The term rare earths refer to 17 elements, such as lanthanum, cerium, praseodymium, neodymium, promethium, samarium, europium, gadolinium, terbium, dysprosium, holmium, erbium, thulium, ytterbium, lutetium, scandium, and yttrium. Rare earths are relatively abundant in the Earth’s crust, but min...
The general trend in the natural abundance of the REEs is that the elements become scarcer with increasing atomic number Z [4, 5]. A consequence of the decreasing abundance across the lanthanide series is that the HREEs are much less abundant than the LREEs. An additional trend is that ...