Ceramics Surface and Interface Group

2022.02.15 Update

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.

Research target

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.


We are developing oxide-based gas sensor materials. However, it is difficult to obtain a high-density target for thin films that has an optimum resistance value. Therefore, we are evaluating the gas sensor by synthesizing SnO2 and In2O3, which are difficult to sinter, and using them as targets to form thin films by sputtering method.



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


Fig. 2




Selected Recent Results


Lanthanum oxide (La2O3) is an unstable material in the air. We stabilized this material and used it for the oxygen diffusion experiment. The figure shows the results of 18O diffusion profile. La(OH)3 is present on the sample surface. Because of this, a large difference in 18O concentration is observed between 400 and 500 ºC.



Figure is a summary of the diffusion coefficients obtained in La2O3 ceramics. Diffusion coefficients in La2O3 were as same as those in cerium oxide. In addition, we are conducting research on synthesis of La2O3 ceramics.



The composition of SnO2 thin film was optimized. Figure shows the response of the thin film to acetone gas. A response characteristic of 893 was obtained at a temperature at 350 ºC.



Figure shows the results of18O diffusion obtained with reduced BaTiO3. The results of the line analysis across the grain boundary are shown. As shown in this figure, grain boundaries have a significant effect on 18O diffusion.


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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 "@")