共查询到20条相似文献,搜索用时 31 毫秒
1.
Hoon-Taek Chung Jeong-Ho Cho Ho-Gi Kim 《Journal of the American Ceramic Society》1999,82(9):2553-2556
The effects of Cd2+ substitution for Pb2+ and Ni2+ ions (on the A-site and B-site of the ABO3 perovskite structure, respectively) on the electrical conductivities in Pb(Ni1/3 -Nb2/3 )O3 -PbZrO3 -PbTiO3 (PNN-PZ-PT) ceramics have been investigated. Generally, the compounds that contain PbO show p -type conductivity, because of PbO evaporation. Thus, the conductivities are known to be proportional to the PbO evaporation. However, PNN-PZ-PT ceramics exhibit a reciprocal relationship between the conductivities and the evaporation of PbO. Generally, no vacancy change is observed with the substitution of the same-charge valence ion. However, in the PNN-PZ-PT ceramic, lead vacancies could be created or annihilated by replacing Pb2+ and Ni2+ ions with Cd2+ ions, because of incomplete substitution. The electrical conductivities are influenced by this incomplete substitution. 相似文献
2.
The compositional range for glass formation below 1600°C in the Sm2 O3 ─Al2 O3 ─SiO2 system is (9–25)Sm2 O3 ─(10–35)Al2 O3 ─(40–75)SiO2 (mol%). Selected properties of the Sm2 O3 ─Al2 O3 ─SiO2 (SmAS) glasses were evaluated as a function of composition. The density, refractive index, microhardness, and thermal expansion coefficient increased as the Sm2 O3 content increased from 9 to 25 mol%, the values exceeding those for fused silica. The dissolution rate in 1 N HCl and in deionized water increased with increasing Sm2 O3 content and with increasing temperature to 70°C. The transformation temperature ( T g ) and dilatometric softening temperature ( T d ) of the SmAS glasses exceeded 800° and 850°C, respectively. 相似文献
3.
Kazunari Sasaki Petr Bohac Ludwig J. Gauckler 《Journal of the American Ceramic Society》1993,76(3):689-698
Phase equilibria in the system ZrO2 ─InO1.5 have been investigated in the temperature range from 800° to 1700°C Up to 4 mol%, InO1.5 is soluble in t -ZrO2 at 1500°C. The martensitic transformation temperature m → t of ZrO2 containing InO1.5 is compared with that of ZrO2 solid solutions with various other trivalent ions with different ionic radii. The diffusionless c → t ' A phase transformation is discussed. Extended solid solubility from 12.4 ± 0.8 to 56.5 ± 3 mol% InO1.5 is found at 1700°C in the cubic ZrO2 phase. The eutectoid composition and temperature for the decomposition of c -ZrO2 solid solution into t -ZrO2 +InO1.5 solid solutions were determined. A maximum of about 1 mol% ZrO2 is soluble in bcc InO1.5 phase. Metastable supersaturation of ZrO2 in bcc InO 1.5 and conditions for phase separation are discussed. 相似文献
4.
Atsumi Nitta Terumi Miura Takayuki Komatsu Kazumasa Matusita 《Journal of the American Ceramic Society》1989,72(1):163-165
Glass-forming regions, valence states, and viscosities in SiO2 –PbO systems containing various transition-metal oxides as a third component were investigated. The glasses were prepared by melting in an open atmosphere. The glass-forming regions ranged as follows: MnO≡ZnO > FeO1.5 >NiO. The ratios Fe2+ /(Fe2+ + Fe3+ ) and Mn3+ / (Mn3+ + Mn2+ ) in the glasses were determined by chemical analysis. The Fe2+ / (Fe2+ + Fe3+ ) ratio in SiO2 –PbO–FeO1.5 glasses ranged from 0.016 to 0.050. The Mn3+ / (Mn3+ + Mn2+ ) ratio in SiO2 –PbO–MnO glasses ranged from 0.056 to 0.30. The fraction of manganese (III) ions in the glasses varies considerably with the glass composition. The effects of transitionmetal oxides on the viscosity are discussed. 相似文献
5.
