| US 7,393,409 B2 | ||
| Method for making large-volume CaF2 single cystals with reduced scattering and improved laser stability, the crystals made by the method and uses thereof | ||
| Lars Ortmann, Jena (Germany); Joerg Kandler, Cospeda (Germany); Andreas Menzel, Jena (Germany); Matthias Mueller, Jena (Germany); Lutz Parthier, Klein-Machnow (Germany); and Gordon Von der Goenna, Jena (Germany) | ||
| Assigned to Schott AG, Mainz (Germany) | ||
| Filed on Feb. 22, 2005, as Appl. No. 11/63,147. | ||
| Claims priority of application No. 10 2004 008 749 (DE), filed on Feb. 23, 2004. | ||
| Prior Publication US 2005/0211160 A1, Sep. 29, 2005 | ||
| Int. Cl. C30B 23/00 (2006.01); C01B 7/19 (2006.01) | ||
| U.S. Cl. 117—73 [117/11; 117/78; 117/81; 117/82; 117/83; 117/3; 117/4; 117/10; 117/940] | 10 Claims |
| 1. A method of making CaF2 single crystals with low scattering, small refractive index differences and few small angle grain boundaries, which are temperable
at elevated temperatures, said method comprising the steps of:
a) washing CaF2 waste with an aqueous surfactant solution and then drying the CaF2 waste to obtain a CaF2 material, said aqueous surfactant solution comprising deionized water and a surface-active compound selected from the group
consisting of non-ionic surfactants, amphoteric surfactants and cationic surfactants;
b) heat treating said CaF2 material for at least five hours at heat treatment temperatures between 1000° C. and 1250° C.;
c) after the heat treating of step b), subliming said CaF2 material at a sublimation temperature of at least 1100° C. while drawing a vacuum of at most 5*10−4 mbar to form a vapor;
d) condensing the vapor at a condensation temperature of at least 500° C. to form a condensate, said condensation temperature
being at least 20° C. below said sublimation temperature;
e) making a CaF2 melt from said condensate;
f) cooling the CaF2 melt so as to grow a CaF2 single crystal; and
g) subsequently tempering the CaF2 single crystal.
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