High-resolution electron microscopy and cathodoluminescence scanning electron microscopy of SrTiO3-based ceramics elucidating their varistor property.

• Autorzy: Shiojiri M. , Isshiki T. , Nishio K. , Saijo H. , Nomura T. , Hitomi A. , Sato S.
• Konferencja: XV Physical Metallurgy and Materials Science Conference on Advanced Materials & Technologies AMT'98, Kraków-Krynica, Poland, 17-21 May, 1998
• Języki publikacji: EN

Abstrakty

EN

Semiconductive SrTiO3-based ceramics practically used as varistors and capacitors have been investigated using HRTEM, EDX and CLSEM. They were produced with and without an additonal reducing treatment at Po2=10 raising to a 12th power Pa in the sintering process at Po2=10 raising to a -8 power Pa, followed by reoxidizing process in the air. (Sr0.35Ba0.35Ca0.30)1.026TiO3 varistors produced without the additional heat-treatment are composed of well-developed crystalline grains with facet boundaries, having a low varistor coefficient (alpha<4). CL revealed that the grain, particularly near varistor surface, has high conductive inside containing oxygen vacancies and less-conductive boundary layer without the oxygen vacancies. The boundary layers may work as the double Shottky barriers. The additional reducing treatment forms a lot of oxygen vacancies in the grains of the varistors and damaged the crystallinity near the grain boundaries. The damaged regions easily introduce oxygen atoms into the grains during the reoxydizing process. The additional treatment, hence, produces thick boundary layers and consequently gives rise to high varistor coefficient (alpha>4), which is favourable for practical use. (Sr0.94Ba0.01Ca0.05)0.99TiO3 capacitors were also produced without the additional reducing treatment. Their grains have the facet boundary structure. The dielectric boundary layer and semiconductive inside of the grain are also observed. The boundary layer is as thin as a few ten nanometers, which cause the ceramic a high capacitance.

Słowa kluczowe

EN

semiconductive ceramics; electron microscopy; scanning electron microscopy; cathodoluminescence; layer; heat treatment; boundary layer; varistor; capacitor

PL

ceramika półprzewodnikowa; mikroskopia elektronowa; mikroskopia elektronowa skaningowa; katodoluminescencja; warstwa; obróbka cieplna; warstwa przyścienna; warystor; kondensator

• Wydawca: Wydawnictwo SIGMA-NOT
• Czasopismo: Inżynieria Materiałowa
• Rocznik: 1998
• Tom: R. XIX, nr 4
• Strony: 779--784
• Opis fizyczny: Bibliogr. 4 poz., rys.

Twórcy

autor

Shiojiri M.

• Kyoto Institute of Technology, Japan

autor

Isshiki T.

• Kyoto Institute of Technology, Japan

autor

Nishio K.

• Kyoto Institute of Technology, Japan
• Kyoto Institute of Technology, Japan

autor

Saijo H.

• Kyoto Institute of Technology, Japan

autor

Nomura T.

• Materials Research Center, Narita, Japan

autor

Hitomi A.

• Materials Research Center, Narita, Japan

autor

Sato S.

• Materials Research Center, Narita, Japan

• Kyoto Institute of Technology

Bibliografia

• [1] H. Saijo, G. Ning, Y. Yabuuchi, Y. Takahashi, T. Isshiki, M. Shiojiri and K. Ogawa, J. Electron Microsc. 43, (1994) 77.
• [2] K.Koseki, Y.Nakano, T.Nomura, T.Isshiki, K.Nishio, H.Saijo and M. Shiojiri, Phys. Stat. Sol. (a) 143, (1994) 245
• [3] Kobayashi, S. Sato, A. Hitomi, T. Isshiki, H. Saijo, T. Nomura and M. Shiojiri, J. Electron Micros. 47, (1998) 101.
• [4] M. Shiojiri, T. Isshiki, H. Saijo, S. Sato and A. Hitomi, Electron Technol. in print.