The origin of antiferroelectricity in PbZrO3

Abstract

Antiferroelectrics are essential ingredients for the widely applied piezoelectric and ferroelectric materials: the most common ferroelectric, lead zirconate titanate is an alloy of the ferroelectric lead titanate and the antiferroelectric lead zirconate. Antiferroelectrics themselves are useful in large digital displacement transducers and energy-storage capacitors. Despite their technological importance, the reason why materials become antiferroelectric has remained allusive since their first discovery. Here we report the results of a study on the lattice dynamics of the antiferroelectric lead zirconate using inelastic and diffuse X-ray scattering techniques and the Brillouin light scattering. The analysis of the results reveals that the antiferroelectric state is a 'missed' incommensurate phase, and that the paraelectric to antiferroelectric phase transition is driven by the softening of a single lattice mode via flexoelectric coupling. These findings resolve the mystery of the origin of antiferroelectricity in lead zirconate and suggest an approach to the treatment of complex phase transitions in ferroics.

Lattice dynamics and antiferroelectricity inPbZrO3tested by x-ray and Brillouin light scattering

“…In systems with real incommensurate phases it often happens that the generally incommensurate modulation is pinned down to the particular commensurate wavevector. The terms in the free energy expansion responsible for this effect are called Umklapp terms 4,24 . In PbZrO 3 we assume the Umklapp terms to be strong enough to drive the phase transition directly to the commensurate AFE state, skipping the incommensurate phase.…”

“…Both the phenomenon itself and its underlying mechanisms are currently under intense investigation and review [2][3][4][5][6][7] . Kittel 8 initially assigned the term "antiferroelectric" to the crystal that has a structural phase transition from a highersymmetry nonpolar parent phase to a lower-symmetry nonpolar phase, distinguished from the parent phase by the anti-parallel ionic shifts.…”

“…Consequently, simultaneous critical increase of 3 generalized susceptibilities might be expected in the high-symmetry phase on approaching the transition temperature. Until recently 4 no observations in favour of or against such critical behavior were reported, except for the dielectric susceptibility 13 that demonstrates the critical divergence with Curie temperature T c =485 K.…”

Magnetic structure of an incommensurate phase of La-dopedBiFe0.5Sc0.5O3: Role of antisymmetric exchange interactions

“…Since the value of 1/4 is not stimulated by symmetry, it can be changed by either external perturbations or changes in chemical composition. This important symmetry aspect has been recently highlighted by Tagantsev et al in the study of lattice dynamics of PbZrO 3 [27]. These authors concluded that the antiferroelectric state is a so-called missed incommensurate phase and that the transition to this state is driven by softening of a single polar lattice mode.…”

“…Due to flexoelectric coupling, the system is expected to be virtually unstable against the incommensurate modulation, as was shown by Axe et al [28]. However, the Umklapp interaction forces the system to go directly to the commensurate lock-in phase, leaving the incommensurate phase as a missed opportunity [27].…”