Patent RU-2742638-C1 (RU)
Title: METHOD FOR PRODUCING CRYSTALS OF ALLOYS OF FLUORITE SOLID SOLUTIONS М1-X М'XF2, WHERE M = CA, SR, BA; M' = PB, CdD, X IS MOLE FRACTION OF VOLATILE COMPONENT M'F2 (VARIANTS)
Inventor: Karimov Denis Nurimanovich
IPC: C30B29/52
Filed: 2020-06-17
Granted: 2021-02-09
Abstract: FIELD: chemical engineering. 
     SUBSTANCE: invention relates to technology of producing fluoride crystals which are widely used in optics, photonics, high-energy physics. One of the variants is the method for producing crystals of fluoride solid solutions М 1-x M' x F 2  where М=Са, Sr, Ва; М'=Pb, Cd where 0<х<1 and is a mole fraction of volatile component М'F 2  including vertical directed crystallization of components in a fluorinating atmosphere. wherein components MF 2   and М'F 2  are pre-melted in a fluorinating atmosphere, said components are ground, then the quantity (1-x) of MF 2  component, determined by the stoichiometry of the grown solid solution M 1-x M' x F 2,  is placed in melting pot 3 in the body 1 of growth furnace containing a heat unit 2 and the necessary quantity of  М'F 2  component, determined by its mole fraction x, is placed in the form of granules in a dosing device 5 which is vacuumed on the top flange of the furnace’s growth chamber, the furnace is then vacuumed to a residual pressure level of 5⋅10 -4 -10 -5  mm hg, filled with He and CF 4  gas mixturein a quantity of 5-10 vol %,  heated to a temperature above the melting point of  MF 2  by 20-50°, hold the melt 4 for 60-120 min for fluoration and homogenization and then, once or as a portion thereof, the granules of the component or mixture of components of  MF 2  are introduced into the melt 4 via a metering device, and then the melting pot 3 with melt 4 is moved into the cold zone of the furnace at a rate of 2-5 mm/h, the melting pot is cooled after crystallization of the melt at a rate of 100-200°C/h to room temperature and the crystal of the fluoride solid solution М 1-x M' x F 2  is extracted. Another variant is a method for producing fluoride solutions М 1-x M' x F 2  in the form of alloys where М=Са, Sr, Ва; М'=Pb, Cd where 0<х<1 and is a mole fraction of volatile component М'F 2  which consists in pre-melting in a fluorating atmosphere of MF 2  and М'F 2  components, said components are ground, the quantity (1-x) of MF 2  component, determined by the stoichiometry of the grown solid solution М 1-x M' x F 2  is then placed in melting pot 3 in a growing furnace and the necessary quantity of the М'F 2  component determined by its mole fractions x is placed in a form of granules in a dosing device 5 which is vacuumed on the top flange of the furnace’s growth chamber, whereupon the furnace is vacuumed to a residual pressure level of 5⋅10 -4 -10 -5  mm hg, the furnace is filled with a mixture of gases He and CF 4   in quantities of 5-10 vol%, is heated to a temperature above the melting point of MF 2  by 20-50°, the melt 4 is held for 60-120 min for fluorination and homogenization and then , once or as a portion thereof, the granules of the component or mixture of components of  M'F 2   are introduced into the melt 4 via a metering device until the М'F 2  component is fully consumed in the metering device the temperature in the furnace is reduced by 100-150° below the melting point of the solid solution М 1-x M' x F 2 , thermostating the melt for 30-60 minutes, then cooling at a rate of 100-200°C/h to room temperature and extracting the homogeneous polycrystalline alloy М 1-x M' x F 2 . 
     EFFECT: invention enables producing high-quality volumetric fluoride crystals with a uniform or specified gradient distribution of the volatile component along the length of the crystals. 
     6 cl, 4 dwg, 2 ex