Chemical vapour deposition of scandium metal

Abstract

An open-tube chemical vapour deposition technique was devised for the growth of scandium metal from its oxide as a starting material. Chlorination of the oxide with carbon tetrachloride vapour at 640 °C was followed by reaction in the vapour phase at about 860 °C between separate streams of scandium chloride and sodium carried by purified argon. The resulting single crystals of scandium grown on the end of the molybdenum tube carrying the sodium stream were typically in the forms of needles, up to 3.5 mm in length with a growth direction along the a axis, and of codepositing smaller plates and dendrites. Polycrystalline coatings and island-like crystallites were deposited on the molybdenum sheet surrounding the parallel streams of reactants, often together with small polyhedrons and hollow prisms.