Transparent polycrystalline sintered ceramic of cubic crystal structure

• US 7,247,589 B2
• Filed: 01/21/2005
• Issued: 07/24/2007
• Est. Priority Date: 01/23/2004
• Status: Active Grant

• Current Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Original Assignee: Fraunhofer Gesellschaft Zur Foerderung Der Angewandten Forsching E.V.
• Inventors: Hutzler, Thomas, Krell, Andreas
• Primary Examiner(s): GROUP, KARL E
• Application Number:
  US11/038,402
• Publication Number:
  US 20050164867A1
• Time in Patent Office: 914 Days
• Field of Search: 501/120, 501/152, 501/103, 501/96.1, 501/98.4
• US Class Current: 501/120
• CPC Class Codes: B82Y 30/00 Nanotechnology for materials or surface science, e.g. nanocomposites
• CPC Class Codes: C04B 2235/3225 Yttrium oxide or oxide-forming salts thereof
• CPC Class Codes: C04B 2235/3869 Aluminium oxynitrides, e.g. AlON, sialon
• CPC Class Codes: C04B 2235/5409 expressed by specific surface values
• CPC Class Codes: C04B 2235/661 Multi-step sintering
• CPC Class Codes: C04B 2235/77 Density
• CPC Class Codes: C04B 2235/781 Nanograined materials, i.e. having grain sizes below 100 nm
• CPC Class Codes: C04B 2235/785 Submicron sized grains, i.e. from 0,1 to 1 micron
• CPC Class Codes: C04B 2235/786 Micrometer sized grains, i.e. from 1 to 100 micron
• CPC Class Codes: C04B 2235/96 Properties of ceramic products, e.g. mechanical properties such as strength, toughness, wear resistance
• CPC Class Codes: C04B 2235/9653 Translucent or transparent ceramics other than alumina
• CPC Class Codes: C04B 35/44 based on aluminates
• CPC Class Codes: C04B 35/443 Magnesium aluminate spinel
• CPC Class Codes: C04B 35/48 based on zirconium or hafnium oxides, zirconates, zircon or hafnates
• CPC Class Codes: C04B 35/486 Fine ceramics
• CPC Class Codes: C04B 35/505 based on yttrium oxide
• CPC Class Codes: C04B 35/581 based on aluminium nitride
• CPC Class Codes: C04B 35/64 Burning or sintering processes C04B33/32 takes precedence ; powder metallurgy B22F
• CPC Class Codes: C04B 35/6455 Hot isostatic pressing

Abstract

Transparent polycrystalline sintered ceramic of cubic crystal structure. The invention relates to the field of technical ceramic and relates to transparent polycrystalline sintered ceramics of cubic crystal structure for applications with increased mechanical stress, e.g., as protective or armoring ceramic. Provided are sintered ceramics that combine a high transmission of RIT>75% of the theoretical maximum value with a distinctly improved hardness. Transparent polycrystalline sintered ceramics of cubic crystal structure with a real in-line transmission RIT>75% of the theoretical maximum value measured on 0.8 mm-thick polished plates and for light of a wavelength between 600 and 650 nm, and with an average grain size D in the range of 60 nm<D<10 μm are provided.

Claims

1. Transparent polycrystalline sintered ceramic composed of Mg—

Al spinel, Al oxynitride, ZrO₂, Y₂O₃ or Y—

Al garnet, or of a mixed structure of these components, of cubic crystal structure, comprising a real in-line transmission RIT>

75% of the theoretical maximum value measured on 0.8 mm-thick polished plates and for light of a wavelength between 600 and 650 nm, and

wherein when the sintered ceramic is composed of Mg—

Al spinel, Al oxynitride, ZrO₂, or Y₂O₃, or of a mixed structure of these components, the average grain size D is in the range of 60 nm<

D<

10 μ

m, and

wherein when the sintered ceramic is composed of Y—

Al garnet, the average grain size D is in the range of 60 nm<

D<

1 μ

m.

2. Sintered ceramic according to claim 1, wherein when the sintered ceramic is composed of Mg—

Al spinel, Al oxynitride, ZrO₂, or Y₂O₃, or of a mixed structure of these components, the average grain size D is in the range of 60 nm<

D<

5 μ

m.

3. Sintered ceramic according to claim 1, wherein when the sintered ceramic is composed of Mg—

Al spinel, Al oxynitride, ZrO₂, or Y₂O₃, or of a mixed structure of these components, the average grain size D is in the range of 60 nm<

D<

2 μ

m.

4. Sintered ceramic according to claim 1, wherein when the sintered ceramic is composed of Mg—

Al spinel, Al oxynitride, ZrO₂, or Y₂O₃, or of a mixed structure of these components, the average grain size D is in the range of 60 nm<

D<

1 μ

m.

5. Sintered ceramic according to claim 1, which contains up to 5% by wt of additional dopants that are present in the crystal lattice as solid solutions, as a separate phase with crystallite size <

250 nm, or in both forms.

6. Sintered ceramic according to claim 1, in which a transparent Mg—

Al spinel ceramic has a Vickers hardness of HV10>

13 GPa.

7. Sintered ceramic according to claim 2, which contains up to 5% by wt of additional dopants that are present in the crystal lattice as solid solutions, as a separate phase with crystallite size <

250 nm, or in both forms.

8. Sintered ceramic according to claim 2, in which a transparent Mg—

Al spinel ceramic has a Vickers hardness of HV10>

13 GPa.

9. Sintered ceramic according to claim 3, which contains up to 5% by wt of additional dopants that are present in the crystal lattice as solid solutions, as a separate phase with crystallite size <

250 nm, or in both forms.

10. Sintered ceramic according to claim 3, in which a transparent Mg—

Al spinel ceramic has a Vickers hardness of HV10>

13 GPa.

11. Sintered ceramic according to claim 4, which contains up to 5% by wt of additional dopants that are present in the crystal lattice as solid solutions, as a separate phase with crystallite size <

250 nm, or in both forms.

12. Sintered ceramic according to claim 4, in which a transparent Mg—

Al spinel ceramic has a Vickers hardness of HV10>

13 GPa.