Porous glass-ceramics with a skeleton of the fast-lithium-conducting crystal Li1+ x Ti2− x Al x (PO4 )3 (where x = 0.3–0.5) were prepared by crystallization of glasses in the Li2 O─CaO─TiO2 ─Al2 O3 –P2 O5 system and subsequent acid leaching of the resulting dense glass-ceramics composed of the interlocking of Li1+ x Ti2− x Al x (PO4 )3 and β-Ca3 (PO4 )2 phases. The median pore diameter and surface area of the resulting porous Li1+ x Ti2− x Al x (PO4 )3 glass-ceramics were approximately 0.2 μm and 50 m2 /g, respectively. The electrical conductivity of the porous glass-ceramics after heating in LiNO3 aqueous solution was 8 × 10−5 S/cm at 300 K or 2 × 10−2 S/cm at 600 K. 相似文献
6.
Gamma irradiation of potassium borate glasses containing about 1.8 mole % Tl+ , Pb2+ , or Bi3+ resulted in two induced absorption bands which the authors call T and L bands. The T band was observed at about 1.1, 1.55, or 1.8 ev, and the L band was observed at about 1.8, 2.6, or 2.7 ev in alkali borate glasses containing Tl+ , Pb2+ , or Bi3+ , respectively. The shifting of the band positions to higher energies was attributed to the increasing polarizing power of these ions as in the case of the F band induced in alkali halides. The effect of the addition of cerium on the intensity of the T and L bands induced in glasses containing lead or thallium and prepared under different melting conditions suggested strongly that these two bands are associated with electron trap centers near these ions. 相似文献
7.
Shingo Ishida Feng Ren Nobuyuki Takeuchi 《Journal of the American Ceramic Society》1993,76(10):2644-2648
A new yellow pigment with the pyrochlore structure Cax Y2− x V x Ti2− x O7 was prepared as a substitute for the decreasing variety of available yellow ceramic pigments due to the severe regulation of toxic lead and cadmium. The solubility limit of vanadium in this pigment was found to be 1.5 wt% as V2 O5 or 0.13 as x in the above formula expression. Characterization of vanadium in the vanadium pyrochlore yellow pigment by electron spectroscopy for chemical analysis and electron spin resonance showed that the oxidation state of vanadium was V5+ and its yellow color mostly originated from V5+ substituted for Ti4+ . Comparison of color characteristics of Cax Y2− x V x Ti2− x O7 with those of commercial V–SnO2 and V–ZrO2 revealed that Ca x Y2− x V x Ti2− O7 had better color strength and brightness than the commercial pigments. 相似文献
8.
R. B. ATKIN R. L. HOLMAN RICHARD M. FULRATH 《Journal of the American Ceramic Society》1971,54(2):113-115
Solid-state substitution of Bi and Nb ions in the perovskite crystal structure of Pb(Ti0.47 Zr0.53 )O3 was investigated by sample weight changes at 1150°C in an "equilibrium" PbO atmosphere. A model is discussed that includes the effect of charge neutralization, requiring weight losses for A-site substitutions and weight gains for B-site substitutions. Experiments support the substitution of Bi as Bi3+ on the Pb2+ A site and Nb as Nb5+ on the (Ti,Zr)4+ B site of lead zirconate-titanate. For each mole of BiO1.5 added to a specimen, 1.5 moles of PbO are lost; for each mole of NbO2.5 added, 0.5 moles of PbO are gained. These results agree with the proposed model and with ionic size arguments. The weight changes were time-dependent during the first 30 to 40 h at 1150°C. This behavior is accounted for by the presence of transient second phases. 相似文献
9.
