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1.
The influence of Cr2O3 on glass forming characteristics and physical properties of PbO-Fe2O3-P2O5 glasses has been investigated by Raman and Mössbauer spectroscopies, X-ray diffraction analysis (XRD), Differential Thermal Analysis (DTA), Scanning Electron Microscopy (SEM) and impedance spectroscopy. Glasses of the general composition xCr2O3-(28.3-x)PbO-28.7Fe2O3-43.0P2O5, 0 ≤ × ≤ 10, (mol%) were prepared by conventional melt-quenching technique. The compositions containing up to 4 mol% Cr2O3 formed fully amorphous samples and their Raman spectra show systematic increase in the fraction of orthophosphate Q0 units with increasing Cr2O3 content and O/P ratio.On the other hand, compositions containing 8 and 10 mol% Cr2O3 partially crystallized during cooling and annealing to Fe7(PO4)6, Fe2Pb3(PO4)4 and Cr2Pb3(PO4)4. A high tendency for crystallization of these melts is related to the high O/P (> 4) and Fe2+/Fetot (≈ 0.60) ratios.Electrical conductivity of xCr2O3-(28.3-x)PbO-28.7Fe2O3-43.0P2O5, 0 ≤ × ≤ 10, (mol%) compositions is independent of Cr2O3 and controlled entirely by the polaron transfer between Fe2+ and Fe3+ ions.  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.
This work studied the properties of glasses with the molar composition 63.8SiO2-(11.6-x)Na2O-(0.7 + x)B2O3-19.2CaO-3MgO-1.5Al2O3-0.2P2O5, in which x = 0, 1, 2, 3. These glasses are of interest for the development of slowly dissolving fibers to be incorporated in composites for medical applications. The thermal properties were recorded using hot stage microscopy, differential thermal analysis, and heat treatments in the range of 800°-1000 °C. The glass crystallization behavior was determined based on calculated values of the activation energy of crystallization and the Johnson-Mehl-Avrami exponent. The structural units in the glass network were identified using infrared spectroscopy. Finally, in vitro dissolution was tested in SBF solution.The addition of B2O3 increased the glass transition temperature and reduced the working temperature. When heat treated at 900 °C, the glass with the smallest amount of B2O3 formed two crystalline phases: magnesium silicate MgSiO3 and wollastonite CaSiO3. In the other compositions, only CaSiO3 was observed after heat treatment at 950 °C. All the glasses crystallized preferentially from the surface. Changes in the liquidus and crystallization temperatures were related to changes in the glass structure. The formation of [BO3] units led to glasses with improved resistance to crystallization and decreased liquidus temperature. In the glasses with 2.7 and 3.7 mol% B2O3, [BO3] units were transformed into [BO4] units. The formation of [BO4] led to an increase in fragility and a decrease in resistance to crystallization. All the glasses dissolved slowly in simulated body fluid.  相似文献   

4.
Glasses in the ternary system PbO-MoO3-P2O5 were prepared in three compositional series (100 − x)[0.5PbO-0.5P2O5]-xMoO3 (A), 50PbO-yMoO3-(50 − y)P2O5 (B) and (50 − z)PbO-xMoO3-50P2O5 (C) and their structure was studied by Raman and 31P NMR spectroscopies. In the compositional series (100 − x)[0.5PbO-0.5P2O5]-xMoO3 homogeneous glasses were prepared in the concentration region of 0-70 mol% MoO3. Their glass transition temperature increases with increasing MoO3 content having a maximum at x = 50 mol% MoO3. 31P MAS NMR spectra reveal that in the glass series (A) the incorporation of MoO3 results in the shortening of phosphate chains and gradual transformation Q2 units into Q2 and Q0 units, prevailing in glasses with a high MoO3 content. Octahedral structural units MoO6 dominate in most glass compositions and they are present also in the structure of Pb(MoO2)2(PO4)2 compound corresponding to the glass composition 50Pb(PO3)2-50MoO3. The analysis of Raman spectra of glasses of the (B) series with a high MoO3 content showed the transformation of octahedral MoO6 units into tetrahedral MoO4 units.  相似文献   

