Provided is alumina material comprising alumina and zirconium, wherein in a radial distribution function obtained by Fourier-transforming an extended X-ray absorption fine structure (EXAFS) spectrum of a K absorption edge of the zirconium in the alumina material, the value of I.sub.B/I.sub.A is 0.5 or less where I.sub.A is a maximum intensity among the intensities of peaks present at 0.1 nm to 0.2 nm, and I.sub.B is a maximum intensity among the intensities of peaks present at 0.28 nm to 0.35 nm.

Disclosed are methods for preparing high-purity boehmite and porous gamma-alumina nano-powder, comprising: adding aluminum isopropoxide into water and stirring the aluminum isopropoxide added water, then adding aluminum hydroxide generated by hydrolysis of high-purity aluminum powder into that stirred water, stirring that aluminum hydroxide added water to obtain a mixed system; carrying out hydrothermal reaction on the mixed system, performing centrifuging, washing, drying and crushing to the reacted mixed system, obtaining high-purity boehmite; calcining the high-purity boehmite to obtain porous gamma (γ)-alumina nano-powder. By strictly controlling the addition of isopropanolic aluminum and the temperature as well as the duration of the hydrothermal reaction, the product boehmite γ-AlOOH obtains good character in terms of crystalline structure, purity, morphology and dispersion; γ-Al.sub.2O.sub.3 obtained after calcining remains basically the same morphology as that of boehmite powder with good powder dispersion and no major changes.

Disclosed are methods for preparing high-purity boehmite and porous gamma-alumina nano-powder, comprising: adding aluminum isopropoxide into water and stirring the aluminum isopropoxide added water, then adding aluminum hydroxide generated by hydrolysis of high-purity aluminum powder into that stirred water, stirring that aluminum hydroxide added water to obtain a mixed system; carrying out hydrothermal reaction on the mixed system, performing centrifuging, washing, drying and crushing to the reacted mixed system, obtaining high-purity boehmite; calcining the high-purity boehmite to obtain porous gamma (γ)-alumina nano-powder. By strictly controlling the addition of isopropanolic aluminum and the temperature as well as the duration of the hydrothermal reaction, the product boehmite γ-AlOOH obtains good character in terms of crystalline structure, purity, morphology and dispersion; γ-Al.sub.2O.sub.3 obtained after calcining remains basically the same morphology as that of boehmite powder with good powder dispersion and no major changes.

A plate-like alumina particle, in which a ratio I (006)/I (113) of a peak intensity 1(006) at 20=41.6±0.3 degrees which corresponds to a (006) face to a peak intensity I(113) at 20=43.3±0.3 degrees which corresponds to a (113) face of diffraction peaks obtained by X-ray diffraction measurement using a Cu—Kα ray, is 0.2 or more. A method for manufacturing the plate-like alumina particle including mixing an aluminum compound including an aluminum element, a molybdenum compound including a molybdenum element, and a shape-controlling agent to produce a mixture and firing the mixture.

A plate-like alumina particle, in which a ratio I (006)/I (113) of a peak intensity 1(006) at 20=41.6±0.3 degrees which corresponds to a (006) face to a peak intensity I(113) at 20=43.3±0.3 degrees which corresponds to a (113) face of diffraction peaks obtained by X-ray diffraction measurement using a Cu—Kα ray, is 0.2 or more. A method for manufacturing the plate-like alumina particle including mixing an aluminum compound including an aluminum element, a molybdenum compound including a molybdenum element, and a shape-controlling agent to produce a mixture and firing the mixture.

An aluminum oxide article containing at least aluminum atoms and oxygen atoms is described. When observed under a transmission electron microscope, a cross section of the aluminum oxide article contains crystallized parts, in which a crystal lattice image is recognizable, and a non-crystallized part, in which no crystal lattice image is recognizable, and has an island-and-sea structure consisting of isolated parts containing the crystallized parts and the continuous non-crystallized part. The isolated parts correspond to island parts in the island-and-sea structure, the continuous non-crystallized part corresponds to a sea part, and a plurality of the island parts are uniformly distributed in the sea part. An aluminum oxide for improving the battery performance of a lithium ion secondary battery, the scratch resistance and hardness of a cured film, and the gas barrier properties of a gas barrier film is provided.

An aluminum oxide article containing at least aluminum atoms and oxygen atoms is described. When observed under a transmission electron microscope, a cross section of the aluminum oxide article contains crystallized parts, in which a crystal lattice image is recognizable, and a non-crystallized part, in which no crystal lattice image is recognizable, and has an island-and-sea structure consisting of isolated parts containing the crystallized parts and the continuous non-crystallized part. The isolated parts correspond to island parts in the island-and-sea structure, the continuous non-crystallized part corresponds to a sea part, and a plurality of the island parts are uniformly distributed in the sea part. An aluminum oxide for improving the battery performance of a lithium ion secondary battery, the scratch resistance and hardness of a cured film, and the gas barrier properties of a gas barrier film is provided.

Provided are alumina particles containing molybdenum and with their shape controlled. The alumina particles contain phosphorus and molybdenum. The alumina particles are preferably plate-like or card house-like. The phosphorus is preferably unevenly distributed in surface layers of the alumina particles. Also provided are a resin composition containing the alumina particles and a resin, a molded body made by molding the resin composition, and a method for producing the alumina particle including a step of firing the aluminum compound in the presence of a molybdenum compound and a phosphorous compound.

The composite particle of the present invention includes an alumina particle having a card-house structure which is formed of three or more pieces of plate-like alumina and in which the pieces of plate-like alumina are fixed to each other; and an inorganic coating part provided on a surface of the plate-like alumina.

The composite particle of the present invention includes an alumina particle having a card-house structure which is formed of three or more pieces of plate-like alumina and in which the pieces of plate-like alumina are fixed to each other; and an inorganic coating part provided on a surface of the plate-like alumina.