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1.
Glasses in the system Na 2O/B 2O 3/Al 2O 3/In 2O 3 were melted and subsequently tempered in the range from 500 to 700 °C. Depending on the chemical composition, various crystalline phases were observed. From samples without Al 2O 3, In 2O 3 could not be crystallized from homogeneous glasses, because either spontaneous In 2O 3 crystallization occurred during cooling, or other phases such as NaInO 2 were formed during tempering. The addition of alumina, however, controlled the crystallization of In 2O 3. Depending on the crystallization temperature applied, the crystallite sizes were in the range from 13 to 53 nm. The glass matrix can be dissolved by soaking the powdered glass in water. This procedure can be used to prepare nano-crystalline In 2O 3-powders. 相似文献
2.
11B ( I=3/2) MAS NMR in the binary glass system xV 2O 5–B 2O 3 ( x=0.053, 0.43) and the ternary glass system xV 2O 5–B 2O 3–PbO (0.1 x1.5) has been investigated at room temperature. In the xV 2O 5–B 2O 3 glasses, one NMR line due to BO 3 unit was observed. Meanwhile in the xV 2O 5–B 2O 3–PbO, two NMR lines which arise from BO 3 and BO 4 units were detected, where the appearance of BO 4 units is produced by the presence of PbO. From the computer-simulation of the 11B NMR central transition line ( m=−1/2↔1/2), the quadrupole parameters ( e2qQ/ h and η) for BO 3 units in xV 2O 5–B 2O 3, and those for BO 3 and BO 4 units in xV 2O 5–B 2O 3–PbO were obtained as a function of x. As the V 2O 5 content increases in xV 2O 5–B 2O 3–PbO, the e2qQ/ h and η values of the BO 3− associated resonance are found to slightly decrease and increase, respectively. Meanwhile, the e2qQ/ h and η values of BO 4− associated resonance in xV 2O 5–B 2O 3–PbO are found to slightly increase and decrease, respectively. By comparing the intensities of the total transitions ( m=−3/2↔−1/2, m=−1/2↔1/2, and 1/2↔3/2) for the 11B NMR line of BO 3 and BO 4 units contained in xV 2O 5–B 2O 3–PbO with those of respective standard samples of 0.053V 2O 5–B 2O 3 and NaBH 4, the quantitative fractions of BO 3 and BO 4 in xV 2O 5–B 2O 3–PbO were obtained as a function of x. 相似文献
3.
The effect of alumina on the phase separation and the crystallization of the glasses of composition (mol%) 18ZnO·30B 2O 3·52SiO 2 and O-40 Al 2O 3 was studied using an electron microscope and IR spectroscopy. The main crystalline phase appears in the microphase for which the compositions are not nearer to the crystal stoichiometry than the mean. The addition of Al 2O 3 suppresses the immiscibility but enhances the crystallizability. 相似文献
4.
The electrical and dielectric properties for three series of MoO 3–Fe 2O 3–P 2O 5 and one series of SrO–Fe 2O 3–P 2O 5 glasses were measured by impedance spectroscopy in the frequency range from 0.01 Hz to 3 MHz and over the temperature range from 303 to 473 K. It was shown in Part I that the MoO 3 is incorporated into phosphate network and the structure/properties are strongly influenced by the overall O/P ratio. The Fe 2O 3 content and Fe(II)/Fe tot ratio in these glasses have significant effects on the electrical conductivity and dielectric permittivity. With decreasing Fe 2O 3 content in MoO 3–Fe 2O 3–P 2O 5 glasses with O/P at 3.5 the dc conductivity, σ dc(ω) decreases for two orders of magnitude, which indicates that the conductivity for these glasses depends on Fe 2O 3 and is independent of the MoO 3 content. Also, the dielectric properties such as ′(ω), ″(ω) and σ ac(ω) and their variation with frequency and temperature indicates a decrease in relaxation intensity with increase in the concentration of MoO 3. On the other hand, the dc conductivity for MoO 3–Fe 2O 3–P 2O 5 glasses with O/P > 3.5 increases with the substitution of MoO 3 which has been explained by an increase in the number of non-bridging oxygens and formation of Fe–O–P bonds that are responsible for formation of small polarons. The increase in the dielectric permittivity, ′(ω) with increasing MoO 3 content is attributed to the increase in the deformation of glass network with increasing bonding defects. For SrO–Fe 2O 3–P 2O 5 glasses the conductivity and dielectric permittivity remained constant with increasing SrO. 相似文献
5.
