Antimony

About Antimony

Antimony is one of the few elements that expands when it freezes — about 0.95 percent — which sounds like trivia until you've ever cast type. That single property kept Linotype matrices crisp for a century: a Pb-Sn-Sb alloy poured into a mold pushed outward as it solidified instead of pulling away, picking up the deepest serif. The bigger modern story is flame retardancy. Antimony trioxide on its own is mediocre at suppressing flame, but in a polymer matrix loaded with a brominated or chlorinated synergist it forms volatile SbX3 in the gas phase and quenches the radical chain that keeps a fire propagating. That synergistic system is in roughly half the world's wire jacketing, vehicle interior textiles, and circuit board laminates. In semiconductor work the element shows up as InSb and GaSb, narrow-gap III-V compounds used for mid-IR detectors and the 3-5 micron imaging arrays in thermal cameras. The metallurgical stibnite supply is geographically concentrated: roughly three-quarters of mine output comes out of one country, which has made antimony a recurring entry on critical-minerals lists.