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1.
Protons were introduced into the surface of an Li2 O·Al2 O3 ·2SiO2 glass fiber (0.5 mm in diameter) by ion exchange in NH4 HSO4 at 366°C for 21 h. Infrared absorption measurements established that the protons were associated with bridging oxygen ions. After ion exchange, the magnitude of the alkali internal friction peak decreased and a new peak appeared at ∼220°C. This new peak is attributed to the interaction of alkali and hydrogen ions, independent of the presence of nonbridging oxygen ions. 相似文献
2.
Koichi Hirai Masahiro Tatsumisago Masanari Takahashi Tsutomu Minami 《Journal of the American Ceramic Society》1996,79(2):349-352
3.
Masanari Takahashi Hiroshi Toyuki Masahiro Tatsumisago Tsutomu Minami Norimasa Umesaki Nobuya Iwamoto 《Journal of the American Ceramic Society》1989,72(8):1524-1526
A 20Li4 SiO4 ·80Li2 WO4 glass was prepared by the rapid quenching technique, and its structure was investigated by X-ray diffraction (XRD) and Raman scattering. The coordination number of the oxygen atoms around a tungsten atom, NO/W , was determined to be 4.8 by XRD and 4.6 by Raman scattering. The deviation of NO/W from 4 resulted from the coexistence of condensed structural units, such as WO6 , Si2 O6− 7 ions containing bridging oxygens, WO2− 4 ions, and SiO4− 4 ions. 相似文献
4.
The Li2 O-TiO2 pseudobinary phase diagram was determined from 50 to 100 mol% TiO2 by DTA, microscopy, and X-ray analysis; Li2 Ti3 O7 effectively melts congruently at 1300° and decomposes eutectoidally at 940°C. A solid solution based on Li2 TlO3 from 50 to ∼65 mol% TiO3 was observed to exist at >930°C. A new metastable phase was discovered with a composition of ∼75 mol% TiO2 and with a hexagonal unit cell (8.78 by 69.86 × 10−1 nm). Discrepancies in the literature regarding some of these phase equilibria are reconciled. 相似文献
5.
The equilibrium phase diagram for the system Li2 O-BeO-SiO2 contains only one ternary compound, Li2 BeSi04 . Liquidus relations for compositions containing 33 mol% SiO2 were determined; 10 liquidus invariant points were located and 7 subsolidus compatibility triangles. The most refractory compositions lie on the join BeO-Li2 BeSiO4 , with a solidus temperature of 1320°C. Metastable phases observed were a high-quartz phase, Li2x (Si1 -x Bex )O2 , x 0.33; phase X which is probably a metastable orthosilicate between Li2 BeSiO4 and Be2 SiO4 ; and phase Y which lies on the join Li2 BeSiO4 -SiO2 . The crystal chemistry and glass network-forming properties of BeO are discussed. 相似文献
6.
Solid-state reactions between Li2 O and Al2 O3 were studied in the region between Li2 O.Al2 O 3 and Al2 O 3 . The compound Li2 O Al2 O 3 melts at 1610°± 15°C. and undergoes a rapid reversible inversion between 1200° and 1300°C. Vaporization of Li2 O from compositions in the system proceeds at an appreciable rate at 1400°C, as shown by fluorescence. Lithium spinel, Li2 O -5Al2 O3 , was the only other compound observed. The effect of Li2 O on the sintering of alumina was investigated. 相似文献
7.
Reaction between CaO powders and CO2 ( g ) is often limited by slow diffusion of CO2 through the CaCO3 product. Additions of Li2 CO3 are shown to increase the reaction rate. At temperatures around 940 K, near to the Li2 CO3 -CaCO3 eutectic temperature, 935 K, complete reaction of the CaO with CO2 can be achieved when the heating rate and Li2 CO3 content are optimized. At lower temperatures Li2 CO3 causes lesser but measurable increases in reaction rates. SEM and surface area observations suggest different reaction paths when Li2 CO3 is present, when Li2 CO3 and eutectic are present, and when eutectic alone is present. 相似文献
8.
