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From the Point of View of Epitaxial Oxide Thin Films
Masayuki SUZUKI
1995 Volume 103 Issue 1203 Pages
1099-1111
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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A new crystal engineering of oxide thin films grown epitaxially was claimed for a future ferroelectric nonvolatile memory (FeRAM) from a point of view of scaling and size effect, and its epitaxial growth technology was reviewed. A few ideal models for epitaxial oxide thin films on Si were proposed as a future oxide-FeRAM. The results are summarized as follows. (1) Bi layer-structured ferroelectric thin film with
c-axis inplane orientation: This structure is not easy to made, but is an ideal model to pick up the merit of ferroelectric anisotoropy. (2) Bi layer-structured ferroelectric thin film with a planar-type, which means that electric field is applied parallel to a film surface: This idea is based on attaching a greater importance to epitaxial growth of a ferroelectric layered oxide. (3) Ferroelectric oxide artificial superlattice thin film: This is basically interesting structure from a point of view of material searching, and has a possibility to create a new function such as ferroelectric properties standing aloof from the conventional size effect. (4) Ferroelectric oxide artificial superlattice thin film with the planar-type: This film includes at least a paraelectric oxide layer, and this may create a new 2-dimensional anisotropy of ferroelectric property as a result.
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Takahisa OMATA, Takashi KAWANO, Hiroyuki IKAWA, Takashi SASAMOTO, Hide ...
1995 Volume 103 Issue 1203 Pages
1112-1116
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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Temperature dependence of the electrical conductivity and the Seebeck coefficient at room temperature of hole-doped Sr
1+xLa
1-xCrO
4+δ(0≤
x≤0.3) were measured and analyzed based on the variablerange hopping (VRH) model. The results are summarized as follows:
(1) Linear relationship between ln σ and
T-1/4 or
T-1/3 was obtained. This shows that the mechanism of the electrical conduction in the materials was well described by three- or two-dimensional VRH model.
(2) The analysis of electrical conductivity based on three-dimensional VRH model showed the larger
T0 values, 10
8K, in this system than that 0.3-7×10
6K of an insulating La
2CuO
4. This suggests the localization length of impurity states in this system is much smaller than that of La
2CuO
4.
(3) The variation of Seebeck coefficients at room temperature suggests that not only the DOS but also the band width nearby the Fermi level were increased upon the hole-doping.
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Hiromi HASE, Hiroyuki NASU, Jun MATSUOKA, Kanichi KAMIYA
1995 Volume 103 Issue 1203 Pages
1117-1121
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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Third-order optical nonlinear susceptibility
x(3) of LiX-Li
2O-TeO
2 and AgX-Ag
2O-TeO
2 (X=Cl, Br, I) glasses was measured by third harmonic generation method, and the influence of halide ions on
x(3) was examined. The
x(3) values were relatively high as 3-5×10
-13 esu for Li-system glasses and -10
-12 esu for Agsystem glasses. The hyperpolarizability of monovalent cation increased with increasing the polarizability of cation (Ag
+>Li
+) and that of the anion increased with anion radius (O
2-<Cl
-<Br
-<I
-).
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Chung-Hsin LU, Jiun-Ting LEE
1995 Volume 103 Issue 1203 Pages
1122-1128
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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The influence of the calcination conditions of MgNb
2O
6 on the perovskite formation and microstructure of Pb(Mg
1/3Nb
2/3)O
3 prepared by the columbite process was investigated. The purity of MgNb
2O
6 was found to significantly affect the formation process of perovskite phase. Lower purity of MgNb
2O
6 led to retard the formation of perovskite phase. Calcination at temperatures above 800°C resulted in the complete formation of MgNb
2O
6. Pure MgNb
2O
6 efficiently reacted with PbO, and accelerated the formation of perovskite phase. On the condition of without adding excess MgO or PbO, heating 1000°C-calcined MgNb
2O
6 with PbO at 800°C for 2h resulted in monophasic Pb(Mg
1/3Nb
2/3)O
3 having submicron size. On the other hand, when MgNb
2O
6 was prepared by 1200°C-calcination, the unfavorable grain-growth of MgNb
2O
6 caused the decrease in the reactivity between MgNb
2O
6 and PbO. The over-calcination of MgNb
2O
6 also led the grain size of Pb(Mg
1/3Nb
2/3)O
3 to greatly increase to be around 2.5μm. Consequently, the calcination conditions of MgNb
2O
6 markedly affected the reaction kinetics and grain size of Pb(Mg
1/3Nb
2/3)O
3.
