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1.
S. M. Abo-Naf R. L. Elwan M. A. Marzouk 《Journal of Materials Science: Materials in Electronics》2012,23(5):1022-1030
SiO2–PbO–Bi2O3 glasses having the composition of 35SiO2–xPbO–(65−x)Bi2O3 (where x = 5, 10, 15, 20, 25, 35, 45; in mol%) have been prepared using the conventional melting and annealing method. Density, molar
volume and Vickers microhardness of the prepared glasses were measured. Infrared (IR) and UV–visible spectroscopic techniques
were used for structural studies of these glasses. Density as well as the microhardness increase systematically and, conversely,
the molar volume decreases with increasing the lead oxide content. This behavior can be explained by the correlation with
the glass structure. Increasing the lead oxide content (≥20 mol%) increases the network former PbO4 groups which can play an important role in increasing the connectivity and compactness of the glass matrix via increasing
the cross-linking with the other constituent silicate and bismuthate structural units. The increased compactness may explain,
in turn, the increase of the density and microhardness. IR spectra reinforce the idea that bismuth participates in the glassy
network predominantly as BiO6 octahedral structural units. UV–VIS optical absorption spectra revealed UV-charge transfer absorption bands related to the
contribution of Pb2+ ions in the region 350–385 nm; in addition to the extrinsic absorption of trace iron impurities in the range 220–290 nm.
In the visible region, three optical bands in the ranges 415–435, 605–650 and 880–890 nm were correlated with the contribution
of electronic transitions in Bi3+ ions. Calculation of the optical mobility gap and the width of the energy tail of glass from the UV–VIS absorption indicated
a slight increase followed by a decrease in their values. The behavior change occurred at the glass in which PbO content is
20 mol% where lead oxide starts to participate into the glassy matrix as a network former. The combination of analytical FTIR
and UV–visible spectroscopy provided a consistent picture of structure–property relations in this glass system. 相似文献
2.
Shaaban M. Salem E. M. Antar A. G. Mostafa S. M. Salem S. A. El-badry 《Journal of Materials Science》2011,46(5):1295-1304
(10Li2O–20GeO2–30ZnO–(40-x)Bi2O3–xFe2O3 where x = 0.0, 3, 6, and 9 mol%) glasses were prepared. A number of studies, viz. density, differential thermal analysis, FT-IR spectra,
DC and AC conductivities, and dielectric properties (constant ε′, loss tan δ, AC conductivity, σ
ac, over a wide range of frequency and temperature) of these glasses were carried out as a function of iron ion concentration.
The analysis of the results indicate that, the density and molar volume decrease with an increasing of iron content indicates
structural changes of the glass matrix. The glass transition temperature T
g and onset of crystallization temperature T
x increase with the variation of concentration of Fe2O3 referred to the growth in the network connectivity in this concentration range, while glass-forming ability parameter ΔT decrease with increase Fe2O3 content, indicates an increasing concentration of iron ions that take part in the network-modifying positions. The FT-IR
spectra evidenced that the main structural units are BiO3, BiO6, ZnO4, GeO4, and GeO6. The structural changes observed by varying the Fe2O3 content in these glasses and evidenced by FTIR investigation suggest that the iron ions play a network modifier role in these
glasses while Bi2O3, GeO2, and ZnO play the role of network formers. The temperature dependence of DC and AC conductivities at different frequencies
was analyzed using Mott’s small polaron hopping model and, the high temperature activation energies have been estimated and
discussed. The dielectric constant and dielectric loss increased with increase in temperature and Fe2O3 content. 相似文献
3.
Glass samples of the system (15Li2O–30ZnO–10BaO–(45 − x)B2O3–xCuO where x = 0, 5, 10 and 15 mol%) were prepared by using the melt quenching technique. A number of studies, viz. density, differential
thermal analysis, FT-IR spectra, a.c. conductivity and dielectric properties (constant εφ, loss tan δ, a.c. conductivity,
σac, over a wide range of frequency and temperature) of these glasses were carried out as a function of copper ion concentration.
