Lanthanum. Source: Wikipedia
Rare earth elements are used in many alternative energy, lifestyle, and defense applications. Alternative energy systems such as wind power generation, fuel cells, hydrogen storage, rechargeable batteries, and the permanent magnets used in electric and hybrid-electric vehicles all rely on rare earths. REEs are used as phosphors in many consumer displays and lighting systems, and are used in fluid cracking catalysts and catalytic converters in the oil and automotive industries.