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1.
Quadrupole interactions of 11 B and 27 Al in SiO2 -B2 O3 -Al2 O3 -R2 O glass systems were investigated to determine the structure of these glasses, which should be amenable to chemical strengthening. The ratio of BO4 units to BO3 units approached unity as the R2 O/Al2 O3 ratio for compounds having fixed B2 O3 contents approached unity. Nuclear quadrupole coupling constants ( e2 Qq/h =2.73 to 2.93 MHz) were measured for the NMR spectra of 11 B triangles. The line shapes of 27 Al spectra varied with chemical composition, but a few glasses exhibited 27 Al line shapes similar to those of the AlO4 triclusters in SiO2 -Al2 O3 -Na2 O glasses. Compositional trends in the formation of BO4 and AlO4 were deduced from the NMR spectra. 相似文献
2.
John M. Jewell Paige L. Higby Ishwar D. Aggarwal 《Journal of the American Ceramic Society》1994,77(3):697-700
Barium gallogermanate glasses were prepared with substitutions of Al2 O3 , Y2 O3 , La2 O3 , and Gd2 O3 for Ga2 O3 . The effects of these substitutions on the glass transformation temperature, viscosity, thermal expansion, and molar volume have been determined. The changes in properties associated with each substitutional ion are consistent with structural roles reported for these ions in other glasses. Aluminum acts as an intermediate with [AlO4 – ] tetrahedra substituting directly for [GaO4 – ] tetrahedra. Yttrium and gadolinium act as "atypical" modifier ions because of their large field strengths. Finally, the properties of the La2 O3 -substituted glasses indicate a possible dual structural role for La3+ ions in these glasses. 相似文献
3.
Tomohiro Yamakawa Junichi Tatami Toru Wakihara Katsutoshi Komeya Takeshi Meguro Kenneth J. D. MacKenzie Shinichi Takagi Masahiro Yokouchi 《Journal of the American Ceramic Society》2006,89(1):171-175
Aluminum nitride (AlN) powders were synthesized by gas reduction–nitridation of γ-Al2 O3 using NH3 and C3 H8 as the reactant gases. AlN was identified in the products synthesized at 1100°–1400°C for 120 min in the NH3 –C3 H8 gas flow confirming that AlN can be formed by the gas reduction–nitridation of γ-Al2 O3 . The products synthesized at 1100°C for 120 min contained unreacted γ-Al2 O3 . The 27 A1 MAS NMR spectra show that Al–N bonding in the product increases with increasing reaction temperature, the tetrahedral AlO4 resonance decreasing prior to the disappearance of the octahedral AlO6 resonance. This suggests that the tetrahedral AlO4 sites of the γ-Al2 O3 are preferentially nitrided than the AlO6 sites. AlN nanoparticles were directly formed from γ-Al2 O3 at low temperature because of this preferred nitridation of AlO4 sites in the reactant. AlN nanoparticles are formed by gas reduction–nitridation of γ-Al2 O3 not only because the reaction temperature is sufficiently low to restrict grain growth, but also because γ-Al2 O3 contains both AlO4 and AlO6 sites, by contrast with α-Al2 O3 which contains only AlO6 . 相似文献
4.
Xian Feng Setsuhisa Tanabe Teiichi Hanada 《Journal of the American Ceramic Society》2001,84(1):165-171
The thermal stability and spectroscopic properties of Er2 O3 -doped TeO2 –GeO2 –ZnO–Na2 O–Y2 O3 glasses for 1.5 μm fiber amplifiers were investigated. The thermal stability of the 75TeO2 ·20ZnO· 5Na2 O glass was improved by introducing GeO2 and Y2 O3 . The radiative transition and the nonradiative transition have a dominant influence on the 4 I13/2 level lifetime of Er3+ in high- and low-GeO2 regions, respectively. Adding Y2 O3 increases the 4 I13/2 level lifetime of Er3+ significantly. The Judd–Ofelt (J-O) parameter Ω6 shows a strong correlation with the 1.5 μm emission bandwidth; and the larger the Ω6 , the wider the bandwidth. 相似文献
5.
Phase relations within the "V2 O3 –FeO" and V2 O3 –TiO2 oxide systems were determined using the quench technique. Experimental conditions were as follows: partial oxygen pressures of 3.02 × 10−10 , 2.99 × 10−9 , and 2.31 × 10−8 atm at 1400°, 1500°, and 1600°C, respectively. Analysis techniques that were used to determine the phase relations within the reacted samples included X-ray diffractometry, electron probe microanalysis (energy-dispersive spectroscopy and wavelength-dispersive spectroscopy), and optical microscopy. The solid-solution phases M2 O3 , M3 O5 , and higher Magneli phases (M n O2 n −1 , where M = V, Ti) were identified in the V2 O3 –TiO2 system. In the "V2 O3 –FeO" system, the solid-solution phases M2 O3 and M3 O4 (where M = V, Ti), as well as liquid, were identified. 相似文献
6.