The analysis of the results indicate that the density increases while molar volume decreases with increasing of copper content
indicates structural changes of the glass matrix. The glass transition temperature, T
g, and crystallization temperature, T
c, increase with the variation of concentration of CuO referred to the growth in the network connectivity in this concentration
range, while glass-forming ability parameter (T
c − T
g) decreases with increasing CuO content, indicates an increasing concentration of copper ions that take part in the network-modifying
positions. The FT-IR spectra evidenced that the main structural units are BO3, BO4, and ZnO4. The structural changes observed by varying the CuO content in these glasses and evidenced by FTIR investigation suggest
that the CuO plays a network modifier role in these glasses while ZnO plays the role of network formers. The dielectric constant
decreased with increase in temperature and CuO content. The variation of a.c. conductivity with the concentration of CuO passes
through a maximum at 5 mol%. In the high temperature region, the a.c. conduction seems to be connected with the mixed conduction
viz., electronic conduction and ionic conduction. 相似文献
4.
S. F. Khor Z. A. Talib W. M. Daud H. A. A. Sidek 《Journal of Materials Science》2011,46(24):7895-7900
Glasses with composition (ZnO)30(MgO)
x
(P2O5)70−x
(x = 5, 8, 10, 13, 15, 18, and 20 mol.%) have been successfully prepared by the melt-quenching technique. Degradation study
has been carried out by means of measuring their chemical durability against buffer solutions with initial pH values of 4.01,
7.00, and 10.01 at an ambient temperature for up to 30 days. The dissolution rate (D
R) was obtained by calculating the measured weight loss of the glasses per unit surface area per unit immersion time. The results
show that the glasses have better corrosion resistance in basic solution. It was also found that the weight loss is related
to the MgO concentration with lower P2O5 concentration exhibiting greater corrosion resistance irrespective of acidic, neutral, or basic solutions as immersion liquid.
All the sample surfaces and edges were corroded and the solutions experienced a decrease in pH values during the duration
of the corrosion test. 相似文献
5.
The glasses of composition (100 − x)TeO2–xCuO (x = 10, 20, 30, 40, 50 mol%) were prepared by melt quenching method. Differential Scanning Calorimetry (DSC), DC conductivity,
Electron Spin Resonance (ESR), and magnetization measurements were undertaken on the glass samples. The glass-transition temperature,
T
g, decreases and the thermal stability (ΔT = T
o − T
g) increases with the increase in CuO content. The electrical conduction in these glasses is due to polaron hopping mechanism
in the adiabatic regime. The ESR spectra of the x = 10 glass consists of a broad symmetrical line characteristic of Cu2+ clusters. The ESR signal linewidth increases and intensity decreases drastically with increase in CuO content from 10 to
20 mol%. No ESR signal could be observed for the glass samples with x ≥ 40. The absence of EPR signal is ascribed to antiferromagnetic interactions between the Cu2+ clusters. The magnetization measurements indicate all the samples to be in paramagnetic state. The M–H plots show a small hysteresis loop in the low-field region. These studies indicate the coexistence of antiferromagnetic (AFM)
as well as ferromagnetic (FM) interactions between Cu 2+ ions in these glasses. The significant change in the properties of the glass at x = 20 is ascribed to the structural changes caused by CuO in the glass matrix. 相似文献
6.
Petru Pascuta 《Journal of Materials Science: Materials in Electronics》2010,21(4):338-342
X-ray diffraction (XRD), Fourier transform infrared (FTIR) and electron paramagnetic resonance (EPR) spectroscopies have been
employed to investigate the xGd2O3 · (95 − x)[2Bi2O3 · B2O3] · 5V2O5 glass system, with 0 ≤ x ≤ 25 mol%. The glass samples have been prepared by melting at 1,100 °C for 10 min followed by rapid cooling at room temperature.
The structure of samples was analyzed by means of XRD. The pattern obtained did not reveal any crystalline phase in the samples
up to 25 mol%. FTIR spectroscopy data suggest that the gadolinium ions play the network modifier role in the studied glasses.
