heavy rare earth element

例句：

1. 1. The rare earth elements are crucial for the development of new technologies.
   稀有金属对发展新技术至关重要。
2. 2. The heavy rare earth elements are used in the production of electric motors and generators.
   重稀土元素用于生产电动机和发电机。
3. 3.The extraction of these elements is a complex process that requires specialized equipment.
   提取这些元素是一个复杂的过程，需要专用设备。