Method of fabricating high-permittivity dielectric material
AssigneeUnited States of America as represented by the Administrator of NASA
InventorsDennis S. Tucker, Terry D. Rolin, Curtis W. Hill
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Abstract
Nano-sized particles of barium-titanate are heated as a gas mixture of 25% hydrogen and 75% nitrogen is passed there through yielding particles of barium-titanate having oxygen vacancies therein. The particles of barium-titanate having oxygen vacancies therein are coated with silica yielding silica-coated particles having a silica coating thickness in a range of 2-5 nanometers. The silica-coated particles are sintered by application of pressure in a range of 35-50 megapascals and temperature in a range of 950-1050° C. The sintered quantity of material is cooled at a cooling rate in a range of 1-3° C. per minute at least until the temperature thereof is less than 120° C.
Claims18
A method of fabricating a high-permittivity dielectric material, comprising steps of:
- heating nano-sized particles of barium-titanate as a gas mixture of 25% hydrogen and 75% nitrogen is passed there through yielding particles of barium-titanate having oxygen vacancies therein;
- coating said particles of barium-titanate having oxygen vacancies therein with silica yielding silica-coated particles having a silica coating thickness in a range of 2-5 nanometers;
- sintering a quantity of said silica-coated particles by a continuous application of a DC electric current to said silica-coated particles to heat said silica-coated particles to a temperature in a range of 950-1050° C., said step of sintering further including a simultaneous application of pressure in a range of 35-50 megapascals;
- and
- cooling said quantity so-sintered to minimize macro-level breaking of said quantity so-sintered, wherein said step of cooling is carried out at a cooling rate in a range of 1-3° C. per minute at least until a temperature of said quantity so-sintered is less than 120° C., wherein a dielectric material having a permittivity of at least 500,000 at a frequency of 1 kHz is fabricated.
A method of fabricating a high-permittivity dielectric material, comprising ire steps of:
- heating, in a vertical-tube furnace, particles of barium-titanate having diameters not to exceed 200 nanometers as a gas mixture of 25% hydrogen and 75% nitrogen is passed there through, wherein particles of barium-titanate having oxygen vacancies therein are generated;
- coating, using atomic layer deposition, said particles of barium-titanate having oxygen vacancies therein with silica yielding silica-coated particles having a silica coating thickness in a range of 2-5 nanometers;
- sintering, in a vacuum, a quantity of said silica-coated particles by a continuous application of a DC electric current to said silica-coated particles to heat said silica-coated particles to a temperature in a range of 950-1050° C., said step of sintering further including a simultaneous application of pressure in a range of 35-50 megapascals;
- discontinuing, following said step of sintering, said continuous application of said DC electric current and said simultaneous application of pressure;
- and
- cooling said quantity so-sintered to minimize macro-level breaking of said quantity so-sintered, wherein said step of cooling is carried out at a cooling rate in a range of 1-3° C. per minute at least until a temperature of said quantity so-sintered is less than 120° C., wherein a dielectric material having a permittivity of at least 500,000 at a frequency of 1 kHz is fabricated.
A method of fabricating a high-permittivity dielectric material, comprising steps of:
- heating, in a vertical-tube furnace, particles of barium-titanate having diameters not to exceed 200 nanometers as a gas mixture of 25% hydrogen and 75% nitrogen is passed there through, wherein particles of barium-titanate having oxygen vacancies therein are generated;
- coating, using atomic layer deposition, said particles of barium titanate having oxygen vacancies therein with silica yielding silica-coated particles having a silica coating thickness in a range of 2-5 nanometers;
- placing a quantity of said silica-coated particles in a die;
- placing said die in a vacuum;
- increasing pressure on said die to achieve a sintering pressure on said quantity of said silica-coated particles in said die of 50 megapascals;
- continuously applying, simultaneously with said step of increasing, a DC electric current to said die to achieve a sintering temperature of said quantity of said silica-coated particles in said die of 1050° C.;
- maintaining said sintering pressure and said sintering temperature for approximately 5 minutes wherein said quantity of said silica-coated particles in said die are transformed to a sintered solid;
- discontinuing said steps of increasing pressure and continuously applying;
- and
- cooling said sintered solid in said die to minimize macro-level breaking of said sintered solid, wherein said step of cooling is carried out at a cooling rate in a range of 1-3° C. per minute at least until a temperature of said sintered solid is less than 120° C., wherein a dielectric material having a permittivity of at least 500,000 at a frequency of 1 kHz is fabricated.
Dependencies are inferred from the claim text.