共查询到20条相似文献,搜索用时 250 毫秒
1.
Yaping Zhang Yunxia Yang Yuwen Ou Wei Hua Jiahua Zheng Guorong Chen 《Journal of the American Ceramic Society》2009,92(8):1881-1883
Glasses with compositions 50Bi2 O3 – x Sb2 O3 –10B2 O3 –(40– x ) SiO2 ( x =0, 1, 3, 5, 8, 10) have been prepared by conventional melt quench technique. Substitution of Sb2 O3 for SiO2 exerted an obvious effect on properties of glasses, especially, increased glass transition temperature ( T g ) and crystalline temperature ( T c ) greatly. Results of infrared transmission spectra attributed the effect to the formation of new bridging bonds of Sb–O–B and Sb–O–Si in glass network. 相似文献
2.
Yong Yan Jan E. Evetts Jin-li Zhang William M. Stobbs 《Journal of the American Ceramic Society》2000,83(5):1266-1272
The microstructure of partial-melt-processed YBa2 Cu3 O x /HfO2 has been studied by transmission electron microscopy. A characteristic spherulitic microstructure is formed in the system. A model for the growth mechanism has been proposed. The critical heterogeneous nucleation of the YBa2 Cu3 O x phase appears to occur from the melt in an epitaxially controlled manner on CuO particles. Subsequent growth of YBa2 Cu3 O x platelets from the nucleus region is repeatedly interrupted by the nucleation of hafnium-rich phases in the liquid at the solid/liquid interface in a manner that again appears to be epitaxially controlled and that promotes the splay of the c orientation of the YBaCuO grain. 相似文献
3.
Won-Hyuk Lee Yoshihiro Abe Eikichi Inukai 《Journal of the American Ceramic Society》1993,76(4):849-856
Ag2 O-doped superconducting Bi2 Sr2 Ca1 Cu2 O x ceramics were prepared by a melt-quenching–reheating method. It is found that the Ag2 O-doped, as-cast specimens exhibit superconductivity ( T c = around 80 K) by heat treatment at temperatures around 800°C even in an evacuated and sealed silica glass tube, while the undoped specimens do not and vaporize by the corresponding heat treatment. Conversion of the Ag2 O-doped, as-cast specimens into superconducting ceramics when heated in an evacuated vessel is explained in terms of the oxygen donor of Ag2 O in the specimen. This finding enables us to fabricate a desired shape of superconducting Bi2 Sr2 Ca1 Cu2 O x ceramics sealed in metals or glasses. The addition of Ag2 O to Bi2 Sr2 Ca1 Cu2 O x melt, however, had deleterious influences on the superconducting properties ( T c and J c ) of the resultant ceramics when obtained by heat treatment in air. 相似文献
4.
Tsuyoshi Honma Yasuhiko Benino Takumi Fujiwara Takayuki Komatsu Ryuji Sato 《Journal of the American Ceramic Society》2005,88(4):989-992
The glass formation region, crystalline phases, second harmonic (SH) generation, and Nd:yttrium aluminum garnet (YAG) laser-induced crystallization in the Sm2 O3 –Bi2 O3 –B2 O3 system were clarified. The crystalline phases of Bi4 B2 O9 , Bi3 B5 O12 , BiBO3 , Sm x Bi1− x BO3 , and SmB3 O6 were formed through the usual crystallization in an electric furnace. The crystallized glasses consisting of BiBO3 and Sm x Bi1− x BO3 showed SH generations. The formation of the nonlinear optical BiB3 O6 phase was not confirmed. The formation (writing) region of crystal lines consisting of Sm x Bi1− x BO3 by YAG laser irradiation was determined, in which Sm2 O3 contents were∼10 mol%. The present study demonstrates that Sm2 O3 –Bi2 O3 –B2 O3 glasses are promising materials for optical functional applications. 相似文献
5.
The dissolution of (Al, Cr)2 O3 into CaO—MgO—Al2 O3 —SiO2 melts, under static and forced-convective conditions was investigated at 1550°C in air. With sufficient MgO in the melt, or sufficient Cr2 O3 in (Al, Cr)2 O3 , a layer consisting of a spinel solid solution, Mg(Al, Cr)2 O4 , formed at the (Al, Cr)2 O3 /melt interface. The dissolution kinetics of 1.5 and 10 wt% Cr2 O3 specimens were determined as a function of immersion time, specimen rotation rate, and magnesia content of the melt. Electron microprobe analysis was used to characterize concentration gradients in the (Al, Cr)2 O3 sample, the Mg(Al, Cr)2 O4 spinel, or in the melt after immersion of specimens containing 1.5 to 78 mol% Cr2 O3 . The dissolution kinetics and microprobe analyses indicated that a steady-state condition was reached during forced-convective, indirect (Al, Cr)2 O3 dissolution such that spinel layer formation was rate limited by solid-state diffusion through the spinel layer and/or through the specimen, and spinel layer dissolution was rate limited by liquid-phase diffusion through a boundary layer in the melt. This is consistent with a model previously developed for the indirect dissolution of sapphire in CMAS melts. 相似文献
6.
