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1.
The effect of Y2O3 addition on the phase transition and growth of yttria-stabilized zirconia (YSZ) nanocrystallites prepared by a sol-gel process with various mixtures of ZrOCl2 · 8H2O and Y(NO3)3 · 6H2O ethanol-water solutions at low temperatures has been studied. DTA/TGA, XRD, SEM, TEM and ED have been utilized to characterize the YSZ nanocrystallites. The crystallization temperature of 3YSZ, in which Y2O3/(Y2O3 + ZrO2) = 0.03, gel powders estimated by DTA/TG is about 427 °C. When 3YSZ and 5YSZ gels are calcined at 500-700 °C, their crystal structures as composed of coexisting tetragonal and monoclinic ZrO2, and tetragonal phase decreases with calcination temperature increasing from 500 to 700 °C. Pure cubic ZrO2 is obtained when added Y2O3 is greater than 8 mol%. A nanocrystallite size distribution between 10 and 20 nm is obtained in TEM observations.  相似文献   

2.
The addition of 2 mol% P2O5 to stoichiometric K-fluorrichterite (KNaCaMg5Si8O22F2, KFR) has been reported to enhance the mechanical properties and improve the in vitro biocompatibility of this glass-ceramic by promoting the formation of enstatite and fluorapatite (FA). Here, the effect of further increasing the P2O5 concentration on phase evolution of KFR has been investigated. XRD data showed that mica crystallized in samples with 4 and 5 mol% P2O5 (GP4 and GP5, respectively) at 650 °C, but no diopside was detected at higher temperatures, in contrast with the general phase evolution in KFR based glass-ceramics. More importantly, however, the addition of ?4 mol% P2O5 induced phase separation of the glass into a silica glass matrix and phosphate rich droplets prior to crystallization. EDS traces taken from samples heat-treated at 600 °C, revealed that the silica glass matrix was deficient in Mg and unlikely to be the host for crystallization of mica. Conversely, the P2O5 rich regions contained excess Mg and were considered to be the host for the formation of mica and FA.  相似文献   

3.
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   

4.
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   

5.
Glasses with the basic compositions 10Na2O · 10CaO · xAl2O3 · (80 − x)SiO2 (x=0, 5, 15, 25) and 16Na2O · 10CaO · xAl2O3 · (74 − x)SiO2 (x=0, 5, 10, 15, 20) doped with 0.25-0.5 mol% SnO2 were studied using square-wave-voltammetry at temperatures in the range from 1000 to 1600 °C. The voltammograms exhibit a maximum which increases linearly with increasing temperature. With increasing alumina concentration and decreasing Na2O concentration the peak potentials get more negative. Mössbauer spectra showed two signals attributed to Sn2+ and Sn4+. Increasing alumina concentrations did not affect the isomer shift of Sn2+; however, they led to increasing quadrupole splitting, while in the case of Sn4+ both isomer shift and quadrupole splitting increased. A structural model is proposed which explains the effect of the composition on both the peak potentials and the Mössbauer parameters.  相似文献   

6.
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   

7.
X.L. Duan  C.F. Song  F.P. Yu  D.R. Yuan 《Journal of Non》2008,354(29):3516-3519
Co2+-doped MgAl2O4 nanocrystalline powders were prepared by co-precipitation method. The gels and/or calcined samples were characterized by means of thermogravimetry and differential scanning calorimetry (TG/DSC), X-ray diffraction (XRD), transmission electron microscope (TEM), Fourier transform infrared (FTIR) spectrum and near-infrared absorption spectrum. MgAl2O4 nanocrystals were produced by calcining the gel above 800 °C, with the crystallite size of 10-30 nm in the temperature range of 800-1100 °C. The influence of pH value of precipitant solution on the dispersing of powders was studied and the result showed that Co:MgAl2O4 nanocrystalline powders exhibited good dispersion when pH = 11. The absorption spectrum of Co2+-doped MgAl2O4 exhibited a broad absorption band in the wavelength range of 1200-1600 nm, which indicated that Co2+ ions substituted for the tetrahedrally coordinated Mg2+ ions in the MgAl2O4 lattice.  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.
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   

