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Jabri KHALED, Takayuki KOMATSU, Ryuji SATO
1997 Volume 105 Issue 1220 Pages
279-283
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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The effect of the substitution of Te for Cu or Pb in nominal compositions on the formation of the high-
Tc phase and on the thermal stability of the high-
Tc phase under reannealing conditions at temperatures (500-800°C) lower than the formation temperatures such as 850°C in Bi-Pb-Sr-Ca-Cu-O (Bi-based system) superconducting glass-ceramics has been investigated. In the case of the substitution of Te for Cu, the formation of the high-
Tc phase is largely enhanced, i.e., a large amount of the high-
Tc phase is obtained by annealing glassy samples at 850°C for periods as shorter as 48h compared with the period of 250h required to obtain similar amount of the high-
Tc phase in the absence of any Te addition. It is, however, found that the high-
Tc phase decomposes by reannealing below 850°C and at the same time Pb-containing compounds of BiPb
2Sr
2.6CaCu
1.6O
x and Pb
2Sr
1.2Ca
1.8CuO
x are formed, meaning that the thermal stability of the high-
Tc phase in the glass-ceramics obtained by the substitution of Te for Cu is low. In the case of the substitution of Te for Pb, it is found that not only the formation of the high-
Tc phase is promoted but also the thermal stability is improved, because any definite decomposition of the high-
Tc phase is not observed at temperatures lower than 830°C. It is concluded that the key factor to improve the thermal stability of the high-
Tc phase is to depress the formation of Pb-containing compounds, and thus to prepare the high-
Tc phase containing a proper amount of Pb.
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Daisuke HAMADA, Wataru SUGIMOTO, Yoshiyuki SUGAHARA, Kazuyuki KURODA
1997 Volume 105 Issue 1220 Pages
284-287
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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The solid solution KCa
2-xR
xNb
3O
10 (R=Nd, Sm, Gd and Ce) was prepared by solid-state reaction using KCa
2Nb
3O
10, KNbO
3, Nb
2O
5, Nb and rare-earth oxides. The solubility limit of the solid solutions was extended with an increase in the ionic radii of the rare earths. All the solid solutions exhibited similar semiconductive behavior with a linear logρ-
T relationship over a wide temperature range. These results suggest that the conduction mechanism is independent of the type of rare earths and also the unit-cell parameters, which agrees well with the tunneling conduction model with a vibrating barrier.
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Kentaro TERASHIMA, Takashi UCHINO, Tadanori HASHIMOTO, Toshinobu YOKO
1997 Volume 105 Issue 1220 Pages
288-293
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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The third order nonlinear optical susceptibilities χ
(3) of BaO-TiO
2-B
2O
3 glasses have been measured by the third harmonic generation (THG) method. Raman spectroscopic investigation revealed that Ti
4+ ions mainly exist as 4-coordinated. It was found that the addition of TiO
2 to BaO-B
2O
3 glass increases the χ
(3) as well as the refractive index. The positive effect of the TiO
2 on the χ
(3) was interpreted in terms of the empty
d-orbital contribution. The largest χ
(3) obtained is 3.0×10
-13 esu for 35BaO⋅55TiO
2⋅10B
2O
3 glass, which is, however, only 10 times larger than that for SiO
2 glass. Such a small enhancement in χ
(3) is ascribed to the large fraction of 4-coordinated Ti
4+ ions in BaO-TiO
2-B
2O
3 glasses. It is concluded that, for TiO
2-containing glasses, the higher χ
(3) values are attained when the optical basicity is low and the amount of Ti
4+ ion is large. It was found that the modified Lines' relationship between χ
(3) and (
nω2+2)
3⋅(
nω2-1)⋅
Ed/
E02 is adopted for this system.
