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1.
Elena R. Andrievskaya Lidiya M. Lopato 《Journal of the American Ceramic Society》1992,75(11):3026-3032
Phase equilibria in the system HfO2 –Y2 O3 –CaO were studied in the temperature range 1250° to 2850°C by both experimental methods (X-ray phase analysis at 20° to 2000°C, petrography, annealing and quenching, differential thermal analysis in He at temperatures to 2500°C, thermal analysis in air using a solar furnace at temperatures to 3000°C, and electron microprobe X-ray analysis) and theoretical means (development of a mathematical model for the liquidus surface by means of the reduced polynomial method). Phase equilibria were determined by the structure of the restricting binary systems. No ternary compounds were found. The liquidus was characterized by the presence of six four-phase, invariant equilibria. Solid solutions were based on monoclinic (M), tetragonal (T), and cubic (F) modifications of HfO2 ; C and H forms of Y2 O3 ; CaO; and CaHfO3 that crystallized in two polymorphous modifications, namely, the cubic and rhombic perovskite-type structure. 相似文献
2.
The phase diagram of the Al2 O3 –ZrO2 –Sm2 O3 system was constructed in the temperature range 1250°–2800°C. The phase transformations in the system are completed in eutectic reactions. No ternary compounds or regions of appreciable solid solution were found in the components or binaries in this ternary system. Two new ternary and one new binary eutectics were found. The minimum melting temperature is 1680°C and it corresponds to the ternary eutectic Al2 O3 +F-ZrO2 +SmAlO3 . The solidus surface projection, the schematic of the alloy crystallization path, and the vertical sections present the complete phase diagram of the Al2 O3 –ZrO2 –Sm2 O3 system. 相似文献
3.
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
4.
The Al2 O3 ZrO2 Y2 O3 system was studied in the range of temperatures 1600°–2800°C by methods of X-ray analysis at 20°C, petrography, DTA in He at temperatures to 2500°C, thermal analysis in air using a solar furnace at temperatures to 3000°C, and electron microprobe X-ray analysis. The stable and metastable phase diagrams were constructed. The liquidus and solidus projections, crystallization paths for the alloys, and polythermal sections are presented in the article. The structure of the restricting systems defines the phase equilibria in the ternary system. No ternary compounds were found. The metastable phase relations were caused by the ambivalent behavior of Y3 Al5 O12 during crystallization. 相似文献
5.
Michael Rozumek Peter Majewski Linda Sauter Fritz Aldinger 《Journal of the American Ceramic Society》2003,86(11):1940-1946
Phase stability studies were performed within the quasi-ternary system LaGaO3 -SrGaO2.5 -"LaMgO2.5 ". Emphasis was cast on the temperature dependence of the homogeneity region of La1− x Sr x Ga1− y Mg y O3−δ perovskite solid solutions. Isothermal sections were determined at 1100°, 1250°, 1400°, and 1500°C in a static air atmosphere. The single-phase homogeneity region was found to considerably diminish with decreasing temperature, indicating a reduction of the solid solubility of Sr and Mg, and below 1100°C the doped perovskite becomes unstable. Consequently, the cubic perovskite phase was found to exist only at elevated temperatures and for high Sr and Mg amounts. Sample preparation was performed by the mixed-oxide process as well as by a modified combustion synthesis. 相似文献
6.
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
7.
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
8.
Jalajakumari Nair Padmakumar Nair Fujio Mizukami Jan G. Van Ommen Giel B. M. Doesburg Julian R. H. Ross Anthonie J. Burggraaf 《Journal of the American Ceramic Society》2000,83(8):1942-1946
Pure Al2 O3 and different compositions of La2 O3 –Al2 O3 samples have been prepared through coprecipitation. Even after heating at 1300°C, the compositions La2 O3 ·11Al2 O3 and La2 O3 ·13Al2 O3 had higher surface area compared to the pure Al2 O3 and the La2 O3 ·Al2 O3 composition. Ethanol washing is an effective way for improving the textural stability of pure Al2 O3 and La2 O3 –Al2 O3 samples. The effect of steam on the thermal stability of La2 O3 ·11Al2 O3 has also been studied. La2 O3 ·11Al2 O3 sample is found to be stable in steam. 相似文献
9.
