Ferrite particles are used in various applications. For example, Patent Document 1 (Japanese Patent Laid-Open No. 6-313176) discloses a fluid catalytic cracking catalyst composed of zeolite as active component and a support matrix wherein the matrix contains ferrite particles having a saturation magnetization of 10 emu/g or less and an average particle diameter of 0.001 to 20 μm.
Patent Document 2 (Japanese Patent Laid-Open No. 2004-189513) discloses a manufacturing method of a functional ferrite particles including the steps of attaching glass particles on the surface of ferrite particles to provide a coating layer of molten glass, applying a coating of titanium oxide on the surface of the ferrite particles provided with glass followed by heat-treating. The functional ferrite particles are useful as photocatalytic material. Examples of the ferrite particles used include Mn—Zn type ferrite, Mg—Cu—Zn type ferrite, and Ni—Cu—Zn type ferrite.
Although Patent Document 1 and 2 disclose that the ferrite particles are used as a catalyst, various properties of the ferrite particles are not focused.
Patent Document 3 (Japanese Patent Laid-Open No. 2007-320847) discloses products containing a plurality of a core fine particle structure containing a plurality of primary fine particles and a plurality of primary pores, and core-shell ceramic fine particles containing a shell surrounding at least a part of the core fine particle structure. The products include a membrane, a sensor, an electrode, and a getter.
The core-shell ceramic fine particles described in Patent Document 3 include a core of yttrium stabilized zirconia and a shell of lanthanum ferrite. So, the ferrite particles are not small in the apparent density, various properties are not maintained in the controllable state and do not fill a specified volume with a small weight because lanthanum ferrite is used as the shell.