X-ray diffraction study of WO3 at high pressure
Résumé
The high-pressure behaviour of microcrystalline tungsten oxide (WO3) has been investigated with angle-dispersive synchrotron x-ray powder diffraction in a diamond anvil cell up to 40 GPa at room temperature. Up to 21 GPa, the pressure dependence of the volume of the monoclinic high-pressure (P21/c) phase is described by a third-order Birch–Murnaghan equation of state with parameters V0 = 210.9(7)Å3, KT = 27(2)GP a and K' = 9.4(5). At 24 GPa, a first-order phase transition occurs with an approximate ΔV of 7.4% to a monoclinic P21/a unit cell with a = 6.1669(8)Å, b = 4.5758(6)Å, c = 5.3159(6)Å, β = 101.440(9)ˆ. A second transition is observed at pressures higher than 31 GPa with an approximate ΔV of 12% to a phase described by a third monoclinic unit cell, with a = 10.3633(22)Å, b = 3.9065(8)Å, c = 9.3459(18)Å and β = 98.539(14)ˆ