High thermal conductivity ceramic body

Claim 2

A process for producing a liquid phase sintered polycrystalline aluminum nitride ceramic body having a composition defined and encompassed by polygon ABCDEFGH excluding line DE of FIG. 2, a porosity of less than about 10% by volume of said body and a thermal conductivity greater than 0.70 W/cm·K at 25° C. which consists essentially of the steps: (a) forming a mixture consisting essentially of an oxygen-containing aluminum nitride powder, a lanthanide oxide selected from the group consisting of erbium oxide, holmium oxide, a mixture and solid solution thereof, and free carbon, shaping said mixture into a compact, said mixture and said compact having a composition wherein the equivalent % of said lanthanide and aluminum ranges from point A up to point E of FIG. 2, said lanthanide ranging from greater than about 0.25 equivalent % to about 8.0 equivalent %, said aluminum ranging from less than about 99.75 equivalent % to about 92.0 equivalent %, said mixture and said compact having an equivalent % composition of Ln, Al, O and N outside the composition defined and encompassed by polygon ABCDEFGH of FIG. 2, (b) heating said compact in a nitrogen-containing nonoxidizing atmosphere at a temperature ranging from about 1350° C. to a temperature sufficient to deoxidize the compact but below its pore closing temperature reacting said free carbon with oxygen contained in said aluminum nitride producing a deoxidized compact, said deoxidized compact having a composition wherein the equivalent % of Al, Ln, O and N is defined and encompassed by polygon ABCDEFGH excluding line DE of FIG. 2, said free carbon being in an amount which produces said deoxidized compact, an (c) sintering said deoxidized compact in a nitrogen-containing nonoxidizing atmosphere at a minimum temperature of about 1840° C. producing said polycrystalline body.

Claim 3

The process according to claim 1 wherein said nitrogen-containing atmosphere in step (b) contains sufficient nitrogen to facilitate deoxidation of the aluminum nitride to produce said sintered body.

Claim 4

The process according to claim 1 wherein said nitrogen-containing atmosphere in step (c) contains sufficient nitrogen to prevent significant weight loss of said aluminum nitride.

Claim 5

The process according to claim 1 wherein said process is carried out at ambient pressure.

Claim 6

The process according to claim 1 wherein said porosity is less than about 4% by volume of said body.

Claim 7

The process according to claim 1 wherein said mixture and said compact have a composition wherein the equivalent % of said lanthanide and aluminum ranges from point A to point F of FIG. 2, said lanthanide ranging from about 8.0 equivalent % to about 0.3 equivalent %, said aluminum ranging from about 92.0 equivalent % to about 99.7 equivalent %, said mixture and said compact having an equivalent % composition of Ln. Al, O and N outside the composition defined and encompassed by polygon ABCFGH of FIG. 2, and wherein said sintered body and said deoxidized compact are comprised of a composition wherein the equivalent percent of Al, Ln, O and N is defined and encompassed by polygon ABCFGH of FIG. 2.

Claim 8

The process according to claim 1 wherein said mixture and said compact have a composition wherein the equivalent % of said lanthanide and aluminum ranges from point A up to point Q of FIG. 2, said lanthanide ranging from about 8.0 equivalent % to greater than about 0.55 equivalent % and said aluminum ranging from about 92.0 equivalent % to less than about 99.45 equivalent %, said mixture and said compact having an equivalent % composition of Ln, Al, O and N outside the composition defined and IO encompassed by polygon ABCQRS of FIG. 2, and said deoxidized compact and sintered body are comprised of a composition wherein the equivalent percent of Al, Ln, O and N is defined and encompassed by polygon ABCQRS excluding line CQ of FIG. 2.

Claim 9

The process according to claim 1 wherein said mixture and said compact have a composition wherein the equivalent % of said lanthanide and aluminum ranges from point I up to point Q of FIG. 2, said lanthanide ranging from about 5.75 equivalent % to greater than about 0.55 equivalent % and said aluminum ranging from about 94.25 equivalent % to less than about 99.45 equivalent %, said mixture and said compact having an equivalent % composition of Ln, Al, O and N outside the composition defined and encompassed by polygon IJKQRS of FIG. 2, and said deoxidized compact and sintered body are comprised of a composition wherein the equivalent % of Al, Ln, O and N is defined and encompassed by polygon IJKQRS but excluding line KQ of FIG. 2.

