X-ray study of the synthesis of boron oxides at high pressure: Phase diagram and equation of state

A systematic study of the of boron/oxygen systems at high pressure and high temperature has been made using the diamond anvil cell and the Paris-Edinburgh large volume press. The phase diagrams at 3 GPa and 6 GPa are determined from in-situ x-ray measurements. The synthesis of B2O3 and B6O only have been observed. No evidence was seen in these experiments for the previously reported B2O compound over the range of pressures and temperatures studied, P<43 GPa and T<2500 K. The equations of state of orthorhombic B2O3 and B6O have also been measured in quasihydrostatic medium to pressures exceeding 40 GPa. Implications for high-pressure material synthesis are discussed.