An Experimental study on the phase relations in the systems MgO-B₂O₃ and MgO-B₂O₃-H₂O

Abstract

Synthesis of minerals and the phase equilibrium relations in the systems MgO-B₂O₃ and MgO-B₂O₃-H₂O were studied. A new result shows that the phase MgO·B₂O₃ is absent at 930°C in air and the phase assemblage 2MgO·B₂O₃ + MgO·2B₂O₃ is stable in stead of the 1:1 compound. Hydrothermal experiments showed that among 13 known ternary phases, only two, 2MgO·B₂O₃·H₂O (szaibelyite) and 2MgO·6B₂O₃·15H₂O (mcallisterite), exist at 300°C and 400°C under 100 MPa. The possible phase diagram of the system MgO-B₂O₃-H₂O at 400°C and 100 MPa is proposed.