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Masafumi KOBUNE, Yamato HAYASHI, Satoshi FUJII
1995 Volume 103 Issue 1203 Pages
1129-1134
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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Ruthenium-doped PbTiO
3 {(1-
x)PbTiO
3+
x RuO
2,
x=0-0.018, (PRT)} twin crystals were grown by the flux cooling method. The pyroelectric properties of the poled PRT crystals with
x=0.005-0.009 were measured. The addition of RuO
2 markedly affected the crystal size and improved the crystal imperfections of PbTiO
3. Based on observations by scanning electron microscopy and the back-reflection Laue method, black platelike crystals with
x=0.009, in particular, exhibited excellent crystallinity. Based on the results of identification and chemical analysis and measurement of pyroelectric properties, the limit of substitutional solubility of Ru
4+ ions for Ti in PbTiO
3 was estimated to be in the vicinity of 1.1mol%. The figures of merit
F.M. for voltage responsivity of pyroelectric IR sensors were satisfactory for samples with
x=0.005-0.009; in particular, the sample with
x=0.009 showed the highest
F.M. of around 5.5×10
-11C·cm/J, which was nearly equal to those of PMT (
x=0.045) single crystals. Judging from the measurement of pyroelectric properties of the PRT crystals, crystals with
x=0.009 are suitable as element materials for pointtype pyroelectric IR sensors.
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Takeshi OGAWA, Motohisa HIROSE, Masaya ABE, Norihiko NAKANO
1995 Volume 103 Issue 1203 Pages
1135-1141
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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Subcritical crack growth (SCG) and creep deformation at elevated temperatures were investigated in three types of silicon nitrides and glass ceramics under quasi-static and cyclic loading conditions. The SCG behavior was observed at lower temperature in the silicon nitrides which has lower flexural strength at elevated temperatures. The critical stress intensity factor for SCG in glass ceramics showed similar temperature dependence to the structural ceramics having grain boundary glass phase. The results revealed that the high temperature SCG behavior, caused by the softening of the grain boundary glass phase, was timedependent under cyclic loading condition, which suggested the creep crack growth mechanism. The observation of the creep deformation under cyclic loading condition indicated that unidirectional creep deformation was much more remarkable than cyclic creep deformation where the direction of the creep deformation is reversed due to load reversals.
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Takao NISHIOKA, Hiroshi NAKAO, Akira YAMAKAWA, Masaya MIYAKE, Yoshio T ...
1995 Volume 103 Issue 1203 Pages
1142-1146
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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The effect of distribution of grain cutting edge on the surface of the wheel on the grindability of silicon nitride ceramics was evaluated with specific grinding energy and strength degradation. The main results are summarized as below. (1) The wheel with homogeneously controlled distribution of grain cutting edge showed lower specific grinding energy, and demonstrated higher fracture strength of the ground workpiece at the same value of stock removal rate. (2) The wheel with homogeneously controlled distribution of grain cutting edge demonstrated small strength degradation and distribution of fracture strength of the ground work-piece through decrease in the mean value of maximum grain depth of cut.
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Toshihiko SAKAI, Kazutaka TAKIZAWA, Jun HORIE, Kazushi SAIKI
1995 Volume 103 Issue 1203 Pages
1147-1154
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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Internal friction of 16.3Na
2O⋅33.7MgO⋅50.0SiO
2 and 24.8Li
2O⋅1.3MgO⋅73.9SiO
2 glasses was measured with an inverted torsion pendulum at frequencies below 1Hz. The gamma distribution function was the most appropriate for approximating the whole shape of the low- and high-temperature peak which appeared separately in the internal friction curve of 16.3Na
2O⋅33.7MgO⋅50.0SiO
2 glass among the tested distribution functions: lognormal, beta and gamma. The intermediate- and high-temperature peaks were separated from the composite peaks observed in the internal friction curves of 24.8Li
2O⋅1.3MgO⋅73.9SiO
2 glass by approximating those peaks with the gamma distribution function and the activation energies for those peaks were determined. The activation energies for oxygen and magnesium diffusion below the glass transition point in the 24.8Li
2O⋅1.3MgO⋅73.9SiO
2 glass were also determined by use of stable isotopes
18O and
26Mg, respectively. Within experimental errors, the activation energies for the intermediate- and high-temperature peak agreed with those for oxygen and magnesium diffusion, respectively.