Qun Zeng Wei Li Jian-lin Shi Xian-lin Dong Jing-kun Guo 《Journal of the American Ceramic Society》2008,91(2):644-647
A group of new y M-phase/(1− y ) Li2+ x Ti1−4 x Nb3 x O3 composite ceramics with adjustable permittivities for low-temperature co-fired ceramic applications was initially investigated in the study. The 0.5 M-phase/0.5 Li2+ x Ti1−4 x Nb3 x O3 ( x =0.01, 0.02, 0.04, 0.06, 0.081) composite ceramics were first investigated to find the appropriate "Li2 TiO3 ss" composition ( x value). The best dielectric properties of ɛr =40.1, Q × f values up to 9318 GHz, τf =25 ppm/°C, were obtained for the ceramics composites at x =0.02. Based on the good dielectric properties, the suitable "Li2 TiO3 ss" composition with x =0.02 was mixed with the Li1.0 Nb0.6 Ti0.5 O3 powder as the ratio of y "M-phase"/(1− y ) "Li2 TiO3 ss" ( y =0.2, 0.4, 0.5, 0.6, 0.8). By adjusting the y values, the group of composite ceramics could exhibit largely are adjustable permittivities varying from ∼20 to ∼60, while Q × f and τf values relatively good. Nevertheless, in this study, because there are interactions between the M-phase and Li2 TiO3 ss during sintering process, their microwave dielectric properties could not be predicted precisely by the empirical model. 相似文献
9.
Fibers of Li2 O.Al2 O3 .2SiO2 glass were ion-exchanged for 1 to 300 min in an NaNO3 bath at 366°C. The internal friction and the Li and Na concentration profiles were measured. As Na progressively replaced Li, the alkali internal friction peak became smaller while a new peak (mixed-alkali peak) appeared and increased in magnitude. These changes in internal friction are similar to those that occur when a second alkali is added to glasses prepared by conventional melting. The magnitudes of both internal friction peaks in the ion-exchanged glass depended on the overall composition of the glass; that of the alkali peak depended on the composition of the unexchanged glass core, whereas that of the mixed-alkali peak depended on the composition of the exchanged layer on the glass surface. When the exchanged surface layer was dissolved, the original alkali peak was restored, and the mixed-alkali peak disappeared. Changing the alkali distribution did not affect the mixed-alkali peak much; however, it caused the alkali peak to shift to higher temperatures and become smaller. The height of the alkali peak can be used to determine the maximum depth of penetration of the second alkali. 相似文献
10.
A. R. WEST 《Journal of the American Ceramic Society》1978,61(3-4):152-155
Phase relations in the system Li2 O-CaO-SiO2 were studied by the quenching method. Four stable ternary compounds were found (Li2 Ca3 Si6 Ol6 , Li2 Ca4 Si4 O13 , Li2 Ca2 Si2 O7 , and Li2 CaSiO4 ) as well as phase Y , which is probably a metastable orthosilicate fairly close to Ca2 SiO4 in composition. X-ray powder data are given for the new phases. Eleven subsolidus compatibility triangles and thirteen liquidus invariant points were located. Melting relations were determined for that part of the system bounded by Li2 SiO3 , Li2 CaSiO4 , Ca2 SiO4 , and SiO2 . The join Li2 SiO3 -CaSiO3 is binary. 相似文献
11.
The kinetics of crystallization of Li2 Si2 O5 from glasses in the Li2 O-SiO2 system were studied using quantitative X-ray diffraction. Analysis of the data using the Johnson-Mehl-Avrami equation showed that crystallization occurred through the nucleation and growth of rods. The spherulitic nature of the crystals was substantiated by petrographic examinations of the partially crystalline glass. Analysis of the temperature dependence of the crystallization rate using a modification of the Johnson-Mehl-Avrami equation showed that the activation energy for nucleation was a function of composition and thermal treatment. 相似文献
12.
