| 摘要 |
High-purity lanthanum characterized in that the purity, in terms of the purity of the lanthanum excluding any rare-earth elements and any gas components, is 5 N or higher and the number of alpha-ray counts is 0.001 cph/cm2 or less; and a process for producing high-purity lanthanum, characterized by electrolyzing crude lanthanum metal, as a raw material, that has a purity, in terms of the purity of the crude metal excluding any gas components, of 4 N or lower, in a molten salt having a bath temperature of 450-700ºC to obtain lanthanum crystals, subsequently desalting the lanthanum crystals, and then melting the desalted lanthanum with electron beams to remove volatile substances therefrom and thereby regulate the purity, in terms of the purity of the lanthanum excluding any rare-earth elements and any gas components, to 5 N or higher and the number of alpha-ray counts to 0.001 cph/cm2 or less. The present invention addresses the problem of providing methods with which it is possible to efficiently and stably provide: high-purity lanthanum reduced in alpha rays; a sputtering target comprising the high-purity-material lanthanum; and a thin film for use as a metal gate, the thin film comprising the high-purity-material lanthanum as the main component. |