On the join LiCrO2 -LiAlO2 , solid solutions of formulas LiCri- x Al x O2 (0< x <0.6) form. On the spinel join LiAl5 O8 -"LiCr5 O8 ," solid solutions of formulas LiAl5- x Al x O8 (0< x <3) form and the order-disorder transition, observed in LiAl5 O8 at 1295°C, occurs at increasingly lower temperatures with increasing Cr content. No evidence was found for the metastable polymorphs of LiAl5 O8 reported by Datta and Roy. Ternary subsolidus equilibria at 1200° to 1300°C were determined for compositions containing <50% Li2 O. 相似文献
7.
A partial molar volume technique was used to estimate the coordination number of oxygen ions around a boron ion in PbO·2B2 O3 and BaO·2B2 O3 melts. The boron coordination number appeared to be lower in the melt than in the crystal of PbO·2B2 O3 , whereas it was nearly the same in the melt and crystal of BaO·2B2 O3 . 相似文献
8.
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
9.
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
10.
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
11.
JUN'ICHI NAKANO TOMOAKI YAMADA SHINTARO MIYAZAWA 《Journal of the American Ceramic Society》1979,62(9-10):465-467
In the ternary system Li2 O-Nd2 O3 -P2 05 , part of the phase diagram relevant to the growth of single LindP4 O12 (LNP) crystals was examined. LNP melts incongruently and decomposes into NdP3 O9 and liquid at the peritectic temperature of 970°C. For the crystal growth, an Li2 O-P2 O5 mixture should be used as a flux. The melt compositions from which LNP nucleates were clarified. 相似文献
12.
Stoichiometric NiAl2 O4 , CuAl2 O4 , and ZnAl2 O4 spinels were prepared and equilibrated at temperatures from 600° to 1400°C. The parameters u and x , denoting the oxygen position and fraction of divalent cations on tetrahedral sites, respectively, were determined from a detailed X-ray diffraction analysis. In NiAl2 O4 , x increased from 0.07 at 595° to 0.26 at 1391°C; in CuAl2 O4 , x decreased from 0.68 at 613° to 0.64 at 1195°C; and in ZnAl2 O4 , x decreased from 0.96 at 905° to 0.94 at 1197°C. The form of the temperature dependence of x could not be described using theoretically based equations advanced in the literature. A more general equation which allows for a non-distributional contribution to the configurational entropy was derived and observed to properly describe the temperature dependence; the results indicate that short-range order is of definite significance in these intermediate aluminate spinels. 相似文献
13.
Jin-Ho Lee Masatomo Yashima Masato Kakihana Masahiro Yoshimura 《Journal of the American Ceramic Society》1998,81(4):894-900
The phase equilibria in the Y2 O3 -Nb2 O5 system have been studied at temperatures of 1500° and 1700°C in the compositional region of 0-50 mol% Nb2 O5 . The solubility limits of the C-type Y2 O3 cubic phase and the YNbO4 monoclinic phase are 2.5 (±1.0) mol% Nb2 O5 and 0.2 (±0.4) mol% Y2 O3 , respectively, at 1700°C. The fluorite (F) single phase exists in the region of 20.1-27.7 mol% Nb2 O5 at 1700°C, and in the region of 21.1-27.0 mol% Nb2 O5 at 1500°C, respectively. Conductivity of the Y2 O3 - x mol% Nb2 O5 system increases as the value of x increases, to a maximum at x = 20 in the compositional region of 0 ≤ x ≤ 20, as a result of the increase in the fraction of F phase. In the F single-phase region, the conductivity decreases in the region of 20-25 mol% Nb2 O5 , because of the decrease in the content of oxygen vacancies, whereas the conductivity at x = 27 is larger than that at x = 25. The conductivity decreases as the value of x increases in the region of 27.5 ≤ x ≤ 50, because of the decrease in the fraction of F. The 20 mol% Nb2 O5 sample exhibits the highest conductivity and a very wide range of ionic domain, at least up to log p O 2 =−20 (where p O 2 is given in units of atm), which indicates practical usefulness as an ionic conductor. 相似文献
14.
Bhaskar Brahmaroutu Gary L. Messing Susan Trolier-McKinstry 《Journal of the American Ceramic Society》1999,82(6):1565-1568
Growth of Sr2 Nb2 O7 particle size in KCl melts occurs by reaction on insoluble Nb2 O5 particles in the melt. Thus, Sr2 Nb2 O7 size is controlled by the initial size of the reactants. By altering the reactant composition to include larger Nb-rich reactants such as SrNb2 O6 , 5-30 µm, anisotropic Sr2 Nb2 O7 particles are formed. 相似文献
15.
