The p–T phase diagram for new ferroelectric bis-thiourea pyridinium bromide

Thermal Properties and Transition Behavior of Host-Guest Compounds Under High Pressure

“…9. Phase diagrams of two thiourea inclusion compounds: (a) bis-thiourea pyridinium nitrate [77] and (b) bisthiourea pyridinium bromide [78]. (The dashed lines show discontinuous transition, whereas the black solid lines show continuous transitions.)…”

“…For bis-thiourea pyridinium nitrate, Bilski et al [77] wrote "For pressures up to 450 MPa, the transition between the ferroelectric and paraelectric phases (III-II phase) is continuous, whereas above 450 MPa, the phase transition between these phases (III-I phase) is discontinuous." For bis-thiourea pyridinium bromide, Bilski et al [78] concluded "The transition from phase I to II is continuous and that from phase III to IV is discontinuous, while that from phase II to III is discontinuous for pressure up to about 300 MPa and continuous above 300 MPa." …”

“…In fact, we found only a few studies of the high pressure properties of thiourea inclusion compounds. However, the phase diagrams of two thiourea inclusion compounds, which form ferroelectric phases, have been studied by Bilski and co-workers [77,78]. Despite the similarity between the compounds, the phase diagrams, which are depicted in Fig.…”