Abstract: The fine barium titanate particles of the present invention have an average primary particle diameter of from 10 nm to less than 20 nm, a sphericity of 1.00 to 1.18, and a ratio of an average secondary particle diameter to the average primary particle diameter of 0.7 to 6.0. The fine barium titanate particles of the present invention can exhibit a small behavior particle diameter and can be readily monodispersed notwithstanding very fine particles, and as a result, can be suitably used as various dielectric materials because the particles are free from aggregation therebetween and have an excellent dispersibility.

Abstract: Spherical tetragonal barium titanate particles of the present invention have a perovskite crystal structure, an average particle diameter of 0.05 to 0.5 ?m, a particle size distribution ?g of not less than 0.70, and a ratio of Ba to Ti of 0.99:1 to 1.01:1. The spherical tetragonal barium titanate particles exhibit an excellent dispersibility as well as a high denseness, a high purity and excellent permittivity properties.

Abstract: The fine barium titanate particles of the present invention have an average primary particle diameter of from 10 nm to less than 20 nm, a sphericity of 1.00 to 1.18, and a ratio of an average secondary particle diameter to the average primary particle diameter of 0.7 to 6.0. The fine barium titanate particles of the present invention can exhibit a small behavior particle diameter and can be readily monodispersed notwithstanding very fine particles, and as a result, can be suitably used as various dielectric materials because the particles are free from aggregation therebetween and have an excellent dispersibility.

Abstract: Magnetic metal particles containing iron as a main component, comprising cobalt in an amount of usually 20 to 50 atm %, calculated as Co, based on whole Fe, aluminum in an amount of usually 3 to 15 atm %, calculated as Al, based on whole Fe and a rare earth element in an amount of usually 3 to 20 atm %, calculated as rare earth element, based on whole Fe, and having an average major axis diameter of usually 0.02 to 0.065 ?m, preferably from 0.02 to less than 0.05 ?m, a coercive force of usually 159.2 to 222.9 kA/m (2,000 to 2,800 Oe), a soluble Na content of usually not more than 30 ppm, a soluble Ca content of usually not more than 100 ppm, and an oxidation stability ??s of usually not more than 10%.

Abstract: Spherical tetragonal barium titanate particles of the present invention have a perovskite crystal structure, an average particle diameter of 0.05 to 0.5 ?m, a particle size distribution ?g of not less than 0.70, and a ratio of Ba to Ti of 0.99:1 to 1.01:1. The spherical tetragonal barium titanate particles exhibit an excellent dispersibility as well as a high denseness, a high purity and excellent permittivity properties.

Abstract: Spherical tetragonal barium titanate particles of the present invention have a perovskite crystal structure, an average particle diameter of 0.05 to 0.5 &mgr;m, a particle size distribution &sgr;g of not less than 0.70, and a ratio of Ba to Ti of 0.99:1 to 1.01:1. The spherical tetragonal barium titanate particles exhibit an excellent dispersibility as well as a high denseness, a high purity and excellent permittivity properties.

Abstract: Spindle-shaped magnetic alloy particles containing Fe and Co as main components of the present invention have a cobalt content of 20 to 50 atm % (calculated as Co) based on whole Fe; an average major axis diameter (L) of 0.03 to 0.10 &mgr;m; a coercive force value of 159.2 to 238.7 kA/m (2,000 to 3,000 Oe); a crystallite size of 100 to 160 Å; and an activation volume (Vact) of 0.01 to 0.07E-4 &mgr;m3. A high-density magnetic recording medium produced by using such spindle-shaped magnetic alloy particles containing Fe and Co as main components, have an excellent output characteristics in a short wavelength region, a considerably reduced noise and an excellent storage stability.

Abstract: Magnetic metal particles containing iron as a main component, comprising cobalt in an amount of usually 20 to 50 atm %, calculated as Co, based on whole Fe, aluminum in an amount of usually 3 to 15 atm %, calculated as Al, based on whole Fe and a rare earth element in an amount of usually 3 to 20 atm %, calculated as rare earth element, based on whole Fe, and having an average major axis diameter of usually 0.02 to 0.065 &mgr;m, preferably from 0.02 to less than 0.05 &mgr;m, a coercive force of usually 159.2 to 222.9 kA/m (2,000 to 2,800 Oe), a soluble Na content of usually not more than 30 ppm, a soluble Ca content of usually not more than 100 ppm, and an oxidation stability &Dgr;&sgr;s of usually not more than 10%.

