The dielectric relaxation of a solid solution of 10‐mol % lead titanate in lead magnesium niobate is found to be similar to the magnetic relaxation in spin‐glass systems.1–3 Based on this analogy, it is proposed that the relaxor ferroelectric is a polar‐glassy system which has thermally activated polarization fluctuations above a static freezing temperature. An activation energy and freezing temperature of 0.0407 eV and 291.5 K, respectively, were found by analyzing the frequency dependence of the temperature of the dielectric maximum using the Vogel–Fulcher relationship.4,5 It has also been shown that a macroscopic polarization is sustained on heating up to this freezing temperature. A coupling between nanometer scale clusters is believed to control the kinetics of the fluctuations and the development of a frustration as the system freezes into states of local equilibrium. The possibility of an orientational freezing associated with the ferroelastic nature of the nanosized polar regions in the rhombohedr...

Freezing of the polarization fluctuations in lead magnesium niobate relaxors

The fundamental physics of antiferroelectric oxides and their properties are reviewed. First, the difficulties in formulating a precise definition of antiferroelectricity are discussed, drawing on previous discussion in the literature. We arrive at the following definition: an antiferroelectric is like a ferroelectric in that its structure is obtained through distortion of a nonpolar high-symmetry reference phase; for ferroelectrics, the distortion is polar, while for antiferroelectrics it is nonpolar. However, not all nonpolar phases thus obtained are antiferroelectric: in addition, there must be an alternative low-energy ferroelectric phase obtained by a polar distortion of the same high-symmetry reference structure, and an applied electric field must induce a first-order transition from the antiferroelectric phase to this ferroelectric phase, producing a characteristic P-E double-hysteresis loop. For analysis of the characteristic properties of antiferroelectrics, we use Landau theory functionals. The microscopic origins of the macroscopic behavior are examined. This is fairly straightforward for systems with clearly-defined reorientable local-dipolar entities, such as antiferroelectric liquid crystals and hydrogen-bonded antiferroelecrics, and these systems are not discussed in any detail in this article. The main focus is on the subtler case of antiferroelectric oxides, for which models based on symmetry-adapted lattice modes prove to be useful. Specific examples of antiferroelectric oxides are presented with available first principles results and discussion of the role of compositional tuning in producing antiferroelectricity, and the nature of the electric-field-induced ferroelectric phases. In thin films and superlattices, additional tuning is possible through the effects of strain and finite size. The article concludes with some remarks on materials design, including the optimization of properties relevant to technological applications of antiferroelectrics.

Antiferroelectricity in Oxides: A Reexamination

This paper comprises studies of: the variation of dielectric constant and lattice parameters with temperature using 'single crystals'; the effects on both of different annealing times; variation with annealing times of order, as deduced from the intensities of superlattice reflections, and of Kanzig region size, as deduced from the breadths of the same reflections. For the dielectric constant, the crystal was annealed in situ. For the lattice parameters, the continuous-recording method was used, giving greater accuracy than in previous investigations. In addition, lattice geometry was checked, and room-temperature lattice parameters measured from twin-spot complexes recorded with Weissenberg cameras and double-radius oscillation cameras.

https://iopscience.iop.org/article/10.1088/0022-3719/19/2/008/pdf

Structural phase transitions and long-range order in ferroelectric perovskite lead indium niobate

Brillouin light scattering was used to obtain the elastic and piezoelectric constants for tetragonal PbTiO3 single crystals at room temperature. Approximately 170 measurements of longitudinal and transverse acoustic wave velocities were inverted using literature dielectric constant values to obtain the full set of elastic and piezoelectric constants. Our data indicate a greater electromechanical anisotropy in the polar c direction than previously reported, but are otherwise in general agreement with previous studies. We discuss briefly the degree to which individual elastic and piezoelectric constants are resolved.

Elastic properties of tetragonal pbtio3 single crystals by brillouin scattering

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

When studying the compounds of the PbNb05B05O3 series it has been established that with a critical ionic radius RB = 085A there occurs a transition from ferroelectric (B-Cr, Fe, Mn, Sc, In) to antiferroelectric (B-Lu, Yb, Tm) The structure of crystals and polycrystalline specimens has been studied by X-ray diffraction techniques, and also the dielectric properties of PbNb05Sc05O3 and PbNb05In05O3 located near the transition boundary from ferroelectrics to antiferroelectrics are discussed It has been established that PbNb05In05O3 corresponds to a ferroelectric with a diffuse phase transition The phase transition in PbNb05Sc05O3 shows a small diffuse nature The temperature-dependences of the unit cell parameters, dielectric constants and loss tangents have been obtained It has been established for the first time that PbNb05In05O3 at room temperature is rhombohedral (R3m) with cell parameters a = 41132 ± 00004A, α = 8997 ± 002° A preliminary determination of the PbNb05Sc05O3

Phase transitions in PbNb0.5B0.5O3(B-Sc, In)

A technique has been developed for refining the atomic displacements in perovskite-type structures by integrated intensity measurements of X-ray reflections obtained from polycrystalline specimens by separating the reflections sensitive to atomic displacements. In this way the temperature changes of atomic displacements in PbTiO3 and PbZrO3 at their phase transitions have been determined. It has been established that the displacements existing in PbTiO3 and PbZrO3 at room temperature monotonously decrease with increasing temperature to certain critical values at the phase transitions. A small abrupt change has been revealed in the atom displacements and unit cell parameters at approximately 150°C. For the first time, displacements of Pb and Hf at room temperature have been determined.

S. M. Zaitsev

Papers

Phase transitions in PbNb0.5B0.5O3(B-Sc, In)

Structural study of PbTiO3, PbZrO3 and PbHfO3