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 共查询到20条相似文献,搜索用时 31 毫秒
1.
B.B. Das 《Journal of Non》2009,355(31-33):1663-1665
Synthesis of the xCuO–(1 ? x)Bi2O3 (0.5 ? x ? 0.9) (C1–C5: x = 0.5, 0.6, 0.7, 0.8, 0.9) glasses was done via nitrate–citrate gel route. Glassy phase is ascertained by XRD studies. Magnetic susceptibility results in the range 4.2–400 K show weak paramagnetic nature with exchange integrals ~0.024–0.13 eV in the glasses. The electron paramagnetic resonance (EPR) in the range 4.2–363 K shows g  2.0 and the trend of the g-matrix elements g|| > g > ge for the glasses C1–C5 at 4.2 K are due to the Cu2+ (3d9) paramagnetic site in the glasses which is in a tetragonally elongated octahedron [O1/2–CuO4/2–O1/2] having D4h symmetry. IR spectroscopic results show the presence of octahedron [BiO6/2]3? and [CuO6/2]4? units and pyramidal [BiO2/2O]? unit in the glasses.  相似文献   

2.
Z. Śniadecki  B. Idzikowski 《Journal of Non》2008,354(47-51):5159-5161
Thermal properties of rapidly quenched alloys from the DyMn6?xGe6?xFexAlx (1 ? x ? 2.5) series produced by melt-spinning have been investigated by differential scanning calorimetry (DSC). The DSC curves show two exothermic effects connected with crystallization processes. Crystallization temperatures and enthalpies ΔH have been estimated. The systematic changes in these parameters allow concluding that the crystallization exothermic events are independent. Effective activation energies E have been determined using the Kissinger analysis and relatively high values up to 480 ± 20 kJ/mol for DyMn4Ge4Fe2Al2 have been found indicating high thermal stability of the amorphous state in this alloy series.  相似文献   

3.
R. Zdyb 《Journal of Non》2008,354(35-39):4176-4180
The growth, crystallographic structure and electronic properties of ultrathin Pb films grown on a vicinal silicon surface are investigated with reflection high energy electron diffraction (RHEED) and specific resistivity measurement techniques. A Si(3 3 5) surface with a perfect distribution of monoatomic steps separated with (1 1 1) terraces induced by a submonolayer amount of Au is used as a substrate. In the early stage, Pb growth is anisotropic. Apparently, the presence of steps forces the growth of short crystalline Pb chains along the steps. The layer is amorphous in the perpendicular direction. With the increasing thickness, a phase transition takes place between 3 and 4 monolayers (ML) that makes crystalline order also across the terraces. A further increase in thickness causes the layer surface to repeat the substrate morphology. It consists of regularly distributed monoatomic steps and narrow (1 1 1) terraces.  相似文献   

4.
M.R. Sahar  K. Sulhadi  M.S. Rohani 《Journal of Non》2008,354(12-13):1179-1181
Er3+-doped tellurite glasses of the (80 ? x)TeO2–20ZnO–(x)Er2O3 system (0.5 mol% ? x ? 2.5 mol%) have successfully been made by melt-quenching technique and their structure has been investigated by means of DTA and Raman spectroscopy. The DTA results show the thermal parameters; such as the glass transition temperature (Tg) and crystallization temperature (Tc) were determined. It is found that this system provides a stable and wide glass formation range in which the glass stability around 99–140 °C may be obtained. The Raman spectroscopy used the structural studies in the glass system. Two Raman shift peaks were observed around 640–670 cm?1 and 720–740 cm?1, which correspond to the stretching vibration mode of TeO4 tbp and TeO3 tp, respectively. It is found that the spectral shift in Raman spectra is depending on the Er2O3 content. This evolution is an indication of the changes in the basic unit of the glass structure.  相似文献   

5.
《Journal of Crystal Growth》2002,240(3-4):355-362
In situ crystallization of α-Fe2O3/α-Al2O3(0 0 0 1) thin films was studied in real-time synchrotron X-ray scattering experiments. We find the coexistence of α-Fe2O3 (hexagonal) and Fe3O4 (cubic) interfacial crystallites (∼50-Å-thick), well aligned [0.02° full-width at half-maximum (FWHM)] to the α-Al2O3[0 0 0 1] direction, in the sputter-grown amorphous films. As the annealing temperature increases up to 750°C, the cubic stacking of the Fe3O4 crystallites gradually changes to the hexagonal α-Fe2O3 stacking, together with the growth of the well-aligned (WA) (0.02° FWHM) grains from the α-Fe2O3 crystallites. In the meanwhile, heterogeneous nucleation starts to occur on the substrate at ∼600°C, resulting in the formation of misaligned (1.39° FWHM) α-Fe2O3 grains. Our study reveals that the interfacial crystallites act as a template for the growth of the WA α-Fe2O3 grains.  相似文献   

