Platinum–iridium alloy

[1][2] This improved hardness has also been considered as beneficial for use in platinum jewellery, particularly watch cases.

The other extremely widespread use for Pt/Ir alloy is fabrication of metal microelectrodes for electrical stimulation of nervous tissue[4] and electrophysiological recordings.

[5][6][7] Pt/Ir alloy has an optimal combination of mechanical and electrochemical properties for this application.

Pure iridium is very difficult to pull into small diameter wires; at the same time, platinum has a low yield strength, which makes pure platinum wires bend too easily during insertion into nervous tissue.

Additionally, platinum–iridium alloys containing oxides of both metals can be electro-deposited onto the surface of microelectrodes.

The international prototype of the kilogram (IPK) is an artifact standard of platinum–iridium alloy that was defined as having a mass of exactly one kilogram .