modification of barium diborate in the glass of stoichi-ometric composition are investigated. This modification is characterized using X-ray diffraction analysis. In
order for the
-BaO · 2B2O3 modification to crystallize, the glass should be purified from dissolved gases and have an undisturbed fire-polished surface. Otherwise, the
modification crystallizes under the same conditions. The melting temperature of the
-BaO · 2B2O3 modification is determined to be Tmelt = 805°C. Upon heating, the
modification in the form of a powder transforms into the modification, whereas the modification in the form of a polycrystalline monolithic sample remains stable up to the melting temperature.