Boron

(Ar. Buraq, Pers. Burah) Boron compounds have been known for thousands of years, butthe element was not discovered until 1808 by Sir Humphry Davy and by Gay-Lussac andThenard.

The element is not found free in nature, but occurs as orthoboric acid usually found incertain volcanic spring waters and as borates in boron and colemantie. Ulexite, anotherboron mineral, is interesting as it is nature's own version of "fiber optics."

Important sources of boron are ore rasorite (kernite) and tincal (borax ore). Both ofthese ores are found in the Mojave Desert. Tincal is the most important source of boronfrom the Mojave. Extensive borax deposits are also found in Turkey.

Boron exists naturally as 19.78% 10B isotope and 80.22% 11B isotope. High-puritycrystalline boron may be prepared by the vapor phase reduction of boron trichloride ortribromide with hydrogen on electrically heated filaments. The impure or amorphous, boron,a brownish-black powder, can be obtained by heating the trioxide with magnesium powder.

Boron of 99.9999% purity has been produced and is available commercially. Elementalboron has an energy band gap of 1.50 to 1.56 eV, which is higher than that of eithersilicon or germanium.