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Hidehiko TANAKA
1997 Volume 105 Issue 1220 Pages
294-298
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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Coalescence of grains was investigated using the two-sphere model to clarify the effects of boundary energy and grain size at the initial stage of sintering. The new rate equations for sintering and grain growth were derived by evaluating total surface energy and grain boundary energy of the system. The derivation was based on Inomata's free energy theory and Tanaka's definition of diffusion area and length for material transport. The rate equations included the ratio of the grain boundary energy to surface energy and the grain size ratio. Using the equations, coalescence of two spherical grains was simulated assuming that the sintering and grain growth phenomena take place simultaneously. The results showed that grain boundary expansion first occurs and then grain growth becomes dominant. It was also found that coalescence proceeds faster when the grain boundary energy is smaller.
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Shenglei CHE, Osamu SAKURAI, Atsushi SAIKI, Hiroshi FUNAKUBO, Kazuo SH ...
1997 Volume 105 Issue 1220 Pages
299-303
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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The evolution of particle structure in the formation of submicron single-crystal spherical palladium particles by spray pyrolysis was investigated by observing the change of the morphology and internal structure of the particles during heat treatment. Below 700°C oxide particles with solid and homogeneous structure were formed. Decomposition of PdO took place within a particle above 700°C and an oxide layer was left on the surface of palladium particles until the decomposition is completed. The yielded palladium clusters sintered immediately and the particles shrank uniformly and dramatically as the decomposition reaction took place. The shrinkage of particles was completed almost simultaneously as the decomposition of PdO was completed, however, a little expansion was observed which is attributed to the decomposition of entrapped oxide in the particles. High temperature lead to rapid grain growth within a particle and allowed the formation of single-crystal palladium particles in the spray pyrolysis process. Particles prepared by ultrasonic spray pyrolysis at above 1200°C were single crystals and had clean surface without any amorphous or oxide layer.
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Kazuo UENO, Takahiro INOUE, Satoshi SODEOKA, Masato SUZUKI, Hiroshi IS ...
1997 Volume 105 Issue 1220 Pages
304-307
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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Si
3N
4 matrix composite reinforced with 5vol% TiN particles was fabricated by the in-situ reaction: 4TiO
2+4AlN→4TiN+2Al
2O
3+O
2, followed by hot-pressing. The internal TiN formation reaction was studied using TiO
2 powders with three different particle sizes (0.28, 0.35 and 1.19μm). The reaction is likely to start from nearly 1150°C and finishes at 1450°C, before the Si
3N
4 matrix is sintered, and TiN formation is confirmed from the unit cell dimension. TiN particle sizes in the composites sintered at 1600°C and 1850°C were measured. When the TiO
2 particle size was large (1.19μm), the particle crumbled into fragments and underwent nitridation to TiN with a smaller size than that of the original TiO
2. Smaller TiO
2(0.28μm) was converted into TiN particles of nearly the same size. These results suggest that the in situ TiN formation proceeds through nitridation of TiO
2 particles.
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Takao TANI, Mitsuru ASAI, Kazumasa TAKATORI, Nobuo KAMIYA
1997 Volume 105 Issue 1220 Pages
308-311
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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Dielectric strength (
Ebd) and breakdown behavior were evaluated for Sr-, Nb-doped lead zirconate titanate (PZT) ceramics under both d.c. and a.c. electric fields. Three types of specimens were prepared, i.e., a concave disc (CSD), partially electroded disc (PED) and wholly electroded disc (WED). The
Ebd values measured under the d.c. field were 17.8kV/mm, 8.6kV/mm and 6.9kV/mm for the CSD, PED and WED, respectively. Breakdown was triggered by crack generation in the CSD and PED. Surface flashover occurred in the WED. No significant dependence of
Ebd on temperature was observed at temperatures below 150°C under the d.c. field. The
Ebd values measured under the a.c. field were 5.2kV/mm, 3.9kV/mm and 4.7kV/mm for the CSD, PED and WED, respectively. Thermal breakdown occurred for all specimens prior to breakdown due to crack generation or surface flashover.
Ebd increased slightly as the frequency of the applied a.c. field decreased. The
Ebd values measured under the d.c. field were slightly higher than those of BaTiO
3 and almost the same as those of BaTiO
3-SrTiO
3. The
Ebd values measured under the a.c. field were slightly lower than those of BaTiO
3.