6.
S. Azianty  A.K. Yahya  M.K. Halimah 《Journal of Non》2012,358(12-13):1562-1568
Ternary tellurite glasses with the chemical formula 80TeO2–(2 ? x)ZnO–xFe2O3 (x = 0–15 mol%) have been prepared by the melt-quenching method. Elastic and structural properties of the glasses were investigated by measuring both longitudinal and shear velocities using the pulse-echo overlap method at 5 MHz and Fourier transform infrared (FTIR) spectroscopy, respectively. Both longitudinal and shear velocity showed a large increase of 3.40% and 4.68%, respectively, at x = 5 mol% before a smaller increase for x > 5 mol%. Interestingly, longitudinal modulus (L), shear modulus (G), bulk modulus (K) and Young's modulus (E) recorded similar trends with increase in Fe2O3. The initial large increases in shear and longitudinal velocity and related elastic moduli observed at x = 5 mol% are suggested to be due to structural modification which enhances rigidity of the glass network. FTIR analysis showed increase in bridging oxygen (BO) as indicated by the relative intensity of the TeO4 assigned peaks and increase in intensity of the FeO6 assigned peak (~ 451 cm? 1) which indicates that Fe acts as a modifier in the glass network. The increase in rigidity of the glass system is suggested to be due to the increase of BO together with the formation of strong covalent FeO bond. Quantitative analysis based on the bulk compression and ring deformation models showed that the kbc/kexp value decreased gradually from 2.41 (x = 0 mol%) to 2.02 (x = 15 mol%) which infers that the glass system became a relatively more open 3D network as Fe2O3 was increased.  相似文献   

7.
TeO2–WO3 (TW), TeO2–WO3–La2O3 (TWL), TeO2–WO3–La2O3–Bi2O3 (TWLB) and TeO2–ZnO–Na2O–Bi2O3 (TZNB) glasses were produced by high-purity oxide mixtures melting in platinum or gold crucible at 800 °C in the atmosphere of purified oxygen. The total content of Cu, Mn, Fe, Co and Ni impurities was not more than 0.1–0.5 ppm wt in the initial oxides and glasses. The stability of TZNB glasses to crystallization, characterized by (Tx ? Tg) value more than 150 °C, was demonstrated by DSC measurements at heating rate 10 K/min. In the case of La2O3-containing glasses the thermal effects of both crystallization and fusion of the crystallized phases were not observed. The hydroxyl groups absorption coefficients of pure tellurite glasses at the maximum of the absorption band (λ ~ 3 μm) were in the region of 0.012–0.001 cm?1. The optical absorption losses, measured by the laser calorimetry method at λ = 1.56 and 1.97 μm, did not exceed 100 dB/km.  相似文献   

8.
Raman scattering spectra of Ga2S3–2MCl (M = K, Rb, Cs) glasses have been conducted at room temperature. Based on the analysis of the local co-ordination surroundings of Cs+ ions, the similarities and differences of Raman spectra for the glass Ga2S3–2CsCl and the bridged molecular GaCl3 were explained successfully. Through considering the effect of M+ ions on mixed anion units [GaS4?xClx] and bridged units [Ga2S6?xClx] and the corresponding microstructural model, the Raman spectral evolution of the Ga2S3–2MCl (M = K, Rb, Cs) glasses was reasonably elucidated.  相似文献   

9.
Glasses with the base compositions xNa2O · 15Al2O3 · (85 ? x)SiO2 (x = 8.5, 11 and 16) doped with 0.5 mol% SnO2 were investigated by both square-wave voltammetry and impedance spectroscopy in the temperature range from 1300 to 1600 °C. Each recorded square-wave voltammogram exhibits a well pronounced peak attributed to the Sn2+/Sn4+-redox pair. Impedance spectra were measured in a frequency range from 0.1 to 105 s?1 as a function of the superimposed dc-potential and were simulated using an equivalent circuit taking into account the resistivity of the melt, the electrochemical double layer, a resistor attributed to a kinetically hindered electron transfer and a Warburg parameter which accounts for the diffusion process of Sn4+ and Sn2+ to and from the electrode. Additionally, two impedance elements, a resistor and a capacitance both attributed to adsorption processes were necessary to fit the impedance spectra.  相似文献   

