Transparent spinel ceramics and method for the production thereof

Patent metadata

Field	Value
Publication number	US-9309156-B2
Application number	US-201414287776-A
Country	US
Kind code	B2
Filing date	May 27, 2014
Priority date	May 27, 2014
Publication date	Apr 12, 2016
Grant date	Apr 12, 2016

Abstract

Transparent spinel ceramics, as they can be used, for example, as protective ceramics, and to a method for the production thereof.
Transparent spinel ceramics which preferably contain no visible defects and which have an in-line transmission of more than 82% in wavelength ranges of infrared light, measured between 1000 nm and 2500 nm, at sample thicknesses≧3 mm.
Spinel ceramics transparent in wavelength ranges of infrared light which are composed of sintered magnesium aluminum spinel having an average structural grain size of ≦10 μm and having maximally 0.5 mass % overall of homogeneously distributed additives of calcium and/or strontium and/or barium which are present in a concentration, expressed respectively as an oxide, of 0.005 to <0.2 mass % CaO and/or 0.005 to <0.5 mass % SrO and/or 0.005 to <0.5 mass % BaO.

First claim

The invention claimed is:

1. Spinel ceramics which are transparent in wavelength ranges of infrared light, composed of sintered magnesium aluminum spinel having an average structural grain size of ≦10 μm and having maximally 0.5 mass % overall of homogeneously distributed additives of calcium and/or strontium and/or barium which are present in a concentration, expressed respectively as an oxide, of 0.005 to <0.2 mass % CaO and/or 0.005 to <0.5 mass % SrO and/or 0.005 to <0.5 mass % BaO.

2. Spinel ceramics which are transparent in wavelength ranges of visible light, composed of sintered magnesium aluminum spinel having an average structural grain size of ≦10 μm and having maximally 0.3 mass % overall of homogeneously distributed additives of calcium and/or strontium and/or barium which are present in a concentration, expressed respectively as an oxide, of 0.005 to <0.2 mass % CaO and/or 0.005 to <0.3 mass % SrO and/or 0.005 to <0.25 mass % BaO.

3. Transparent spinel ceramics according to claim 1 in which the average structural grain size of the sintered magnesium aluminum spinel is <5 μm.

4. Transparent spinel ceramics according to claim 1 in which maximally 0.3 mass % overall of homogeneously distributed additives are present.

5. Transparent spinel ceramics according to claim 2 in which maximally 0.2 mass % overall of homogeneously distributed additives are present.

6. Transparent spinel ceramics according to claim 1 in which calcium is present as an additive in a concentration, expressed as CaO, of 0.01 to 0.1 mass %.

7. Transparent spinel ceramics according to claim 1 in which strontium and/or barium are present as additives in a concentration, expressed as SrO and/or BaO, of 0.01 to 0.4 mass % of SrO and/or 0.01 to 0.4 mass % of BaO, wherein maximally 0.3 mass % of additives of strontium and/or barium are present.

8. Transparent spinel ceramics according to claim 2 in which strontium and/or barium are present as additives in a concentration, expressed as SrO and/or BaO, of 0.01 to 0.2 mass % of SrO and/or 0.01 to 0.15 mass % of BaO, wherein maximally 0.2 mass % of additives of strontium and/or barium are present.

9. Transparent spinel ceramics according to claim 1 which show an in-line transmission of >82%, at least in the range of infrared wavelengths, measured between 1000 nm and 2500 nm, at thicknesses of ≧3 mm.

10. Transparent spinel ceramics according to claim 2 which show an RIT of >80%, at least in the range of infrared visible wavelengths, measured between 600 nm and 650 nm, at thicknesses of ≧3 mm.

11. Transparent spinel ceramics according to claim 1 which contain no visible defects.

12. Transparent spinel ceramics according to claim 1 which contain visible defects of greater than 20 μm at a frequency of <300/cm 3 .

13. Transparent spinel ceramics according to claim 12 which contain visible defects greater than 20 μm at a frequency of 50/cm 3 to 150/cm 3 .

14. Transparent spinel ceramics according to claim 1 in which HV10 Vickers hardnesses of ≧12.5 GPa are present.

15. Method for producing transparent spinel ceramics according to claim 1 in which the addition of maximally 0.5 mass % overall of additives of calcium and/or strontium and/or barium in a concentration, expressed respectively as an oxide, of 0.005 to <0.2 mass % CaO and/or 0.005 to <0.5 mass % SrO and/or 0.005 to <0.5 mass % BaO in the form of undissolved compounds containing Ca, Sr and/or Ba and/or compounds containing Ca, Sr and/or Ba dissolved in water and/or compounds containing Ca, Sr and/or Ba dissolved in organic solvents to magnesium aluminum spinel powder is carried out, the additives are homogeneously distributed, and the materials are subsequently sintered to form a transparent spinel ceramic.