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Masafumi KOBUNE, Atsushi MINESHIGE, Satoshi FUJII, Yasumori MAEDA, Jun ...
1997 Volume 105 Issue 1220 Pages
312-316
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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The results of this study are summarized as follows:
(1) High density lanthanum-modified lead zirconate titanate (PLZT) ceramics with compositions of {(Pb
0.925La
0.075)(Zr
yTi
1-y)
0.981O
3+0.5 mass% MnO
2}, where
y=0-0.10, were successfully synthesized by hot isostatic pressing.
(2) All the pressed samples had the high relative density of 99.9% of theoretical density.
(3) The relative dielectric constant ε
r at room temperature was in the range of 290 to 334 which was satisfactory for requirements of maintaining appropriately low ε
r(-350).
(4) The rates of linear increase
m1 and decrease
m2 calculated from the slope of the linear plot of ε
r and the Curie temperature
TC with
y were approximately 4.0/mol% Zr and 0.6°C/mol% Zr, respectively.
(5) Assuming that the volume specific heat
Cv of the PLZT samples with
y=0-0.10 are 3.2×10
6J/m
3·K,
y=0.10 PLZT sample exhibited the highest figures of merit F.M. for voltage responsivity of around 0.20×10
-12C·m/J and F.M.D* for specific detectivity D* of around 0.57×10
-10C·m/J, among the nine samples studied here.
(6) The figure of merit F.M.D* of
y=0.10 PLZT sample matched ε
r of element materials with those of FET used in the sensor circuit was superior to those of PLZT(4/44/56) ceramic and
x=0.005 PLMT ceramic that have been previously reported.
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Toshio SHIMOO, Daisuke SHIBATA, Takuya YAMASAKI, Kiyohito OKAMURA
1997 Volume 105 Issue 1220 Pages
317-321
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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In relation to the joining of silicon nitride ceramics to metal, the reaction products and reaction mechanism between Si
3N
4 and Fe-Cr alloy have been investigated under Ar atmosphere at temperatures from 1223 to 1573K. Using Si
3N
4/Fe-62.5mass%Cr alloy powder mixture, the reaction rates were thermogravimetrically determined, and the reaction products were identified by X-ray diffraction. Cr
2N was produced below 1273K. Above 1273K, the solid solution and silicides were produced, resulting in the mass loss. At higher temperatures and on prolonged heating, the silicides changed in the following order: Cr
3Si, Cr
5Si
3 and CrSi. Two types of Cr
5Si
3 were found; hexagonal crystal above 1323K and tetragonal crystal above 1423K. Iron is considered to form the solid solution with chromium silicides. The initial rate was described by the linear rate law. The activation energy was 264kJ/mol. An interfacial reaction may be the rate-determining step. When the alloy particles were covered with the reaction product layer, the kinetics obeyed the parabolic rate law. The reaction rate is probably controlled by the solid-state diffusion through the reaction layer.
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Danping CHEN, Yoshinari MIURA, Yasuaki MURATA, Tokuro NANBA, Akiyoshi ...
1997 Volume 105 Issue 1220 Pages
322-328
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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Photochromic properties were investigated for glass in the system CdO-Bi
2O
3-Al
2O
3. Optical density increased with increasing BiO
1.5 content in the glasses at fixed CdO content. The darkening degree could be effectively enhanced by oxidation treatments. The composition dependence and effect of oxidation treatment were studied by X-ray photoelectron and Raman scattering spectroscopies. With increasing BiO
1.5 content the Lewis basicity of oxygen atoms increased and the fraction of covalently bonded cadmium decreased. The trap density of holes increased and the photogeneration yield decreased. The darkening degree showed a maximum around BiO
1.5=13 cation%. The effect of oxidation treatment on the darkening degree may be related to production of a large amount of monovalent O
- ions with holes in their 2p valence band, and to formation of electron centers in cadmium atoms.
