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 30.3em0exGPa and 60.3em0exGPa 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<430.3em0exGPa and T<25000.3em0exK. The equations of state of orthorhombic B₂O₃ and B₆O have also been measured in quasihydrostatic medium to pressures exceeding 400.3em0exGPa. Implications for high-pressure material synthesis are discussed.