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 degrees C by an in situ X-ray diffraction method. The single phase with the alpha-PbO2 type structure was obtained at 12.7 GPa and 750 degrees C. The phase was almost quenchable to ambient condition. Its orthorhombic cell parameters were a(0) = 4.590(1) angstrom, b(0) = 5.555(1) angstrom and c(0) = 5.048(1) angstrom 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 degrees C and to have the rutile-CaCl2-alpha-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 or-PbO2 type phase was determined to be K-0 = 98.0(7) GPa. (C) 2008 Elsevier Ltd. All rights reserved.