Marianne Færøyvik Tor Grande Stein Julsrud Arne Seltveit 《Journal of the American Ceramic Society》1999,82(1):190-196
The phase diagram of the pseudoternary reciprocal system NaF–CaF2 –NaAlSiO4 –CaAl2 Si2 O8 is reported in this paper. The phase relations in the system have been investigated by differential thermal analysis, quenching melts, X-ray diffractometry, and optical and electron microscopies. The stable diagonal CaF2 –NaAlSiO4 divides the system in two pseudoternary systems. The solidus temperatures in the two subsystems NaF–CaF2 –NaAlSiO4 and CaF2 –NaAlSiO4 –CaAl2 Si2 O8 are 805°± 2°C and 1095°± 4°C, respectively. An extensive region of liquid–liquid immiscibility is evident in the NaF–CaF2 –NaAlSiO4 subsystem. The compositions of the two liquids fall outside the compositional surface NaF–CaF2 –NaAlSiO4 –CaAl2 Si2 O8 , but only a small deviation from the ternary behavior is observed. 相似文献
10.
K. G. Vasantha Kumari P. Divya Vasu Viswanathan Kumar Thangavelu Asokan 《Journal of the American Ceramic Society》2002,85(3):703-705
Formation of spinel phases in ZnO–Sb2 O3 and ZnO–Sb2 O3 –Bi2 O3 systems is studied by the use of X-ray diffraction. The formation of nonstoichiometric Zn2.33 Sb0.67 O4 phase is observed in both the systems at ∼900°C. However, in these systems, at higher temperatures ( T ≥ 1100°C), formation of the inverse spinel phase Zn7 Sb2 O12 is observed. The study has been extended to understand the effect of CrO3 doping on the stability of the different spinel phases in the previously mentioned systems. Interestingly, in both the systems, samples doped with CrO3 , displayed the presence of Zn2.33 Sb0.67 O4 phase <1200°C, indicating the stabilization of the spinel phase by CrO3 . 相似文献
11.
The thermodynamic data for the YO1.5 –BaO, BaO-CuOx , and YO1.5 –CuOx quasi-binary systems were optimized from experimental phase diagrams. They were used to calculate tentative phase diagrams for the YO1.5 –BaO—CuOx quasi-ternary system. The equilibrim liquidus surface and the isothermal sections of the ternary system at 900°, 925°, 950°, 975°, and 1000°C were calculated. The isopleths containing YBa2 Cu3 O7-δ were also calculated. 相似文献
12.
The Bi2 O3 –Nb2 O5 –NiO phase diagram at 1100°C was determined by means of solid-state synthesis, X-ray diffraction, and scanning electron microscopy. A ternary eutectic with a melting point below 1100°C was found to exist in the field between NiO, Bi2 O3 , and the end-member of the δBi2 O3 –Nb2 O5 solid solution. The existence of the previously reported Bi3 Ni2 NbO9 phase was disproved. A pyrochlore homogeneity range around Bi1.5 Ni0.67 Nb1.33 O6.25 was determined together with all the phase relations in this phase diagram. 相似文献
13.
