EP0277811A2
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EP
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Optically transparent yttrium oxide
Assignee: Raytheon Co
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Filing: 1988-02-02
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Granted: —
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Expires: 2008-02-02
Abstract
Abstract A transparent yttrium oxide ceramic is made by densifying a yttrium oxide powder without addition of dopants. The yttrium oxide powder is consolidated into a body of a predetermined shape and sintered to a density such that any remaining porosity is sealed from the surrounding atmosphere. The closed porosity body is then subjected to an elevated pressure and temperature to provide the body with substantially 100% of theoretical density. The resulting body has substantial transparency over the wavelength range of .6 mu m to 7 mu m.
Inventors
- 👤 Tom Hartnett
- 👤 Michael Greenberg
- 👤 Richard L. Gentilman
Bibliographic Details
Application Number
—
Jurisdiction
EP
Data Source
google_patents
Last Synchronized
2026-11-08 08:11
CPC Classifications
C; C04; C04B; C04B35/00; C04B35/50; C04B35/505; H; H01; H01J; H01J61/00; H01J61/02; H01J61/30; H01J61/302
Claims Analysis
Total Claims: 29
Claim 1
Independent Claim
47 words
A body comprising at least 99.9% yttrium oxide having a density of at least 99% of theoretically density, a sample of said body having an in-line transmission of at least 73%, over a wavelength range of 2-5 microns with said sample having a thickness of 0.375 inches.
Claim 2
Dependent Claim
47 words
A body comprising at least 99.9% yttrium oxide having a density of at least 99% of theoretically density, a sample of said body having an in-line transmission of at least 73%, over a wavelength range of 2-5 microns with said sample having a thickness of 0.375 inches.
Claim 3
Dependent Claim
22 words
A body according to claim 1, characterised in that the average grain size of the body is less than about 150 microns.
Claim 4
Dependent Claim
24 words
A body according to claim 2, characterised in that the coefficient absorption is less than about 0.1 cm⁻¹ at a wavelength of four microns.
Claim 5
Dependent Claim
56 words
A body comprising about 99.99% pure yttrium oxide having an average grain size of about 150 microns and a density of at least 99% of theoretical density, a sample of said body having an in-line transmission of at least 80%, over a wavelength range of 3-5 microns with said sample having a thickness of 0.040 inches.
Claim 6
Dependent Claim
56 words
A body comprising about 99.99% pure yttrium oxide having an average grain size of about 150 microns and a density of at least 99% of theoretical density, a sample of said body having an in-line transmission of at least 80%, over a wavelength range of 3-5 microns with said sample having a thickness of 0.040 inches.
Claim 7
Dependent Claim
25 words
A body according to claim 4, characterised by a coefficient of absorption which is less than about 0.1 cm⁻¹ at a wavelength of 4.0 microns.
Claim 8
Dependent Claim
22 words
A body according to claim 5, characterised by an in-line transmission of at least 76% over the wavelength range of 3-7 microns.
Claim 9
Dependent Claim
38 words
A body according to claim 3 or 6, characterised in that said yttrium oxide has a thermal conductivity of at least 15 W/M-°K at 0°C, and at least 7 W/M-°K over the temperature range of 0 to 300°C.
Claim 10
Dependent Claim
89 words
A body consisting essentially of at least 99.9% pure polycrystalline cubic yttrium oxide having an average grain size of about 150 microns, a thermal conductivity characteristic of at least 15 W/M-°K at 0° and at least 7 W/M-°K over the temperature range of 0°C to 300°C, and a density of at least 99.9% of theoretical density, a sample of said body having an in-line transmission of at least 80% over a wavelength range of at least 2.5 to 6.8 microns with said sample having a thickness of 0.04 inches.