5.
G. Upender 《Journal of Non》2011,357(3):903-909
Infrared, EPR and optical absorption studies on (90-x)TeO2-10GeO2-xWO3 (7.5 ≤ x ≤ 30) glasses containing Cu2+ spin probe have been carried out. The Infrared spectral studies show that the structure of glass network consists of [TeO4], [TeO3]/[TeO3 + 1], [WO4], [WO6] and [GeO6] units in the disordered manner. Physical parameters such as density (ρ), molar volume (Vm), oxygen packing density (OPD), oxygen molar volume (Vo), optical basicity (Λ), oxide ion polarizability (αO2−), inter ionic distances and the concentration of ions per unit volume of Te, Ge, W, Cu and O have been determined. The spin-Hamiltonian parameters (g||, g and A||) of Cu2+ ions in the present glasses have been estimated from EPR spectra at 300 K. Bonding parameters such as α2, β12, β2, Γσ, and Γπ have been calculated from both optical absorption and EPR data. The observed variations in spin-Hamiltonian parameters and bonding parameters have been correlated to the structural modifications due to the WO3 incorporation into the TeO2 glass network at constant 10 mol% GeO2 content.  相似文献   

6.
In MoO3–Nd2O3–B2O3 and MoO3–Nd2O3–La2O3–B2O3 systems, glasses were obtained in the region between 20 and 30 mol% Ln2O3. A liquid-phase separation region was observed near the MoO3–B2O3 side up to 20 mol% Ln2O3 (La, Nd). The amorphous phases were characterized by X-ray diffraction (XRD), differential thermal analysis (DTA), UV–VIS and infrared spectroscopy (IR). According to DTA data B2O3-rich glasses are stable up to 630 °C while glasses rich in MoO3 are stable up to 430 °C. The glasses are transparent in the visible region. Structural models for the glasses network were suggested on the basis of IR spectral investigations. It was established that BO3 (1380 cm−1), BO4 (1100–950 cm−1) and MoO4 (860 cm−1) groups build up the glass network. MoO6 units (band at 880 cm−1) together with BO3 units participate in the formation of the glass network with a high MoO3 content (80–90 mol%).  相似文献   

7.
H. Doweidar 《Journal of Non》2009,355(6):348-354
Studies on xRO · 30Bi2O3 · (70−x)B2O3 glasses have been carried out (0 ? x ? 30 mol%, R = Zn, Ba). Elastic properties and Debye temperature have been investigated using sound velocity measurements at 4 MHz. The ultrasonic parameters along with the IR spectroscopic studies have been employed to explore the role of divalent cations in the structure of the studied glasses. Analysis of infrared spectra indicates that RO is preferentially incorporated into the borate network, forming BO4 units. It is assumed that Bi2O3 enters the structure in the form of BiO6 only. The change of density and molar volume with RO content reveals that BO4 units linked to R2+ cations are denser than those linked to positive sites in the Bi2O3 network. Predicted values of four co-ordinated boron put forward questions about the reliability of assignment of structural units that Bi2O3 may form.  相似文献   

