Diboride

Magnesium diboride (MgB₂) is a simple ionic binary compound that has proven to be an inexpensive and useful superconducting material.

Rhenium diboride (ReB_{2) is a synthetic superhard material. It was first synthesized in 1962[2] and re-emerged recently due to hopes of achieving high hardness comparable to that of diamond.[3] However, the ultrahigh hardness has not been confirmed.}

Titanium diboride (chemical formula TiB₂) is an extremely hard ceramic compound composed of titanium and boron which has excellent resistance to mechanical erosion. TiB2 is also a reasonable electrical conductor,[1] an unusual property for a ceramic, so it can be used as a cathode material in aluminium smelting and can be shaped by electrical discharge machining.

Zirconium diboride (ZrB₂) is a highly covalent refractory ceramic material with a hexagonal crystal structure. ZrB₂ is an Ultra High Temperature Ceramic (UHTC) with a melting point of 3246 °C.