Claim 10

The process according to claim 1 wherein said mixture and said compact have a composition wherein the equivalent % of said lanthanide and aluminum ranges from point M up to point Q of FIG. 2, said lanthanide ranging from about 3.75 equivalent % to greater than about 0.55 equivalent % and said aluminum ranging from about 96.25 equivalent % to less than about 99.45 equivalent %, said mixture and said compact having an equivalent % composition of Ln, Al, O and N outside the composition defined and encompassed by polygon MNOQRS of FIG. 2, said deoxidized compact and sintered body are comprised of a composition wherein the equivalent % of Al, Ln, O and N is defined and encompassed by polygon MNOQRS excluding line OQ of FIG. 2, and wherein said minimum sintering temperature is about 1850° C.

Claim 11

The process according to claim 1 wherein said mixture and said compact have a composition wherein the equivalent % of said lanthanide and aluminum ranges from point S up to point F of FIG. 2, said lanthanide ranging from about 2.4 equivalent % to greater than about 0.3 equivalent % and said aluminum ranging from about 97.6 equivalent % to less than about 99.7 equivalent %, said mixture and said compact having an equivalent % composition of Ln, Al, O and N outside the composition defined and encompassed by polygon SRQFGH of FIG. 2, said deoxidized compact and sintered body are comprised of a composition wherein the equivalent percent of Al, Ln, O and N is defined and encompassed by polygon SRQFGH, excluding line QF of FIG. 2, and wherein said minimum sintering temperature ranges from about 1890° C. to about 1920° C.

Claim 12

The process according to claim 1 wherein said mixture and said compact have a composition wherein the equivalent % of said lanthanide and aluminum ranges from point K to point O of FIG. 2, said lanthanide ranging from about 1.8 equivalent % to about 0.8 equivalent % and said aluminum ranging from about 98.2 equivalent % to about 99.2 equivalent %, said mixture and said compact having an equivalent % composition of Ln, Al, O and N outside the composition defined by line KO of FIG. 2, and said deoxidized compact and sintered body are comprised of a composition wherein the equivalent percent of Al, Ln, O and N is defined by line KO of FIG. 2.

Claim 13

The process according to claim 1 wherein said mixture and said compact have a composition wherein the equivalent % of said lanthanide and aluminum ranges from point O to point F of FIG. 2, said Ln ranging from about 0.8 equivalent % to about 0.3 equivalent % and said aluminum ranging from about 99.2 equivalent % to about 99.7 equivalent %, said mixture and said compact having an equivalent % composition of Ln, Al, O and N outside the composition defined by line OF, said deoxidized compact and said sintered body are comprised of a composition wherein the equivalent percent of Al, Ln, O and N is defined by line OF of FIG. 2, and wherein said minimum sintering temperature is about 1850° C.

Claim 14

The process according to claim 1 wherein said mixture and said compact have a composition wherein the equivalent % of said lanthanide and aluminum ranges between points K and E but does not include points K and E of FIG. 2, said lanthanide ranging from less than about 1.8 equivalent % to greater than about 0.25 equivalent %, said aluminum ranging from greater than about 98.2 equivalent % to less than about 99.75 equivalent %, said mixture and said compact having an equivalent % composition of Ln, Al, O and N outside the composition defined by polygon KLEF of FIG. 2, and said deoxidized compact and said sintered body are comprised of a composition wherein the equivalent percent of Al, Ln, O and N is defined and encompassed by polygon KLEF but does not include lines LE and KF of FIG. 2.

Claim 15

A process for producing a sintered polycrystalline aluminum nitride ceramic body having a composition defined and encompassed by polygon ABCDEFGH excluding line DE of FIG. 2, a porosity of less than about 10% by volume of said body and a thermal conductivity greater than 0.70 W/cm· at 25° C. which consists essentially the steps: (a) forming a mixture consisting essentially of an oxygen-containing aluminum nitride powder, a lanthanide oxide selected from the group consisting of erbium oxide, holmium oxide, a mixture and solid solution thereof or precursor therefor, and a carbonaceous additive selected from the group consisting essentially of free carbon, a carbonaceous organic material and mixture thereof, said carbonaceous organic material thermally decomposing at a temperature ranging from about 50° C. to about 1000° C. to free carbon and gaseous product of decomposition which vaporizes away, shaping said mixture into a compact, said mixture and said compact having a composition wherein the equivalent % of said lanthanide and aluminum ranges from point A up to point E of FIG. 2, said lanthanide ranging from greater than about 0.25 equivalent % to about 8.0 equivalent %, said aluminum ranging from less than about 99.75 equivalent % to about 92.0 equivalent % aluminum, said mixture and said compact having an equivalent % composition of Ln, Al, O and N outside the composition defined and encompassed by polygon ABCDEFGH of FIG. 2, (b) heating said compact in a nonoxidizing atmosphe,re at a temperature up to about 1200° C. thereby providing lanthanide oxide and free carbon, (c) heating said compact in a nitrogen-containing nonoxidizing atmosphere at a temperature ranging from about 1350° C. to a temperature sufficient to deoxidize the compact but below its pore closing temperature reacting said free carbon with oxygen contained in said aluminum nitride producing a deoxidized compact, said deoxidized compact having a composition wherein the equivalent % of Al, Ln, O and N is defined and encompassed by polygon ABCDEFGH excluding line DE of FIG. 2, said free carbon being in an amount which produces said deoxidized compact, and (d) sintering said deoxidized compact in a nitrogen-containing nonoxidizing atmosphere at a minimum temperature of about 1840° C. producing said polycrystalline body.

