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1.
R. W. TAYLOR 《Journal of the American Ceramic Society》1963,46(6):276-279
Liquidus temperatures in the system FeO–Fe2 O3 –TiO2 have been estimated from data in the literature supplemented with experimental determinations of the liquidus temperature for about fifty different compositions within the system using the quenching method. 相似文献
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Subsolidus phase relationships in the Ga2 O3 –Al2 O3 –TiO2 system at 1400°C were studied using X-ray diffraction. Phases present in the pseudoternary system include TiO2 (rutile), Ga2−2 x Al2 x O3 ( x ≤0.78 β-gallia structure), Al2−2 y Ga2 y O3 ( y ≤0.12 corundum structure), Ga2−2 x Al2 x TiO5 (0≤ x ≤1 pseudobrookite structure), and several β-gallia rutile intergrowths that can be expressed as Ga4−4 x Al4 x Ti n −4 O2 n −2 ( x ≤0.3, 15≤ n ≤33). This study showed no evidence to confirm that aluminum substitution of gallium stabilizes the n =7 β-gallia–rutile intergrowth as has been mentioned in previous work. 相似文献
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The system TiO2 -P2 O5 was investigated in the compositional range TiO2 .P2 O5 to 100% TiO2 . Two compounds exist, TiO2 .P2 O5 and 5TiO2 .-2P2 O5 . TiO2 .P2 O5 begins to lose P2 O5 at 1400°C. and both fusion and vaporization proceed rapidly at 1500°C. 5TiO2 .2P2 O6 melts congruently at 1260°± 3°C. to a glass which can be retained in substantial quantities at room temperature. Physical properties of certain compositions are described. 相似文献
4.
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
5.
The subsolidus miscibility gap for the TiO2 -SnO2 system was redetermined. The critical temperature, 1430°C, is intermediate between that determined by Padurow, 1330°C, and that determined by Garcia and Speidel, 1475°C. Although the phase boundary is slightly asymmetric (the critical composition occurs at 47 mol% TiO2 ), it fits the regular-solution model down to 1200°C. Calculations of the coherent spinodal using the regular-solution model indicated depression of the spinodal below Tc , by 105°, 310°, and 387° for composition fluctuations along the [001], <101>, and <100> directions, respectively. These depressions of the spinodal are much greater than those calculated by Stubican and Schultz; this discrepancy is believed to result from an error in the latter workers' calculations. During the present work, positive deviations from Vegard's law were found in this system. Both the magnitude and the sign of the deviation can be predicted using a theory based on nonlinear second-order elasticity. 相似文献
6.
BILL BERGMAN 《Journal of the American Ceramic Society》1986,69(8):608-611
Diffusion couples are used to study the reaction between CaO powder and Fe2 O3 All heat treatments were performed in air. The growth and morphology of calcium ferrites is studied at different temperatures. It is shown that CaO·2Fe2 O3 , starts to form at about 1125°C, while the accepted phase diagram for equilibrium with air predicts a temperature of 1155°C. 相似文献
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Oxide crystallite formation and growth from freeze-dried sulfates were studied for the representative materials Al2 O3 and Fe2 O3 . Transmission and scanning electron micrographs showed the formation and growth of chainlike aggregates of crystallites. Aggregation occurred as part of the nucleation and growth of the oxide, and discrete oxide particles were never present. Orientation of the chain aggregates was related to the ice structure formed during freezing. X-ray line broadening data showed that crystallite size is a function of the 1/5 to 1/7 power of time for isothermal treatments. A qualitative analysis of material transport favored the surface diffusion mechanism. 相似文献
10.
Gallium orthoferrite (Ga2- x Fe x O3 ) has a maximum thermal stability which coincides roughly with liquidus temperatures at oxygen pressures near atmospheric. As a result, changes in ambient oxygen pressure between 0.2 and 10 atm have a pronounced effect on equilibria. The compound exhibits a wide range in Ga:Fe ratio on both sides of the stoichiometric GaFeO3 but is essentially invariant in oxygen content to 1500°C in air. The orthoferrite bears many similarities to the corresponding aluminum compound Al2 - x Fe x O3 . 相似文献
11.
Measurements were made of temperature and ternary composition for coexisting liquid and crystalline phases on the air isobar in the system Fe2 O3 -Fe3 O4 -YFeO3 with particular regard to the stability range and compositional limits of yttrium iron garnet. Phase equilibrium relations were determined by conventional quenching techniques combined with measurements of loss in weight at the reaction temperature to locate true ternary compositions. The intersection of the air isobar with the ternary univariant boundary curve for coexisting magnetite, garnet, and liquid phases results in a eutectic-type situation at the composition Y0.27 Fe1.73 O2.87 and 1469°± 2°C. A similar intersection of the isobar with the boundary curve for coexisting garnet, orthoferrite, and liquid phases gives rise to a peritectic-type reaction at 1555° 3°C. and Y0.44 Fe1.56 O2.89 The yttrium iron garnet crystallizing from liquids within these temperature and composition limits contains up to 0.5 mole % iron oxide in excess of the stoichiometric formula in terms of the starting composition 37.5 mole % Y2 O3 , 62.5 mole % Fe2 O3 . At 1470° C. the garnet phase in equilibrium with oxide liquid contains 2 mole % FeO in solid solution. The small solubility of excess of iron oxide and partial reduction of the garnet phase in air are unavoidable during equilibrium growth from the melt. 相似文献
12.
