摘要
I. INTRODUCTIONRare earth elements and their compounds have been extensively investigated and a great progress in this field has been made in recent years because of their important significance in science and the growing practical applications in industry. It is well known that China is the country rich in RE resources. Its reserve of RE minerals amounts to 80% of the total in the world; and its RE output is placed in the first position. In order to effectively
