Barium borate Barium borate Barium borate is an inorganic compound, a borate of barium with a chemical formula BaBO or Ba(BO). It is available as a hydrate or dehydrated form, as white powder or colorless crystals. The crystals exist in the high-temperature α phase and low-temperature β phase, abbreviated as BBO; both phases are birefringent, and BBO is a common nonlinear optical material. Barium borate exists in two major crystalline forms: alpha and beta. The low-temperature beta phase converts into the alpha phase upon heating to 925 °C. β-Barium borate (BBO) differs from the α form by the positions of the barium
Chemical element element (by mass) making up Earth, while oxygen is the most common element in the Earth's crust. Chemical elements constitute all of the ordinary matter of the universe. However astronomical observations suggest that ordinary observable matter makes up only about 15% of the matter in the universe: the remainder is dark matter; the composition of this is unknown, but it is not composed of chemical elements. The two lightest elements, hydrogen and helium, were mostly formed in the Big Bang and are the most common elements in the universe. The next three elements (lithium, beryllium and boron) were formed mostly