Abstract: Spindle-shaped magnetic alloy particles containing Fe and Co as main components of the present invention have a cobalt content of 20 to 50 atm% (calculated as Co) based on whole Fe; an average major axis diameter (L) of 0.03 to 0.10 &mgr;m; a coercive force value of 159.2 to 238.7 kA/m (2,000 to 3,000 Oe); a crystallite size of 100 to 160 Å; and an activation volume (Vact) of 0.01 to 0.07E-4 &mgr;m3. A high-density magnetic recording medium produced by using such spindle-shaped magnetic alloy particles containing Fe and Co as main components, have an excellent output characteristics in a short wavelength region, a considerably reduced noise and an excellent storage stability.

Abstract: Spherical tetragonal barium titanate particles of the present invention have a perovskite crystal structure, an average particle diameter of 0.05 to 0.5 &mgr;m, a particle size distribution &sgr;g of not less than 0.70, and a ratio of Ba to Ti of 0.99:1 to 1.01:1. The spherical tetragonal barium titanate particles exhibit an excellent dispersibility as well as a high denseness, a high purity and excellent permittivity properties.

Abstract: The present invention relates to spindle-shaped goethite particles and spindle-shaped hematite particles, which have a narrow particle size distribution, include no dendrites, and have an appropriate particle shape and a large aspect ratio (major axial diameter/minor axial diameter); and spindle-shaped magnetic iron based alloy particles which are obtained from the spindle-shaped goethite particle or spindle-shaped hematite particles as a beginning material and which have a high coercive force and an excellent coercive force distribution. Such spindle-shaped goethite particles comprises: goethite seed containing 0.5 to 25 atm % of Co based on the total Fe in the spindle-shaped goethite particles, and goethite surface layer containing 0.5 to 15 atm % of Al based on the total Fe in the spindle-shaped goethite particles; and having an average major axial diameter of 0.05 to 1.0 &mgr;m.

Abstract: The present invention relates to spindle-shaped goethite particles and spindle-shaped hematite particles, which have a narrow particle size distribution, include no dendrites, and have an appropriate particle shape and a large aspect ratio (major axial diameter/minor axial diameter); and spindle-shaped magnetic iron based alloy particles which are obtained from the spindle-shaped goethite particle or spindle-shaped hematite particles as a beginning material and which have a high coercive force and an excellent coercive force distribution. Such spindle-shaped goethite particles comprises: goethite seed containing 0.5 to 25 atm % of Co based on the total Fe in the spindle-shaped goethite particles, and goethite surface layer containing 0.5 to 15 atm % of Al based on the total Fe in the spindle-shaped goethite particles; and having an average major axial diameter of 0.05 to 1.0 .mu.m.

Abstract: Disclosed herein are a process for producing acicular goethite particles comprising the steps of: blowing an oxygen-containing gas into a ferrous salt reaction solution containing colloidal ferrous hydroxide or iron-containing colloidal precipitates which is obtained by reacting an aqueous ferrous salt solution with less than one equivalent of an aqueous alkali hydroxide solution and/or an aqueous alkali carbonate solution based on Fe.sup.2 + in said aqueous ferrous salt solution so as to oxidize said colloidal ferrous hydroxide or iron-containing colloidal precipitates and to produce acicular goethite nucleus particles, adding to the resultant aqueous ferrous salt reaction solution containing said acicular goethite nucleus particles not less than one equivalent of an aqueous alkali carbonate solution based on Fe.sup.

Abstract: The present invention relates to a method of preparing Si-containing goethite (.alpha.-FeOOH) by the precipitation of Fe(II) salts with an excess of base, and subsequent oxidation in the presence of a silicate solution.

Abstract: Disclosed herein are spinel-type spherical black iron oxide particles containing 1.5 to 17.0 wt % of Zn, and having a specific surface area of 5 to 15 m.sup.2 /g, a magnetization of not less than 70 emu/g in an external magnetic field of 1 kOe and a coercive force (Hc) of not more than the value obtained from the following expression:Hc(Oe)=15+3.times.(specific surface area of the particles).and a process for producing the same.