Teresa Durán Sara Serena Pilar Pena Ángel Caballero Salvador De Aza Antonio H. De Aza 《Journal of the American Ceramic Society》2008,91(2):535-543
The isoplethal sections CaAl2 O4 –MgO and CaAl4 O7 –MgO of the Al2 O3 –MgO–CaO ternary system have been experimentally established at 1 bar total pressure and air of normal humidity. The sections obtained provide new data and information that are in disagreement with thermodynamic evaluations and optimizations of the Al2 O3 –MgO–CaO ternary system published to date. These differences arise mainly from the inclusion, or exclusion, of the binary compound Ca12 Al14 O33 , mayenite, as a stable phase in the reported studies of the system. The presence or absence of this compound within the system has an important impact on the solid state and melting relationships of the whole ternary system. The present study confirms the solid-state compatibility CaAl2 O4 –MgO and CaAl2 O4 –MgO–MgAl2 O4 up to 1372°± 2°C, the peritectic melting point of the later mentioned subsystem. 相似文献
14.
Sara Serena Maria Antonia Sainz Angel Caballero 《Journal of the American Ceramic Society》2004,87(12):2268-2274
Phase relations in the ternary system ZrO2 –CaO–MgO were experimentally established at 1600°, 1700°, and 1750°C. The investigation was based on powder X-ray diffractometry, scanning electron microscopy–energy dispersive spectroscopy, and electron probe microanalysis, on 24 ternary compositions. The compositions were prepared using attrition milling of respective oxides and carbonates as raw materials. The results obtained allowed construction of the corresponding isothermal sections, which verified the existence of the cubic-ZrO2 –CaZrO3 phase compatibility field at the three temperatures. Finally, experimental results also were compared with the thermodynamic assessment previously reported of the system ZrO2 –CaO–MgO. 相似文献
15.
Perovskite lead hafnate (PbHfO3 , PH) nanoparticles that were free from halides and organics were synthesized via the oxidant peroxo method. Stoichiometric amounts of hafnium nitrate (HfO(NO3 )2 ) and lead nitrate (PbHfO3 ) were dissolved in a diluted hydrogen peroxide (H2 O2 ) aqueous solution, which was slowly added to a solution of H2 O2 and ammonia (NH3 ) (pH 11). The lead–hafnium precipitate obtained was filtered and washed, to eliminate all nitrate ions. The precipitate was dried, ground, and calcined at temperatures of 400°–900°C. A tetragonal intermediate phase was identified using X-ray diffractometry and Raman spectroscopy during the calcination process, followed by the crystallization of the orthorhombic PH phase at ∼700°C. 相似文献
16.
Daijitsu Harada Yukio Hinatsu Nobuyuki Masaki Akio Nakamura 《Journal of the American Ceramic Society》2002,85(3):647-652
Powder X-ray diffractometry (XRD) and 151 Eu Mössbauer spectroscopy were performed for samples prepared in the temperature range 1500–1500°C for the hafnia–europia (HfO2 –Eu2 O3 ) system Eu x Hf1− x O2− x /2 (0 ≤ x ≤ 1.0). The XRD results showed that two types of solid solution phases formed in the composition range 0.25 ≤ x ≤ 0.725: an ordered pyrochlore-type phase in the middle-composition range (0.45 < x < 0.575) and a disordered fluorite-type phase, enveloping the pyrochlore-type phase on both sides, in the composition ranges 0.25 ≤ x ≤ 0.40 and 0.60 ≤ x ≤ 0.725. 151 Eu Mössbauer spectroscopy sensitively probes local environmental changes around trivalent europium (Eu3+ ) caused by the formation of these solid solution phases. In addition to the broad, single Mössbauer spectra observed in this study for the Eu3+ , the values of isomer shift (IS) exhibited a pronounced minimum in the neighborhood of the stoichiometric pyrochlore phase ( x ≈ 0.5). Such IS behavior of Eu3+ was interpreted based on the XRD crystallographic information that the ordered pyrochlore phase has a longer (in fact, the longest) average Eu–O bond length than those of the disordered fluorite phases on both sides or the monoclinic (and C-type) Eu2 O3 at x = 1.0. 相似文献
17.
