Stable phase with the α-PbO2 type structure in MgF2 under high pressure and high temperature

High-pressure and high-temperature behavior of MgF2 was observed up to 15 GPa and 750 ∘C by an in-situ X-ray diffraction method. The single phase with the α-PbO2 type structure was obtained at 12.7 GPa and 750 ∘C. The phase was almost quenchable to ambient condition. Its orthorhombic cell parameters were a0=4.590(1)Å, b0=5.555(1)Å and c0=5.048(1)Å and its volume per chemical formula was 1.1% smaller than that of the rutile phase at ambient condition. MgF2 was confirmed to have a stable region for the phase at around 13 GPa and 600 ∘C and to have the rutile-CaCl2-α-PbO2-PdF2 type phase transition series under high pressure and high temperature, as predicted by a previous theoretical calculation method. The bulk modulus of the α-PbO2 type phase was determined to be K0=98.0(7)GPa.