METHOD FOR GROWING MIXED CRYSTALS OF COBALT-NICKEL-POTASSIUM SULFATE FOR OPTICAL FILTERS OF ULTRAVIOLET RANGE Russian patent published in 2021 - IPC C30B7/08 C30B29/10 

FIELD: single crystals growing.

SUBSTANCE: invention relates to the field of growing mixed single crystals of cobalt-nickel-potassium sulfate K₂(Co,Ni)(SO₄)₂⋅6H₂O (KCNSH) from aqueous solutions and can be used in optical instrumentation for the manufacture of sun-blind filters. The method for growing mixed crystals of cobalt-nickel-potassium sulfate for optical filters of the ultraviolet range contains the operation of preparing a mother liquor with subsequent cooling of the mother liquor in a crystallizer, inside which a seed crystal is placed, while an aqueous solution of salts of nickel, cobalt and potassium sulfates is used as the mother liquor with the ratio K₂Ni(SO₄)₂·6Н₂О/K₂Co(SO₄)₂·6Н₂О in the range from 2:1 to 1:2 by weight, which is heated to the temperature of dissolution (homogenization) 8-10°С above the liquidus temperature of the given solution until the complete dissolution of these salts in a water thermostat with a mechanical stirrer, then the solution is cooled to a temperature of 8-10°С below its liquidus and kept for a day with constant stirring, providing the nucleation and growth of spontaneous crystals, then the solution is defended for 1 h in a thermostat without stirring with the precipitation of a solid phase, after which a part of the solution is filtered through a membrane filter with a pore size of 0.2 mcm into a growth container (crystallizer), after which the crystallizer with a seed fixed on a hermetically sealed lid is placed in a dry thermostat with the possibility of turning around the horizontal axis by 180° during the growth process, heated to a temperature of 8-10°С above the liquidus for 24 hours, cooled to a temperature of 1-5°С above the liquidus and injecting the seed into the solution by turning the crystallizer by 180°, further cooling is carried out first at a rate of 1 to 2 deg/h to a temperature of 1°С below the liquidus, then to a temperature of 9-10°С below the liquidus for 1 to 2 months, excluding forced stirring of the solution and ensuring the maintenance of supercooling of the solution not less than 5°С, after which the grown crystal is freed from the solution by turning the crystallizer by 180° and cooled to room temperature. High-quality crystals of cobalt-nickel-potassium sulfate with a transmission level in the UV region of the spectrum of 90% were obtained. In the visible region of the spectrum, the transmission is of the order of 0.01%, i.e. absent. In the IR region of the spectrum, the peaks do not exceed 0.6%.

EFFECT: such optical characteristics meet the requirements for materials for UV filters, which increases the sensitivity of equipment based on such materials.

1 cl, 1 dwg, 1 tbl