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Creep and Stress Relaxation
Hiroyuki MUTO, Mototsugu SAKAI
1997 Volume 105 Issue 1220 Pages
329-334
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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The grain-boundary sliding and interlocking of polycrystalline ceramics are investigated by means of the model arrays, i.e., two-dimensional arrays of square or hexagonal elastic grains embedded in a contiguous grain-boundary melt. A nonlinear Maxwell type constitutive equation is derived in an universal manner by considering two fundamental processes associated with elastic deformation of grains and squeezing-in/out of a viscous fluid between adjacent grains. The equation applied to creep deformation and stress relaxation yields several important predictions for the nonlinear viscoelastic behavior of polycrystalline ceramics with grain-boundary phase.
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Hiroshi YAMASHITA, Tomohiro TANIGUCHI, Kanako TANAKA, Takashi MAEKAWA
1997 Volume 105 Issue 1220 Pages
335-340
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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Spherical porous silica particles were synthesized by the sol-gel process from tetramethoxysilane and methyltrimethoxysilane in W/O emulsion. The difference in structure change by calcination is remarkable between air and nitrogen atmospheres. By calcination of the particles under N
2 gas atmosphere their pore structures can be maintained up to 1000°C. This is due to the fact that Si-CH
3 bond remains at high temperature. The
29Si MAS NMR spectra revealed that the intensity of T
3 structural unit, whose origin is Si-C bonding, increased with an increase in methyltrimethoxysilane in a starting solution.
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Substitution of Group II Elements (Ca, Cd)
Hiroshi HAYAKAWA, Etsuo AKIBA
1997 Volume 105 Issue 1220 Pages
341-346
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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Metallic-type conducting oxide, Cu
6O
8In
1-xM
xCl (M=Ca and Cd) whose In site is substituted by Ca or Cd was synthesized by decomposition of molten salt. The crystal structure and electric conductivity of these compounds were investigated. All the compounds synthesized are isostructural to the original compound, Cu
6O
8InCl. The limits of substitution were
x=0.17 for M=Cd and
x=0.20 for Ca. The lattice parameter of Cu
6O
8In
1-xM
xCl (M=Ca and Cd) increased with increasing amount of substitution obeying Vegard's rule. The lattice parameters at the limit of substitution were
a=0.918nm for M=Cd and
a=0.919nm for Ca. Crystallite size decreased from 90nm at
x=0.00 to 45nm at
x=0.20 with increasing
x. However, lattice strain was constant in the range of
x studied. Electric resistivity increased with increasing of
x for all the compounds studied and superconductivity was not observed down to 12K. It suggests that doping of a hole by substitution of a divalent cation to In
3+ is not effective in changing the charge of Cu in Cu
6O
8In
1-xM
xCl (M=Ca and Cd), which controlls the conductivity of superconducting copper oxides.
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Fumio MUNAKATA, Makoto TANIMURA, Yoshio AKIMUNE, Chikai SATOU, Yasuhid ...
1997 Volume 105 Issue 1220 Pages
347-350
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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The firing behavior of α-Si
3N
4 powder corroded under hydrothermal conditions was investigated by X-ray diffraction (XRD) and transmission electron microscopy (TEM). XRD and TEM analysis suggest that the hydorothermal treatment enhances the α-β phase transition in α-Si
3N
4 and the formation of Si
2ON
2 phase from α-Si
3N
4 during firing at high temperature. In paticular, TEM analysis indicate that the grown β-Si
3N
4 grains contain an α-Si
3N
4 core under the α-β phase transition in α-Si
3N
4.
