Provided are: a MnZn-based ferrite which allows to have a low magnetic core loss and to suppress a time-dependent change of magnetic property under a high-temperature environment by a control of ambient oxygen concentration and an increase of the magnetic core loss, and a method for manufacturing the same. The MnZn-based ferrite is characterized in that Fe ranges from 53.25 mol % or more to 54.00 mol % or less on the basis of Fe.sub.2O.sub.3, Zn ranges from 2.50 mol % or more to 8.50 mol % or less on the basis of ZnO and Mn is the remainder on the basis of MnO, Si ranges from more than 0.001 mass % to less than 0.02 mass % on the basis of SiO.sub.2, Ca ranges from more than 0.04 mass % to less than 0.4 mass % on the basis of CaCO.sub.3, Co is less than 0.5 mass % on the basis of Co.sub.3O.sub.4, Bi is less than 0.05 mass % on the basis of Bi.sub.2O.sub.3, Ta is less than 0.05 mass % on the basis of Ta.sub.2O.sub.5, Nb is less than 0.05 mass % on the basis of Nb.sub.2O.sub.5, Ti is less than 0.3 mass % on the basis of TiO.sub.2, and Sn is less than 0.3 mass % on the basis of SnO.sub.2, and note that the converted total amount of Ta.sub.2O.sub.5 and Nb.sub.2O.sub.5 is less than 0.05 mass % and the converted total amount of TiO.sub.2 and SnO.sub.2 is less than 0.3 mass %.

Radiofrequency and other electronic devices can be formed from textured hexaferrite materials, such as Z-phase barium cobalt ferrite Ba.sub.3Co.sub.2Fe.sub.24O.sub.41 (Co.sub.2Z) having enhanced resonant frequency. The textured hexaferrite material can be formed by sintering fine grain hexaferrite powder at a lower temperature than conventional firing temperatures to inhibit reduction of iron. The textured hexaferrite material can be used in radiofrequency devices such as circulators or telecommunications systems.

A sintered Ni ferrite body having a composition comprising, calculated as oxide, 47.0-48.3% by mol of Fe.sub.2O.sub.3, 14.5% or more and less than 25% by mol of ZnO, 8.2-10.0% by mol of CuO, and more than 0.6% and 2.5% or less by mol of CoO, the balance being NiO and inevitable impurities, and having an average crystal grain size of more than 2.5 μm and less than 5.5 μm.

To provide a zinc oxide-based varistor that exhibits adequate characteristics without using antimony. Disclosed is a sintered body for a varistor, including zinc oxide as a main component; 0.6 to 3.0 mol % of bismuth oxide in terms of bismuth (Bi); 0.2 to 1.4 mol % of cobalt oxide in terms of cobalt (Co); 0.1 to 1.5 mol % of chrome oxide in terms of chrome (Cr); and 0.1 to 1.5 mol % of manganese oxide in terms of manganese (Mn), wherein the contents of antimony (Sb), a rare earth element and tin (Sn) are not more than a level of impurities.

A ferrite composition comprises a main component and a subcomponent. The main component includes 32.0 to 46.4 mol % of iron oxide in terms of Fe.sub.2O.sub.3, 4.4 to 14.0 mol % of copper oxide in terms of CuO, and 8.4 to 56.9 mol % of zinc oxide in terms of ZnO. The subcomponent includes 0.53 to 11.00 parts by weight of a silicon compound in terms of SiO.sub.2, 0.1 to 12.8 parts by weight of a tin compound in terms of SnO.sub.2, and 0.5 to 7.0 parts by weight of a bismuth compound in terms of Bi.sub.2O.sub.3, with respect to 100 parts by weight of the main component.

There is provided a ferrite sintered magnet having a high residual magnetic flux density. A ferrite sintered magnet 2 includes a plurality of main phase particles 5 including ferrite having a hexagonal structure, the number of core-shell structured particles 5A having a core 7 and a shell 9 covering the core 7, among the main phase particles 5, is smaller than the number of the main phase particles 5 other than the core-shell structured particles 5A.

A sintered ferrite magnet comprising (a) a ferrite phase having a hexagonal M-type magnetoplumbite structure comprising Ca, an element R which is at least one of rare earth elements and indispensably includes La, an element A which is Ba and/or Sr, Fe, and Co as indispensable elements, the composition of metal elements of Ca, R, A, Fe and Co being represented by the general formula of Ca.sub.1-x-yR.sub.xA.sub.yFe.sub.2n-zCo.sub.z, wherein the atomic ratios (1-x-y), x, y and z of these elements and the molar ratio n meet the relations of 0.3≦(1-x-y)≦0.65, 0.2≦x≦0.65, 0≦y≦0.2, 0.03≦z≦0.65, and 4≦n≦7, and (b) a grain boundary phase indispensably containing Si, the amount of Si being more than 1% by mass and 1.8% or less by mass (calculated as SiO.sub.2) based on the entire sintered ferrite magnet, and its production method.

An oxide ceramic having a principal component formed of a ferrite compound containing at least Sr, Co, and Fe, and zirconium in an amount of 0.05 to 1.0 wt. % on an oxide equivalent basis, and a ceramic electronic component using the oxide ceramic.

Radiofrequency and other electronic devices can be formed from textured hexaferrite materials, such as Z-phase barium cobalt ferrite Ba.sub.3Co.sub.2Fe.sub.24O.sub.41 (Co.sub.2Z) having enhanced resonant frequency. The textured hexaferrite material can be formed by sintering fine grain hexaferrite powder at a lower temperature than conventional firing temperatures to inhibit reduction of iron. The textured hexaferrite material can be used in radiofrequency devices such as circulators or telecommunications systems.

The invention relates to a method for the preparation of a blank of a ceramic material, wherein a first ceramic material and then a second ceramic material of different compositions are filled into a die and wherein the materials are pressed and after pressing are sintered. A layer of the first ceramic material is thereby filled into the die and a first cavity formed in the layer, the second ceramic material is then filled into the first open cavity and the materials pressed together and then heat-treated.