Fine powder of aluminum nitride, composition and sintered body thereof and processes for their production
AssigneeTokuyama Soda Kabushiki Kaisha
InventorsNobuyuki Kuramoto, Hitofumi Taniguchi
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Abstract
A fine powder of aluminum nitride having an average particle diameter of not more than 2 microns and comprising at least 94% by weight of aluminum nitride, at most 3% by weight of bound oxygen and at most 0.5% by weight as metal of metal compounds as impurities. The fine aluminum nitride powder is prepared from a fine alumina powder and a fine carbon powder as starting materials. The fine aluminum nitride powder provides a sintered body having a high purity and a high density such as at least 2.9 g/cm.sup.3. The fine aluminum nitride powder is also useful as a raw material for alpha-Sialon, beta-Sialon and AlN polytypes, as an addition aid in various ceramics.
Claims36
A fine powder of aluminum nitride
- (a) having an average particle diameter of not more than 2 microns.
- (b) comprising at least 97% by weight of aluminum nitride, and at most 0.5% by weight as metal of metal compounds as impurities, or at most 0.5% by weight, as impurities, of carbon or silicon as carbon or silicon compounds, wherein at most 0.1% by weight of the metal of the metal compounds is selected from the group consisting of iron, chromium, nicket, cobalt, copper, zinc and titanium, and
- (c) containing at most 1.5% by weight of bound oxygen.
A process for producing a fine powder of aluminum nitride, which comprises
- (1) intimately mixing a fine powder of alumina having an average particle diameter of not more than 2 microns with a fine powder of carbon having an ash content of at most 0.2% and an average particle diameter of not more than 1 micron in a liquid dispersing medium, the weight ratio of the fine alumina powder to the fine carbon powder being from 1:0.36 to 1:1,
- (2) firing the resulting intimate mixture at a temperature of 1,400.degree. to 1,700.degree. C. in an atmosphere of nitrogen or ammonia after drying it, and
- (3) thereafter heating the resulting fine powder at a temperature of 600.degree. to 900.degree. C. to remove the unreacted carbon, thereby forming a fine powder of aluminum nitride having an average particle diameter of not more than 2 microns and containing at least 94% by weight of aluminum nitride, at most 3% by weight of bound oxygen and at most 0.5% by weight, calculated as metal, of metal compounds as impurities, or at most 0.5% by weight, as impurities, of carbon or silicon as carbon or silicon compounds.
a process for producing an intimate composition of a fine powder of aluminum nitride, which comprises
- (1) intimately mixing a fine powder of alumina having an average particle diameter of not more than 2 microns, a fine powder of carbon having an ash content of at most 0.2% by weight and an average particle diameter of not more than 1 micron and a compound of a metal selected from the group consisting of alkaline earth metals, lanthanum group metals and yttrium in a liquid medium, the weight ratio of the fine alumina powder to the fine carbon powder being from 1:0.36 to 1:1 and the amount of the compound of the metal being 0.02 to 5.0% by weight as a metal oxide having the highest atomic valence based on the resulting composition,
- (2) after or without drying the resulting intimate mixture, firing it at a temperature of 1,400.degree. to 1,700.degree. C. in an atmosphere of nitrogen or ammonia, and
- (3) thereafter, heating the resulting fine powder at a temperature of 600.degree. to 900.degree. C. in an atmosphere containing oxygen to remove the unreacted carbon, thereby forming an intimate composition of a fine powder of aluminum nitride comprising at least 93% by weight of aluminum nitride, at most 3% by weight of bound oxygen, 0.02 to 5.0% by weight as an oxide having the highest atomic valence of at least one metal element selected from the group consisting of alkaline earth metals, lanthanum group metals and yttrium or a compound thereof, and at most 0.3% by weight as metal of metal compounds as impurities selected from the group consisting of iron, chromium, nickel, cobalt, copper, zinc and titanium.
a process for producing an intimate composition of a fine powder of aluminum nitride, which comprises intimately mixing a fine powder of aluminum nitride having an average particle diameter of not more than 2 microns, comprising at least 97% by weight of aluminum nitride, and at most 0.5% by weight as metal of metal compounds as impurities, wherein at most 0.1% by weight of the metal of the metal compounds is selected from the group consisting of iron, chromium, nickel, cobalt, copper, zinc and titanium, and containing at most 1.5% by weight of bound oxygen with a compound of at least one metal selected from the group consisting of alkaline earth metals, lanthanum group metals and yttrium in such proportions that the content of the compound of said metal is 0.02 to 5.0% by weight as a metal oxide having the highest atomic valence in the resulting composiition, thereby to form an intimate composition of a fine powder of aluminum nitride comprising at least 93% by weight of aluminum nitride, at most 3% by weight of bound oxygen, 0.02 to 5.0% by weight as an oxide having the highest atomic valence of at least one metal element selected from the group consisting of alkaline earth metals, lanthanum group metals and yttrium or a compound thereof, and at most 0.3% by weight as metal of metal compounds as impurities selected from the group consisting of iron, chromium, nickel, cobalt, copper, zinc and titanium.
