Order-disorder behaviour in the transition of PbTiO₃

Pressure and Temperature Dependence of the Ferroelectric–Paraelectric Phase Transition in PbTiO3

“…Ramirez et al (10) stated the presence of a cross-over between the two types of phase transition (first and second order) and located it at 1.8 GPa at room temperature. The results here reported are in agreement with this statement, since the change of slope of z 1=2 has often been interpreted as an indication of a change in the order of the phase transition (7).…”

“…Recently, Sicron et al (5) observed the presence of local distortions above T C revealing nonnegligible order-disorder character of the phase transition, confirming the results obtained by means of Raman spectroscopy (6) and neutron scattering (7).…”

A closed-shell furnace for neutron single-crystal diffraction

“…Subtle changes of the crystal structure (e.g. of atomic displacement parameters) near structural phase transitions have been repeatedly detected by single-crystal neutron diffraction studies (see, for example, Nelmes, Kuhs, Howard, Tibballs & Ryan, 1985;Nelmes, Piltz, Kuhs, Tun & Restori, 1990). Neutron diffraction at nonambient temperatures has an added advantage over X-ray work in that the low absorption of the sample-environment apparatus itself is less damaging to the data quality.…”

“…The furnace has been used in a series of neutron diffraction experiments between 330 and 1100 K and has proven its reliability and simple handling (see, for example, Nelmes et al, 1990;S/inger & Kuhs, 1992).…”

Lead-Based Piezoelectric Materials

“…Lead titanate undergoes a first-order phase transition at 493 • C into cubic O 1 4 − Pm3m paraelectric form. This phase transition was considered in the past to be a prototypic displacive phase transition (Lines and Glass 1979) but recent results have suggested that it exhibits mixed displacive and order-disorder character (Nelmes et al 1990). …”