Spinel optoceramics
A transparent, polycrystalline ceramic is described. The ceramic comprises crystallites of the formula A x C u B y D v E z F w , whereby A and C are selected from the group consisting of Li + , Na + , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Al 3+ , Ga 3+ , In 3+ , C 4+ , Si 4+ , Ge 4+ , Sn 2+/4+ , Sc 3+ , Ti 4+ , Zn 2+ , Zr 4+ , Mo 6+ , Ru 4+ , Pd 2+ , Ag 2+ , Cd 2+ , Hf 4+ , W 4+/6+ , Re 4+ , Os 4+ , Ir 4+ , Pt 2+/4+ , Hg 2+ and mixtures thereof, B and D are selected from the group consisting of Li + , Na + , K + , Mg 2+ , Al 3+ , Ga 3+ , In 3+ , Si 4+ , Ge 4+ , Sn 4+ , Sc 3+ , Ti 4+ , Zn 2+ , Y 3+ , Zr 4+ , Nb 3+ , Ru 3+ , Rh 3+ , La 3+ , Lu 3+ , Gd 3+ and mixtures thereof, E and F are selected mainly from the group consisting of the divalent anions of S, Se and O and mixtures thereof, x, u, y, v, z and w satisfy the following formulae 0.125<( x+u )/( y+v )≦0.55 z+w =4 and at least 95% by weight of the crystallites display symmetric, cubic crystal structures of the spinel type, with the proviso that when A=C=Mg 2+ and B=D=Al 3+ , E and F cannot both be O.
1. A method for manufacturing an optoceramic having crystallites of the formula A x C u B y D v E z F w , whereby A and C are selected from the group consisting of Li + , Na + , Be 2+ , Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Al 3+ , Ga 3+ , In 3+ , C 4+ , Si 4+ , Ge 4+ , Sn 2+/4+ , Sc 3+ , Ti 4+ , Zn 2+ , Zr 4+ , Mo 6+ , Ru 4+ , Pd 2+ , Ag 2+ , Cd 2+ , Hf 4+ , W 4+/6+ , Re 4+ , Os 4+ , Ir 4+ , Pt 2+/4+ , Hg 2+ and mixtures thereof, B and D are selected from the group consisting of Li + , Na + , K + , Mg 2+ , Al 3+ , Ga 3+ , In 3+ , Si 4+ , Ge 4+ , Sn 4+ , Sc 3+ , Ti 4+ , Zn 2+ , Y 3+ , Zr 4+ , Nb 3+ , Ru 3+ , Rh 3+ , La 3+ , Lu 3+ , Gd 3+ and mixtures thereof, E and F are selected mainly from the group consisting of the divalent anions of S, Se and O and mixtures thereof,
x, u, y, v, z and w satisfy the following formulae
0.125<( x+u )/( y+v )≦0.55 z+w= 4
and at least 95% by weight of said crystallites display symmetric, cubic crystal structures of the spinel type, with the proviso that when A=C=Mg 2+ and B=D=Al 3+ , E and F cannot both be O, which comprises the following steps:
(1) production of a homogeneous powder mixture by mixing powder raw materials having an average primary particle diameter of 20 nm to 1 μm in accordance with a desired composition, optionally with addition of additives such as binders, sintering aids and dispersants in a solvent to form a slurry and drying said slurry to give a powder,
(2) production of a preform from said powder obtained in step (1),
(3) optionally burning-out of any dispersants and binders present from said preform at temperatures of 500 to 900° C.,
(4) sintering said preform at temperatures of 1400 to 1900° C. to obtain an optoceramic,
(5) optionally pressure sintering said optoceramic obtained in step (4) at 1400 to 2000° C. under a pressure of 10 to 300 MPa, and
(6) optionally oxidation of said optoceramic obtained in step (4) or (5) in a stream of O 2 at temperatures of up to 1000° C. for 5 to 10 hours in order to remove any discoloration which may occur.
2. The method of claim 1 , wherein A and C are selected from the group consisting of Mg 2+ , Ca 2+ , Sr 2+ , Ba 2+ , Sc 3+ , Zn 2+ , Cd 2+ , Hf 4+ and mixtures thereof.
3. The method of claim 1 , wherein A and C are selected from the group consisting of Mg 2+ , Ca 2+ , Sr 2+ , Zn 2+ and mixtures thereof.
4. The method of claim 1 , wherein B and D are selected from the group consisting of Mg 2+ , Al 3+ , Ga 3+ , In 3+ , Sc 3+ , Zn 2+ , Y 3+ , Nb 3+ , Ru 3+ , Rh 3+ , La 3+ , Gd 3+ and mixtures thereof.
5. The method of claim 1 , wherein B and D are selected from the group consisting of Al 3+ , Ga 3+ , In 3+ , Y 3+ , La 3+ , Gd 3+ and mixtures thereof.
6. The method of claim 1 , wherein x, u, y and v satisfy the following relationship,
0.4<( x+u )/( y+v )≦0.5.
7. The method of claim 1 , wherein x, u, y and v satisfy the following relationship,
0.45<( x+u )/( y+v )≦0.5.
8. The method of claim 1 , wherein E and F comprise at least 95% divalent anions of S, Se and O and mixtures thereof.
9. The method of claim 1 , wherein E and F comprise at least 98% divalent anions of S, Se and O and mixtures thereof.
10. The method of claim 1 , wherein said optoceramic has a refractive index from 1.74 to 2.3.
11. The method of claim 1 , wherein said optoceramic has a refractive index from 1.75 to 2.0.
12. The method of claim 1 , wherein said optoceramic has an Abbe number from 50 to 70.
13. The method of claim 1 , wherein said opticeramic has a stress-induced birefringence of <10 nm/cm.
14. The method of claim 1 , wherein said optoceramic has a stress-induced birefringence of <5 nm/cm.
15. The method of claim 12 , wherein said powder raw materials have an average primary particle diameter of 20 to 500 nm.
16. The method of claim 12 , wherein said optional pressure sintering of step 5 is performed under a pressure of 50 to 250 MPa.
17. The method of claim 12 , wherein said optional pressure sintering of step 5 is performed under a pressure of 100 to 200 MPa.
18. The method of claim 12 , wherein said optoceramic has a transparency of >80% in a window having a width of at least 200 nm in the region of visible light having wavelengths from 380 nm to 800 nm at a sample thickness of 2 mm.