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1.
Akira Kato Hisao Yamashita Hiroshi Kawagoshi Shimpei Matsuda 《Journal of the American Ceramic Society》1987,70(7):157-C
Mixtures of La2 O3 and Al2 O3 with various La contents were prepared by co-precipitation from La(NO3 )3 and Al(NO3 )3 solutions and calcined at 800° to 1400°C. The addition of small amounts of La2 O3 (2 to 10 mol%) to Al2 O3 gives rise to the formation of lanthanum β-alumina (La 2 O3 ·11–14Al2 O3 ) upon heating to above 1000°C and retards the transformation of γ-Al2 O3 to α-Al2 O3 and associated sintering. 相似文献
2.
Koji Tsukuma 《Journal of the American Ceramic Society》2000,83(12):3219-3221
Composites of β-Ce2 O3 ·11Al2 O3 and tetragonal ZrO2 were fabricated by a reductive atmosphere sintering of mixed powders of CeO2 , ZrO2 (2 mol% Y2 O3 ), and Al2 O3 . The composites had microstructures composed of elongated grains of β-Ce2 O3 ·11Al2 O3 in a Y-TZP matrix. The β-Ce2 O3 ·11Al2 O3 decomposed to α-Al2 O3 and CeO2 by annealing at 1500°C for 1 h in oxygen. The elongated single grain of β-Ce2 O3 ·11Al2 O3 divided into several grains of α-Al2 O3 and ZrO2 doped with Y2 O3 and CeO2 . High-temperature bending strength of the oxygen-annealed α-Al2 O3 composite was comparable to the β-Ce2 O3 ·11Al2 O3 composite before annealing. 相似文献
3.
Wioletta Kuncewicz-Kupczyk Dietmar Kobertz Miroslaw Miller Christian Chatillon Lorenz Singheiser Klaus Hilpert 《Journal of the American Ceramic Society》2002,85(9):2299-2305
The vaporization of the samples of the compositions Ga2 O3 + LaGaO3 , LaGaO3 + La4 Ga2 O9 , and La4 Ga2 O9 + La2 O3 was investigated using Knudsen effusion mass spectrometry in the temperature range 1494–1937 K. The partial pressures of the gaseous species O2 , Ga, GaO, Ga2 O, and LaO were determined over the samples investigated. The equilibrium partial pressures were used for the calculation of the thermodynamic activities of the components at 1700 K. Gibbs energies of formation of LaGaO3 ( s ) and La4 Ga2 O9 ( s ) at 1700 K from the component oxides were derived from the thermodynamic activities as −46.4 ± 4.7 and −99.2 ± 7.9 kJ·mol−1 , respectively. The results were compared with the literature data obtained using other methods. 相似文献
4.
Hwack Joo Lee Hyun Min Park Yang Koo Cho Sahn Nahm 《Journal of the American Ceramic Society》2003,86(8):1395-400
Microstructural characterizations on the (1− x )La2/3 TiO3 · x LaAlO3 (LTLA) system were conducted using transmission electron microscopy. The presence of La2 Ti2 O7 and La4 Ti9 O24 phases in pure La2/3 TiO3 is confirmed by the electron diffraction pattern. When x = 0.1, the ordering due to the A-site vacancies could be confirmed by the presence of antiphase boundaries (APBs) and return ½(100) superlattice reflection. As x increases, the ordering decreases and finally disappears when x = 0.6. The tilting of oxygen octahedra could be demonstrated by the presence of the ferroelastic domains in the matrix and return ½(111) and return ½(110) superlattice reflections in selected area electron diffraction patterns. In pure LaAlO3 , only the antiphase tilting of oxygen octahedra is present due to the presence of return ½(111) superlattice reflection. In the LTLA system of x = 0.1, both the antiphase and in-phase tiltings of the oxygen octahedra are involved; however, in the range of x from 0.3 to 0.9, the antiphase tilting of oxygen octahedra has appeared. The growth of the ferroelastic domains is influenced by the APBs in the matrix. 相似文献
5.