Eric R. Vance Clifford J. Ball Bruce D. Begg Melody L. Carter R. Arthur Day Gordon J. Thorogood 《Journal of the American Ceramic Society》2003,86(7):1223-1225
Trivalent Pu can be incorporated in the silicate apatite structure to form Ca2 Pu8 (SiO4 )6 O2 by sintering under reducing conditions, while the incorporation of tetravalent Pu in the Ca/rare earth sites in oxidizing or neutral conditions is limited to only 0.6 formula units (f.u.). The d -spacings and intensities of the X-ray pattern of hexagonally structured Ca2 Pu8 (SiO4 )6 O2 after firing at 1250°C are given, and the a and c lattice parameters are 0.95611 and 0.70281 nm, respectively. The respective solid solubility limits of U and Hf in Ca2 Gd8– x (U/Hf) x (SiO4 )6 O2 apatite samples were 0.3 and 0.2 f.u. 相似文献
18.
The crystalline nature and expansion characteristics of compositions in the region surrounding the cordierite area of the system MgO–Al2 O3 –SO2 were investigated. The selected compositions were fired to temperatures of 1250°, 1300°, 1350°, and 1400°C., and the thermal expansion characteristics were determined with the interferometer. Coefficients of linear thermal expansion were determined in the temperature range of 20° to 300°C. and were found to lie between 9.8 ± 10–7 and 50.5 ± 10–7 . The qualitative, as well as the quantitative, determination of crystalline constituents was made utilizing strontium fluoride as an internal standard in the X-ray spectrometer. In the compositions studied crystalline cordierite ranged from 38 to 97%. There was a close correlation between the linear thermal expansion coefficient and the crystalline cordierite content of the bodies. 相似文献
19.
Phase Relations and Volume Changes of Hafnia under High Pressure and High Temperature 总被引:1,自引:0,他引:1
Osamu Ohtaka Hiroshi Fukui Taichi Kunisada Tomoyuki Fujisawa Kenichi Funakoshi Wataru Utsumi Tetsuo Irifune Koji Kuroda Takumi Kikegawa 《Journal of the American Ceramic Society》2001,84(6):1369-1373
Using multi-anvil high-pressure devices and synchrotron radiation, X-ray in situ observations of HfO2 under high pressure and high temperature have been performed to investigate its phase relations and compression behavior. An orthorhombic phase (orthoI) is stable from 4 to 14.5 GPa below 1250°–1400°C and transforms to a tetragonal phase, which is one of the high-temperature forms of HfO2 , above these temperatures. Another orthorhombic phase (orthoII) with a cotunnite-type structure appears above 14.5 GPa. OrthoII is stable up to 1800°C at 21 GPa. OrthoII is quenchable to ambient conditions. The orthoI-to-orthoII transition is accompanied by ∼8 vol% decrease. The bulk moduli of orthoI and orthoII at room temperature are 220 and 312 GPa, respectively. This low compressibility of orthoII indicates that it is a potential candidate for very hard materials. 相似文献
20.
La0.8 Sr0.2 Cr0.9 Ti0.1 O3 perovskite has been designed as an interconnect material in high-temperature solid oxide fuel cells (SOFCs) because of its thermal expansion compatibility in both oxidizing and reducing atmospheres. La0.8 Sr0.2 Cr0.9 Ti0.1 O3 shows a single phase with a hexagonal unit cell of a = 5.459(1) Å, c = 13.507(2) Å, Z = 6 and a space group of R -3 C . Average linear thermal expansion coefficients of this material in the temperature range from 50° to 1000°C were 10.4 × 10−6 /°C in air, 10.5 × 10−6 /°C under a He–H2 atmosphere (oxygen partial pressure of 4 × 10−15 atm at 1000°C), and 10.9 × 10−6 /°C in a H2 atmosphere (oxygen partial pressure of 4 × 10−19 atm at 1000°C). La0.8 Sr0.2 Cr0.9 Ti0.1 O3 perovskite with a linear thermal expansion in both oxidizing and reducing environments is a promising candidate material for an SOFC interconnect. However, there still remains an air-sintering problem to be solved in using this material as an SOFC interconnect. 相似文献