Emission properties of PbO–Bi2 O3 –Ga2 O3 glasses doped with Ho3+ were investigated for fiber-optic amplification at the 1.18 μm wavelength region. When the glasses were doped with Ho3+ ions only, there was a weak emission at 1.18 μm with a lifetime of ∼200 μs. However, when Yb3+ ions were codoped, the lifetime of the 1.18 μm emission increased to 630 μs together with a significant increase in intensity. A similar enhancement in the intensity and lifetimes was realized for the 2.05 μm emission. These effects are due to energy transfer from the Yb3+ :2 F5/2 to the Ho3+ :5 I6 level. Devitrification of the ternary PbO–Bi2 O3 –Ga2 O3 glasses was efficiently suppressed by adding 10 mol% GeO2 . Optimum Ho3+ concentration was ∼0.4 mol%, whereas Yb3+ ions can be added up to the solubility limit. 相似文献
7.
Kentaro Terashima Sae-Hoon Kim Toshinobu Yoko 《Journal of the American Ceramic Society》1995,78(6):1601-1605
The third-order nonlinear optical susceptibilities χ(3) of M2 O-B2 O3 (M = Li, Na, K, Rb, Cs, and Ag) binary borate glasses have been measured by the third harmonic generation (THG) method. It is found that the enhancement of χ(3) by the structural change of BO3 units to BO4 units is small, while the enhancement of χ(3) due to the formation of non- bridging oxygen is rather significant. The effects of alkali cations on the χ(3) of alkali borate glasses are discussed in terms of the M-O bond character, focusing on the covalency of Li2 O-B2 O3 glasses. Comparison of the χ(3) values for Cs2 O-B2 O3 and Ag2 O-B2 O3 glasses which contain cations of comparable polarizability reveals that the χ(3) value is much greater for Ag2 O-B2 O3 glasses than for Cs2 O-B2 O3 glasses, which is possibly due to the great contribution of Ag(4 dz2 + 5 s + 5 pz ) hybrid orbitals to the nonlinear optical response. 相似文献
8.
Daniel Caurant Odile Majérus Edward Fadel Marion Lenoir Christel Gervais Olivier Pinet 《Journal of the American Ceramic Society》2007,90(3):774-783
Crystallization of the poorly durable Na2 MoO4 phase able to incorporate radioactive cesium must be avoided in SiO2 –Al2 O3 –B2 O3 –Na2 O–CaO glasses developed for the immobilization of Mo-rich nuclear wastes. Increasing amounts of B2 O3 and MoO3 were added to a SiO2 –Na2 O–CaO glass, and crystallization tendency was studied. Na2 MoO4 crystallization tendency decreased with the increase of B2 O3 concentration whereas the tendency of CaMoO4 to crystallize increased due to preferential charge compensation of BO4 − entities by Na+ ions. 29 Si MAS NMR showed that molybdenum acts as a reticulating agent in glass structure. Trivalent actinides surrogate (Nd3+ ) were shown to enter into CaMoO4 crystals formed in glasses. 相似文献
9.
Mark I. Pownceby Keri K. Constanti-Carey Michael J. Fisher-White 《Journal of the American Ceramic Society》2003,86(6):975-980
Subsolidus phase equilibria in the system Fe2 O3 –Al2 O3 –TiO2 were investigated between 1000° and 1300°C. Quenched samples were examined using powder X-ray diffraction and electron probe microanalytical methods. The main features of the phase relations were: (a) the presence of an M3 O5 solid solution series between end members Fe2 TiO5 and Al2 TiO5 , (b) a miscibility gap along the Fe2 O3 –Al2 O3 binary, (c) an α-M2 O3 ( ss ) ternary solid-solution region based on mutual solubility between Fe2 O3 , Al2 O3 , and TiO2 , and (d) an extensive three-phase region characterized by the assemblage M3 O5 +α-M2 O3 ( ss ) + Cor( ss ). A comparison of results with previously established phase relations for the Fe2 O3 –Al2 O3 –TiO2 system shows considerable discrepancy. 相似文献
10.
