Aspects of coloured precious metal intermetallic compounds

Abstract

This paper provides a review on coloured gold, platinum, and palladium intermetallic compounds, and discusses the models that were developed to obtain these materials. These compounds have a crystal structure of high symmetry, such as the CaF2 or CsCl structures, ensuring distinct electron band structures. Various examples of coloured gold, platinum, and palladium intermetallic compounds are provided. More in-depth discussion is provided on the purple gold (AuAl2) and yellow platinum-aluminium (PtAl2) compounds with CaF2 structure, as well as the purplish-pink palladium-indium (PdIn) compound with CsCl structure. Precious metal intermetallic compounds are used in jewellery and provide a new dimension to design. Some of these compounds have also found use as barrier coatings on turbine blades for jet engines, and more recently, research has been conducted into their potential use as catalysts, electro-catalysts, sensors, capacitors, and for decorative coatings.