CaO and Ga2 O3 form three compounds: 3CaO-Ga2 O3 , CaO-Ga2 O3 , and CaO-2Ga2 O3 . 3CaO-Ga2 O3 melts incongruently to CaO plus liquid at 1263°C.; CaO Ga2 O3 and CaO 2Ga2 O3 melt congruently at 1369° and 1504°C. respectively. Eutectics are located at the following temperatures and compositions (in mole% Ga2 O3 ): between 3CaO Ga2 O3 and CaO Ga2 O3 , 1245°C. and 37.5%; between CaO Ga2 O3 and CaO-2Ga2 O3 ,1323o C. and 57.0%; and between CaO -2Ga2 O3 and β-Ga2 O3 ,1457°C. and 68.0%. There is a peritectic at 1263°C. and 36.0%. Three polymorphs of CaO Ga2 O3 are described. Compositions from approximately 35 to 70 mole% Ga2 O3 can be quenched to yield homogeneous glasses. 相似文献
16.
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
17.
The phase relations for the Sc2 O3 -Ta2 O5 system in the composition range of 50-100 mol% Sc2 O3 have been studied by using solid-state reactions at 1350°, 1500°, or 1700°C and by using thermal analyses up to the melting temperatures. The Sc5.5 Ta1.5 O12 phase, defect-fluorite-type cubic phase (F-phase, space group Fm 3 m ), ScTaO4 , and Sc2 O3 were found in the system. The Sc5.5 Ta1.5 O12 phase formed in 78 mol% Sc2 O3 at <1700°C and seemed to melt incongruently. The F-phase formed in ∼75 mol% Sc2 O3 and decomposed to Sc5.5 Ta1.5 O12 and ScTaO4 at <1700°C. The F-phase melted congruently at 2344°± 2°C in 80 mol% Sc2 O3 . The eutectic point seemed to exist at ∼2300°C in 90 mol% Sc2 O3 . A phase diagram that includes the four above-described phases has been proposed, instead of the previous diagram in which those phases were not identified. 相似文献
18.
Phase equilibria data, obtained both by differential thermal analysis and by quenching, are presented for the system Na2 O-Nb2 O5 . Five compounds corresponding to the formulas 3Na2 O.1Nb2 06 , lNa2 O. 1Nb2 O5 , lNa2 O 4Nb2 O6 , lNaz O.7Nb2 O5 , and lNa2 O. 10Nb2 O6 have been found. The compound 3Naz 0.lNb2 O5 melts congruently at 992°C. The compounds 1Na2 O. 4Nb2 O6 , lNa2 O.7Nb2 O, and 1Na2 O. 1Onb2 O5 melt incongruently at 1265°, 1275°, and 1290°C., respectively. The well-known perovskite structure phase NaNbO3 was found to melt congruently at 1412°C. The transition temperatures in NaNbO5 were checked by thermal analysis and only the major structural changes at 368° and 640°C. could be detected. A new disordered form of NaNbO3 could be preserved to room temperature by very rapid quenching. 相似文献
19.
Osamu Yokota Masatomo Yashima Naoki Yamamoto Masahiro Yoshimura 《Journal of the American Ceramic Society》1997,80(9):2429-2432
Melts of x mol% Ta2 O5 –Y2 O3 (x = 0–32.5) were rapidly quenched to investigate the formation of metastable fluorite solid solutions. C-type Y2 O3 , fluorite, and fergusonite phases existed in the compositional regions of 0 x 16, 8 x 32.5, and 27.5 x 32.5, respectively. Their lattice parameters were precisely measured through either Rietveld analysis or a least-squares fit of the individual X-ray diffraction peak positions. The lattice parameter of the fluorite phase decreased linearly with increasing Ta2 O5 content, strongly suggesting the formation of compositionally homogeneous metastable solid solutions. Ta2 O5 was almost insoluble into Y2 O3 at 1700°C in the equilibrium state. 相似文献
20.
Terry J. Garino Tina M. Nenoff Tae-Jin Park Alexandra Navrotsky 《Journal of the American Ceramic Society》2009,92(9):2144-2146
Barium (Ba)-substituted CsTiSi2 O6.5 materials of two types, Cs x Ba1− x TiSi2 O(7− x /2) and Cs x Ba(1− x )/2 TiSi2 O6.5 were synthesized with the pollucite structure with 1≥ x ≥0.6. When the Ba-substituted precursor materials were heat treated to 850°C for 4 h, a mixture of amorphous and unidentifiable phases formed. However, with the addition of 10 wt% of crystalline CsTiSi2 O6.5 to the Ba-containing precursors, nearly single-phase pollucite was obtained after 20 h at 750°C for x ≥0.6. The added crystalline CsTiSi2 O6.5 particles act as nuclei that allow the Ba-containing materials to crystallize into the pollucite phase and to avoid the formation of unwanted phases that would otherwise nucleate and grow. These new materials can be used to study the stability of CsTiSi2 O6.5 as a durable ceramic waste form, which could accommodate with time both Cs and its decay product, Ba. 相似文献