Masao Morishita Alexandra Navrotsky Martin C. Wilding 《Journal of the American Ceramic Society》2004,87(8):1550-1555
The relative partial molar enthalpies, Δ SiO2 , of SiO2 in SiO2 –M2 O (M = Li, Na, K and Cs) binary and SiO2 –CaO–Al2 O3 ternary melts were directly measured by drop-solution calorimetry at 1465 K and 1663 K. Δ SiO2 changes from exothermic to endothermic as silica content increases, confirming the tendency toward immisciblity seen from activity measurements. It is concluded that Δ SiO2 is negative due to acid-base reactions and charge-coupled substitutions when the melt is composed of fewer Q 4 and more Q 3 and Q 2 species, but positive due to structural strain when the melt is composed of mostly Q 4 species. The Δ SiO2 obtained by calorimetry is a useful measure of basicity, when comparing different alkali and alkaline earth oxides. 相似文献
11.
Tsuyoshi Honma Yasuhiko Benino Takumi Fujiwara Takayuki Komatsu Ryuji Sato 《Journal of the American Ceramic Society》2005,88(4):989-992
The glass formation region, crystalline phases, second harmonic (SH) generation, and Nd:yttrium aluminum garnet (YAG) laser-induced crystallization in the Sm2 O3 –Bi2 O3 –B2 O3 system were clarified. The crystalline phases of Bi4 B2 O9 , Bi3 B5 O12 , BiBO3 , Sm x Bi1− x BO3 , and SmB3 O6 were formed through the usual crystallization in an electric furnace. The crystallized glasses consisting of BiBO3 and Sm x Bi1− x BO3 showed SH generations. The formation of the nonlinear optical BiB3 O6 phase was not confirmed. The formation (writing) region of crystal lines consisting of Sm x Bi1− x BO3 by YAG laser irradiation was determined, in which Sm2 O3 contents were∼10 mol%. The present study demonstrates that Sm2 O3 –Bi2 O3 –B2 O3 glasses are promising materials for optical functional applications. 相似文献
12.
The glass-forming regions in the ternary systems M2 O-In2 O3 -GeO2 (M = Li,Na,K) were determined. The region in each of the three ternaries is less extensive than in either of the analogous systems M2 O-Al2 O3 -GeO2 and M2 O-Ga2 O3 -GeO2 ; this behavior reflects the restrictive coordination requirements of the larger In ion. The In2 O3 -containing glasses exhibit higher densities and refractive indices than the corresponding Al2 O3 and Ga2 O3 -containing glasses. Refractive index and density maxima are observed along lines of constant In2 O3 in each of the three alkali indogermanate systems. 相似文献
13.
James J. De Yoreo Alexandra Navrotsky Don B. Dingwell 《Journal of the American Ceramic Society》1990,73(7):2068-2072
Heats of solution in molten 2PbO·B2 O3 at 973 K are reported for glasses x NaT3+ O2 –(1 – x )SiO2 for T = Fe, Ga. These measurements, combined with previous data for T = Al, B, give a relative measure of the enthalpy of the charge-coupled substitution Si4+ → Na+ + T3+ . The heats of solution become more endothermic with increasing x for x → 0.5 and exhibit a maximum near x = 0.5. This indicates an exothermic enthalpy for the substitution and an overall stabilization of the glasses. The degree to which the glasses are stabilized decreases in the order Al > Ga > Fe > B. On the basis of molecular orbital calculations, X-ray scattering, and Raman spectroscopy, it is argued that this trend is primarily due to a decrease in the range of energetically favorable T–O–T bond angles as Al, Ga, Fe, and B are substituted for Si. 相似文献
14.
Marko Udovic Matjaz Valant Danilo Suvorov 《Journal of the American Ceramic Society》2004,87(4):591-597
Solid-state synthesis of compositions from the Bi2 O3 –TeO2 system show that, under an oxygen atmosphere, Te4+ oxidizes to Te6+ and yields four room-temperature stable compounds: Bi2 Te2 O8 , Bi2 TeO6 , Bi6 Te2 O15 , and new a compound with the nominal composition 7Bi2 O3 ·2TeO2 . Dense ceramics can be prepared from all these compounds by sintering between 650° and 800°C under an oxygen atmosphere. The permittivity of these compounds varies from ∼30 to ∼54, the Q × f value from 1.100 to 41.000 GHz (∼5 GHz), and the temperature coefficient of resonant frequency from −43 to −144 ppm/K. Bi6 Te2 O15 and 7Bi2 O3 ·2TeO2 do not react with silver, and, therefore, they have the potential to be used for applications in low-temperature cofired ceramic (LTCC) technology. 相似文献
15.