10.
Reduction in the temperature coefficient of the optical path length, dS/dT of Li2O-Al2O3-SiO2 glass-ceramics with near-zero thermal expansion coefficient was attempted using control of the temperature coefficient of electronic polarizability, ?, and the thermal expansion coefficient, α. The dS/dT value of 2.6 mol% B2O3-doped glass-ceramic was 12.5  × 10−6/°C, which was 0.9 ×  10−6/°C smaller than that of B2O3-free glass-ceramic. On the other hand, reduction in dS/dT through B2O3 doping was not confirmed in precursor glasses. Results showed that reduction in dS/dT of the glass-ceramic through B2O3 doping is caused by the reduction in ?. The reduction in ? from B2O3 doping was probably attributable to numerical reduction in non-bridging oxide ions with larger ? value by the concentration of boron ions in the residual glass phase. In addition, application of hydrostatic pressure during crystallization was effective to inhibit precipitation of β-spodumene solid solution, which thereby decreases dS/dT. The dS/dT value of B2O3-doped glass-ceramic crystallized under 196 MPa was 11.7 ×  10−6/°C. That value was slightly larger than that of silica glass. The α value of this glass-ceramic was smaller than that of silica glass.  相似文献   

11.
N. Baizura 《Journal of Non》2011,357(15):2810-2815
Tellurite 75TeO2-(10 − x)Nb2O5-15ZnO-(x)Er2O3; (x = 0.0-2.5 mol%) glass system with concurrent reduction of Nb2O5 and Er2O3 addition have been prepared by melt-quenching method. Elastic properties together with structural properties of the glasses were investigated by measuring both longitudinal and shear velocities using the pulse-echo-overlap technique at 5 MHz and Fourier Transform Infrared (FTIR) spectroscopy, respectively. Shear velocity, shear modulus, Young's modulus and Debye temperature were observed to initially decrease at x = 0.5 mol% but remained constant between x = 1.0 mol% to x = 2.0 mol%, before increasing back with Er2O3 addition at x = 2.5 mol%. The initial drop in shear velocity and related elastic moduli observed at x = 0.5 mol% were suggested to be due to weakening of glass network rigidity as a result of increase in non-bridging oxygen (NBO) ions as a consequence of Nb2O5 reduction. The near constant values of shear velocity, elastic moduli, Debye temperature, hardness and Poisson's ratio between x = 0.5 mol% to x = 2.0 mol% were suggested to be due to competition between bridging oxygen (BO) and NBO ions in the glass network as Er2O3 gradually compensated for Nb2O5. Further addition of Er2O3 (x > 2.0 mol%) seems to further reduce NBO leading to improved rigidity of the glass network causing a large increase of ultrasonic velocity (vL and vS) and related elastic moduli at x = 2.5 mol%. FTIR analysis on NbO6 octahedral, TeO4 trigonal bipyramid (tbp) and TeO3 trigonal pyramid (tp) absorption peaks confirmed the initial formation of NBO ions at x = 0.5 mol% followed by NBO/BO competition at x = 0.5-2.0 mol%. Appearance of ZnO4 tetrahedra and increase in intensity of TeO4 tbp absorption peaks at x = 2.0 mol% and x = 2.5 mol% indicate increase in formation of BO.  相似文献   

12.
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   

13.
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   

14.
Shengchun Li  B. Li  J.J. Wei 《Journal of Non》2010,356(43):2263-2267
(30 − x/2)Li2O·(70 − x/2)B2O3·xAl2O3(x = 0, 5 and 10) composite gels have been fabricated by the sol-gel method. LiOCH3, B(OC4H9)3, and Al(OC4H9)3 were used as precursor for Li2O, B2O3, and Al2O3, respectively. B(OC4H9)3 and Al(OC4H9)3 were hydrolyzed separately and then mixed. The crystallization behavior and structure of the gels upon thermal treatment temperatures between 150 and 550 °C are characterized on the basis of SEM, XRD and IR analyses. Xerogel with x = 0 exhibits non-crystal features, whereas crystalline phases are found in the xerogels with x = 5 and 10. The crystalline phases are not found with increasing heat treatment temperatures from 150 to 450 °C, but crystalline phases appear present at 550 °C. The xerogel with x = 0, subject to thermal treatment below 450 °C, is found to be still amorphous, and a 550 °C heat treatment leads its structure changing from glassy to crystalline.  相似文献   