IAN M. HODGE MALCOLM D. INGRAM ANTHONY R. WEST 《Journal of the American Ceramic Society》1976,59(7-8):360-366
Conductivity was measured for Li4 SiO4 and its solid solutions with Li4 GeO4 over a wide frequency range to separate clearly the effects of electrode polarization, conductance relaxations, etc., and to obtain true "dc" conductivities. The conductivities of all the electrolytes are markedly temperature-dependent, ranging from 10−8 to 10−10 Ω−1 cm−1 at 100°C to 10−2 to 1010 Ω−1 cm−1 at 700°C. For solid solutions with the Li4 GeO4 structure, conductivities fit the Arrhenius equation over a wide temperature range, but at higher temperatures a change in activation energy occurs, corresponding to a first-order phase transition. In contrast, solid solutions with the Li4 SiO4 structure show changes in activation energy which do not correspond to phase transitions, but which appear to indicate changes in the conduction mechanism. 相似文献
13.
G. Bhattacharya S. Zhang D. D. Jayaseelan W. E. Lee 《Journal of the American Ceramic Society》2007,90(1):97-106
Lithium borate (Li2 B4 O7 ) and sodium borate (Na2 B4 O7 ) mineralize spinel formation from stoichiometric MgO and Al2 O3 between 1000° and 1100°C. Mineralization with both compounds is shown to be mediated by B-containing liquids which form glass on cooling. However, the liquid compositions depend on the type of mineralizer and temperature, suggesting that templated grain growth or dissolution–precipitation mechanisms are operating, one dominating over the other under certain conditions. Na2 B4 O7 -mineralized compositions show predominantly templated grain growth at 1000°C, which changes to dissolution–precipitation at 1100°C, whereas Li2 B4 O7 -mineralized compositions show dissolution–precipitation from 1000°C. Li2 B4 O7 is a stronger mineralizer as spinel formation is complete with 3 wt% Li2 B4 O7 at 1000°C and with ≥1.5 wt% addition at 1100°C, whereas Na2 B4 O7 -mineralized compositions are found to retain some unreacted corundum even at 1100°C. 相似文献
14.
MITSUTOSHI KAYASHIMA NOBUO SANO YUKIO MATSUSHITA 《Journal of the American Ceramic Society》1978,61(7-8):311-314
Systematic detection of an EPR signal was conducted for three alkali oxide-Al2 O3 −SiO2 glass systems. Observed EPR spectra, having a main line with g=2.03 and a broad and anisotropic shape, are attributed to the unsaturated bridging oxygen bond resulting from the breakup of the SiO2 random network. This signal appears in the area AValkali atom ratio >1 for the Na2 0 and K2 O systems, indicating that the collapse of the Al 4-coordinated structure begins at an equimolar ratio when alumina is substituted for the alkali oxide, whereas somewhat different behavior was observed for the Li2 O system. 相似文献
15.
Porous glass-ceramics with a skeleton of the fast-lithium-conducting crystal Li1+ x Ti2− x Al x (PO4 )3 (where x = 0.3–0.5) were prepared by crystallization of glasses in the Li2 O─CaO─TiO2 ─Al2 O3 –P2 O5 system and subsequent acid leaching of the resulting dense glass-ceramics composed of the interlocking of Li1+ x Ti2− x Al x (PO4 )3 and β-Ca3 (PO4 )2 phases. The median pore diameter and surface area of the resulting porous Li1+ x Ti2− x Al x (PO4 )3 glass-ceramics were approximately 0.2 μm and 50 m2 /g, respectively. The electrical conductivity of the porous glass-ceramics after heating in LiNO3 aqueous solution was 8 × 10−5 S/cm at 300 K or 2 × 10−2 S/cm at 600 K. 相似文献
16.
Above 755°C, compounds along the spinel join LiFe5 O8 -Li4 Ti5 O12 form a complete solid solution and below that temperature a two-phase region separates the ordered LiFe5 O8 and the disordered spinel phase. At 800° and 900°C, cubic LiFeO2 ( ss ) and monoclinic Liz Ti03 ( ss ) exist on the monoxide join LiFeO2 -Li2 TiO3 . The distributions of cations in both the spinel and monoxide structures were calculated as a function of equilibrium temperature and composition. Sub-solidus equilibria in the system Li2 O-Fe2 O3 -TiO2 at 800° and 900°C were determined for compositions containing ∼50 mol% Li2 O. 相似文献
17.