Raman spectra of ternary sodium aluminosphosphate glasses indicate that for glasses with Al 2O 3/P 2O 5<0.63, the glass network is mainly built up of (PO 3) nn- chains and rings or different kinds of phosphate groups and AlO 4 tetrahedra; for glasses with Al 2O 3/P 2O 5>0.63, the glass network is mainly built up of AlPO 4 groups. 相似文献
6.
The colorless and transparent glasses in the Al 2O 3---B 2O 3---SiO 3 system with high B 2O 3 and SiO 2 content were prepared from gels at low temperature. Their IR spectra not only revealed the evolution of the gel to glass conversion, but also showed that the formation of mixed bonds in the glasses obtained did not show any effect due to the B 2O 3 content. The accuracy of the glass composition is dependent upon the SiO 2/B 2O 3 molar ratio. The higher the ratio, the less the deviation of the analyzed compositions of the resulting glasses from their original calculated values. It is obvious that the higher the ratio, the lower the thermal expansion coefficient and the higher the transformation temperature of the glass, and the temperature at which the thermal contraction reaches an equilibrium is higher. 相似文献
7.
Fresnoite type compound Sr 2TiSi 2O 8 was found as a new nonlinear optical material. This compound was synthesized by substituting Sr 2+ for Ba 2+ in fresnoite Ba 2TiSi 2O 8. X- ray diffraction data showed Sr 2TiSi 2O 8 and fresnoite are isostructural. The second harmonic generation (SHG) effect of Sr 2TiSi 2O 8 is about 8 times larger than that of KH 2PO 4 (KDP). The ultraviolet absorption edge of Sr 2TiSi 2O 8 is around 270nm. 相似文献
8.
Glass formation in the P 2O 5---WO 3---K 2O---Al 2O 3 system was investigated and the glass-forming regions are presented. the properties of the glasses in the P2O5---WO3---K2O---Al2O3 system (Al2O3 8 mol.%) are reported. The colouration of glass was studied. It was found that W5+ ions make glass blue. Infrared spectra were measured by means of making KBr pills. Results of the investigation suggest that P---O---P, P---O---W, and W---O---W bonds form a continuous network in the phosphate glasses. So we suggest that tungsten trioxide is a glass former. 相似文献
9.
Alkoxide derived gels were prepared in the system Na 2O---B 2O 3---SiO 2. The gel compositions were situated in the liquid-liquid immiscibility area of the phase equilibrium diagram. Hydrolytic resistance tests were performed on the gels heat-treated at temperatures ranging between 120 to 850 °C. The Na2O, B2O3 and SiO2 extracted from the attack gels were analyzed. The experimental results indicate that the amount of B2O3 has a significant influence on the chemical durability of the heat-treated gels. At temperatures of 850 °C the greater the B2O3 mol% the greater are the amounts of Na2O and B2O3 extracted. Different behaviour was observed for gels heat-treated at 600 °C where the amounts of B2O3 and Na2O extracted slightly increases as the B2O3 mol% increases. Small amounts of extracted SiO2 were always observed. These results are complemented with other measurements so that an explanation of the controlling mechanism is given. 相似文献
10.