8.
Bing Zhang  Li Song  Fengzhen Hou 《Journal of Non》2008,354(18):1948-1954
Glasses in the ternary system ZnO-Sb2O3-P2O5 were investigated as potential alternatives to lead based glasses for low temperature applications. The glass-forming region of ZnO-Sb2O3-P2O5 system has been determined. Structure and properties of the glasses with the composition (60 − x)ZnO-xSb2O3-40P2O5 were characterized by infrared spectra (IR), differential thermal analysis (DTA) and X-ray diffraction (XRD). The results of IR indicated the role of Sb3+ as participant in glass network structure, which was supported by the monotonic and remarkable increase of density (ρ) and molar volume (VM) with increasing Sb2O3 content. Glass transition temperature (Tg) and thermal stability decreased, and coefficient of thermal expansion (α) increased with the substitution of Sb2O3 for ZnO in the range of 0-50 mol%. XRD pattern of the heat treated glass containing 30 mol% Sb2O3 indicated that the structure of antimony-phosphate becomes dominant. The improved water durability of these glasses is consistent with the replacement of easily hydrated phosphate chains by corrosion resistant P-O-Sb bonds. The glasses containing ?30 mol% Sb2O3 possess lower Tg (<400 °C) and better water durability, which could be alternatives to lead based glasses for practical applications with further composition improvement.  相似文献   

9.
Transparent glasses composition of which can be expressed by the formula: (100−x) · (K2O · 2TiO2 · P2O5) · x(K2O · 2B2O3 · 7SiO2), where x=5, 10, 15 and 20 mol% (KTP-xKBS), were obtained by melt quenching technique. The structure and crystallization behavior of these glasses have been examined by Fourier transform infrared spectroscopy, differential thermal analysis and X-ray diffraction. In spite of their nominal composition, the studied glasses exhibit a similar oxygen polyhedra distribution. However, significant differences were found in the trigonal BO3 units amount. During DTA runs all the examined glasses devitrify in two steps. In the former, very small crystals of an unknown crystalline phase are produced. In KTP-5KBS and KTP-10KBS glasses anatase phase was also detected. Attempts were made in order to identify the unknown phase (UTP) for which a AB3(XO4)2(OH)6 Crandallite-type structure was proposed where the A, B and X sites were occupied by K, Ti and/or Al, and P, respectively. In the second devitrification step the crystallization of the KTiOPO4 phase occurs while the UTP phase previously formed disappears. Isothermal heat treatments performed at temperature just above Tg have allowed one to obtain transparent crystal-glass nanocomposites, formed by crystalline nanostructure of the UTP phase uniformly dispersed in the amorphous matrix.  相似文献   

10.
This study was explored in series of the optical, thermal, and structure properties based on 60P2O5-10Al2O3-30ZnO (PAZ) glasses system that doped with varied rare-earth (RE) elements Yb2O3/Er2O3. The glass transition temperature, softening temperature and chemical durability were increased with RE-doping concentrations increasing, whereas thermal expansion coefficient was decreased. In the optical properties, the absorption and emission intensities also increase with RE-doping concentrations increasing, When Er2O3 and Yb2O3 concentrations are over than 3 mol% in the Er3+-doped PAZ system and Yb3+-doped concentration is over than 3 mol% for Er3+/Yb3+-codoped PAZ system, the emission intensity significantly decreases presumably due to concentration quenching, formation of the ions clustering, and OH groups in the glasses network. It is suggested that the maximum emission cross-section (σe) is 7.64 × 10− 21 cm2 at 1535 nm is observed for 3 mol% Er3+-doped PAZ glasses. Moreover, the maximum σe × full-width-at-half-maximum is 327.8 for 5 mol% Er3+-doped PAZ glasses.  相似文献   

11.
Local structure of the SnO-B2O3 glasses was investigated using several spectroscopic techniques. 11B MAS-NMR spectra suggested that BO4 tetrahedral units maximized at around the composition with 50 mol% SnO. The BO4 units were still present at compositions with high SnO content (67 mol% SnO), suggesting that SnO acted not only as a network modifier but also as a network former. O1s photoelectron spectra revealed that the addition of small amounts of SnO formed non-bridging oxygens (NBO) (B-O?Sn) and the amounts of NBO increased with an increase in SnO content. 119Sn Mössbauer spectra indicated that Sn was present only as Sn(II) in the glasses. The structure of the SnO-B2O3 glasses was compared with that of conventional alkali borate glasses and lead borate glasses. The thermal and viscous properties of these glasses were discussed on the basis of the glass structure revealed in the present study.  相似文献   

