Iwao Yamai

Nagoya Institute of Technology

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Toshitaka Ota

Nagoya Institute of Technology

Hajime Saito

Iwate Medical University

Toru Matsushita

Sanyo-Onoda City University

Toshitaka Oota

Nagoya Institute of Technology

Mitsunori Yokoyama

Sumitomo Electric Industries (Japan)

Kohei Kodaira

Hokkaido University

Junichi Takahashi

Yokohama National University

Junichi Takahashi

Asia University

Manabu TAKATSU

Osaka Metropolitan University

Ryoichi Yoshida

Tokai University Hospital

Cooperative Institutions

Hokkaido University

Nagoya University

Nagoya Institute of Technology

Tohoku University

Tokyo Institute of Technology

National Institute of Advanced Industrial Science and Technology

University of Tsukuba

American Ceramic Society

Shizuoka University

The University of Tokyo

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Flux growth of yttria-stabilized zirconia crystals

Journal of Crystal Growth (1986)

Mitsunori Yokoyama Toshitaka Ota Iwao Yamai

Monoclinic crystal system

10.1016/0022-0248(86)90108-9

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Citations (4)

Effects of Oxide Additives on Sintering of Sb2O3-Doped SnO2 Ceramics

Journal of the Ceramic Association Japan (1972)

Toru Matsushita Iwao Yamai

The optimum calcination for the Sb2O3-doped SnO2 ceramics was obtained at 1000°C for 2 to 4hrs. The solubility of Sb2O3 in SnO2 was 20 to 25wt% under the calcinating conditions. Lattice constants of the Sb-doped SnO2 ceramic specimens were decreased up to 15% Sb2O3 and increased above 15% Sb2O3. Their density was increased up to 10 to 15% Sb2O3 and decreasd above 15% Sb2O3. Sintering of the ceramic specimens was markedly promoted by the addition of ZnO, MnO2, or CuO with the best. It is assumed that the addition of ZnO or MnO2 produces a substitution of Sn4+ ions in the SnO2 lattice. These substitutions give a charge unbalance creating oxygen vacancies. The CuO addition causes a liquid phase sintering. It is conjectured that both of the oxyen vacancies and the liquid phase promote sintering. High density of the ceramic specimens gives high flexural strength. Electrical resistivities of the Sb2O3-doped specimens with ZnO were 5 to 50Ω-cm and those of the Sb2O3-doped ones with CuO, 1 to 104Ω-cm at room temperature. Those of the Sb2O3-doped ones with MnO2 were extremely high.

Lattice constant

10.2109/jcersj1950.80.924_305

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Citations (11)

Synthesis of potassium hexatitanate fibers by the hydrothermal dehydration method

Journal of Crystal Growth (1979)

Toshitaka Oota Hajime Saito Iwao Yamai

Hydrothermal reaction

Dehydration reaction

Hydrothermal Synthesis

Molar ratio

10.1016/0022-0248(79)90081-2

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Citations (24)

ChemInform Abstract: LOW‐THERMAL‐EXPANSION POLYCRYSTALLINE ZIRCONYL PHOSPHATE CERAMIC

Chemischer Informationsdienst (1985)

Iwao Yamai Toshitaka Oota

Abstract Die Synthese von Wärmeschock‐beständigem Material aus 2 ZrO 2 ‐ P 2 O 5 wird untersucht.

10.1002/chin.198533008

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Preparation of potassium hexatitanate long fibres by the flux evaporation method using Na2O-K2O-B2O3 flux

Journal of Materials Science Letters (1994)

Mitsunori Yokoyama Toshitaka Ota Iwao Yamai

Flux method

10.1007/bf00420801

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Citations (4)

Grain Size‐Microcracking Relation for NaZr₂(PO₄)₃ Family Ceramics

Journal of the American Ceramic Society (1993)

Iwao Yamai Toshitaka Ota

The grain size‐microcracking relation was examined for low thermal expansion NaZr 2 (PO 4 ) 3 family ceramics. By measurements of the strength, Young's modulus, thermal expansion, and grain size of polycrystalline ceramics sintered at appropriate conditions, the critical grain size for microcracking was determined. The critical grain size was proportional to the inverse square of the maximum thermal expansion difference.

