Solid-solid transition temperatures in SrCl 2 from differential thermal analyses to 0.6 GPa

Abstract

The reversible phase transition between the high-temperature, cubic C1 and the low-temperature, orthorhombic C23 polymorphs of SrCl 2 has been investigated by differential thermal analysis under hydrostatic pressure to 0.63 GPa. The C23→C1 transition temperature varies linearly with pressure at the rate of 0.42 4 μK(Pa) −1 from the highest pressures down to ca. 0.34 GPa, and also linearly with slope 1.73 μK(Pa) −1 at pressures ≲0.26 GPa; the reverse, C1→C23 transition is not observed or deduced ≲0.21 GPa. The observed curvature for the C1–C23 phase boundary over the range ≲0.26–0.34 GPa, 1000–1050 K can be attributed to intersection with the “diffuse” transition in C1; the latter transition, however, could not be observed unambiguously. Linear extrapolation to 0.1 MPa places the C23→C1 transition near 553 K, which implies that C23 - not C1 - is the stable low-temperature polymorph. The recently-investigated transitions in PbF 2 closely parallel these in in SrCl 2.