B2O3

B2O3, or boron trioxide, is the chemical compound that serves as the anhydride of boric acid. It is a colorless to white, hard, brittle solid at room temperature and forms a glassy material when cooled from the melt. In practical use, it is often encountered as a component of borosilicate glasses and related ceramics.

In the solid state, B2O3 forms a covalent network composed of boron-oxygen units. The structure includes boron in three-coordinate (BO3) and four-coordinate (BO4) environments, which can organize into boroxol rings in vitreous forms. These structural features give B2O3 a low glass transition tendency and make it a strong glass former. When heated, it can temporarily soften and form a vitreous phase before any vaporization or decomposition occurs at higher temperatures.

Production and sources are typically linked to the dehydration of boron-containing materials. Commercially, boric acid (H3BO3) can be heated to remove water and yield B2O3: 2 H3BO3 → B2O3 + 3 H2O. It can also be obtained by the dehydration of borate minerals or as a product of processing borates used in industrial applications.

Chemical properties include hydrolysis in water to boric acid: B2O3 + 3 H2O → 2 H3BO3. Consequently, B2O3 is moisture-sensitive and tends to form borates in aqueous environments. Safety considerations include its irritant properties and potential toxicity with inhalation or prolonged exposure.

Applications are dominated by glass and ceramics technology. It is a key flux and glass former in borosilicate glasses, enamel coatings, and specialized ceramics, contributing to low thermal expansion and improved durability.