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Hideyuki NEGISHI, Nobuyuki KOURA, Yasushi IDEMOTO
1997 Volume 105 Issue 1220 Pages
351-355
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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The Preparation of a Tl-2223 superconductor coating using the electrophoretic deposition method, the preparation conditions of the electrophoretic deposition coating and the deposition mechanism have been investigated. The maximum amount of the deposit was obtained when 1.5mg I
2 and 0.2g superconducting powder were added to the 10ml cyclohexanone bath, and a uniform coating was obtained with an applied voltage under 300V. The electrification mechanism of the particles in the deposition bath revealed that H
+ ion was produced in the I
2-added cyclohexanone bath after which H
+ ion was adsorbed on to the particle surface. The maximum zeta potential of the particle was 92mV when 1.0mg I
2 was added to the 10ml cyclohexanone bath. The deposition current density was proportional to the inverse of the square root of the deposition time (
t-1/2) and the amount of the deposit was proportional to the square root of the deposition time (
t1/2) during the formation of the particle layer by electrophoretic deposition. Accordingly, the diffusion of H
+ ions through a small opening in the oxide layer was considered to be a diffusion controlled process for the electrode reaction during the electrophoretic deposition.
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Atsunori JOYAMA, Satoshi TAKAYAMA, Yasunari KANEKO
1997 Volume 105 Issue 1220 Pages
356-360
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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Foaming of green bodies is induced using an acrylic mold; namely, the green body is produced by two simultaneous reactions, a hydrogen generation reaction involving aluminum particles and sodium hydroxide, and a gelling and setting reaction involving sodium silicate and sodium aluminate. Foam formation ratio, porosity and pore size of green bodies are examined for various particle sizes and amounts of aluminum powder added to mixed slurry for the evaluation of green bodies.
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Ryou SUZUKI, Ryuichi NAGASE, Tsuneo SUZUKI
1997 Volume 105 Issue 1220 Pages
361-365
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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Alpha-Fe
2O
3 powder was ground by ball-mill with alumina and zirconia balls. Densification behavior with respect to both specific surface area and the amount of impurities from the balls was investigated. The onset temperature of shrinkage for the powders milled with alumina balls decreased with increasing specific surface area and decreasing impurity contents. On the other hand, the onset temperatures for the powder milled with zirconia balls increased, although the specific surface area of the powder was increased by milling. Density and microstructure of the samples sintered at 1100°C for 10h were evaluated. Relative densities of sintered samples by the powders with 3.5mol% and 1.1mol% Al
2O
3 were 99.4% and 99.3%, respectively. Average grain sizes of these samples were 5.4μm and 10.1μm, respectively. The relative density of sintered sample by the powder with 0.7mol% ZrO
2 was 97.8%. This value was lower than those by the powders milled with alumina balls, although there was no difference in specific surface area in these powders. This result indicates that Al
2O
3 does not influence the densification of α-Fe
2O
3, however ZrO
2 inhibits densification. The cause of densification inhibition by ZrO
2 was considered that the diffusion rate of oxigen ion is decreased by the decrease of oxigen ion vacancies, which is caused by the dissolution of ZrO
2 in α-Fe
2O
3.
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Gakuji UOZUMI, Masaru MIYAYAMA
1997 Volume 105 Issue 1220 Pages
366-368
Published: April 01, 1997
Released on J-STAGE: August 06, 2010
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CuO-ZnO composites with or without ultrafine Au particles were fabricated by infiltrating cupric solution with or without gold cyanide into a porous ZnO matrix and firing. The particle size of Au was controlled within 5-100nm by changing heating process of the cupric solution and gold cyanide concentration. The rectifying current (
I)-voltage (
V) characteristics and gas sensitivity largely depended on the Au particle size. Evident nonlinear
I-V characteristics, due to p-n junction of CuO and ZnO semiconductors, were not observed in composites with Au particles. When the Au particle size was about 10nm, the gas sensitivity of the composite was substantially improved; the current was increased about 20 times by an introduction of CO and H
2 gas (4000ppm) at 150°C in the bias region within ±6V. However, in composites with Au particles smaller than 10nm and larger than 20nm, current changes by introduction of the gases were only below 10% of the current in air. The interface capacitance of the composites also showed changes by the gases depending on the Au particle size, which is similar to those in gas sensitivity. It was found that the addition of Au particles with controlled size is effective to improve gas sensitivity in CuO-ZnO composites.
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