BIPRODAS DUTTA ROBERT H. MAGRUDER III ROBERT A. WEEKS DONALD L. KINSER 《Journal of the American Ceramic Society》1988,71(12):1100-1103
Thermally stimulated polarization and depolarization current (TSPC/TSDC) and dc conductivity measurements on a series of lead silicate glasses were made between −196° and 190°C. The general composition of the glasses was xPbO·(100 − x )SiO2 , where x = 30, 40, 45, 50, and 65. The dc conductivity exhibits a monotonic increase with increasing PbO content. For x > 45, the rise in conductivity with increasing PbO content is much less than for x < 45. Two TSDC peaks have been observed in all the glasses. The smaller of the two TSDC peaks, occurring at lower temperatures, increases linearly in size with increasing concentrations of PbO. The high-temperature TSDC peak does not saturate from −196° to 190°C. Direct current conductivity in these glasses is ionic and due to the motion of Pb2+ ions. The behavior of the low-temperature TSDC peak is consistent with the hypothesis that it is caused by short-range motion (orientational polarization) of Pb2+ ions. The origin of the high-temperature TSDC peak is tentatively attributed to space charge polarization of Pb2+ ions. 相似文献
10.
Jeong-Ho Cho In-Kil Park Ho-Gi Kim Hoon-Taek Chung 《Journal of the American Ceramic Society》1997,80(6):1523-1534
Substituting Cd2+ ions into the A and B sites in a Pb(Ni1/3 Nb2/3 )O3 PbZrO3 PbTiO3 (PNNPZPT) ternary perovskite material made it possible to determine the effects of the Cd2+ ion substitution site on sintering behavior. The substitution site of the Cd2+ ion was identified by using X-ray photoelectron spectroscopy spectra. Although Cd2+ ions were substituted into the A and B sites in PNNPZPT, the Cd2+ ions preferred the A site over the B site. When Cd2+ ions replaced Pb2+ ions, a weight gain was observed during sintering. On the other hand, replacing Ni2 ions with Cd2+ ions promoted weight loss. Those weight changes indicated that Cd2+ ions change the bonding strength between the B-site cations and the oxygen of the octahedron in a perovskite structure. Density was influenced by the Cd2+ ion substitution site, and the A-site-doped compositions had higher densities than the B-site-doped compositions. 相似文献
11.
Cristina Leonelli Tiziano Manfredini Mariano Paganelli Gian Carlo Pellacani Jose Luis Amoros Albaro Jose Emilio Enrique Navarro Maria Jose Orts Silvia Bruni Franco Cariati 《Journal of the American Ceramic Society》1991,74(5):983-987
In order to verify the possibility of using glass-ceramic materials as tile coatings, the devitrification processes of three industrial formulations belonging to the Li2 O─Al2 O3 ─SiO2 glass-ceramic system were investigated by differential thermal analysis, X-ray diffractometry, scanning electron microscopy, and IR spectroscopy. Compositional variations were made by addition of large amounts of MgO or CaO or PbO (ZnO) oxides as well as through smaller additions of other oxides. In these systems the surface crystallization contributes appreciably to the bulk crystallization mechanism. All the systems investigated show a high tendency toward crystallization even at very high heating rates, developing a very close network of interlocked crystals of synthetic β-spodumene-silica solid solutions (LiAlSi4 O10 ). The results of this research are expected to establish the conditions under which these glass-ceramic systems can be practically used as tile glazes. 相似文献
12.
Jie Fu 《Journal of the American Ceramic Society》2000,83(4):1004-1006
Glasses with compositions Li1.2 M0.2 Ge1.8 (PO4 )3 (M = Al, Ga, Y, Gd, Dy, and La) were prepared and converted to glass-ceramics by heat treatment. The effects of the M3+ ions on the conductivity of the glasses and glass-ceramics were studied. The main phase present in the glass-ceramics was the conductive phase LiGe2 (PO4 )3 . Al3+ and Ga3+ ions entered the LiGe2 (PO4 )3 structure by replacing Ge4+ ions, but lanthanide ions did not. The glass-ceramics exhibited much higher conductivity than the glasses. With increased ionic radius of the M3+ ions, the conductivity remained almost unchanged at ∼3 × 10−12 S/cm for the glasses, but it decreased from 1.5 × 10−5 to 8 × 10−9 S/cm for the glass-ceramics at room temperature. The higher conductivity for Al3+ - and Ga3+ -containing glass-ceramics was suggested to result from the substitutions of Al3+ and Ga3+ ions for Ge4+ ions in the LiGe2 (PO4 )3 structure. 相似文献
13.