Claim 11
Dependent Claim
89 words
A body consisting essentially of at least 99.9% pure polycrystalline cubic yttrium oxide having an average grain size of about 150 microns, a thermal conductivity characteristic of at least 15 W/M-°K at 0° and at least 7 W/M-°K over the temperature range of 0°C to 300°C, and a density of at least 99.9% of theoretical density, a sample of said body having an in-line transmission of at least 80% over a wavelength range of at least 2.5 to 6.8 microns with said sample having a thickness of 0.04 inches.
Claim 12
Dependent Claim
29 words
A body according to claim 8, characterised in that said yttrium oxide has a coefficient of absorption of less than about 0.1 cm⁻¹ at a wavelength of 4.0 microns.
Claim 13
Independent Claim
100 words
A method of fabricating a body comprising at least 99.9% yttrium oxide, comprises the steps of: providing a starting powder of at least 99.9% yttrium oxide; compacting said yttrium oxide powder to form a body of at least 99.9% yttrium oxide; sintering said compacted 99.9% yttrium oxide body at an elevated temperature to provide the body having a closed porosity state; and densifying said closed porosity 99.9% yttrium oxide body by heating said body to an elevated temperature at an elevated gas pressure for a period of time until said body achieves a density of substantially 100% of theoretical density.
Claim 14
Independent Claim
100 words
A method of fabricating a body comprising at least 99.9% yttrium oxide, comprises the steps of: providing a starting powder of at least 99.9% yttrium oxide; compacting said yttrium oxide powder to form a body of at least 99.9% yttrium oxide; sintering said compacted 99.9% yttrium oxide body at an elevated temperature to provide the body having a closed porosity state; and densifying said closed porosity 99.9% yttrium oxide body by heating said body to an elevated temperature at an elevated gas pressure for a period of time until said body achieves a density of substantially 100% of theoretical density.
Claim 15
Dependent Claim
23 words
A method according to claim 10, characterised in that said starting powder has an average particle size of about 1.0µm to 2.0 µm.
Claim 16
Dependent Claim
21 words
A method according to claim 10, characterised in that the sintering step occurs in a high vacuum tungsten heating element furnace.
Claim 17
Dependent Claim
40 words
A method according to claim 12, characterised by the step of: annealing said body having substantially 100% of theoretical density by heating said body in an atmosphere comprised of air to restore the surface of the material to stoichiometric composition.
Claim 18
Dependent Claim
36 words
A method according to claim 12, characterised in that said densifying step occurs at a temperature in the range of 1700°C to 1900°C at an elevated pressure in the range of 25,000 psi to 30,000 psi.
Claim 19
Dependent Claim
23 words
A method according to claim 14, characterised in that said temperature of the sintering step is in the range of 1700°C to 1900°C.
Claim 20
Dependent Claim
23 words
A method according to claim 15, characterised in that said temperature of the sintering step is in the range of 1800°C to 1900°C.
Claim 21
Dependent Claim
19 words
A method according to claim 13, characterised in that said annealing step occurs at a temperature of about 1450°C.
Claim 22
Independent Claim
166 words
A method of fabricating a body comprising at least 99.99% yttrium oxide, comprises the steps of: providing a yttrium oxide powder of 99.99% yttrium oxide, said powder having an average particle size between 1 and 2.0 micrometers, and having a maximum agglomerated particle size of 10 micrometers: consolidating said powder to provide a body of at least 99.99% yttrium oxide having a density of about 75% of theoretical density; densifying the 75% dense body to a closed porosity state in a vacuum at a temperature in the range of 1700-1900°C for a period of time at the maximum temperature of about 30 minutes; densifying the closed porosity body to substantially 100% of theoretical density by subjecting the body to a temperature in the range of 1700-1900°C at an argon gas pressure in the range of 25,000-30,000 psi; and annealing said body in an air atmosphere at a temperature in the range of 1400°C-1800°C for a period of between 30 and 60 minutes at the elevated temperature.