Tellurite containing vanadate (50− x)V 2O 5– xBi 2O 3–50TeO 2 glasses with different bismuth ( x=0, 5, 10, 15, 20 and 25 wt%) contents have been prepared by rapid quenching method. Ultrasonic velocities (both longitudinal and shear) and attenuation (for longitudinal waves only) measurements have been made using a transducer operated at the fundamental frequency of 5 MHz in the temperature range from 150 to 480 K. The elastic moduli, Debye temperature, and Poisson’s ratio have been obtained both as a function of temperature and Bi 2O 3 content. The room temperature study on ultrasonic velocities, attenuation, elastic moduli, Poisson’s ratio, Debye temperature and glass transition temperature show the absence of any anomalies with addition of Bi 2O 3 content. The observed results confirm that the addition of Bi 2O 3 modifier changes the rigid formula character of TeO 2 to a matrix of regular TeO 3 and ionic behaviour bonds (NBOs). A monotonic decrease in velocities and elastic moduli, and an increase in attenuation and acoustic loss as a function of temperature in all the glass samples reveal the loose packing structure, which is attributed to the instability of TeO 4 trigonal bipyramid units in the network as temperature increases. It is also inferred that the glasses with low Bi 2O 3 content are more stable than with high Bi 2O 3 content. 相似文献
11.
Ultraviolet transmission, densities, and supersonic velocities of the Li 2O---(LiCl) 2---B 2O 3---Al 2O 3 glasses were measured. Adiabatic compressibilities of all these glasses were calculated. The results were interpreted from the viewpoint of the glass structure. 相似文献
12.
Gallate glasses containing no conventional glass formers were obtained in the systems (Na 2O, K 2O or Cs 2O)-Ta 2O 5---Ga 2O 3 and (Sr or BaO)-Ta 2O 5---Ga 2O 3 by an ordinary crucible-melting technique. The glasses showed high optical transmission in the infrared as well as in the visible region. Infrared spectroscopic analysis suggested that the Ga 3+ ions are tetrahedrally coordinated in the glasses. The glass-forming tendency of the melt and the infrared transmission of the glasses are discussed in terms of the glass structure. 相似文献
13.
A solvothermal route has been developed to synthesize K 2V 3O 8 nanorods via the reduction of V 2O 5 using ethanol as the reducing agent as well as the solvent at 200°C. X-ray diffraction and selected area electron diffraction analysis revealed that the as-synthesized products are of tetragonal structure K 2V 3O 8. Transmission electron spectroscopy image showed that the obtained K 2V 3O 8 comprises rod-like nanocrystallites. The formation mechanism of K 2V 3O 8 was studied. 相似文献
14.
The high viscosity in melts of the Li 2O---B 2O 3 system makes it very difficult to grow large crystals of lithium triborate. The viscosity and IR characteristics of molten li 2O---B 2O 3 system are reported in this paper. When the temperature increases the viscosity of li 2O---B 2O 3 system decreases and follows an Arrhenius-type relationship. With an increasing 13203 ratio in Li 2O---B 2O 3 melts, the viscosity rises gradually to a maximum with a composition Li 2O: 3.513203 then it falls rapidly. In order to find active agents to reduce the viscosity, Na 2O, NaCl, LiF, P205, M003, W03 etc oxides were added to Li 2O---B 2O 3 samples respectively and investigated using the orthogonal method. The experimental results show that the addition of acidic oxides can significantly decrease the viscosity in the Li 2O---B 2O 3 system. For Li 2O: 4.513203, an ideal additive agent is 20wt% Li 2O:: 2MoO 3. Near the composition for crystal growth, the percentage reduction of viscosity is 62.2%. The IR spectra of Li 2O---B 2O 3 system revealed that the BO 4−/NO 3− ratio is reduced in the melt using Li 2O: 2MoO 3 as an additive. It is proposed that the M003 reduced the concentration of bridging oxygen atoms of BO 4−. The change of structure explains the decline in the viscosity. In the crystal structures of lithium triborate, the matrix spaces are so small that larger other cations than Li+ are very difficult to enter the crystal matrix. So the use of additive agents to reduce the viscosity is a possible method if no new phase appears. 相似文献
15.