A sintered body of aluminum nitride having a high purity, a high density and light-transmitting properties, said sintered body having a density of at least 3.16 g/cm.sup.3 and a light transmittance of at most 68 cm.sup.-1 calculated from in-line transmittance to light having a wavelength of 6 .mu.m and comprising at least 94% by weight of aluminum nitride, at most 1.5% by weight of bound oxygen and at most 0.5% by weight as metal of metal compounds as impurities, or at most 0.5%, as impurities, by weight of carbon or silicon as carbon or silicon compounds.
A process for producing a sintered body of aluminum nitride having a high purity and a high density, which comprises molding a fine powder of aluminum nitride having an average particle diameter of not more than 2 microns, comprising at least 97% by weight of aluminum nitride, and at most 0.5% by weight as metal of metal compounds as impurities, or at most 0.5% by weight, as impurities, of carbon or silicon as carbon or silicon compounds, wherein at most 0.1% by weight of the metal of the metal compounds is selected from the group consisting of iron, chromium, nickel, cobalt, copper, zinc and titanium, and containing at most 1.5% by weight of bound oxygen and sintering the molded article at a temperature of 1,700.degree. to 2,100.degree. C. in an inert atmosphere thereby to form a sintered body of aluminum nitride.
A sintered body of aluminum nitride having a high purity, a high density and light-transmitting properties, said sintered body having a density of at least 3.16 g/cm.sup.3 and a light transmittance of at most 68 cm.sup.-1 calculated from in-line transmittance to light having a wavelength of 6 .mu.m and comprising at least 93% by weight of aluminum nitride, at most 3% by weight of bound oxygen, 0.02 to 5.0% by weight as an oxide having the highest atomic valence of at least one metal element selected from the group consisting of alkaline earth metals, lanthanum group metals and yttrium or a compound thereof, and at most 0.3% by weight as metal of metal compounds as impurities selected from the group consisting of iron, chromium, nickel, cobalt, copper, zinc and titanium.
A process for producing a sintered body of aluminum nitride having high purity and density, which comprise molding, an intimate composition of a fine powder of aluminum nitride comprising at least 93% by weight of aluminum nitride, at most 3% by weight of bound oxygen, 0.02 to 5.0% by weight as an oxide having the highest atomic valence of at least one metal element selected from the group consisting of alkaline earth metals, lanthanum group metals and yttrium or a compound thereof, and at most 0.3% by weight as metal of metal compounds as impurities selected from the group consisting of iron, chromium, nickel, cobalt, copper, zinc and titanium and sintering the molded article at a temperature of 1,600.degree. to 2,100.degree. C. in an inert atmosphere, thereby to form a sintered body of aluminum nitride having a high purity, a high density and lighttransmitting Properties, said sintered body having a density of at least 3.16 g/cm.sup.3 and a light transmittance of at most 68 cm.sup.-1 calculated from in-line transmittance to light having a wavelength of 6 .mu.m and comprising at least 93% by weight of aluminum nitride, at most 3% by weight of bound oxygen, 0.02 to 5.0% by weight as an oxide having the highest atomic valence of at least one metal element selected from the group consisting of alkaline earth metals, lanthanum group metals and yttrium or a compound thereof, and at most 0.3% by weight as metal of metal compounds as impurities selected from the group consisting of iron, chromium, nickel, cobalt, copper, zinc and titanium.
A sintered body of aluminum nitride having a high density, a mechanically fractured surface of said sintered body being formed of closely packed fine crystal grains distinct from each other by clear contours, said clear contours of the fine crystal grains at the fractured surface being polygonal, and at least 70% of said crystal grains having a particle diameter in the range of 0.5 D to 1.5 D wherein D in microns is the average particle diameter of the fine crystal grains at said fractured surface defined by the clear contours.
Dependencies are inferred from the claim text.