Debao Zhang Baoyu Chen Zhuping Liu Shunguang Li Lili Hu 《Journal of the American Ceramic Society》2004,87(12):2228-2231
Er3+ -doped sodium lanthanum aluminosilicate glasses with compositions of (90− x )(0.7SiO2 ·0.3Al2 O3 )· x Na2 O·8.2La2 O3 · 0.6Er2 O3 ·0.2Yb2 O3 ·1Sb2 O3 (in mol%) ( x = 12, 20, 24, 40, 60 mol%) were prepared and their spectroscopic properties were investigated. Judd–Ofelt analysis was used to calculate spectroscopic properties of all glasses. The Judd–Ofelt intensity parameter Ω t ( t = 2, 4, 6) decreases with increasing Na2 O. Ω2 decreases rapidly with increasing Na2 O while Ω4 and Ω6 decrease slowly. Both the fluorescent lifetime and the radiative transition rate increase with increasing Na2 O. Fluorescence spectra of the 4 I 13/2 to 4 I 15/2 transition have been measured and the change with Na2 O content is discussed. It is found that the full width at half-maximum decreases with increasing Na2 O. 相似文献
6.
MADELEINE H. WARZEE MARCEL MAURICE FRANZ HALLA WALTER R. RUSTON 《Journal of the American Ceramic Society》1965,48(1):15-17
In the binary system PbO–Laz O3 only one compound, 4PbO.La2 O3 , exists; it is flanked by two eutectics. The structure of the compound, although of lower symmetry, is intimately related to the C modification of the rare earths. Below 800° to 1000°C, metastable solid solutions are formed from oxide mixtures coprecipitated from mixed solutions of the nitrates, the cubic parameter a = 5.66 A, if extrapolated to pure La2 O3 , corresponding to half the a parameter of the C form of La2 O3 . The solid solutions existing between the compositions La2 O3 –2Pb0 and pure La2 O3 have a cubic face–centered lattice and obey Vegard's rule. The systems of PbO with Sm2 O3 and Gd2 O8 are quite similar to that with La2 O3 . The compound Sm2 O3 .4Pb0 decomposes at 1000°C with evaporation of PbO; Sm2 O3 remains in the B modification. 相似文献
7.
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
8.
Cristina Siligardi Luca Lusvarghi Monia Montorsi Cecilia Vernia 《Journal of the American Ceramic Society》2008,91(3):990-995
In this work several complementary techniques have been employed to carefully characterize the sintering and crystallization behavior of CaO–Al2 O3 –ZrO2 –SiO2 glass powder compacts after different heat treatments. The research started from a new base glass 33.69 CaO–1.00 Al2 O3 –7.68 ZrO2 –55.43SiO2 (mol%) to which 5 and 10 mol% Al2 O3 were added. The glasses with higher amounts of alumina sintered at higher temperatures (953°C [lower amount] vs. 987°C [higher amount]). A combination of the linear shrinkage and viscosity data allowed to easily find the viscosity values corresponding to the beginning and the end of the sintering process. Anorthite and wollastonite crystals formed in the sintered samples, especially at lower temperatures. At higher temperatures, a new crystalline phase containing ZrO2 (2CaO·4SiO2 ·ZrO2 ) appeared in all studied specimens. 相似文献
9.
Yttria-ceria-doped tetragonal zirconia (Y,Ce)-TZP)/alumina (Al2 O3 ) composites were fabricated by hot isostatic pressing at 1400° to 1450°C and 196 MPa in an Ar–O2 atmosphere using the fine powders prepared by hydrolysis of ZrOCl2 solution. The composites consisting of 25 wt% Al2 O3 and tetragonal zirconia with compositions 4 mol% YO1.5 –4 mol% CeO2 –ZrO2 and 2.5 mol% YO1.5 –5.5 mol% CeO2 –ZrO2 exhibited mean fracture strength as high as 2000 MPa and were resistant to phase transformation under saturated water vapor pressure at 180°C (1 MPa). Postsintering hot isostatic pressing of (4Y, 4Ce)-TZP/Al2 O3 and (2.5Y, 5.5Ce)-TZP/Al2 O3 composites was useful to enhance the phase stability under hydrothermal conditions and strength. 相似文献
10.
Mechanochemical Synthesis of Lanthanum Aluminate by Grinding Lanthanum Oxide with Transition Alumina 总被引:1,自引:0,他引:1
Grinding lanthanum oxide (La2 O3 ) with Al2 O3 was conducted to investigate their mechanochemical reactions to form lanthanum aluminate (LaAlO3 ) powder using a planetary ball mill. Grinding for 120 min allowed us to obtain single-phase LaAlO3 with a large surface area when transition alumina was used, whereas no formation of LaAlO3 was achieved when α-Al2 O3 was used. The mechanochemical process can be applied to synthesize other rare-earth (RE) aluminates (REAlO3 ) from mixtures of a rare-earth oxide and transition alumina. 相似文献
11.
