Scandium is a soft, silvery metallic element. Its atomic number is 21, making it the lightest of the transition metals. Scandium is not particularly rare - its occurrence in crustal rocks is 22 around ppm. This makes scandium generally more abundant than lead, mercury, and precious metals. Despite this fairly common occurrence, scandium rarely concentrates in nature. It does not selectively combine with the common ore-forming anions, so time and geologic forces only rarely form scandium concentrations over 100 ppm. There is currently no dedicated single mine source and it estimated that only 15 tonnes of scandium are produced globally each year.
Scandium exists in nature in its oxide form. It is very difficult to reduce to its pure elemental state. In fact, it was not isolated in pure form until 1937 and the first pound of pure elemental scandium metal was not produced until 1960. Scandium in oxide form is referred to as scandia or scandium oxide, and the chemical formula is Sc2O3. Processed scandium oxide, a white powder, is stable at ambient temperature and is the standard scandium form for commerce.
Despite scandium’s scarcity and high cost, interest in the metal is high and multiple high value commercial uses have been developed. Of particular interest is the alloy of scandium into aluminum metal products. When used in combination with other common aluminum alloys scandium can produce stronger, more corrosion resistant, heat tolerant, weldable aluminum products. Aluminum products are being increasingly incorporated into transportation applications (aircraft and automobile) in order to meet fuel efficiency requirements.
Aircraft manufacturers are particularly interested in scandium alloyed aluminum materials. Aircraft designers believe use of Al-Sc alloys can reduce aircraft weights by 15%-20%. In addition, the ability to employ weldable structures promises similar cost reduction potential.
Scandium also exhibits exceptional electrical conductivity and heat stabilization qualities and the largest volume current use is in solid oxide fuel cells (“SOFCs”). Incorporation of scandium in SOFCs enables a lower operating temperature resulting in longer lived equipment and less costly materials of construction. Bloom Energy is the leading SOFC manufacturer and currently single largest scandium user.
Al-Sc alloys may reduce aircraft weights by 15%-20%
Numerous other applications have been identified and are under research, most notably high intensity lighting (“stadium lighting”) and high voltage power transmission and additive layer parts manufacturing (“3D Printing”).