Claim 23
Independent Claim
166 words
A method of fabricating a body comprising at least 99.99% yttrium oxide, comprises the steps of: providing a yttrium oxide powder of 99.99% yttrium oxide, said powder having an average particle size between 1 and 2.0 micrometers, and having a maximum agglomerated particle size of 10 micrometers: consolidating said powder to provide a body of at least 99.99% yttrium oxide having a density of about 75% of theoretical density; densifying the 75% dense body to a closed porosity state in a vacuum at a temperature in the range of 1700-1900°C for a period of time at the maximum temperature of about 30 minutes; densifying the closed porosity body to substantially 100% of theoretical density by subjecting the body to a temperature in the range of 1700-1900°C at an argon gas pressure in the range of 25,000-30,000 psi; and annealing said body in an air atmosphere at a temperature in the range of 1400°C-1800°C for a period of between 30 and 60 minutes at the elevated temperature.
Claim 24
Dependent Claim
21 words
A method according to claim 18, characterised in that the sintering step occurs in a high vacuum tungsten heating element furnace.
Claim 25
Dependent Claim
19 words
A method according to claim 19, characterised in that said annealing step occurs at a temperature of about 1450°C.
Claim 26
Independent Claim
245 words
A method of fabricating a non-planar body comprised of at least 99.9% yttrium oxide having an uncorrected in-line transmittance of at least 80% for a sample having a thickness of about 0.04 inches, comprises the steps of: providing a yttrium oxide powder having an average particle size of 1 to 2.0 micrometers and having a maximum agglomerated particle size of 10 microns; adding a binder vehicle and dispersent to the powder and spray-drying the powder to provide a free flowing powder; directing the free flowing powder into a non-planar mold and subjecting the powder in the non-planar mold to an isostatic pressure in the range of 25,000-30,000 psi; removing the binder vehicle by subjecting the powder to a temperature in the range of 1350-1450°C for a predetermined period of time in an atmosphere of air; densifying the powder to a closed porosity state in a vacuum at a temperature in the range of 1700-1900°C for a period of time at the maximum temperature of typically 30 minutes or less; densifying the closed porosity body to substantially 100% of theoretical density by subjecting the body to a temperature in the range of 1700-1900°C at an argon gas pressure in the range of 25,000-30,000 psi until the body is substantially 100% of theoretical density; and annealing said body in an atmosphere comprising hydrogen and watr vapor at a temperature in the range of 1700-1800°C for a period of between 30 and 60 minutes at the elevated temperature.
Claim 27
Independent Claim
245 words
A method of fabricating a non-planar body comprised of at least 99.9% yttrium oxide having an uncorrected in-line transmittance of at least 80% for a sample having a thickness of about 0.04 inches, comprises the steps of: providing a yttrium oxide powder having an average particle size of 1 to 2.0 micrometers and having a maximum agglomerated particle size of 10 microns; adding a binder vehicle and dispersent to the powder and spray-drying the powder to provide a free flowing powder; directing the free flowing powder into a non-planar mold and subjecting the powder in the non-planar mold to an isostatic pressure in the range of 25,000-30,000 psi; removing the binder vehicle by subjecting the powder to a temperature in the range of 1350-1450°C for a predetermined period of time in an atmosphere of air; densifying the powder to a closed porosity state in a vacuum at a temperature in the range of 1700-1900°C for a period of time at the maximum temperature of typically 30 minutes or less; densifying the closed porosity body to substantially 100% of theoretical density by subjecting the body to a temperature in the range of 1700-1900°C at an argon gas pressure in the range of 25,000-30,000 psi until the body is substantially 100% of theoretical density; and annealing said body in an atmosphere comprising hydrogen and watr vapor at a temperature in the range of 1700-1800°C for a period of between 30 and 60 minutes at the elevated temperature.
Claim 28
Dependent Claim
16 words
A method according to claim 21, characterised in that said non-planar body is a hemispherical dome.
Claim 29
Dependent Claim
28 words
A method according to claim 22, characterised in that the removing step occurs for a period of time until the body has achieved about 75% of theoretical density.
References Cited (Backward Citations)
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