Polyhedral Arrangements in Lanthanum Aluminoborate Glasses 总被引:3,自引:0,他引:3
Richard K. Brow David R. Tallant Gary L. Turner 《Journal of the American Ceramic Society》1997,80(5):1239-1244
We have used magic-angle spinning nuclear magnetic resonance (MAS NMR) and Raman spectroscopy to examine the polyhedral arrangements in ternary lanthanum aluminoborate glasses. We have characterized two glass-forming series: x Al2 O3 ·(1− x )LaB3 O6 and 0.25La2 O3 · y Al2 O3 (1− y )-B2 O3 . 11 B MAS NMR reveals a decrease in the fraction of four-coordinated boron atoms with increases in the Al2 O3 content in both series. 27 Al MAS NMR has detected four-, five- and six-coordinated aluminum atoms in complex aluminoborate networks similar to those reported elsewhere for alkaline-earth aluminoborate glasses. Raman spectroscopy reveals a variety of borate and aluminoborate moieties, including isolated groups as well as methaborate chains and rings. These results indicate that the La3+ ion acts as a modifier to the aluminoborate network. 相似文献
12.
The phase relations in the region of the Fe2 O3 - and Al2 O3 -rich sides of the quaternary system SrO─Fe2 O3 –Al2 O3 –B2 O3 and the location of conjugation lines between magnetoplumbite solid solution SrO·(6 − x)Fe2 O3 ·xAl2 O3 and corundum (α-Fe2 O3 , α-Al2 O3 ) phases were determined at 1100°C in air by using the flux-growth method based on the Ostwald ripening mechanism. Activity–composition relations and the lattice parameters along the magnetoplumbite solid solutions were also obtained. 相似文献
13.
Yasuhiro Shimizu Hideaki Okada Hiromichi Arai 《Journal of the American Ceramic Society》1989,72(3):436-440
The humidity-sensitive characteristics of La2 O3 –TiO2 –V2 O5 glass-ceramics were investigated as a function of additive amount of V2 O5 to the precursor glass and the heating temperature of the glass to iduce phase separation. The microstructure of each glass-ceramic was strongly dependent upon the heating temperature. The specific impedance was lowered by increasing the amount of V2 O5 additive. Among the elements studied, the LTV 2–2 element, which was prepared from as-cast glass, consisted of Na2 O:B2 O3 :La2 O3 : TiO2 : V2 O5 = 8.3:32.9:7.2:31.6:20.0 (molar ratio) after heating at 450°C for 12 h and subsequent leaching at 85°C for 24 h, and was found to be the most suitable material from the standpoint of humidity sensitivity, measurability, and response time. 相似文献
14.
Zhen-Kun Huang Shih-Yu Liu Anatoly Rosenflanz I-Wei Chen 《Journal of the American Ceramic Society》1996,79(8):2081-2090
Sintering aids with a formulation of rare-earth (R) melilite solid solution M'(R) have been introduced to several SiAlON composites to obtain high-density bodies by pressureless and gas-pressure sintering. These compositions include ones along the Si3 N4 –R2 O3 :9AlN line, which contain no Al2 O3 and are known to have excellent strength but very poor sinterability. Phase analysis and property (hardness, toughness, strength, and oxidation resistance) measurements reveal a complex set of structure–property–processing relationships that are composition-dependent. Of the most importance is the Al—O content in various phases, which is dictated by the starting composition as well as Al—O solubility in M'(R). This influences the sinterability, strength, and phase assemblage through the compositions of the intermediate liquid and the final β'-SiAlON. La2 O3 is further established as an effective sintering aid that does not affect the equilibrium phase assemblage. Overall, M'(R) and La2 O3 show promise as SiAlON sintering aids that allow high density to be achieved without compromising intrinsic mechanical and thermal properties. 相似文献
15.
A. T. PRINCE 《Journal of the American Ceramic Society》1951,34(2):44-51
The system MgO–Al2 O3 –2CaO·SiO2 comprises a plane through the tetrahedron CaO–MgO–Al2 O3 –SiO2 . A total of 108 compositions were prepared having an alumina content below the line joining 2CaO·Al2 O3 SiO2 (gehlenite) and MgO·Al2 O3 (spinel). Quenching experiments were carried out on 96 of these compositions at temperatures up to 1590°C. Three binary eutectic systems and two ternary eutectic systems are described. Compositions on this plane are of significance in an investigation of the constitution of basic refractory clinkers made from Canadian dolomitic magnesites. They also concern the compositions of certain blast furnace slags. 相似文献
16.
