Raman spectroscopy and X-ray diffraction studies on celestite

High-pressure Raman spectroscopy and X-ray diffraction studies of celestite (SrSO₄) were carried out in a diamond anvil cell at room temperature. Variation in the Raman vibrational frequency and change of lattice parameters with pressure indicate that a transformation occurs in celestite. This transformation caused an adjustment in the SrO polyhedra that affected the stretching-force constant of SO₄. Moreover, compressibilities along the crystallographic axes decreased in the order a to c to b. From the compression data, the bulk modulus of the celestite was 87 GPa. Both X-ray and Raman data show that the transition in celestite is reversible.