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Akio IKESUE, Kiichiro KAMATA
1995 Volume 103 Issue 1203 Pages
1155-1159
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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Polycrystal, transparent Y
2O
3 ceramics containing 1.1 mol% Ce was fabricated by the solid-state reaction method using high powders and utilizing a capsule-free HIP'ing. The optical transmittance of Ce:Y
2O
3 ceramics obtained was 70-85% in visible to infrared wavelength regions. Although the absorptions by Ce ions were observed at near 450 and 2600 nm, the fluorescence by Ce ions was hardly observed as seen in the Ce
3+-doped YAG (Y
3Al
5O
12) single crystal fabricated by Czochralski method due to the formation of Ce
4+ ions. The absorption coefficients of Ce:Y
2O
3 ceramics in near-infrared to infrared wavelength regions were very small like Nd-doped Y
2O
3 single crystals by Verneuil method or Nd-doped YAG single crystals by floating-zone method.
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Minoru TAKAHASHI, Jun SHIMIZU, Hidero UNUMA, Shigeharu MATSUBAYASHI, M ...
1995 Volume 103 Issue 1203 Pages
1160-1166
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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Consolidation behavior in slip casting of a well-dispersed alumina slurry was experimentally analyzed, using wall-sealed, bottom-sealed and unsealed cylindrical plaster molds. Solid front (the interface between the consolidated layer and slurry in the cavity) and liquid front (the interface between the dry and saturated part in the plaster) were simultaneously measured. Both fronts grew not in one dimension but in three dimensions, depending on the type of mold. There was a similarity in the growth patterns between solid and liquid fronts. It was found that three dimensional suction potential of the plaster mold caused the curved growth patterns. The region deposited at early stages of casting yielded a higher bulk density than the region deposited at late stages of casting. The mean bulk density and homogeneity of cast bodies were also dependent on the type of mold.
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Kozo YOKOTA, Yutaka HASHIZUKA, Masae NAKAHARA, Yoshihito KONDO
1995 Volume 103 Issue 1203 Pages
1167-1171
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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Although new preparation methods for ceramic raw materials have been investigated, ball milling is still the most popular and useful preparation method. In this paper, characteristics of ground Bayer's α-alumina powders by wet rotation ball milling were investigated. The average particle size, the crystallite size and lattice strain of the ground alumina powder after 168-h grinding were 0.21μm, 28nm and 1%, respectively. The particle surface was remarkably irregular. Lattice interplanar spacing of alumina expanded and the lattice constant of
c-axis increased by grinding. Annealing the ground powders resulted in liberation of lattice distortion and particle shape changed to nearly spherical form.
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Kiyoshi HIRAO, Masaki YASUOKA, Shuzo KANZAKI
1995 Volume 103 Issue 1203 Pages
1172-1176
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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Powder compacts with mullite composition (3Al
2O
3⋅2SiO
2) were prepared by mixing γ-alumina and colloidal silica, followed by pressurized filtration. The compacts were sintered by means of viscous flow of amorphous silica phase at relatively low temperature (1200-1250°C) under various water vapor pressures with dew points of -35, +25 and +60°C, and the effect of partial pressure of water vapor on the viscous sintering of mullite was investigated. Densification was enhanced with an increase in water vapor pressure. It was attributed to the fact that the water vapor terminates the silica network, which lowers the viscosity of amorphous silica. Apparent viscosity in the viscous sintering could be determined by applying theoretical models derived in the system composed of only vitreous phase. A compact with nearly full density (≅99%) was obtained under high water vapor pressures by optimizing sintering temperature and time.
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Tomohiro YANAI, Yoshiaki KINEMUCHI, Kozo ISHIZAKI
1995 Volume 103 Issue 1203 Pages
1177-1181
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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The purpose of the present work is to propose a toughening method of Si
3N
4 ceramics by forming a nanocomposite grain-boundary phase of SiC nanoparticles in the weak grain-boundary phase. The SiC nanoparticles are formed by in-situ reaction between an oxide phase on the surface of Si
3N
4 powder and carbon, which is coated on Si
3N
4 powder by thermal decomposition of methane (CH
4) gas. The surface oxygen content can increase by an oxidation process or decrease by washing process. The sintered bodies are obtained by hot-pressing at 1800°C for 1h in N
2 atmosphere under 30 MPa of applied pressure. By increasing the carbon content, both of the fracture toughness and the bending strength first increase, then reach the maximum value at the same amount of carbon, and decrease. TEM observation showed that the precipitated SiC particles dispersed in the grain-boundary phase, at the Si
3N
4-Si
3N
4 interface and inside of the Si
3N
4 grain. The precipitated SiC content depends on the coated carbon and surface oxygen content on the Si
3N
4 powder surface. The reacted carbon content shifts to higher carbon content as oxygen content increases. When the reacted carbon content increases, the resultant SiC content also increases. Therefore, the carbon content at which the fracture toughness and bending strength exhibit the maximum values increases with increasing the surface oxygen content. A surface oxidized Si
3N
4 powder is generally regarded as an inferior powder; however, the oxidized powder can be used to produce high quality Si
3N
4 ceramics by applying the present carbon coating method.