Claim 16

A process for producing a sintered polycrystalline aluminum nitride ceramic body having a composition defined and encompassed by polygon ABCDEFGH excluding line DE of FIG. 2, a porosity of less than about 10% by volume of said body and a thermal conductivity greater than 0.70 W/cm· at 25° C. which consists essentially the steps: (a) forming a mixture consisting essentially of an oxygen-containing aluminum nitride powder, a lanthanide oxide selected from the group consisting of erbium oxide, holmium oxide, a mixture and solid solution thereof or precursor therefor, and a carbonaceous additive selected from the group consisting essentially of free carbon, a carbonaceous organic material and mixture thereof, said carbonaceous organic material thermally decomposing at a temperature ranging from about 50° C. to about 1000° C. to free carbon and gaseous product of decomposition which vaporizes away, shaping said mixture into a compact, said mixture and said compact having a composition wherein the equivalent % of said lanthanide and aluminum ranges from point A up to point E of FIG. 2, said lanthanide ranging from greater than about 0.25 equivalent % to about 8.0 equivalent %, said aluminum ranging from less than about 99.75 equivalent % to about 92.0 equivalent % aluminum, said mixture and said compact having an equivalent % composition of Ln, Al, O and N outside the composition defined and encompassed by polygon ABCDEFGH of FIG. 2, (b) heating said compact in a nonoxidizing atmosphe,re at a temperature up to about 1200° C. thereby providing lanthanide oxide and free carbon, (c) heating said compact in a nitrogen-containing nonoxidizing atmosphere at a temperature ranging from about 1350° C. to a temperature sufficient to deoxidize the compact but below its pore closing temperature reacting said free carbon with oxygen contained in said aluminum nitride producing a deoxidized compact, said deoxidized compact having a composition wherein the equivalent % of Al, Ln, O and N is defined and encompassed by polygon ABCDEFGH excluding line DE of FIG. 2, said free carbon being in an amount which produces said deoxidized compact, and (d) sintering said deoxidized compact in a nitrogen-containing nonoxidizing atmosphere at a minimum temperature of about 1840° C. producing said polycrystalline body.

Claim 17

The process according to claim 14 wherein said nitrogen-containing atmosphere in step (c) contains sufficient nitrogen to facilitate deoxidation of the aluminum nitride to produce said sintered body.

Claim 18

The process according to claim 14 wherein said nitrogen-containing atmosphere in step (d) contains sufficient nitrogen to prevent significant weight loss of said aluminum nitride.

Claim 19

The process according to claim 14 wherein said process is carried out at ambient pressure.

Claim 20

The process according to claim 14 wherein said porosity is less than about 4% by volume of said body.

Claim 21

The process according to claim 14 wherein said mixture and said compact have a composition wherein the equivalent % of said lanthanide and aluminum ranges from point A to point F of FIG. 2, said lanthanide ranging from about 8.0 equivalent % to about 0.3 equivalent %, said aluminum ranging from about 92.0 equivalent % to about 99.7 equivalent %, said mixture and said compact having an equivalent % composition of Ln, Al, O and N outside the composition defined and encompassed by polygon ABCFGH of FIG. 2, and wherein said sintered body and said deoxidized compact are comprised of a composition wherein the equivalent percent of Al, Ln, O and N is defined by polygon ABCFGH of FIG. 2.

Claim 22

The process according to claim 14 wherein said mixture and said compact have a composition wherein the equivalent % of said lanthanide and aluminum ranges from point A up to point Q of FIG. 2, said lanthanide ranging from about 8.0 equivalent % to greater than about 0.55 equivalent % and said aluminum ranging from about 92.0 equivalent % to less than about 99.45 equivalent %, said mixture and said compact having an equivalent % composition of Ln, Al, O and N outside the composition defined and encompassed by polygon ABCQRS of FIG. 2, and said deoxidized compact and sintered body are comprised of a composition wherein the equivalent percent of Al, Ln, O and N is defined and encompassed by polygon ABCQRS excluding line CQ of FIG. 2.