Subsolidus Phase Relationships in Part of the System Si,Al,Y/N,O: The System Si3 N4 ─AIN─YN─Al2 O3 ─Y2 O3
Wei-Ying Sun Tseng-Ying Tien Tung-Sheng Yen 《Journal of the American Ceramic Society》1991,74(11):2753-2758
The subsolidus phase relationships in the system Si,Al,Y/N,O were determined. Thirty-nine compatibility tetrahedra were established in the region Si3 N4 ─AIN─Al2 O3 ─Y2 O3 . The subsolidus phase relationships in the region Si3 N4 ─AIN─YN─Y2 O3 have also been studied. Only one compound, 2YN:Si3 N4 , was confirmed in the binary system Si3 N4 ─YN. The solubility limits of the α'─SiAION on the Si3 N4 ─YN:3AIN join were determined to range from m = 1.3 to m = 2.4 in the formula Y m /3 Si12- m Al m N16 . No quinary compound was found. Seven compatibility tetrahedra were established in the region Si3 N4 ─AIN─YN─Y2 O3 . 相似文献
14.
An Xie Ximing Yuan Yu Shi Fengxiang Wang Juanjuan Wang 《Journal of the American Ceramic Society》2009,92(10):2254-2258
A series of novel red phosphors LiEu1− x Bi x (WO4 )0.5 (MoO4 )1.5 ( x =0, 0.05, 0.10, 0.15, 0.20, 0.30, 0.40, and 0.50) were synthesized by the conventional solid-state reaction method. The spectrum and the crystal structure of the phosphors were characterized by Fluorescence spectrophotometry and X-ray diffraction, respectively. The photoluminescent results show that all samples can be excited efficiently by UV (396 nm) and blue (467 nm) light and that they emit red light at 615 nm with line spectra, which are coupled well with the characteristic emissions from UVLED and blue light-emitting diode (LED), respectively. There is an efficient energy transfer from Bi3+ to Eu3+ ions, leading to the emission intensity of Eu3+ being enhanced by 1.5 times, and even more when Bi3+ ions are introduced into LiEu (WO4 )0.5 (MoO4 )1.5 . The introduction of Bi3+ ions broadened the excitation band of the phosphor, and the optimum doping concentration is found to be 10 mol% of Bi3+ . 相似文献
15.
The formation mechanism, the temperature range for the growth, and the thermal stability of the 2223 phase in Bi(Pb)─Sr─Ca─Cu─O have been investigated using DTA/TG, XRD, SEM/EDAX, TEM, EPMA, four-probe resistance and acsusceptibility measurement. The formation of the 2223 phase was found to follow a dissolution–precipitation process. A 2212 phase first reacts with the liquid phase formed via an incongruent melting of the Ca2 PbO4 phase, and a dissolution of CaO and CuO takes place. The 2201 phase, which has the largest negative free energy, is then precipitated from the melt; the nucleation and growth of the 2223 phase are subsequently developed by the reaction between the 2201 phase precipitates and ions of Ca2+ and Cu2+ present in the liquid phase. The 2223 phase is formed at temperatures in the range 827°C T < 856°C. The optimum temperature T f for the formation of 2223 phase is 845°± 5°C. The 2223 phase is thermodynamically unstable at temperatures above 856°C. 相似文献
16.
