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1.
A new phase was prepared from Bi2 O3 ·15 mol% PbF2 by heating it at 700°C and then quenching to room temperature. The crystal structure (tetragonal, a =0.765 and c = 1.77 nm, P42 /nmc) is related to that of the β-phase of Bi2 O3 by a supercell which is 3 times larger in the c direction. 相似文献
2.
Phase relations in the system Sc2 O3 -WO3 were characterized. Two stable binary compounds were, found. The 1:3 compound, SC2 (WO4 )3 , melts congruently at 1640°±10°C and forms a simple eutectic with WO3 at ∼90 mol% WO3 and 1309°+10°C. The 3 : 1 compound, Sc6 WO12 , forms a simple eutectic with the 1:3 compound at -69 mol% WO2 , and 1580°+10°C. The melting temperature of SC6 WO12 was >1600°C. 相似文献
3.
The existence of stable and metastable forms of 2ZrO2 ·P2 O5 and the subsolidus phase relations in the system ZrO2 -ZrP2 O7 were confirmed before investigation of the ternary system. The synthesis and thermal behavior of ZrW2 O8 were reinvestigated, and the system WO3 -P2 O5 was examined cursorily. A ternary compound, 2ZrO2 ·WO3 ·P2 O5 , was found, and compatibility triangles for the system between 1105° and 1150°C were established. The ternary compound is compatible with ZrO2 , WO3 , and three binary compounds, giving rise to five composition triangles. In addition, ZrP2 O7 , WO3 , and "W2 O3 (PO4 )2 " were compatible. 相似文献
4.
The Bi2 O3 -PbO phase diagram was determined using differential thermal analysis and both room- and high-temperature X-ray powder diffraction. The phase diagram contains a single eutectic at 73 mol% PbO and 635°C. A body-centered cubic solid solution exists above ∼600°C within a composition range of 30 to 65 mol% PbO. The compounds α-Bi2 O3 , σ5-Bi2 O3 , and γ-PbO (litharge) have wide solubility ranges. Four compounds, 6Bi2 O3 ·PbO, 3Bi2 O3 ·2PbO, 4Bi2 O3 ,5PbO, and Bi2 O3 ·3PbO, are formed in this system and the previously unreported X-ray diffraction patterns of the latter three compounds are reported. Diffraction patterns for some of these mixed oxides have been observed in ZnO-based varistors grown using Bi2 O3 and PbO as sintering aids. 相似文献
5.
Jin-Seong Kim Ngoc-Huan Nguyen Myung-Eun Song Jong-Bong Lim Dong-Soo Paik Sahn Nahm Jong-Hoo Paik Byung-Hyun Choi Soon-Jae Yu 《International Journal of Applied Ceramic Technology》2009,6(5):581-586
Bi2 O3 was added to a nominal composition of Zn1.8 SiO3.8 (ZS) ceramics to decrease their sintering temperature. When the Bi2 O3 content was <8.0 mol%, a porous microstructure with Bi4 (SiO4 )3 and SiO2 second phases was developed in the specimen sintered at 885°C. However, when the Bi2 O3 content exceeded 8.0 mol%, a liquid phase, which formed during sintering at temperatures below 900°C, assisted the densification of the ZS ceramics. Good microwave dielectric properties of Q × f =12,600 GHz, ɛr =7.6, and τf =−22 ppm/°C were obtained from the specimen with 8.0 mol% Bi2 O3 sintered at 885°C for 2 h. 相似文献
6.
Two cubic pyrochlore phases exist in the system ZnO–Bi2 O3 –Sb2 O5 . Neither has the supposed "ideal" stoichiometry, Zn2 Bi3 Sb3 O14 . One, P 1 , is a solid solution phase, Zn2+ x Bi2.96−( x − y ) Sb3.04− y O14.04+δ where 0< x <0.13(1), 0< y <0.017(2) and a =10.4285(9)−10.451(1) Å. The other, P 2 , is a line phase, Zn2 Bi3.08 Sb2.92 O13.92 with a =10.462(2) Å. Subsolidus phase relations at 950°C involving phases P 1 and P 2 in the ZnO–Bi2 O3 –Sb2 O5 phase diagram have been determined. 相似文献
7.
