Structural phase transitions of SrF2 at high pressure

The high-pressure behavior of SrF2 has been investigated by angle-dispersive synchrotron X-ray powder diffraction measurement up to 50.3 GPa at room temperature. Two phase transformations were observed at 6.8 and 29.5 GPa, and the two high pressure phases were identified as orthorhombic (Pnma) phase and hexagonal (P63/mmc) phase by Rietveld refinement. Upon decompression, retransformation was observed and the sample recovered under ambient conditions consisted of a mixture of cubic phase and orthorhombic phase. The compressing characteristics of SrF2 as the pressure increases were discussed, indicating higher incompressibility of SrF2 under high pressure. - Graphical abstract: The high-pressure behavior of SrF2 has been investigated by angle-dispersive synchrotron X-ray powder diffraction measurement up to 50.3 GPa at room temperature. Highlights: ► The high-pressure study on SrF2 up to 50.3 GPa at room temperature. ► Two first-order phase transformations were observed at 6.8 and 29.5 GPa. ► The three stable structures are confirmed by Rietveld refinements. ► The cubic and orthorhombic phase co-exist at pressures down to ambient pressure. ► The bulk modulus indicates higher incompressibility of SrF2 under high pressure.