12.
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   

13.
S. Rada  E. Culea 《Journal of Non》2011,357(7):1724-1728
Glasses in the quaternary system 0.05Al2O3·0.95[xGd2O3·(100-x)(7GeO2·3PbO)] with 0 ≤ x ≤ 40 mol% have been prepared from melt quenching method. In this paper, we investigated structural and optical properties in gadolinium-alumino-lead-germanate glasses through investigations of FTIR (Fourier-Transform Infrared Spectroscopy) and UV-VIS (Ultra-Violet) spectroscopy.The observations presented in these mechanisms show that by increasing Gd2O3 content up to 40 mol%, the glass network modification has taken place mainly in the germanate part, while the excess of oxygen can be accommodated in the host network by the creation of shorter rings of [Ge2O7] structural units and the formation of [AlO4] structural units. The affinity pronounced of the gadolinium cations towards germanate structural units produces the formation of the Gd2Ge2O7 crystalline phase.The UV-VIS spectroscopy data show the charge transfer transitions of Pb+ 2-O− 2, Al+ 3-O− 2 and Gd+ 3-O− 2, respectively. The additional absorption in the range of 300 to 600 nm was attributed to other types of defects such as: non-bridging oxygen ions, change in valency of ions and other color centers.The values of the direct optical band gap of the glasses are determined from the optical absorption spectra. By increasing Gd2O3 content in the glass matrix, the optical band gap energy increases indicating changes of the lattice parameters by Gd2O3 incorporation.  相似文献   

14.
It is shown that the B10 spectra for sodium borate glasses are sensitive to the different structural groups in the glasses. Five boron sites are inferred from the data: two 4-coordinated sites and three 3-coordinated sites. The two 4-coordinated boron sites are identified as BO4 units connected to all BO3 units, and BO4 units connected to one BO4 unit and three BO3 units. The three 3-coordinated boron sites are identified as BO3 units connected to: (1) all BO3 units; (2) a mixture of BO3 and BO4 units; and (3) all BO4 units. These five sites can be interpreted in terms of Krogh-Moe's structural model of alkali borate glasses, wherein the fraction of each structural group can be determined for eight sodium borate glasses spanning the compositional range from 0 to 35 mol% Na2O. The resulting fractions are consistent with Krogh-Moe's structural model.  相似文献   

15.
Glasses, whose basic composition was based on the CaO-MgO-SiO2 system and doped with B2O3, P2O5, Na2O, and CaF2, were prepared by melting at 1400 °C for 1 h. Raman and infrared (IR) spectroscopy revealed that the main structural units in the glass network were predominantly Q1 and Q2 silicate species. The presence of phosphate and borate units in the structure of the glasses was also evident in these spectra. X-ray analysis showed that the investigated glasses devitrified at 750 °C and higher temperatures. The crystalline phases of diopside and wollastonite dominated, but weak peaks, assigned to akermanite and fluorapatite, were also registered in the diffractograms. The presence of B2O3, Na2O, and CaF2 had a negligible influence on the assemblage of the crystallized phases, but it caused a reduction of crystallization temperature, comparing to similar glasses of the CaO-MgO-SiO2 system.  相似文献   

