Hexaboride

Part of speech: noun

Definitions

1. A chemical compound formed when a metal combines with six boron atoms, often used in high-temperature electronics and cathode materials
2. A binary compound in which one metal is bonded to six boron atoms, valued for its hardness and heat resistance
3. A boron-rich material consisting of a metal joined to six boron atoms, used in electron emitters and abrasives

Etymology: A hexaboride is a compound of six boron atoms with one atom of another element, and the name is a plain piece of chemical bookkeeping. "Hexa-" is the Greek prefix for six, the same stem found in "hexagon" and "hexameter," and "boride" is the chemist's term for a compound of boron with a more electropositive element, built from "boron" with the ending used for other binary compounds such as "oxide" or "nitride." Joined together, the two parts give a name that states the ratio directly. The most useful fact here is what the name leaves out. It describes the stoichiometry, six boron atoms per metal atom, rather than the structure, which in many hexaborides is a cage-like framework of boron octahedra surrounding the metal. Compounds such as lanthanum hexaboride have become familiar as electron emitters in some electron microscopes, but the word itself carries no trace of that. It is a formula written out in English.