On the possibility that PbZrO3 not be antiferroelectric

Abstract

Lead zirconate (PbZrO3) is considered the prototypical antiferroelectric material with an antipolar ground state. Yet, several experimental and theoretical works hint at a partially polar behaviour in this compound, indicating that the polarization may not be completely compensated. In this work, we propose a simple ferrielectric structure for lead zirconate. First-principles calculations reveal this state to be more stable than the commonly accepted antiferroelectric phase at low temperatures, possibly up to room temperature, suggesting that PbZrO3 may not be antiferroelectric at ambient conditions. We discuss the implications of our discovery, how it can be reconciled with experimental observations and how the ferrielectric phase could be obtained in practice.

Phase Competition in High-Quality Epitaxial Antiferroelectric PbZrO3 Thin Films

“…The ideal antiferroelectric proposed by Kittel, regarded as two interpenetrating sublattices with equal and opposite polarization, has fully compensated polarization and has been questioned and reexamined in recent years. Various ground states and low-energy metastable states were proposed via theoretical studies. ,, The SHG signal together with the uncompensated Pb shift and remnant polarization in our single-crystal films give clear evidence to reconsider the nature of the antiferroelectricity of PZO. Multiple soft modes in PZO would lead to small energy differences between several low-energy phases and thus a complex temperature phase diagram .…”

“…Various ground states and low-energy metastable states were proposed via theoretical studies. 22,23,57 The SHG signal together with the uncompensated Pb shift and remnant polarization in our single-crystal films give clear evidence to reconsider the nature of the antiferroelectricity of PZO. Multiple soft modes in PZO would lead to small energy differences between several lowenergy phases and thus a complex temperature phase diagram.…”

“…16−18 In contrast, several independent studies have observed additional weak piezoelectricity and ferroelectricity in PZO at room temperature 19−21 and attributed it to the noncentrosymmetric (i.e., polar) Pba2 orthorhombic structure with unbalanced oxygen atom shifts along the c o direction. In addition, recent theoretical studies have reexamined the ground state of PZO, and several different space group assignments, such as an 80 atom Pnam structure and even a ferrielectric structure, have been proposed, 22,23 which made the gound state of PZO more controversial. In addition, during the antiferroelectric−paraelectric phase transition, an intermediated ferroelectric phase in a narrow temperature region between paraelectric and antiferroelectric has been reported in some previous studies.…”

“…For the room-temperature orthorhombic phase, theoretical studies report that the centrosymmetric (i.e., nonpolar) Pbam structure has the lowest energy, and this structure is commonly accepted as the ground state for PZO. − In contrast, several independent studies have observed additional weak piezoelectricity and ferroelectricity in PZO at room temperature − and attributed it to the noncentrosymmetric (i.e., polar) Pba 2 orthorhombic structure with unbalanced oxygen atom shifts along the c o direction. In addition, recent theoretical studies have reexamined the ground state of PZO, and several different space group assignments, such as an 80 atom Pnam structure and even a ferrielectric structure, have been proposed, , which made the gound state of PZO more controversial. In addition, during the antiferroelectric–paraelectric phase transition, an intermediated ferroelectric phase in a narrow temperature region between paraelectric and antiferroelectric has been reported in some previous studies. , Meanwhile, some other studies argue that the intermediate phase region does not exist and the observed ferroelectricity is not intrinsic and proposed that poor sample quality and defects (nonstoichiometry or chemical impurity) could be responsible for the observed weak ferroelectricity. − Last but not least, due to the relatively low dielectric breakdown strength (the threshold field for the antiferroelectric–-ferroelectric transitionin undoped bulk PZO could be even higher than the breakdown field), it has been a long-standing challenge to obtain reliable, fully saturated hysteresis loops even at room-temperature.…”

A new look at the temperature-dependent properties of the antiferroelectric model PbZrO3: an effective Hamiltonian study

“…Moreover, new low-energy phases were recently predicted by first-principles calculations in PZO, such as those of Ima2 and P nam symmetries containing 30 atoms and 80 atoms per primitive cell, respectively 7,22,23 . The energy difference between these phases is very small and dramatically depends on the pseudopotentials and other computational details, further emphasizing that PZO is rather challenging to understand and to correctly simulate.…”