TAKESHI KIKUCHT 《Journal of the American Ceramic Society》1977,60(3-4):148-150
The subsolidus phase equilibria in the system Bi2 O3 -TiO2 -Nb2 O5 at 1100°C were determined by solid-state reaction techniques and X-ray powder diffraction methods. The system was found to contain 4 ternary compounds, i.e. Bi3 TiNbO9 , Bi7 Ti4 NbO21 , a cubic pyrochlore solid solution having a compositional range of 3Bi2 O3 · x TiO2 (7– x )Nb2 O5 where x ranges from 2.3 to 6.75, and an unidentified phase, 4Bi2 O3 ·11TiO2 ·5Nb2 O5 . 相似文献
8.
The existence of compounds between Si3 N4 -CeO2 and Si3 N4 -Ce2 O3 was investigated for firing temperatures of 1600° to 1700°C. The two new monoclinic compounds found were Ce2 O3 ·2Si3 N4 with lattice parameters a = 16.288, b = 4.848, and c =7.853 Å and β=91.54° and Ce4 Si2 O7 N2 with lattice parameters a = 10.360, b = 10.865, and c =3.974 Å and β=90.33°. Cerium orthosilicate (Ce 4.67 (SiO4 )3 O) is present during firing as a glassy intermediate phase which promotes sintering and densification and then reacts with silicon nitride to form cerium silicon oxynitrde (CeSiO2 N). 相似文献
9.
Grain growth in a high-purity ZnO and for the same ZnO with Bi2 O3 additions from 0.5 to 4 wt% was studied for sintering from 900° to 1400°C in air. The results are discussed and compared with previous studies in terms of the phenomenological kinetic grain growth expression: G n — G n 0 = K 0 t exp(— Q/RT ). For the pure ZnO, the grain growth exponent or n value was observed to be 3 while the apparent activation energy was 224 ± 16 kJ/mol. These parameters substantiate the Gupta and Coble conclusion of a Zn2+ lattice diffusion mechanism. Additions of Bi2 O3 to promote liquidphase sintering increased the ZnO grain size and the grain growth exponent to about 5, but reduced the apparent activation energy to about 150 kJ/mol, independent of Bi2 O3 content. The preexponential term K 0 was also independent of Bi2 O3 content. It is concluded that the grain growth of ZnO in liquid-phase-sintered ZnO-Bi2 O3 ceramics is controlled by the phase boundary reaction of the solid ZnO grains and the Bi2 O3 -rich liquid phase. 相似文献
10.
Phase stability, sinterability, and microwave dielectric properties of Bi2 W2 O9 ceramics and their cofireability with Ag, Cu, and Au electrodes have been investigated. Single-phase Bi2 W2 O9 powder was synthesized by solid-state reaction in air at 800°C for 3 days. X-ray powder diffraction data show Bi2 W2 O9 to have an orthorhombic crystal structure described by the noncentrosymmetric space group Pna 21 , with lattice parameters a =5.4401(8), b =5.4191(8), c =23.713(4) Å. Ceramics fired at temperatures up to 865°C remain single-phase but above this temperature ferroelectric Bi2 WO6 appears as a secondary phase. The measured relative permittivity of Bi2 W2 O9 ceramics increases continuously from 28.6 to 40.7 for compacts fired between 860° and 885°C. The bulk relative permittivity of Bi2 W2 O9 corrected for porosity was calculated as 41.3. Bi2 W2 O9 ceramics fired up to 875°C exhibit moderate quality factors, Q × f r , ∼7500–7700 GHz and negative temperature coefficient of resonant frequency, ∼−54 to −63 ppm/°C. Chemical compatibility experiments show Bi2 W2 O9 ceramics to react with both Ag and Cu electrodes, but to form good contacts with Au electrodes. 相似文献
11.