These data show that the glass network consists of BiO3, BiO6, BO3, BO4, and VO4 structural units. The FTIR data show that a conversion among these units takes place and this process mainly depends on the
Gd2O3 content. The EPR spectra of the studied glasses exhibit three important features with effective g-values of ≈5.9, 2.85, 2.0 and a weaker feature at g
eff ≈ 4.8. For low Gd2O3 contents (x ≤ 10 mol%), the EPR spectra have the typical ‘‘U’’-type shape. For higher contents of Gd2O3 (x > 10 mol%), the spectral features are broadened and finally are dominated by a single broad absorption line located at g
eff ≈ 2.0. This broad EPR line is associated to the Gd3+ ions present predominantly as clustered species. 相似文献
7.
Glasses of the 0.5Er3+/2.5Yb3+ co-doped (40Bi2O3–20GeO2–(30 − x)PbO–xZnO–10Na2O system where x = 0.0, 5, 10, 15, 20, 25, and 30 mol%) have been characterized by FT-IR spectroscopy measurements to obtain information about
the influence of ZnO-substituted PbO on the local structure of the glass matrix. The density and the molar volume have been
determined. The influences of the ZnO-substituted PbO on the structure of glasses have been discussed. The dc conductivity
measured in the temperature range 475–700 K obeys Arrhenius law. The conductivity decreases while the activation energy for
conduction increases with increase ZnO content. The optical transmittance and reflectance spectrum of the glasses have been
recorded in the wavelength range 400–1100 nm. The values of the optical band gap E
opt for all types of electronic transitions and refractive index have been determined and discussed. The real and imaginary parts
ε1 and ε2 of dielectric constant have been determined. 相似文献
8.
A. Prnová A. Domanická R. Klement J. Kraxner M. Polovka M. Pentrák D. Galusek P. Šimurka J. Kozánková 《Optical Materials》2011,33(12):1872-1878
The undoped, and Nd-, Er-doped low silica high alumina yttrium aluminosilicate (YAS) glasses were prepared by flame synthesis in the form of transparent glass microbeads with diameters ranging from a few to several tens of micrometers. The silica content ranged between 5 and 20 mol.%. The prepared glass microbeads were characterized by optical microscopy, SEM XRD, FT-IR and UV–VIS–NIR spectroscopy. The glass forming ability of glasses, expressed in terms of the difference between the glass transition temperature, Tg, and the onset of crystallization, Tx, improved with increasing silica content. Doping of YAS15 glass with neodymium or erbium at the level of 1–5 mol.% leads to decrease of both the Tg and Tx. However, the glass forming ability was not affected. The UV–VIS–NIR reflectance spectra in the spectral range from 300 to 1800 nm shows characteristic absorptions, due to the optically active Nd3+ and Er3+ ions in the host glass. 相似文献
9.
In order to further elucidate the local structure of ternary xGd2O3(100 − x)[0.7TeO2 · 0.3V2O5] glasses with x = 0, 5, 10, 15, 20 mol%, FTIR spectroscopy, XRD diffraction and density measurement were performed. FTIR and density data
show that by increasing the gadolinium ions content of the samples the excess of oxygen may be accommodated by the inter-conversion
of some [VO4] into [VO5] structural units and of [TeO3] into [TeO4] units. The composition of the heat-treated glasses was found to consist mainly of the Te2V2O9 crystalline phase. Varying x between 15 and 20 mol% Gd2O3 produces structural modification having as result an increase of the glass network polymerization degree. Accordingly, the
gadolinium ions play a particular role related to the improvement of the homogeneity of the glasses and in accommodating the
glass network with the excess of oxygen. 相似文献
10.
K. V. Shah M. Goswami S. Manikandan V. K. Shrikhande G. P. Kothiyal 《Bulletin of Materials Science》2009,32(3):329-336
The degradation behaviour of phosphate glass with nominal composition, 40Na2O-10BaO-xB2O3-(50-x)P2O5, where 0 ≤ x ≤ 20 mol%, was studied in water, HCl and NaOH solutions at room temperature to 60°C for different periods extending up to
300 h. These glasses were synthesized by conventional melt-quench technique. Dissolution rates were found to increase with
B2O3 content in the glass. The dissolution rates for the glass having 10 mol% B2O3 were found to be 0·002 g/cm2 and 0·015 g/cm2 in distilled water and 5% NaOH solution, respectively, at room temperature after 225 h of total immersion period, whereas
it increased considerably to 0·32 g/cm2 in 5% NaOH at 60°C after 225 h. However, glass samples with x = 15 and 20 mol% B2O3 were dissolved in 5% HCl solution after 5 h immersion. The degradation behaviour has been correlated with the structural
features present in the glass. The optical microscopy of the corroded surface revealed that the corrosion mechanism were different
in acid and alkali media. 相似文献
11.
