penetrates into the glass. The electron is the dominant charge carrier in the electric conduction of W-rich glasses, whereas proton conduction is predominant in Nb-rich glasses in hydrogen atmosphere. A Raman scattering experiment revealed that Nb contributes to depolymerize the –P–O–P– chains in the phosphate glass producing non-bridging oxygen. A possible model was proposed for the water decomposition and proton conduction processes. 相似文献
20.
Odile Majérus Daniel Caurant Jean-Luc Dussossoy Pascal Loiseau 《Journal of Non》2011,357(14):2744-2751
The environment of Nd3+ ions has been studied using optical absorption spectroscopy and EXAFS at the Nd L3-edge, in a series of soda lime aluminoborosilicate glasses with increasing B2O3 content. The proportion of BO4 units has been determined by 11B MAS NMR in an equivalent glass series with La3+ ions replacing the majority of Nd3+ ions, and complementary information has been obtained by measuring the Nd3+ decay fluorescence times in these latter glasses. In these glasses with low Al2O3 content, the R′ ratio, with R′ = [Na2Oexc] / [B2O3] and [Na2Oexc] = [Na2O] − [Al2O3] − [ZrO2], plays a key role in controlling the structural organization and crystallization resistance, in a similar way as the R ratio in the Dell and Bray model of sodium borosilicate glasses. At R′ > 0.5, the Nd3+ ions are located in a mixed silicate-borate environment and, by slow cooling of the melt, they tend to crystallize within a silicate apatite phase close to the Ca2Nd8(SiO4)6O2 composition. At R′ < 0.5, the structural results are compatible with Nd3+ ions located in a borate-type environment (not excluding Si neighbors), and, by slow cooling of the melt, they segregate with Ca2+ ions within a Si-depleted separated borosilicate phase. 相似文献