Phase relations in the system Li2 O–B2 O3 –SiO2 were studied by quenching and solid-state reactions. No ternary compounds were detected in the portion of the system containing less than 53% Li2 O. Compatibility triangles were formed from the binary borate and silicate compounds. Liquidus data obtained by quenching are reported for four joins, Li2 O·2SiO2 –Li2 O·2B2 O3 , Li2 O·SiO2 -Li2 O·2B2 O3 , Li2 O·SiO2 -Li2 O·B2 O3 , and Li2 O·2B2 O3 -SiO2 . The last join cuts across the two-liquid region and is not a true binary system. Some probable ternary invariant points were located in the portion of the system which was quenchable to glass and adjacent to the two-liquid region. Further data on the previously reported immiscible liquid formation are given and the significance is discussed. Data on the thermal expansion behavior of certain glasses are presented. 相似文献
18.
MASAHIRO TATSUMISAGO KAZUYA YONEDA TSUTOMU MINAMI 《Journal of the American Ceramic Society》1988,71(9):766-769
Oxysulfide glasses were prepared in a wide range of compositions in the system LiBO2 -LiBS2 . Temperatures of glass transition ( Tg ), crystallization ( Tc ), and liquidus ( Tl ) were determined; a maximum of Tg was observed near the composition with 20 mol% LiBS2 . The electrical conductivity at 500 K ranges from 5×10−4 to 5×10−3 S·cm−1 with the maxima in conductivity observed near the composition 55LiBO2 ·45LiBS2 . This conductivity enhancement with a mixing of two components, which can be called the mixed-anion effect, is accompanied by a decrease in the degree of undercooling of glass expressed by the ratio ( Tl - Tg )/ Tl . The infrared and Raman spectra showed that the structural units with bridging oxygens B-O-B and nonbridging sulfurs B-S− predominated rather than those with nonbridging oxygens B-O− and bridging sulfurs B-S-B in these glasses. 相似文献
19.
John Gerard Fisher Min-Soo Kim Ho-Yong Lee Suk-Joong L. Kang 《Journal of the American Ceramic Society》2004,87(5):937-942
Abnormal grain growth in Pb(Mg1/3 Nb2/3 )O3 –35 mol% PbTiO3 (PMN-35PT) ceramics doped with Li2 O and PbO has been investigated. Replacing the PbO dopant with up to 2 mol% Li2 O caused an increase in the number of abnormal grains. For the composition containing 2 mol% Li2 O and 6 mol% PbO, the amount of abnormal grain growth decreased with increasing sintering temperature. Single crystals of ∼6 mm × 6 mm × 2 mm thickness were grown from the 2 mol% Li2 O, 6 mol% PbO-containing composition via the templated grain growth method. Grain growth behavior with temperature is explained in terms of the effect of Li2 O on interface-reaction-controlled grain growth and the critical driving force. 相似文献
20.
Venkataraman Thangadurai Heiko Kaack Werner J. F. Weppner 《Journal of the American Ceramic Society》2003,86(3):437-440
Lithium metal oxides with the nominal composition Li5 La3 M2 O12 (M = Nb, Ta), possessing a garnetlike structure, have been investigated with regard to their electrical properties. These compounds form a new class of solid-state lithium ion conductors with a different crystal structure compared with all those known so far. The materials are prepared by solid-state reaction and characterized by powder XRD and ac impedance to determine their lithium ionic conductivity. Both the niobium and tantalum members exhibit the same order of magnitude of bulk conductivity (∼10−6 S/cm at 25°C). The activation energies for ionic conductivity (<300°C) are 0.43 and 0.56 eV for Li5 La3 Nb2 O12 and Li5 La3 Ta2 O12 , respectively, which are comparable to those of other solid lithium conductors, such as Lisicon, Li14 ZnGe4 O16 . Among the investigated materials, the tantalum compound Li5 La3 Ta2 O12 is stable against reaction with molten lithium. Further tailoring of the compositions by appropriate chemical substitutions and improved synthesizing methods, especially with regard to minimizing grain-boundary resistance, are important issues in view of the potential use of the new class of compounds as electrolytes in practical lithium ion batteries. 相似文献