Abstract: It is an object to provide a product having a good crystal particle size distribution of a high-purity potassium fluorotantalate crystal or a high-purity potassium fluoroniobate crystal without using a physical method for particle classification. To that end, a method for manufacturing a high-purity potassium fluorotantalate crystal or a high-purity potassium fluoroniobate crystal is used, wherein the recrystallizing step comprising a first cooling process of cooling a saturated solution with a temperature of 60° C. to 90° C. obtained in the dissolving step at a cooling speed of T° C./hour until the solution temperature of the saturated solution becomes a temperature of the range of 35 to 50° C., and a second cooling process of cooling the solution at a cooling speed of [T?18]° C./hour to [T?1]° C./hour from the end of the first cooling process to the solution temperature becoming a temperature of 10 to 20° C.

Abstract: Disclosed herein is a method for producing potassium fluorotantalate crystals, comprising heating, to 60° C. or higher, a starting solution prepared by adding hydrofluoric acid and hydrochloric acid, and, if necessary, water to a highly pure tantalum solution, adding potassium chloride to this starting solution, and cooling the mixture to 40° C. or lower at a cooling rate of less than 15° C./h to precipitate potassium fluorotantalate crystals, wherein the concentration of the hydrofluoric acid in the starting solution is not more than 20% by weight. By this method, highly pure, large-sized potassium fluorotantalate crystals can successfully be obtained in high yield. Moreover, disadvantages to equipment and operation in the prior art can be overcome to a significant extent with this method.

Abstract: An object of the present invention is to provide a method for preventing concentration of a radioactive substance in a generated extraction residue in a method of producing tantalum, niobium, or a similar substance including collecting and refining a raw material containing the substances through a fluoridation process by use of a hydrofluoric acid-containing solution. The object can be attained by employing an ingredient-regulated raw material prepared from an ore or a concentrate and, as an additive, a substance insoluble to hydrofluoric acid or a mixed acid containing hydrofluoric acid as an essential component; or by increasing the amount of the extraction residue through addition of the insoluble substance to a solvent during the fluoridation process, to thereby reduce the relative radioactive substance content to an arbitrary value.

Abstract: It is an object to provide a product having a good crystal particle size distribution of a high-purity potassium fluorotantalate crystal or a high-purity potassium fluoroniobate crystal without using a physical method for particle classification. To that end, a method for manufacturing a high-purity potassium fluorotantalate crystal or a high-purity potassium fluoroniobate crystal is used, wherein the recrystallizing step comprising a first cooling process of cooling a saturated solution with a temperature of 60° C. to 90° C. obtained in the dissolving step at a cooling speed of T° C./hour until the solution temperature of the saturated solution becomes a temperature of the range of 35 to 50° C., and a second cooling process of cooling the solution at a cooling speed of [T-18]° C./hour to [T-1]° C./hour from the end of the first cooling process to the solution temperature becoming a temperature of 10 to 20° C.

Abstract: Disclosed herein is a method for producing potassium fluorotantalate crystals, comprising heating, to 60° C. or higher, a starting solution prepared by adding hydrofluoric acid and hydrochloric acid, and, if necessary, water to a highly pure tantalum solution, adding potassium chloride to this starting solution, and cooling the mixture to 40° C. or lower at a cooling rate of less than 15° C./h to precipitate potassium fluorotantalate crystals, wherein the concentration of the hydrofluoric acid in the starting solution is not more than 20% by weight. By this method, highly pure, large-sized potassium fluorotantalate crystals can successfully be obtained in high yield. Moreover, disadvantages to equipment and operation in the prior art can be overcome to a significant extent with this method.

Abstract: An object of the present invention is to provide a method for preventing concentration of a radioactive substance in a generated extraction residue in a method of producing tantalum, niobium, or a similar substance including collecting and refining a raw material containing the substances through a fluoridation process by use of a hydrofluoric acid-containing solution. The object can be attained by employing an ingredient-regulated raw material prepared from an ore or a concentrate and, as an additive, a substance insoluble to hydrofluoric acid or a mixed acid containing hydrofluoric acid as an essential component; or by increasing the amount of the extraction residue through addition of the insoluble substance to a solvent during the fluoridation process, to thereby reduce the relative radioactive substance content to an arbitrary value.