Temperature dependencies of the specific heat (left axis) and the entropy (right axis). Inset: DSC runs on heating and cooling showing the hysteresis observed at and the lack of the hysteresis at .
Structural signatures of the phase transitions of compound. (a) The appearance in the INT phase of the (−2 0 2) Bragg peak indexed in the lattice and of the (1 0 −2) one in the LT phase indexed in the lattice are associated with the successive symmetry breaking during the continuous phase transition around 240 K and discontinuous phase transition around 206 K (vertical lines). Small anomalies are observed in the lattice parameters and (b), and and (c), given here in the HT lattice.
Projection of the crystal structure along (left) and (right) for the HT (top, 265 K), LT (bottom 150 K), and INT phases (middle 208 K). The change in translation symmetry along is associated with alternating tilting and ordering of the cations. In the INT phase, ordered and disordered channels alternate along the axis.
Permittivity in for a few frequencies of the measuring field; and denote temperatures of the phase transitions.
Crystal data and structure refinement measured at 265, 208, and 150 K. The CCDC Reference No. of the intermediate phase is 694619.
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