15.
Glasses in the ternary ZnO-P2O5-TeO2 system were prepared and studied in two compositional series (100 − x)[0.5ZnO-0.5P2O5]-xTeO2 (X-series) and 50ZnO-(50 − y)P2O5-yTeO2 (Y-series) within the concentration range of x = 0-60 and y = 0-40 mol% TeO2. Their structure was studied by Raman and 31P MAS NMR spectroscopies. The incorporation of TeOx units into the structural network is associated with the depolymerisation of phosphate chain structure as revealed by both methods. At a high TeO2 content isolated PO4 tetrahedra are formed in the structure of glass series Y, while diphosphate O3P-O-PO3 groups are present in the structure of the glass series X. In the structure of glass series Y tellurium atoms form predominantly TeO3 trigonal pyramids, whereas in the X glass series TeO4 trigonal bipyramids prevail in the glass structure. The addition of TeO2 to the parent zinc metaphosphate glass results in a decrease of glass transition temperature in both compositional series associated with the replacement of stronger P―O bonds by weaker Te―O bonds.  相似文献   

16.
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   

17.
Ultrathin La2O3 gate dielectric films were prepared on Si substrate by ion assistant electron-beam evaporation. The growth processing, interfacial structure and electrical properties were investigated by various techniques. From XRD results, we found that the La2O3 films maintained the amorphous state up to a high annealing temperature of 900 °C for 5 min. From XPS results, we also discovered that the La atoms of the La2O3 films did not react with silicon substrate to form any La-compound at the interfacial layer. However, a SiO2 interfacial layer was formed by the diffusion of O atoms of the La2O3 films to the silicon substrate. From the atomic force microscopy image, we disclosed that the surface of the amorphous La2O3 film was very flat. Moreover, the La2O3 film showed a dielectric constant of 15.5 at 1 MHz, and the leakage current density of the La2O3 film was 7.56 × 10−6 A/cm2 at a gate bias voltage of 1 V.  相似文献   

18.
Room temperature electron spin resonance (ESR) spectra and temperature dependent magnetic susceptibility measurements have been performed to investigate the effect of iron ions in 41CaO · (52 − x)SiO2 · 4P2O5 · xFe2O3 · 3Na2O (2 ? x ? 10 mol%) glasses. The ESR spectra of the glass exhibited the absorptions centered at g ≈ 2.1 and g ≈ 4.3. The variation of the intensity and linewidth of these absorption lines with composition has been interpreted in terms of variation in the concentration of the Fe2+ and Fe3+ in the glass and the interaction between the iron ions. The magnetic susceptibility data were used to obtain information on the relative concentration and interaction between the iron ions in the glass.  相似文献   

19.
B. Ko?cielska 《Journal of Non》2008,354(14):1549-1552
The studies of electrical conductivity of NbN-SiO2 films are reported. To obtain these films, sol-gel derived xNb2O5-(100 − x)SiO2 (where x = 100, 90, 80, 70, 60, 50 mol%) coatings were nitrided at 1200 °C. The nitridation process leads to the formation of some disordered structures, with NbN metallic grains dispersed in insulating SiO2 matrix. The structure of the samples was studied using X-ray diffraction (XRD) and atomic force microscopy (AFM). The electrical conductivity was measured with the conventional four-terminal method in the temperature range from 5 to 280 K. The superconducting transition was not observed even for the sample that does not contain silica. All the samples exhibit negative temperature coefficient of resistivity. The results of conductivity versus temperature may be described on the grounds of a model proposed for a weakly disordered system.  相似文献   

20.
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   

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