Claim 23

The process according to claim 14 wherein said mixture and said compact have a composition wherein the equivalent % of said lanthanide and aluminum ranges from point I up to point Q but excludes line KQ of FIG. 2, said lanthanide ranging from about 5.75 equivalent % to greater than about 0.55 equivalent % and said aluminum ranging from about 4.25 equivalent % to less than about 99.45 equivalent %, said mixture and said compact having an equivalent % composition of Ln, Al, O and N outside the composition defined and encompassed by polygon IJKQRS of FIG. 2, and said deoxidized compact and sintered body are comprised of a composition wherein the equivalent percent of Al, Ln, O and N is defined and encompassed by polygon IJKQRS but excluding line KQ of FIG. 2.

Claim 24

The process according to claim 14 wherein said mixture and said compact have a composition wherein the equivalent % of said lanthanide and aluminum ranges from point M up to point Q of FIG. 2, said lanthanide ranging from about 3.75 equivalent % to greater than about 0.55 equivalent % and said aluminum ranging from about 96.25 equivalent % to less than about 99.45 equivalent %, said mixture and said compact having an equivalent % composition of Ln, Al, O and N outside the composition defined and encompassed by polygon MNOQRS of FIG. 2, said deoxidized compact and sintered body are comprised of a composition wherein the equivalent % of Al, Ln, O and N is defined and encompassed by polygon MNOQRS excluding line OQ of FIG. 2, and wherein said minimum sintering temperature is about 1850° C.

Claim 25

The process according to claim 14 wherein said mixture and said compact have a composition wherein the equivalent % of said lanthanide and aluminum ranges from point S up to point F of FIG. 2, said lanthanide ranging from about 2.4 equivalent % to greater than about 0.3 equivalent % and said aluminum ranging from about 97.6 equivalent % to less than about 99.7 equivalent %, said mixture and said compact having an equivalent % composition of Ln, Al, O and N, outside the composition defined and encompassed by polygon SRQFGH of FIG. 2, said deoxidized compact and sintered body are comprised of a composition wherein the equivalent percent of Al, Ln, O and N is defined and encompassed by polygon SRQFGH excluding line QF of FIG. 2, and wherein said minimum sintering temperature ranges from about 1890° C. to about 1920° C.

Claim 26

The process according to claim 14 wherein said mixture and said compact have a composition wherein the equivalent % of said lanthanide and aluminum ranges from point K to point O of FIG. 2, said lanthanide ranging from about 1.8 equivalent % to about 0.8 equivalent % and said aluminum ranging from about 98.2 equivalent % to about 99.2 equivalent %, said mixture and said compact having an equivalent % composition of Ln, Al, O and N outside the composition defined by line KO of FIG. 2, and said deoxidized compact and sintered body are comprised of a composition wherein the equivalent percent of Al, Ln, O and N is defined by line KO of FIG. 2.

Claim 27

The process according to claim 14 wherein said mixture and said compact have a composition wherein the equivalent % of said lanthanide and aluminum ranges from point O to point F of FIG. 2, said Ln ranging from about 0.8 equivalent % to about 0.3 equivalent % and said aluminum ranging from about 99.2 equivalent % to about 99.7 equivalent %, said mixture and said compact having an equivalent % composition of Ln, Al, O and N outside the composition defined by line OF, said deoxidized compact and said sintered body are comprised of a composition wherein the equivalent percent of Al, Ln, O and N is defined by line OF of FIG. 2, and wherein said minimum sintering temperature is about 1850° C.

Claim 28

The process according to claim 14 wherein said mixture and said compact have a composition wherein the equivalent % of said lanthanide and aluminum ranges between points K and E but does not include points K and E of FIG. 2, said lanthanide ranging from less than about 1.8 equivalent % to greater than about 0.25 equivalent %, said aluminum ranging from greater than about 98.2 equivalent % to less than about 99.75 equivalent %, said mixture and said compact having an equivalent % composition of Ln, Al, O and N outside the composition defined by polygon KLEF of FIG. 2, and said deoxidized compact and said sintered body are comprised of a composition wherein the equivalent percent of Al, Ln, O and N is defined and encompassed by polygon KLEF but does not include lines LE and KF of FIG. 2.