16.
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   

17.
P. Srinivasa Rao 《Journal of Non》2011,357(21):3585-3591
The variation in physical, structural and electrical properties has been studied as a function of Bi2O3 content in 20ZnF2-(10 + x) Bi2O3-(70-x) P2O5, 0 ≤ x ≤ 10 mol% glasses, which were prepared by melt quenching technique and characterized by differential thermal analysis (DTA). Colorless samples, which have no absorption peaks, are obtained for 10 and 12 mol% of Bi2O3 and the glasses are slowly becoming brownish from 15 to 20 mol% of Bi2O3 which exhibit two absorption peaks at ~ 370 nm, ~ 450 nm correspond to Bi° transitions 4S3/2 → 2P3/2 and 4S3/2 → 2P1/2 respectively. The decrease in 3P1 → 1S0 transition of Bi3+ photo luminescence emission for 18 and 20 mol% of Bi2O3 and increase in optical absorption area shows the reduction of Bi3+ to Bi°. From FTIR studies it is observed that an addition of Bi2O3 decreases the P―O―P covalent bond by forming P―O―Bi bonds due to high polarizing nature of Bi3+ ions. Dielectric parameters like ε', tan δ and a.c. conductivity σac are found to increase and activation energy for a.c. conduction is found to decrease with the increase in the concentration of Bi2O3. Density of defect energy states is found to increase for higher concentration of Bi2O3 and is discussed according to quantum mechanical tunneling (QMT) model.  相似文献   

18.
Nobuaki Terakado 《Journal of Non》2008,354(18):1992-1999
Oxy-chalcogenide glasses with compositions of xGeO2-(100 − x)GeS2, where 0 ? x ? 100 mol%, have been prepared and studied in terms of their structures and optical properties. X-ray fluorescence spectroscopy shows that Ge:S ratio can deviate from GeS2 by ∼10 at.%, depending critically upon the preparation conditions. Raman scattering spectroscopy suggests that stoichiometric GeO2-GeS2 glasses have a heterogeneous structure in the scale of 1-100 nm. The optical gaps are nearly constant at 3.0-3.5 eV for glasses with 0 ? x ? 80 mol% and abruptly increase to ∼6 eV in GeO2. This dependence suggests that the optical gap is governed by GeS2 clusters, which are isolated and/or percolated. Composition-deviated glasses appear as orange and brown, and these glasses seem to have more inhomogeneous structures.  相似文献   

19.
Anomalous physical properties (refractive index and density) of B2O3BaTiO3Na2O ternay glasses are determined and discussed on the basis of the structure present in the glasses and evidenced by vibrational Raman spectroscopy.These glasses behave in a manner analogous to the alkali B2O3X2O binary glasses for molar ratio R = basic oxide/B2O3 up to 0.3, with oxygen binding by means of bridging bonds while boron coordination changes from the trigonal to tetrahedral type. The phenomenon is indicated by a progressive weakening of the 806 cm?1 peak (attributable to a breathing vibration of the boroxol unit) and by a concomitant strengthening of the ~775 cm?1 peak (attributable to a vibrational mode of boroxol units, or derived units, containing at least one 4-coordinate boron atom). For higher R values the Raman spectra bring to light the progressive demolition of the structural units responsible for the 775 cm?1 Raman peak, which gives rise (the transformation is complete for R ~ 1) to two new main structural units, orthoborate [BTi4O10]?1 (peak at 845 cm?1) and metaborate BO2? (peak at 715 cm?1).  相似文献   

20.
A combined nuclear magnetic resonance, infrared and Raman spectroscopic study on the effect of water dissolution on the structure of B-bearing aluminosilicate glasses is presented. The base composition was albite (NaAlSi3O8) to which different amounts of B2O3 (4.8, 9.1, 16.7 wt%) were added. Hydrous glasses containing 4.4 ± 0.1 wt% water were synthesized at pressures of 2000 bar. The results show that B dissolves in both dry and hydrous glasses by forming predominantly trigonal BO3 groups although some tetrahedral BO4 is also present. In anhydrous glasses prepared at high pressures (above 10 kbar) the fraction of BO4 increased. The hydrous glasses contain more BO4 groups compared to the dry counterparts, suggesting that this species is stabilized by water. The Raman and NMR (17O, 27Al, 29Si) spectra show that B interacts with the aluminosilicate network by formation of Si-O-B and probably Al-O-B units. In the hydrous glasses the water speciation changes significantly towards higher hydroxyl concentrations with increasing B-content. The NIR peaks, which are related to OH groups and molecular H2O, develop additional shoulders, suggesting that possibly B-OH complexes are formed.  相似文献   

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