10.1111/j.1151-2916.1993.tb03811.x

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Citations (47)

Effect of Starting Materials on the Formation of Zn2SnO4 Crystals by Vapor Phase Method and Formation Reaction

Journal of the Ceramic Association Japan (1976)

Ryoichi Yoshida Yuji YOSHIDA Masayuki OKAWA Iwao Yamai Kohei Kodaira

The effect of starting materials on the formation of Zn2SnO4 crystals by vapor phase method and formation reaction were discussed.As starting material the ZnO-Sn system and Zn-SnO2 system were found to be superior. Of various combinations of all starting materials stoichiometric mixing ratio for the formation reaction of Zn2SnO4 gave the maximum yield of crystals.It was estimated that a reaction temperature of about 1200°C with a heating time of 2-3h were the most suitable conditions for this crystal forming reaction.It was estimated that vaporizing species of all starting materials were Zn and SnO which had about the same vapor pressure at 1200°C. From the grown state of crystals it was surmised that these vaporizing species formed as dendrites at first at the upper part of porcelain crucible with a high concentration of oxygen, after which the oxygen diffused down through the layer of dendrites to the lower part of crucible to form needle crystals.

Stoichiometry

Crucible (geodemography)

Crystal (programming language)

Vapor phase

10.2109/jcersj1950.84.975_557

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Vapor phase growth of Zn2SnO4 needle crystals

Journal of Crystal Growth (1976)

Ryoichi Yoshida Yūji Yoshida Iwao Yamai Kohei Kodaira Toru Matsushita

Crucible (geodemography)

Vapor phase

Crystal (programming language)

10.1016/0022-0248(76)90232-3

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Citations (16)

Thermal Expansion Behavior of NaZr₂(PO₄)₃Type Compounds

Journal of the American Ceramic Society (1986)

Toshitaka Oota Iwao Yamai

The thermal expansion of the skeletal framework was essentially zero for NaZr 2 (PO 4 ) 3 ‐type compounds; the interstitialion, e.g., Na + , was primarily responsible for the total thermal expansion. The composition dependence of the thermal expansion is discussed in terms of the amounts, crystallographic sites, and ionic radii of the interstitial ions. The mechanism which results in low thermal expansion was clarified, particularly for KZr 2 (PO 4 ) 3 , in which a larger ion is substituted for Na + , and NbZr(PO 4 ) 3 , which does not contain Na + . Polycrystalline ceramics formed from these crystals might be useful as thermal‐shock‐resistant materials.

Ionic radius

Thermal shock

Negative Thermal Expansion

10.1111/j.1151-2916.1986.tb04682.x

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Citations (162)

Effect of Nb2O5 additive on the sintering of SnO2

Journal of the Ceramic Association Japan (1975)

Junichi Takahashi Iwao Yamai Hajime Saito

The effect of Nb2O5 additive on the sintering of SnO2 was investigated by measuring density, shrinkage and grain size in the temperature range 1200 to 1400°C in O2, air and N2. The sinterability of SnO2 compacts was increased with Nb2O5 content, and at a concentration of 5wt% Nb2O5, high-density bodies of 95% of theoretical were obtained after sintering at 1400°C for 10hr in O2. From electrical resistivity and X-ray diffraction data, it might be consideredthat niobium ion was soluble in SnO2 up to about 3wt%. Electron microscopic observation of polished specimens showed that Nb2O5 second-phase particles inhibited the grain growth and grain growth kinetics could be described by D=ktm; the values of time exponent “m” were found to be 1/4 and 1/6 for the specimens with Nb2O5 content of 3wt% and 5wt%, respectively.In the initial stage of the sintering, relatively fast shrinkage occurred by addition of Nb2O5 without formation of liquid phase, and then Nb2O5 second-phase particles decreased the grain growth rate which dominated the sintering kinetics during the later stage.

Shrinkage

10.2109/jcersj1950.83.959_362

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Citations (12)