16. Method for producing transparent spinel ceramics according to claim 2 in which the addition of maximally 0.3 mass % overall of additives of calcium and/or strontium and/or barium in a concentration, expressed respectively as an oxide, of 0.005 to <0.2 mass % CaO and/or 0.005 to <0.3 mass % SrO and/or 0.005 to <0.25 mass % BaO in the form of undissolved compounds containing Ca, Sr and/or Ba and/or compounds containing Ca, Sr and/or Ba dissolved in water and/or compounds containing Ca, Sr and/or Ba dissolved in organic solvents to magnesium aluminum spinel powder is carried out, the additives are distributed homogeneously, and the materials are subsequently sintered to form a transparent spinel ceramic.

17. Method according to claim 15 in which the addition of the additives is carried out during the slurry preparation or packing preparation of the ceramic, or as part of an impregnation or infiltration of the additives into open pores of a dry ceramic body, or is realized by ion exchange between wet magnesium aluminum spinel bodies and solutions according to the invention containing Ca, Sr and/or Ba.

18. Transparent spinel ceramics according to claim 2 in which the average structural grain size of the sintered magnesium aluminum spinel is <5 μm, advantageously <2.5 μm, more advantageously <1 μm.

19. Transparent spinel ceramics according to claim 2 in which calcium is present as an additive in a concentration, expressed as CaO, of 0.01 to 0.1 mass %.

20. Transparent spinel ceramics according to claim 2 which contain no visible defects.

21. Spinel ceramics which are transparent in wavelength ranges of infrared light, composed of sintered magnesium aluminum spinel having an average structural grain size of ≦10 μm and having maximally 0.5 mass % overall of homogeneously distributed additives of calcium and/or strontium and/or barium which are present in a concentration, expressed respectively as an oxide, of 0.005 to <0.2 mass % CaO and/or 0.005 to <0.5 mass % SrO and/or 0.005 to <0.5 mass % BaO, and
contain a non-zero amount of visible defects of greater than 20 μm at a frequency of <300/cm 3 .

22. Spinel ceramics which are transparent in wavelength ranges of visible light, composed of sintered magnesium aluminum spinel having an average structural grain size of ≦10 μm and having maximally 0.3 mass % overall of homogeneously distributed additives of calcium and/or strontium and/or barium which are present in a concentration, expressed respectively as an oxide, of 0.005 to <0.2 mass % CaO and/or 0.005 to <0.3 mass % SrO and/or 0.005 to <0.25 mass % BaO, and
contain a non-zero amount of visible defects of greater than 20 μm at a frequency of <300/cm 3 .

23. Transparent spinel ceramics according to claim 2 which contain visible defects of greater than 20 μm at a frequency of <300/cm 3 .

24. Transparent spinel ceramics according to claim 23 which contain visible defects greater than 20 μm at a frequency of 50/cm 3 to 150/cm 3 .

25. Transparent spinel ceramics according to claim 2 in which HV10 Vickers hardnesses of ≧12.5 GPa are present.

26. Method according to claim 16 in which the addition of the additives is carried out during the slurry preparation or packing preparation of the ceramic, or as part of an impregnation or infiltration of the additives into open pores of a dry ceramic body, or is realized by ion exchange between wet magnesium aluminum spinel bodies and solutions according to the invention containing Ca, Sr and/or Ba.

27. Transparent spinel ceramics according to claim 1 in which the average structural grain size of the sintered magnesium aluminum spinel is <2.5 μm.

28.

Assignees

• Fraunhofer Ges Forschung

Inventors

• Hutzler Thomas
• Krell Andreas

Classifications

• C04B2235/3215

  Barium oxides or oxide-forming salts thereof · CPC title

• C04B2235/786

  Micrometer sized grains, i.e. from 1 to 100 micron · CPC title

• C04B2235/3208

  Calcium oxide or oxide-forming salts thereof, e.g. lime · CPC title

• C04B2235/963

  Surface properties, e.g. surface roughness · CPC title

• C04B2235/785

  Submicron sized grains, i.e. from 0,1 to 1 micron · CPC title