Magnetic and Electronic Properties of BaTiO3–(Ni,Cu,Zn)Fe2O4 Ceramic Composite: Reflection of Kepler Conjecture

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概要

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• Ceramic composites [$x$Ni0.15Cu0.30Zn0.55Fe2O4–($1-x$)BaTiO3] were successfully prepared by a direct solid-state reaction of raw materials (BaCO3, CuO, $\alpha$-Fe2O3, NiO, TiO2, and ZnO). The composites are so homogeneous that the ferrite and BaTiO3 grains do not react with each other. The $x$-dependent permeability and permittivity are found to obey Maxwell–Garnett effective medium theory, which suggests that the composites consist of ferrite particles with barium titanate medium. This model, however, starts to deviate from the experimental data at $x = 0.75$, and the roles of medium and inclusions seem to be exchanged. It can be qualitatively explained by the fact that geometrical close-packing of spheres is limited up to about 74 vol % (Kepler conjecture).

• 2009-12-15

著者

• WATANABE Kowashi

  RIKEN (The Institute of Physical and Chemical Research)

• Hiratsuka Nobuyuki

  Graduate School Of Science And Engineering Saitama University

• Naganuma Hiroshi

  Graduate School Of Engineering Tohoku University

• Kakizaki Koichi

  Graduate School Of Science And Engineering Saitama University

• Nagashima Yoshitaka

  Graduate School Of Science And Engineering Saitama University

• Kamishima Kenji

  Graduate School Of Science And Engineering Saitama University

• Naganuma Hiroshi

  Graduate School of Engineering, Tohoku University, Aoba, Aramaki, Aoba-ku, Sendai 980-8579

• Kamishima Kenji

  Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570

• Nagashima Yoshitaka

  Graduate School of Science and Engineering, Saitama University, 255 Shimo-Okubo, Sakura-ku, Saitama 338-8570

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