Byung-Hae Jung Do-Kyung Lee Sang-Ho Sohn Hyung-Sun Kim 《Journal of the American Ceramic Society》2003,86(7):1202-1204
Because of their thermal, dielectric, and optical properties, new glass compositions and thick-filmed transparent dielectrics containing neodymium oxide (Nd2 O3 ) were studied as a source of purer images in plasma display panels. In the present study, PbO–B2 O3 –SiO2 and PbO–B2 O3 –SiO2 –ZnO–Al2 O3 were used as starting glass compositions, to which up to 25 wt% of Nd2 O3 then was added. Increased amounts of Nd2 O3 increased the glass transition temperature and dielectric constant of the bulk glasses and decreased the coefficient of thermal expansion. The fired thick films (around 30 μm) allowed selectively visible light to penetrate and showed deep absorption properties at 585 nm that were related to an extraneous gas from neon discharge. 相似文献
17.
The ternary phase diagram of Al2 O3 -La2 O3 -TiO2 at 1400°C was determined with 12 compatibility triangles. Al2 O3 stabilizes the A-site-deficient La2/3 TiO3 perovskite structure. According to XRD and microstructural investigations, the solid solution extends along the La2/3 TiO3 -LaAlO3 tie line from at least 4 mol% LaAlO3 to pure LaAlO3 . With increasing LaAlO3 content, the stabilized La2/3 TiO3 structure changes from orthorombic via tetragonal to cubic. 相似文献
18.
Suitable Glass-Ceramic Sealant for Planar Solid-Oxide Fuel Cells 总被引:4,自引:0,他引:4
Sung-Bum Sohn Se-Young Choi Gyeung-Ho Kim Hue-Sup Song Goo-Dae Kim 《Journal of the American Ceramic Society》2004,87(2):254-260
Various glass-ceramics were prepared based on the BaO–Al2 O3 –B2 O3 –SiO2 system with the addition of La2 O3 , ZrO2 , or NiO in an attempt to develop a suitable sealant for planar solid-oxide fuel cells operating at 800°C. To estimate the applicability of these glasses as suitable sealants, their thermal and chemical stabilities as well as the crystallization behavior and bonding characteristics of their parent glasses were investigated. The thermal properties and crystallization behavior of the parent glasses were dependent on the type of additive used, and the bonding characteristics were strongly influenced by the B2 O3 /SiO2 value in the glass composition. Observation of microstructural change and chemical reaction at the glass-ceramic/electrolyte interface confirmed that the prepared glass-ceramics possessed long-term stability during heat treatment at the operation temperature for up to 1000 h. 相似文献
19.
Measurements of electrical resistance in the composition systems Al2 O3 –SiO2 , SiO2 –TiO2 , Al2 O3 –Cr2 O3 , and MgO–NiO were made using, in general, dry-pressed disks about 3 cm. in diameter and 0.4 cm. thick and fired to 1500°C. In the Al2 O3 –SiO2 series minimum resistance was shown by the samples containing 50% SiO2 , 50% Al2 O3 . The resistance of Al2 O3 was increased by the addition of small amounts of Cr2 O3 . The same effect was observed in the higher temperature range with small additions of NiO to MgO. In other instances the addition of the relatively inert SiO2 , Al2 O3 , and MgO to the semiconductors TiO2 , Cr2 O3 , and NiO resulted in a dilution effect. The resistance of Cr2 O3 was decreased by the addition of a slight amount of MgO. 相似文献
20.
Hong-Yang Lu Wei-Lin Wang Wei-Hsing Tuan Ming-Hong Lin 《Journal of the American Ceramic Society》2004,87(10):1843-1847
The microstructure of vitrified kaolin ceramic tapes has been studied via scanning and transmission electron microscopy (SEM and TEM). The sintered samples contained crystalline phase of predominantly stoichiometric mullite (3Al2 O3 ·2SiO2 ), which consisted of high aspect ratio, acicular crystals that are often referred to as secondary mullite. These crystals were interlocked and embedded in an aluminosilicate glass matrix of inhomogeneous composition. The glass matrix contained an average of ∼3.63 wt% K as determined by energy-dispersive X-ray analysis (EDS), whose composition could be approximated to 5Al2 O3 ·16SiO2 ·0.1MgO·0.3K2 O·0.15TiO2 ·0.12Fe2 O3 . The acicular crystals have approximately the stoichiometric composition of Al2 O3 :SiO2 = 3:2. They have grown along a specific crystallographic orientation along the [001] axis. The crystal growth front exhibited facetting on the {110) planes with microfacetting on both the {100) and {010) planes. 相似文献