10.
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   

11.
The 70Li2S · (30 ? x)P2S5 · xP2O5 (mol%) oxysulfide glasses were prepared by the melt quenching method. The glasses were prepared in the composition range 0  x 10. The glass–ceramics were prepared by heating the glasses over crystallization temperatures. The POnS3?n (n = 1–3) oxysulfide units were produced in the glasses and glass–ceramics by partial substituting P2O5 for P2S5. In particular, the P2OS64? unit would be produced by substituting a small amount of P2O5 for P2S5. The oxygen atoms were incorporated into the Li7P3S11 crystal structure because the diffraction peaks of the oxysulfide glass–ceramic shifted to the higher angle side. The glass–ceramic with 3 mol% of P2O5 exhibited the highest conductivity of 3.0 × 10?3 S cm?1 and the lowest activation energy for conduction of 16 kJ mol?1. The P2OS64? dimer units in the oxygen-incorporated Li7P3S11 crystal would improve conductive behavior of the Li2S–P2S5 glass–ceramics.  相似文献   

12.
The mixed glass former effect (MGFE) is defined as the non-linear and non-additive change in the ionic conductivity with changing glass former fraction at constant modifier composition between two binary glass former compositions. In this study, sodium borophosphate glasses, 0.35Na2O + 0.65[xB2O3 + (1 ? x)P2O5] with 0  x  1, have been prepared and their glass transition temperatures (Tg) have been examined as an alternative indicator of the MGFE and as an indicator of changes in the short range order (SRO) structural network units that could cause or contribute to the MGFE. The changes in Tg show a positive non-additive and non-linear trend over the changing glass former fraction, x. The increase in Tg is related to the increasing number of bridging oxygens (BO) in the glass samples, which is caused by the increase in the number of tetrahedral boron, B4, units in the SRO structure.  相似文献   

13.
14.
A series of Bi2O3–BaO–SiO2–RxOy (designated BiBaSi glass) glass sealants doped with different contents of α-Al2O3 have been investigated. Al2O3 was added as a modifier to affect the structure and the behavior of the glass. The thermal properties such as glass transition temperature (Tg), softening temperature (Tf) and coefficient of thermal expansion (CTE) were measured by a dilatometer. The sealing performance was investigated by sealing a SOFC single cell stack and measuring its open circuit voltage (OCV). Tg, Tf and suitable usage temperature of the sealants increased with increasing Al2O3 content in the glass, while CTE decreased. When the Al2O3 content was lower than 10 wt.%, excellent sealing performance was observed.  相似文献   

15.
m-Plane GaN was grown selectively by metal–organic chemical vapor deposition (MOCVD) on patterned Si(1 1 2) substrates, where grooves aligned parallel to the Si〈1 1 0〉 direction were formed by anisotropic wet etching to expose the vertical Si{1 1 1} facets for growth initiation. The effect of growth conditions (substrate temperature, chamber pressure, and ammonia and trimethylgallium flow rates) on the growth habits of GaN was studied with the aim of achieving coalesced m-plane GaN films. The epitaxial relationship was found to be GaN(1 1? 0 0) || Si(1 1 2), GaN[0 0 0 1] || Si[1 1 –1], GaN[1? 1? 2 0] || Si[1 1? 0]. Among all growth parameters, the ammonia flow rate was revealed to be the critical factor determining the growth habits of GaN. The distribution of extended defects, such as stacking faults and dislocations, in the selectively grown GaN were studied by transmission electron microscopy in combination with spatially resolved cathodoluminescence and scanning electron microscopy. Basal-plane stacking faults were found in the nitrogen-wing regions of the laterally overgrown GaN, while gallium-wings were almost free of extended defects, except for the regions near the GaN/Si{1 1 1} vertical sidewall interface, where high dislocation density was observed.  相似文献   

16.
Sulphide glasses doped with rare-earth ions have been demonstrated to be suitable for photonic applications such as optical amplifiers, up-converters and fiber lasers. The substitution of metal halides into the glass network has been shown to result glasses with desirable properties in terms of quantum efficiency and fiber manufacture [J.R. Hector, J. Wang, D. Brady, M. Kluth, D.W. Hewak, W.S. Brocklesby, D.N. Payne, Journal of Non-Crystalline Solids 239 (1998) 176]. To assist in the understanding of this improvement a structural analysis of glasses with a composition xCsCl(1 ? x)Ga2S3 has been undertaken in order to examine the nature of the gallium environment. Information collected by high energy X-ray diffraction and neutron diffraction have been analyzed to permit the identification of the structural units as Ga centered tetrahedra. The interconnection between the tetrahedra was found to be predominantly corner sharing.  相似文献   