The phase diagram for the CuO-rich part of the La2 O3 ─CuO join was redetermined. La2 Cu2 O5 was found to have a lower limit of stability at 1002°± 5°C and an incongruent melting temperature of ∼1035°C. LagCu7 O19 had both a lower (1012°± 5°C) and an upper (1027°± 5°C) limit of stability. Subsolidus phase relations were studied in the La2 O3 ─CuO─CaO system at 1000°, 1020°, and 1050°C in air. Two ternary phases, La1.9 Ca1.1 Cu2 O5.9 and LaCa2 Cu3 O8.6 , were stable at these temperatures, with three binary phases, Ca2 CuO3 , CaCu2 O3 , and La2 CuO4 . La2 Cu2 O5 and La8 Cu7 O19 were stable only at 1020°C, and did not support solid-solution formation. 相似文献
17.
An optimal set of thermodynamic functions for the ZrO2 ─YO1.5 system are obtained using phase diagram and thermodynamic data. The liquid is described by a subregular solution model. Both cubic ZrO2 and YO1.5 solid solutions are regarded as one cubic solution, which is also treated as a subregular solution. The ordered Zr3 Y4 O12 phase is treated as a stoichiometric compound. A regular solution model is applied to the other solid solutions. Tentative equilibrium boundaries between monoclinic and tetragonal ZrO2 solid solutions are evaluated from information about the T 0 line. The calculated phase diagram and thermodynamic functions agree well with experimental data. 相似文献
18.
Synthesis of lead tantalate pyrochlores by the reaction of PbO and Ta2 O5 in various molar ratios between 1.5 and 4.0 at low temperatures (500–650°C) has been carried out. It has been shown that when PbO is reacted with Ta2 O5 in various molar ratios at low temperatures, metastable lead tantalate pyrochlore solid solutions having cubic symmetry are formed. X-ray diffraction data give evidence for an increase in the a lattice parameter with increasing PbO content and partial occupancy of Pb in the Ta sites leading to the formula Pb1.5+ x 2+ (Ta2− y Pb y 4+ )O7−δ (0.0 < x < 0.5; 0.0 < y < 0.6) for this phase. It has also been found that the intermediate members of the solid solutions are metastable and tend to segregate into Pb-deficient and Pb-excess compositions leading to significant compositional inhomogeneity for the intermediate members. 相似文献
19.
PbTiO3 -doped sodium bismuth titanate (Na1/2 Bi1/2 )1− x Pb x TiO3 of perovskite structure is one of the best-known piezoelectrics/ferroelectrics. However, it has not been properly investigated in any thin-film forms. In this study, the dielectric properties of (Na1/2 Bi1/2 )0.87 Pb0.13 TiO3 thin films synthesized via a sol–gel route were investigated. They exhibit a strong frequency dispersion of the dielectric permittivity at relatively high frequencies, which is shifted to lower frequencies with increasing temperature. The electrical behavior can be fitted using Jonscher's universal law for dielectric relaxation. The peculiar dielectric behaviors observed can be ascribed to the coexistence of two different dielectric phases in the films, which is believed to be associated with the growth of the local Pb2+ TiO3 nanoclusters upon substitution of Pb2+ for Na+ /Bi3+ in the (Na1/2 Bi1/2 )1− x Pb x TiO3 films. 相似文献
20.
Toshinobu Yoko Toshio Nishiwaki Kanichi Kamiya Sumio Sakka 《Journal of the American Ceramic Society》1991,74(5):1112-1116
The ion-exchange mechanism between copper and alkali ions, when 20R2 O · 10Al2 O3 · 70SiO2 (R = Li, Na, and K) glasses are immersed in divalent copper-containing molten salts in air and nitrogen at 550°C, has been investigated. In molten CuCl2 , the ion-exchange behavior in both air and nitrogen was very close to that in molten CuCl in air reported previously. This is explained by assuming that CuCl2 decomposes into CuCl and Cl2 at 550°C and the Cu+ ions thus formed mainly diffuse in glasses to replace alkali ions, where Cl2 acts as an oxidizing agent just like oxygen. In the case of molten CuSO4 ─2 SO4 , a small amount of Cu+ which is present in the molten state plays a primary role in the Cu ⇌ R+ ion exchange process, although the contribution of direct Cu2+ ⇌ 2R+ ion exchange cannot be ignored. 相似文献