Composite ultrafine particles of aluminum nitride and rare earth nitride, method for production and sintered article thereof

An aggregate of composite ultrafine particles comprising:

• (A) ultrafine particles of aluminum nitride having a morphologically anisotropic structure, said particles having a shape and size selected from the group consisting of (a) a hexagonal column or whisker 5 to 200 nm in width or thickness and 50 to 1,000 nm in length and (b) a strip 5 to 50 nm in thickness and 10 to 1,000 nm in width or length, and said particles substantially comprising any one of a composite phase of aluminum nitride and nitride of a rare earth element, a solid solution of rare earth element in aluminum nitride, and a single crystal of aluminum nitride;
• and
• (B) ultrafine particles of nitride of the rare earth element mixed with said ultrafine particles of aluminum nitride.

An ultrafine particle of aluminum nitride having a morphologically anisotropic structure, which particle having a shape of strip 5 to 50 nm in thickness and 10 to 1,000 nm in width or length, said ultrafine particle of aluminum nitride containing a rare earth element or nitride of said rare earth element therein.

An ultrafine particle of aluminum nitride according to claim, 5 wherein said rare earth element is yttrium.

An ultrafine particle of aluminum nitride having a morphologically anisotropic structure, which particle having a shape of hexagonal column 5 to 200 nm in width or thickness and 50 to 1,000 nm in length, said ultrafine particle of aluminum nitride containing a rare earth element or nitride of said rare earth element therein.

An ultrafine particle of aluminum nitride having a morphologically anisotropic structure, which particle having shape of whisker 5 to 200 nm in width or thickness and 50 to 1,000 nm in length, said ultrafine particle of aluminum nitride being a single crystal of aluminum nitride.