17.
S. Rada  M. Culea  E. Culea 《Journal of Non》2008,354(52-54):5491-5495
Glasses in the system (1 ? x)TeO2 · xB2O3 glasses (with x = 0.3 and 0.4) have been prepared from melt quenching method. The structural changes were studied by FTIR spectroscopy and DFT calculations. From the analysis of the FTIR spectra it is reasonable to assume that when increasing boron ions content the tetrahedral [BO4] units are gradually replaced by trigonal [BO3] units. The increase in the number of non-bridging oxygen atoms would decrease the connectivity of the glass network, would depolymerize of borate chains and would necessite quite a radical rearrangement of the network formed by the [TeO6] octahedral. This is possible considering that tellurium dioxide brings stoichiometrically two oxygen atoms in [TeO4] and needs an additional oxygen atom for the formation of [TeO6] octahedra. This additional oxygen atom is evidently taken off from the boron co-ordination and thus boron atoms transfer their [BO4] co-ordination into [BO3] co-ordination. We used the FTIR spectroscopic data in order to compute two possible models of the glasses matrix. We propose two possible structural models of building blocks for the formation of continuous random network glasses used by density functional theory (DFT) calculations.  相似文献   

18.
Glasses with a high content of niobium oxide are of significant interest for electro-optics and nonlinear optics. In the present paper we report the results of the investigation of the submicroscopic structure and nonlinear optical properties of (1-x)KNbO3xSiO2 (KNS) glasses (x = 0.05–0.30) by XRD, SANS, electron microscopy and second harmonic generation (SHG) technique. Vitreous samples were fabricated by rapid melt cooling, via pressing the melt by steel plates, quenching between rotating metal rolls or splat cooling in air or nitrogen flow. Glasses with x < 0.15 are shown to possess a micro-inhomogeneous structure with regions enriched by SiO2. On the contrary, as-quenched glasses with x > 0.15 are found by SANS to be homogeneous, but form nanostructures enriched by SiO2 after heat-treatment. At temperatures below ~(Tg + 50 °C), SiO2-enriched regions grow slightly, whereas their chemical composition shifts considerably closer to SiO2. The data on the nano-inhomogeneous structure enables clarifying the complicated Tg(x) dependence of KNS glasses. SHG-active KNbO3 phase precipitates at later stages of crystallization when the glass starts to lose its transparency, and crystallization of perovskite-like KNbO3 is accompanied by the enhancement of SHG efficiency by several orders of magnitude.  相似文献   

19.
Gao Tang  Cunming Liu  Zhiyong Yang  Lan Luo  Wei Chen 《Journal of Non》2009,355(31-33):1585-1589
Microstructure of the chalcohalide glasses: GeSe2–Ga2Se3–CsI and GeSe2–Ga2Se3–PbI2 ternary system were investigated by Raman spectra, lifetime of Dy3+ infrared emission and glass transition temperature (Tg). The evolution of the Raman spectra shows that the fundamental structural groups of these studied glasses consist of [Ge(Ga)Se4] tetrahedral and some complex structure units [Ge(Ga)IxSe4?x](x = 1–4). The x value varied when the different iodide was added in Ge–Ga–Se matrix. For GeSe2–Ga2Se3–CsI glasses, the [Ge(Ga)IxSe4?x](x = 1–4) mixed-anion tetrahedral and [Ga2I7]? units occurred. For GeSe2–Ga2Se3–PbI2 glasses, the [Ge(Ga)I2Se2], [Ge(Ga)I3Se] units can be formed. The changes of Dy3+ infrared emission lifetime and Tg support the results. Additionally, [PbIn] structural units will be formed in GeSe2–Ga2Se3–PbI2 glasses due to high form-ability of these units when the PbI2 content is high.  相似文献   

20.
M. Shapaan 《Journal of Non》2009,355(16-17):926-931
This paper presents the results of kinematical studies of glass transition and crystallization in the unconventional glassy system (60?x)V2O5xAs2O3–20Fe2O3–10CaO–10Li2O (x = 0, 10, 20, 30, 40 mol%) using differential scanning calorimetry (DSC). The glass transition temperatures (Tg), the onset crystallization temperatures (Tc), and the peak temperatures of crystallization (Tp) were found to be dependent on the compositions and the heating rates. From the dependence on heating rates of (Tg) and (Tp) the activation energy for glass transition (Eg) and the activation energy for crystallization (Ec) are calculated. The thermal stability of (60?x)V2O5xAs2O3–20Fe2O3–10CaO–10Li2O was evaluated in term of, criteria ΔT = Tc ? Tg. All the results confirm that the thermal stability increase with increasing As2O3 contents. From the electric–dielectric measurements it was found that, σdc, σac(ω) and θD/2 decrease with increasing As2O3 contents. It is also observed that the dielectric constant (ε1(ω)) and the loss factor (tan δ) decrease with increasing As2O3 contents in this glass system.  相似文献   

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