Glasses in the system xFe2O3·(100 − x)[7GeO2·3PbO] with 0 ≤ x ≤ 60 mol% have been prepared from melt quenching method. In this article, we investigated changes in germanium coordination
number in iron–lead–germanate glasses through molar volume analysis, measurements of densities, investigations of FTIR, and
UV–VIS spectroscopy. The observations present in these mechanisms show that the lead ions have an affinity pronounced toward
[GeO5] and [FeO4] structural units with non-bridging oxygens. The excess of oxygen can be supported into the glass network by the formation
of [FeO6] structural units and the apparition of the germanate anomaly. At higher content of iron (III) oxide, the anomaly behavior
of the germanium is due to the formations of [FeO6] structural units. Our results show that the presence of fivefold germanium as a possible transitional phase from four to
sixfold germanium it is necessary for the formation of the [FeO6] structural units and the apparition of the Fe2O3 crystalline phase. Pb+2 ions with 6s2 configuration show strong absorption in the ultraviolet due to parity allowed s2-sp transition. 相似文献
12.
Glasses in the system xGd2O3·(100 − x)[TeO2·GeO2] with 0 ≤ x ≤ 50 mol% have been prepared from melt quenching method. In this paper, we investigated changes of the coordination numbers
of germanium, tellurium, and gadolinium ions by investigations of FTIR, EPR, and UV–VIS spectroscopy. By analyzing the structural
changes resulted from the IR spectra we found that the bending modes of [GeO4] structural units and the deformed modes of the Te–O–Te linkages produce intercalation of the [GdO
n
] entities in the germanate–tellurate chain network and densification of the glasses by increasing the number of [GeO6] structural units. EPR spectra of the studied samples reveal that the gadolinium ions play a role of network former. The
UV–VIS spectra show broad UV absorption bands located in the 250–350 nm region. Their intensity increase with the increasing
of Gd2O3 content showing that these stronger transitions can be due to the presence of the O=Ge bonds (n–π* excitations) of [GeO5] structural units. The [GeO5] structural units are more stable thermodynamically than their analogues and the [GeO6] structural units produce the improvement of the amorphous character of these glasses. 相似文献
13.
C. Horea D. Rusu I. Ardelean 《Journal of Materials Science: Materials in Electronics》2009,20(9):905-910
Glasses from xFe2O3 · (100 − x)[P2O5 · TeO2] system, with 0 ≤ x ≤ 50 mol%, were investigated by X-ray diffraction, FT-IR and EPR spectroscopies. The XRD patterns show a vitreous state of
studied samples for x ≤ 35 mol% Fe2O3. The FT-IR spectrum of the P2O5 · TeO2 glass matrix reveals a structure formed from PO4, TeO4 and TeO3 units. The addition and the increasing of Fe2O3 content modify progressively the structure of the glass matrix. The local structure in the investigated glasses was revealed
by means of EPR using Fe3+ (3d5; 6S5/2) ions as paramagnetic probes. The EPR spectra present two resonance absorption lines characteristic to Fe3+ ions centred at geff ≈ 2.0, for 0.5 ≤ x ≤ 35 mol% and geff ≈ 4.3, for 0.5 ≤ x ≤ 5 mol%. The variation of the EPR parameters, the intensity and line-width of these absorption lines, with iron ions composition
has been followed. 相似文献
14.