Susumu Nishigaki Shinsuke Yano Hiroshi Kato Takami Hirai Toshio Nonomura 《Journal of the American Ceramic Society》1988,71(1):11-C-
Microwave ceramic resonators composed of BaO-TiO2 -WO3 were developed. The effect of WO3 addition on the system of BaO·xTiO2 ·(1+x)yWO3 (x=4 and 4.5, y=0 to 0.04) was studied. The ceramics of this system are composed of crystallines including Ba2 Ti9 O20 , BaTi4 O9 , BaWO4 , and TiO2 . At y=0.02, the BaO·4TiO2 ·0.1WO3 ceramic was found to have excellent microwave properties such as ε=35, Q=8400 at 6 GHz, and nearly 0 ppm/°C of τf . 相似文献
12.
Tentative phase relations in the binary system BnOa-A12 O3 are presented as a prerequisite to the understanding of the system Li2 O-B2 O3 -Al2 O3 . Two binary compounds, 2A12 O3 .B2 O3 and 9A12 O3 .-2B2 O3 , melted incongruently at 1030° f 7°C and about 144°C, respectively. Two ternary compounds were isolated, 2Li2 O.A12 O3 .B2 O3 and 2Li2 O. 2AI2 O3 . 3B2 03 . The 2:1:1 compound gave a melting reaction by differential thermal analysis at 870°± 20° C, but the exact nature of the melting behavior was not determined. The 2:2:-3 compound melted at 790°± 20° C to Liz O.-5Al2 O3 and liquid. X-ray diffraction data for the compounds are presented and compatibility triangles are shown. 相似文献
13.
Yangyang Ji Jingkui Liang Sishen Xie Yude Yu 《Journal of the American Ceramic Society》1995,78(3):765-768
The "subsolidus" phase relations at room temperature in the system CaO-B2 O3 -BaO are investigated. Specimens of various compositions were prepared from appropriate ratios of CaCO3 , B2 O3 , and BaCO3 , and fired from 780° to 1040°C according to their melting points. There are three ternary compounds in this system. The crystal structures of these compounds were determined by X-ray diffraction (XRD). CaBa2 (BO3 )2 and Ca5 Ba2 B10 O22 are monoclinic structures. The lattice constants a = 14.221 Å, b = 4.569 Å, c = 11.926 A, β= 99.947°, and V = 763.4 å3 for CaBa2 (BO3 )2 and a = 15.714 å, b = 6.184 å, c = 10.204 å, β= 93.954°, and V = 989.29 å3 for Ca5 Ba2 B10 O22 are obtained. The third compound, CaBa2 (B3 O6 )2 , is isostructural with the high form of BaB2 O4 with lattice constants a = 7.167 å and c = 35.298 å. Powder second harmonic generation efficiencies of these ternary compounds were measured using a homemade apparatus. 相似文献
14.
Hyuk-Joon Youn Tomohiro Sogabe Clive A. Randall Tom R. Shrout Michael T. Lanagan 《Journal of the American Ceramic Society》2001,84(11):2557-2562
Dielectric properties and phase formation of Bi-based pyrochlore ceramics were evaluated for the Bi2 O3 –ZnO–Ta2 O5 system. The compositional range r Bi2 (Zn1/3 Ta2/3 )2 O7 · (1− r )(Bi3/2 Zn1/2 )(Zn1/2 Ta3/2 )O7 (0 ≤ r ≤ 1) in Bi2 O3 –ZnO–Ta2 O5 was investigated to determine the relative solubility of BZT cubic (α-BZT, r = 0) and the pseudo-orthorhombic (β-BZT, r = 1) end members. It was found that extrinsic factors, such as kinetically limited phase formation and bismuth loss, contribute to apparent phase boundaries in addition to thermodynamic stability of each phase. Considering this, the locations of true phase boundaries were r < 0.30 and r ≥ 0.74 for α and β phases, respectively. Dielectric constants between 58 and 80 and low dielectric loss (tan δ < 0.003) were measured for the complete compositional range. The temperature coefficient of capacitance was controlled by composition, which was found to be <30 ppm/°C at the edge of β-phase solid solution. In addition to the excellent dielectric properties these materials can be sintered at low temperatures, which make Bi-based pyrochlores promising candidates for high-frequency electronic applications. 相似文献
15.