Crystallization of In 2O 3 occured in closed porcelain crucibles in air at 960–1200°C by vapor phase reaction of In 2O or In vapor with the oxygen diffusing into the system. The In 2O or In vapors were thermally generated from mixtures such as graphite/In 2O 3, graphite/In, In 2O 3/In and graphite/In 2O 3/In. The graphite/In 2O 3 system at a mole ratio of 30/1 and 1000°C produced yellow, transparent needle crystals with a maximum size of 0.5 X 0.5 X 8 mm and electrical resistivity of 5.5 X 10 -2 ω cm at 25°C. 相似文献
16.
Structural peculiarities, as for example segregation and crystallization in vitroceramic materials, may have a significant influence on the electrical volume resistance of materials. Interesting characteristics can be detected in the case of the system BaO---Fe 2O 3---B 2O 3. This paper presents results showing that very different conductivity behaviours can be obtained by a suitable modification of the composition of the materials and by heat treatment. 相似文献
17.
11B Fourier transform spectra have been used to study the structure of Na 2O---B 2O 3---SiO 2 glasses of mid-alkali content. Based on the measurements of the fraction N4 of four-coordinated borons, it has been found that for K = mol.% SiO 2/mol.% B 2O 3 8 and R = mol.% Na 2O/mol.% B 2O 3 = 1, N4 is obviously smaller than 1 rather than equal to 1 as assumed in the relevant literature. Only when R reaches a value appropriately greater than 1, can the case where N4 = 1 occur. A structural model suggested in this paper can satisfactorily explain the fact. 相似文献
18.
The short range structures of B 2O 3 (90 mol%)---Cs 2O (10 mol%) and B 2O 3 (80 mol%)---Cs 2O (20 mol%) liquids were analyzed at 973 and 1053 K, respectively, by an X-ray diffraction method, and the effects of Cs 2O addition on the boron-oxygen bonding were investigated. The existence of BO 3 triangles, which form the so-called boroxol ring structure, was confirmed in B 2O 3---Cs 2O liquids, as well as in B 2O 3 liquid, but some fraction of the BO 3 triangles was thought to be converted to BO 4 tetrahedra. Similar results have previously been observed also in B 2O 3---Cs 2O glasses. A Cs atom was found to be surrounded by six O atoms; four Cs---O interatomic distances were about 3.2 Å but the other two were at 3.8–3.9 Å. These distances indicate that distorted Cs---O octahedra may exist in these B 2O 3---Cs 2O liquids. 相似文献
19.
A novel compound with the chemical formula of La 2SrB 10O 19 has been successfully synthesized from the La 2O 3--- SrO---B 2O 3 system via a solid state reaction. The powder X-ray diffraction data is reported. It is found that the data show little difference from that of La 2CaB 10O 19 which demonstrate that they are isostructural. The powder second harmonic generation effect of La 2SrB 1)O 19 is about twice that of KH 2PO 4(KDP). The investigation of crystal growth is in progress. 相似文献
20.
The surface morphology of Na 2O–B 2O 3–Al 2O 3–SiO 2 vitrified bond with and without calcium oxide was studied by soaking vitrified bonded microcrystalline alumina composites in water. The content of water introduced to the vitrified bond was determined by thermal gravity analysis, and the effects of water and calcium on the phase separation and nucleation of the vitrified bond were investigated using scanning electron microscope and energy-dispersive X-ray spectrometer. Soaked in water for 72 h, the Na 2O–B 2O 3–Al 2O 3–SiO 2 vitrified bond presented a porous surface, and its bending strength declined with increasing sintering temperature. However, the Na 2O–CaO–B 2O 3–Al 2O 3–SiO 2 vitrified bond was more durable against aqueous coolant even needle-shape crystals were found clustered on the surface of the vitrified bond. The crystals were enriched with aluminosilicate tested by energy-dispersive X-ray spectrums. The appearance of crystals lessened the dissolution of the vitrified bond and made the bending strength increase in the sintering temperature region between 870 °C and 930 °C. 相似文献
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