Atomic number: 73
Used in: Almost all handheld electronics
Criticality rating: not rated
Your smartphone or tablet computer is a veritable wonder of modern materials technology, with its touchscreen interface incorporating indium (page 40), compact lithium-ion battery and tiny processors packed with nanoscale transistors (see hafnium).
This also extends to its capacitors, the humble components that store energy and smooth power flow in electronic circuits. It is thanks to two-faced tantalum that they remain so slimline. In its pure form, this metal forms one of two conducting plates on which charge is stored. As an oxide, meanwhile, it makes a highly effective insulator, only a thin layer of which is needed to prevent leakage between the plates. As a bonus, the oxide is self-healing, rapidly reforming to plug any leak that lets current through.
It is fortunate, then, that the US Geological Survey believes that tantalum is in plentiful supply, with known deposits covering projected need. In fact, during the recent global economic slowdown, several mines were temporarily shut down as demand dropped.