J. P. COUTURES 《Journal of the American Ceramic Society》1985,68(3):105-107
A tentative phase diagram for the system Al2 03 -Nd2 O3 is presented. Three compounds were obtained: a β -A12 O3 -type compound, the perovskite NdAlO3 , and Nd4 Al2 O9 . The perovskite melts congruently (mp 2090°C), and the two other compounds exhibit incongruent melting behavior: β -Nd/Al2 O3 , mp 1900°C; Nd4 Al2 O9 , mp 1905°C. Two eutectics exist with the following compositions and melting points: 80 mol% Al2 O3 , 1750°C; 23 mol% Al2 O3 ,1800°C. Nd4 Al2 O9 decomposes in the solid state at 1780°C. 相似文献
16.
Doreen D. Edwards Pollyanna E. Folkins Thomas O. Mason 《Journal of the American Ceramic Society》1997,80(1):253-257
Subsolidus phase relationships in the Ga2 O3 –In2 O3 system were studied by X-ray diffraction and electron probe microanalysis (EPMA) for the temperature range of 800°–1400°C. The solubility limit of In2 O3 in the β-gallia structure decreases with increasing temperature from 44.1 ± 0.5 mol% at 1000°C to 41.4 ± 0.5 mol% at 1400°C. The solubility limit of Ga2 O3 in cubic In2 O3 increases with temperature from 4.X ± 0.5 mol% at 1000°C to 10.0 ± 0.5 mol% at 1400°C. The previously reported transparent conducting oxide phase in the Ga-In-O system cannot be GaInO3 , which is not stable, but is likely the In-doped β-Ga2 O3 solid solution. 相似文献
17.
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
18.
pela Kunej Sreo D. kapin Danilo Suvorov 《Journal of the American Ceramic Society》2009,92(10):2373-2377
In this study we used solid-state synthesis to determine the phase relations in the pyrochlore-rich part of the Bi2 O3 −TiO2 −Nd2 O3 system at 1100°C. The samples were analyzed using X-ray powder diffraction and scanning electron microscopy with energy- and wavelength-dispersive spectroscopy. A single-phase pyrochlore ceramic was obtained with the addition of 4.5 mol% of Nd2 O3 . We determined the solubility limits for the three solid solutions: (i) the pyrochlore solid solution Bi(1.6–1.08 x ) Nd x Ti2 O(6.4+0.3 x ) , where 0.25< x <0.96; (ii) the solid solution Bi4− x Nd x Ti3 O12 , where 0< x <2.6; and (iii) the Nd2− x Bi x Ti2 O7 solid solution, where 0< x <0.35. The determined phase relations in the pyrochlore-rich part are presented in a partial phase diagram of the Bi2 O3 −TiO2 −Nd2 O3 system in air at 1100°C. 相似文献
19.
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
20.
David H. Chmielewski Kenneth H. Sandhage 《Journal of the American Ceramic Society》1995,78(9):2504-2512
Bi2 Sr2 Ca2 Cu2 O8±δ -type compound thick films were exposed to oxygen-argon-gas mixtures (1% to 20% oxygen gas) at elevated pressures (up to 207 MPa) and temperatures (500° to 940°C) for times ranging from 5 to 96 h. At a sufficiently high oxygen fugacity and temperature, Bi2 Sr2 Ca1 Cu2 O8±δ decomposed via a solid-state reaction. Room-temperature X-ray diffractometry and electron probe microanalysis of decomposed films revealed the presence of Bi2 (Sr,Ca)2 -Cu1 O6±θ ro-type compound, Bi2 Sr2 ,Ca1 O8±δ -type compound, and CuO. Bi2 Sr2 Ca1 Cu2 O8±δ decomposition was accompanied by a modest weight gain, which was consistent with an oxidation reaction. The solid-state decomposition reaction could be reversed by heat treatment of decomposed films at 860°C in pure, flowing oxygen at ambient pressure. 相似文献