Raman spectra of sodium borosilicate glasses with a wide range of Na2O/B2O3 ratios were systematically measured. Variations of the spectra with glass composition were studied to interpret the implied
distribution of Na+ ions between silicate and borate units. When Na2O/B2O3 is less than 1, all Na+ ions are associated with borate units as indicated by the absence of the 1100 cm−1 band of Si-O− non-bridging bond stretching. For the (1−x)Na2O · SiO2 ·xB2O3 glass withx≦0.4 the peak-height ratio of the 950 cm−1 band to the 1080 cm−1 band was used to analyse semiquantitatively the distribution of the Na+ ions between silicate and borate units. Sodium ions are divided between silicate and borate units approximately in proportion
to the amount of SiO2 and B2O3 present in these glasses. Some of the high sodium content glasses were crystallized and their spectra were compared with
the bulk glass spectra. The distribution of Na+ ions in the glass was quite different from their distribution after crystallization. Spectra of high silica glasses that
had been heat-treated for phase separation indicated exclusion of borate units from the silica network and the formation of
borate groups. For high boron content glasses, no change was observed on heat treatment. Raman bands due to borate groups
seem to be little affected by their environments.
Also affiliated with the Department of Geosciences. 相似文献
15.
K. V. Shah V Sudarsan M. Goswami A. Sarkar S. Manikandan Rakesh Kumar B. I. Sharma V. K. Shrikhande G P Kothiyal 《Bulletin of Materials Science》2003,26(7):715-720
Sodium aluminophosphate glasses having compositions of xAl2O3(1-x)NaPO3 (x = 0.05-0.2) were prepared using conventional melt-quench technique. Density, glass transition temperature, microhardness
(MH), thermal expansion coefficient (TEC) and transmission characteristics were measured as a function of alumina content
for different samples. They were found to depend on O/P ratio with pronounced changes taking place for O/P ratio ≥3.5. Density,
glass transition temperature and microhardness were found to increase up to 15 mol% of alumina and then they showed a decreasing
trend. Thermal expansion coefficient decreased continuously with alumina content. Optical gaps for different glass samples
as measured from transmission characteristics were found to be in the range 3.13–3.51 eV. It initially decreased with alumina
content up to 15 mol% and then increased. The behaviour was explained on the basis of change in the average aluminum coordination
number from six Al(6) to four Al(4) (i.e. Al(OP)6/Al(OP)4 ratio) along with the changes in polyhedra linkages in the glass network due to change in O/P ratio. 相似文献
16.
Abdeslam Chagraoui Imane Yakine Abdelmjid Tairi Abdenajib Moussaoui Mohamed Talbi Mohamed Naji 《Journal of Materials Science》2011,46(16):5439-5446
A glass-forming domain is found and studied within Bi2O3–Sb2O3–TeO2 system. The glasses composition were obtained in pseudo-binary xSbO1.5, (1−x)TeO2 for 0.05 ≤ x ≤ 0.20. The constitution of glasses in the system Sb2O3–TeO2 was investigated by DSC, Raman, and Infrared spectroscopy. The influence of a gradual addition of the modifier oxides on
the coordination geometry of tellurium atoms has been elucidated based Infrared and Raman studies and showed the transition
of TeO4, TeO3+1, and TeO3 units with increasing Sb2O3 content. XRD results reveal the presence of three crystalline: γ-TeO2, α-TeO2, and SbTe3O8 phases during the crystallization process. The density of glasses has been measured. The investigation in the ternary system
by the solid state reaction using XRD reveals the existence of a solid solution Bi1−x
Sb1−x
Te2x
O4 isotopic to BiSbO4 with 0 ≤ x ≤ 0.1. 相似文献
17.
V. I. Mikla V. V. Mikla 《Journal of Materials Science: Materials in Electronics》2009,20(11):1095-1105
Structural transformations are examined by the employment of Raman scattering measurements for amorphous Se-rich As
x
Se1−x
(0 ≤ x ≤ 0.2) alloys. It is found that the molecular structure of amorphous Se (a-Se) on the scale of medium-range order differs
from the structure of most inorganic glasses and may be placed between 3-dimensional network glasses and polymeric ones. Further
experiments show the existence of successive phases in laser-induced glass—crystalline transition with pronounced threshold
behavior. By comparing peak width, peak location and Raman intensity in the range of bond modes it is derived that the changes
occur not monotonically with increasing As content. The composition-induced changes of the spectra are explained by cross-linking
of Se chains. Under laser irradiation, the changes in the optical transmission, holographic recording properties and Raman
spectra of amorphous As
x
Se1−x
films with 0 < x ≤ 0.2 have been examined. The dependence of the transmissivity and diffraction efficiency on the irradiation energy density
shows two qualitatively different regions. Below the energy density threshold, E
th, only small changes in the local structure of the system can be detected. In the low-energy region, transient changes in
transmissivity are observed. Qualitative explanation of this behavior may be based on associating such with alternating of
deep defect states. Above E
th, the changes were attributed to crystallization transformation. The corresponding Raman spectra reveal transformation of
the system from amorphous into the crystalline phase under laser irradiation. Although several articles and texts have provided
reviews on various properties and applications of chalcogenide glasses, there is no thorough study of local atomic structure
and its modification for Se-rich amorphous As
x
Se1−x
. The present paper is concerned with this problem. 相似文献
18.
