Origin of relaxor behavior in barium-titanate based lead-free perovskites

TL;DR

This paper investigates the origin of relaxor behavior in lead-free barium titanate-based perovskites, highlighting the role of heterovalent substitution, charge imbalances, and defects in disrupting long-range polar order.

Contribution

It introduces an effective charge mediated mechanism for relaxor behavior at low substitution levels, advancing understanding of lattice disruption in chemically modified ferroelectrics.

Findings

Relaxor behavior occurs at low (<10%) heterovalent substitution levels.

Charge imbalances and defects significantly disrupt lattice order.

The study supports a charge-mediated mechanism for relaxor phenomena.

Abstract

It is well known that disordered relaxor ferroelectrics exhibit local polar correlations. The origin of localized fields that disrupt long range polar order for different substitution types, however, is unclear. Currently, it is known that substituents of the same valence as Ti4+ at the B-site of barium titanate lattice produce random disruption of Ti-O-Ti chains that induces relaxor behavior. On the other hand, investigating lattice disruption and relaxor behavior resulting from substituents of different valence at the B-site is more complex due to the simultaneous occurrence of charge imbalances and displacements of the substituent cation. The existence of an effective charge mediated mechanism for relaxor behavior appearing at low (< 10%) substituent contents in heterovalent modified barium titanate ceramics is presented in this work. These results will add credits to the current understanding of relaxor behavior in chemically modified ferroelectric materials and also acknowledge the critical role of defects (such as cation vacancies) in lattice disruption, paving the way for chemistry-based materials design in the field of dielectric and energy storage applications.