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Takeo TOKIAI, Takashi UESUGI, Kunihito KOUMOTO
1995 Volume 103 Issue 1203 Pages
1182-1187
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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We have developed p-type bismuth telluride of (Bi
2Te
3)
0.25(Sb
2Te
3)
0.75 system with modified PIES method, which shows the figure of merit and compressive strength of 1.6×10
-3/K(25°C), and 9.8 MPa, respectively. Thermoelectric properties showed no anisotropy of electrical transport phenomena because the microstructure had no orientation of the grain growth. The improved compressive strength was presumably due to small grain sizes. The milling mechanism obeyed Kick's law.
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Tatsuro HORIUCHI, Toyohiko SUGIYAMA, Kaoru MIZUNO, Toshihiko OSAKI, Sh ...
1995 Volume 103 Issue 1203 Pages
1188-1192
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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Recently, the amount of lead leaching from tableware has come under strict regulation. Firing in a watervapor atmosphere has been shown to reduce greatly the leaching of lead by some investigations. However, the mechanism of the reduction of lead leaching has not been discussed. In this study, the effectiveness of water-vapor in reducing the lead leaching was confirmed. Furthermore, in order to understand the role of water-vapor in reducing the lead leaching, the amount of lead vaporized from PbO and lead-containing glasses was measured between 750 and 900°C in dry and water-vapor atmospheres. The amount of vaporized lead increased about ten times in the water-vapor atmosphere for PbO. For the lead-containing glasses, the enhancement of lead vaporization was also observed in the water-vapor atmosphere. The change of surface composition due to the vaporization of lead is thought to be the cause of the observed reduction in lead leaching.
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Jong-Kook LEE, Hidehiko TANAKA
1995 Volume 103 Issue 1203 Pages
1193-1196
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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Microstructural variation between the surface and the inside of SiC ceramics sintered with an additive of yttrium aluminum garnet (YAG) was investigated. The variation was caused by a difference in the concentration of the oxide liquid phase during sintering. The gradual change in grain size and shape was found on the surface of which thickness was about 250μm. The grain growth and transformation of β- to α-SiC proceeded at a slower rate on the surface than inside the SiC ceramics. Grains on the surface were small and spherical, but those inside were large and platelike.
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Yoshihiro HIRATA, Ryoko YAMASHITA, Manabu MATSUDA, Masaki SHIBUYA
1995 Volume 103 Issue 1203 Pages
1197-1200
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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The interfaces of Si-Ti-C-O fiber/mullite matrix composite hot-pressed at 1500°C in N
2 atmosphere were characterized by analytical transmission electron microscopy. Partial decomposition of Si-Ti-C-O fibers produced graphite layers 30-60 nm thick on the surface of fibers and crystalline Ti-C-N particles of about 800 nm in size at the triple points among fibers. Diffusion of Al and O from mullite matrix into Si-Ti-C-O fibers was interpreted as being due to the reaction between mullite and C or SiC segregated on the surface of fibers.
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Yoshiro MORIYA, Hidenori SHIMODA, Ryoji HINO
1995 Volume 103 Issue 1203 Pages
1201-1204
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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Oxide films of nominal composition of 80SiO
2⋅20TiO
2 were coated using partially hydrolyzed complex alkoxide solutions on the porous silica which had mesopores of about 3 nm width and narrow pore diameter distribution (PDD). After coating, the larger pores present in the porous silica decreased and the PDD became narrower. No micropores were observed even after coating. No apparent effect on PDD was observed by the repetition of the coating procedure.
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Ichiro TAKAHASHI, Takakazu YOSHIOKA
1995 Volume 103 Issue 1203 Pages
1205-1207
Published: November 01, 1995
Released on J-STAGE: August 06, 2010
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Corrosion tests of various ceramics sustained in low concentration-H
2SO
4 were carried out. We also tried to qualitatively detect the damaged surface layer by using the change in the natural frequency of a specimen. The following results were obtained. (1) The weight of Si
3N
4 and SiAlON decreased rapidly after 5×10
3 min of corrosion time. However, the weights of Al
2O
3, SiC and ZrO
2 did not change. (2) The weight loss was hardly affected by the concentration of sulfuric acid. (3) The damaged surface layer was qualitatively detected by using the natural frequency change of a specimen.
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