Rupali Jadhav Deepti Kulkarni Vijaya Puri 《Journal of Materials Science: Materials in Electronics》2010,21(5):503-508
Spinel structured NTC thermistor Ni(1−x)Cu
x
Mn2O4 (0 ≤ x ≤ 1) ceramics was prepared by oxalic precursor method and fritless thick films screen printed on alumina. The composition
dependent structural and electrical properties are reported in this paper. The results show that with increasing copper ion
substitution both Cu2+ and Mn4+ predominantly occupy the octahedral site. The concentration of Cu2+ ions in octahedral site increases while that of Ni2+ ions decreases linearly. The thick film Ni(1−x)Cu
x
Mn2O4 ceramic comply with Arrhenius equation. A thermistor constant of ~1,200 K has been obtained for fritless thick film NTC ceramics
using inorganic binders in the RT/90 thermal range. 相似文献
19.
In this paper, we have examined and analyzed the effects of systematic intercalation of the lead ions on vanadate–tellurate
glass ceramics with interesting results. The structural properties of the lead–vanadate–tellurate glass ceramics of compositions
xPbO·(100 − x)[6TeO2·4V2O5], x = 0 − 100 mol%, are reported for the first time. It has been shown by X-ray diffraction that single-phase homogeneous glasses
with a random network structure can be obtained in this system. Among these unconventional lead–vanadate–tellurate glass ceramics,
we found that network formers are good host material for lead ions and are capable to intercalate a variety of species such
as Te2V2
5+O9, Pb3(V5+O4)2, Pb2V2
5+O7, and V2O5-rich amorphous phase. On the other hand, these glass ceramics contain V4+ and V5+ ions necessary for the electrical conduction. Based on these experimental results, we propose that the V4+=O bonds are created by two different mechanisms: the first of reduction of V5+ ions to V4+ ions and thus of creation of V4+=O bonds. 相似文献
20.
L. Koudelka J. Jirák P. Mošner L. Montagne G. Palavit 《Journal of Materials Science》2006,41(14):4636-4642
Mixed lithium–zinc borophosphate glasses were prepared and studied in three compositional series xLi2O–(50−x)ZnO–50P2O5, xLi2O–(50−x)ZnO–10B2O3–40P2O5 and xLi2O–(50−x)ZnO–20B2O3–30P2O5 with x = 0, 10, 20, 30, 40 and 50 mol% Li2O. The obtained glasses were characterized by the measurements of the density (ρ), molar volume (V
M), glass transition temperature (T
g) and thermal expansion coefficient (α). For the investigation of structural changes 11B and 31P MAS NMR and Raman spectroscopy were applied. The replacement of zinc by lithium in borophosphate glasses slightly decreases V
M and T
g, while α increases. In Li–Zn metaphosphate glasses the compositional dependence of T
g reveals a minimum, while at the borophosphate series T
g decreases monotonously with increasing Li2O content. Chemical stability of Li–Zn borophosphate glasses is very good for glasses with x = 0–30 mol% Li2O. Spectral studies showed in the glass series with 10 mol% B2O3 only the presence of BO4 sites. In the glasses with 20 mol% B2O3 the presence of BO3 and two BO4 sites was revealed in ZnO-rich glasses and only one BO4 site in Li2O-rich glasses; the number of BO3 groups decreases with increasing Li2O content which is ascribed to the formation of P–O–Zn covalent bonds in ZnO-rich glasses. 相似文献