Takashi Harada Hiromichi Takebe Makoto Kuwabara 《Journal of the American Ceramic Society》2006,89(1):247-250
The glass transition temperature increases and the thermal expansion coefficient and density decrease with increasing B2 O3 concentration in a series of (100− x )(50BaO–50P2 O5 )− x B2 O3 where x =0–10 mol% for bulk samples. According to Raman spectroscopy, the bulk BaO–P2 O5 –B2 O3 (BaP–B) glasses consist of metaphosphate Q 2 units with ring-type metaborate, diborate, and PO4 –BO4 groups. X-ray photoelectron spectroscopy results reveal qualitatively that P–O–B bonds are formed at the surface of BaP–B glass samples ground in laboratory air over 6 mol% B2 O3 only. The P–O–B bonds are related to the suppression of the crystallization of powdered BaP–B glasses with >6 mol% B2 O3 during differential thermal analysis. 相似文献
16.
Suguru Suzuki Minoru Takahashi Yasio Hikich 《Journal of the American Ceramic Society》1987,70(9):213-C
The free-volume fraction (Vf ) defined by Simha and Boyer was measured for network-forming oxide glasses in the systems P2 O5 -(GeO2 , TeO2 ,Sb2 O3 .V2 O5 ). The Vf values varied from 0.06 to 0.25. The systems P2 O5 -TeO2 : and P2 O5 -Sb2 O3 have Vf ∼0.1, which is near the magnitude of the free-volume fraction for normal metaphosphate glasses and many organic high polymers. 相似文献
17.
Marko Udovic Matjaz Valant Botjan Janar Danilo Suvorov Anton Meden Anton Koevar 《Journal of the American Ceramic Society》2006,89(11):3462-3469
Using X-ray diffraction analysis and scanning electron microscopy it was revealed that in an atmosphere of flowing oxygen in the temperature range 700°–800°C, three new compounds are formed in the Bi2 O3 –TiO2 –TeO2 pseudoternary system. These compounds are Bi2 Ti3 TeO12 , Bi2 TiTeO8 , and Bi6 Ti5 TeO22 , and all the compounds include Te6+ . All three crystal structures were solved and refined using X-ray powder diffraction data. Based on the results of the phase formation, a solid-state compatibility diagram is proposed. 相似文献
18.
Kentaro Fukuda Teiichi Hanada Setsuhisa Tanabe Takeshi Yao 《Journal of the American Ceramic Society》2002,85(4):915-920
Amorphous films in the system Al2 O3 –Y2 O3 were prepared by the rf sputtering method in the range of 0–76 mol% Y2 O3 , and their density, refractive index, and elastic constants were measured. All of the physical properties of the amorphous Al2 O3 –Y2 O3 films had a similar compositional dependence; that is, they increased continuously, but not linearly with increasing Y2 O3 content. To confirm the coordination states of aluminum and yttrium ions in the amorphous Al2 O3 –Y2 O3 films, the Al K α X-ray emission spectra and the X-ray absorption near edge structures (XANES) were measured. The average coordination number of aluminum ions in the amorphous films containing up to about 40 mol% Y2 O3 content was 5, that is a mixture of 4-fold- and 6-fold-coordinated states. In the region of more than about 50 mol% Y2 O3 , the fraction of the 6-fold-coordinated aluminum ions increased with increasing Y2 O3 content, while the results led to the conclusion that the coordination number of yttrium ions was always 6, regardless of composition. These results indicate that, in amorphous films in the system Al2 O3 –Y2 O3 , the change of the coordination state of aluminum ions has an important effect on physical properties. 相似文献
19.
Taigo Takaishi Masahide Takahashi Jisun Jin Takashi Uchino Toshinobu Yoko Masahide Takahashi 《Journal of the American Ceramic Society》2005,88(6):1591-1596
Structure of x PbO–(100− x )SiO2 ( x =25–89) glasses has been investigated by means of the X-ray and neutron diffraction and 29 Si MAS NMR measurements. In the radial distribution functions of all the glasses, the Pb–O correlation was observed at 0.23 nm, indicating that the PbO3 trigonal pyramids units do exist in the whole glass forming composition range. Furthermore the existence of the first Pb–Pb correlation at ∼0.385 nm in the whole composition range suggests that the basic structural unit is considered to be a Pb2 O4 unit, which consists of the edge-shared PbO3 trigonal pyramids. These results strongly imply that the Pb2 O4 units participate in the glass network constructed by SiO4 tetrahedra even at low PbO content. Differing from other lead-containing glass systems, these structural characteristics of Pb ions in the PbO–SiO2 glass system are responsible for the extremely wide glass-forming region. 相似文献