Synthesis of Borates

Anhydrous metal borates are conveniently prepared by heating hydrated salts or by direct fusion or firing of one or more metal oxides with H3BO3 or B2O3. Because the melting points of most borates fall well below 1500 ◦C, heating suitable reagents for only a few hours near 1000 ◦C generally produces homogeneous microcrystalline powders - http://www.science-chemistry.com/synthesis-of-borates