Atomic number: 72
Used in: computer chips
Criticality rating: not rated
Hafnium's peerless heat resistance has taken it to the moon and back as part of the alloy used in the nozzle of rocket thrusters fitted to the Apollo lunar module. Since 2007, though, it has also been found much closer to home, in the minuscule transistors of powerful computer chips.
That's because hafnium oxide is a highly effective electrical insulator. Compared with silicon dioxide, which is conventionally used to switch transistors on and off, it is much less likely to let unwanted currents seep through. It also switches 20 per cent faster, allowing more information to pass. This has enabled transistor size to shrink from 65 nanometres with silicon dioxide first to 45 nm and now to 32 nm.
Such innovations keep our smartphones smart and small. And hafnium will probably not be the thing that slows that progress: despite its low profile, it is a relatively abundant element. Making up several parts per million of the Earth's crust, it is distributed widely around the globe.