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Ceramics Surface and Interface Group

Ceramics have surface, interface and grains. Especially, the surface and interface (grain boundary) in ceramics show the electrical properties. Our group focuses on the surface and interface as reaction field during the sintering to fabricate the oxide with poor sinterability and stability in air. In order to achieve above purpose, we used soft-chemical method, solid-state reaction method, and ion beam techniques. By the integration of the information on ceramics fabrication, we proceed with a basic ceramics science.

Objective

The research target is to fabricate the dense ceramics such as SnO2, La2O3, In2O3 and Ga2O3 etc. These materials are well known as the semiconductor and dielectric materials. For example, SnO2 and In2O3 are the sensor materials, and show the poor sinterability. La2O3 has a problem on the stability under the humidity atmosphere. We synthesize the dense ceramics and use them the target for rf- sputtering and PLD methods. Finally, we measure the gas sensor property for hydrogen and ethanol of these thin films.


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We are working on thinning of oxide gas sensor material. But, SnO2 is poor sinterable oxide-materials and it is difficult to obtain a target with high density for thin films. Therefore, we are synthesizing ceramic synthesis of SnO2 and In2O3 which is difficult to sinter. Using these materials, thin films are formed by sputtering method, and then gas sensing properties are evaluated. We prepare the thin films from nano-sized powder and evaluate gas sensor characteristics.


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The group evaluates hydrogen and oxygen defects in densified ceramics. These are help to understand the deterioration mechanism. We are also evaluating the gas sensor characteristics of thin films and powder films. In order to understand the characteristics, we evaluate structure and chemical composition on the surface layer, and develop it into the study of the reaction mechanism of the gas at the surface.


Facilities

This is a secondary ion mass spectrometry (SIMS). This is helpful to detect light element, isotope and impurities.(Fig. 1)

This is ion implantor. This is useful the surface modification. We also use to make a standard sample for SIMS analysis.(Fig. 2)

"Fig. 1" Image

Fig. 1


"Fig. 2" Image

Fig. 2




Selected Recent Results

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An electron spin-polarized He+ ion source. The maximum beam polarization of about 25% was achieved by a new optical pumping scheme of circularly and linearly polarized 1083 nm radiation tuned to D0 line (He metastables 23S1 → 23P1 transition).


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A new mechanism of spin-dependent He+ ion - surface atom interaction. Due to spin-orbit coupling for a hole virtually created in a target atom during the collisional intermediate state, the scattering cross section of a He+ ion differs between spins.


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With respect to densification of SnO2 ceramics, illustration is additives with relative density exceeding 90% and temperature range. SnO2 is ordinarily densified by ZnO and other co-doping, and the relative density reaches 99%. The electrical resistance of ceramic disk is controlled by the addition of donor and acceptor.


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The Group is working to improve densify such as SnO2 and In2O3 and other oxides. Furthermore, we are trying to synthesize ceramics of various compositions, and at the same time we are exploring the characteristics. On the other hand, we also control the shape of oxide nano-particles using soft chemical methods.


Group Leader

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Ceramics Surface and Interface Group
1-1 Namiki, Tsukuba, Ibaraki, 305-0044 JAPAN
TEL: +81-29-860-4434
E-Mail: SAKAGUCHI.Isao=nims.go.jp(Please change "=" to "@")
National Institute for Materials Science (NIMS)
1-2-1 Sengen, Tsukuba, Ibaraki 305-0047, JAPAN
TEL.+81-(0)-29-859-2000
FAX.+81-(0)-29-859-2029