Subsolidus phase relationships in the Ga2 O3 –In2 O3 –SnO2 system were studied by X-ray diffraction over the temperature range 1250–1400°C. At 1250°C, several phases are stable in the ternary system, including Ga2 O3 ( ss ), In2 O3 ( ss ), SnO2 , Ga3− x In5+ x Sn2 O16 , and several intergrowth phases that can be expressed as Ga4−4 x In4 x Sn n −4 O2 n −2 where n is an integer. An In2 O3 –SnO2 phase and Ga4 SnO8 form at 1375°C but are not stable at 1250°C. GaInO3 did not form over the temperature range 1000–1400°C. 相似文献
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Solid solutions of Fe304-FeV204 and Fe304-FeCr204 were prepared and equilibrated with Pt under controlled streams of CO/CO, gas mixtures at 1673 K. The concentration of Fe in Pt was used to determine the activity of Fe304 in the solid solutions. The activity of the second component was calculated by Gibbshhem integration. From these data, the Gibbs energy of mixing was derived for both systems. The experimental results and theoretical values which are determined from calculated cation distribution compare favorably in the case of vanadite solid solutions but not in the case of chromite solid solutions. The difference is attributed to a heat term arising from lattice distortion due to cation size difference. The positive heat of mixing will give rise to a miscibility gap in the system Fe304-FeCr204 at lower temperatures. 相似文献
15.
The subsolidus compatibility relations in the system SrO-B2 O3 - SiO2 were determined by solid-state reaction techniques and X-ray powder diffraction methods. The system was found to contain 11 subsolidus compatibility relations, one stable ternary compound (Sr3 B2 SiO8 ), and one metastable ternary compound with a probable composition SrB2 Si2 O8 . 相似文献
16.
The sintering of acicular Fe2 O3 powder has been studied in comparison with an ordinary equiaxed powder. The acicular powder gave a dense material more than 99 % theoretical even from the relatively low green density. Oriented granular structures were observed in the 1200°C compacts. The observed densification behavior has been attributed to the pore configuration in the green compact. 相似文献
17.
A. G. CROUCH 《Journal of the American Ceramic Society》1972,55(11):558-563
The effects of stress, temperature, grain size, porosity, and O2 partial pressure on the creep of polycrystalline Fe2 O3 were studied in the range 770° to 1105°C by tests in 4-point bending and compression. Deformation rates are controlled by the stress-directed diffusion of either oxygen or iron. Diffusion coefficients computed from the Nabarro-Herring formula modified by including an empirical porosity-correction term are also consistent with the values reported for oxygen and iron. 相似文献
18.
Solid-state reactions of equimolar mixtures of Bi2 O3 and Fe2 O3 from 625° to 830°C and their kinetics were investigated. The reaction rates were determined from the integrated X-ray diffraction intensities of the strongest peaks of the reactants and products. The activation energy for the formation of BiFeO3 was 96.6±9.0 kcal/mol; that for a second-phase compound, Bi2 Fe4 O9 , which formed above 675°C, was 99.4±9.0 kcal/mol. Specific rate constants for these simultaneous reactions were obtained. The preparation of single-phase BiFeO3 from the stoichiometric mixture of Bi2 O3 and Fe2 O3 is discussed. 相似文献
19.
M. F. YAN 《Journal of the American Ceramic Society》1980,63(7-8):443-447
Sintering and microstructural evolution were studied in Fe3 O4 as a model system for spinel ferrites. Fe3 O4 powder, purified by the salt-crystallization method, was sintered to ∼99.5% density in a CO-CO2 atmosphere. The p O2 Of the sintering atmosphere drastically affects the microstructure (grain size) of sintered Fe3 O4 without significantly affecting density. The measured grain-boundary mobilities, M , of Fe3 O4 fit the equation M=M 0 ( T ) p O2 −1/2 with M 0 ( T ) = 2.5×105 exp[-(609kJ·mol-1 / RT ](m/s)(N/m2 )−l . The grain-boundary migration process appeared to be pore-drag controlled, with lattice diffusion of oxygen as the most likely rate-limiting step. 相似文献
20.
A detailed study of the system PbO-Fe2 O3 , largely by X-ray diffraction analysis, has been made. The results indicate the existence of three intermediate phases: (1) a phase (beta) extending from PbO·5Fe2 O3 to PbO·6Fe2 O3 , (2) a phase (gamma) extending from PbO - 2Fe2 O3 to PbO -21/2 Fe2 O3 , and (3) a phase (delta) 2PbO·– Fe2 O3 . Structures are proposed for the beta and gamma phases that explain their solubility limits, magnetic properties, and very great similarity in structure and in lattice dimensions. 相似文献