Fragmented charged domain wall below the tetragonal-orthorhombic phase transition in BaTiO3

TL;DR

This study investigates how the phase transition from tetragonal to orthorhombic in BaTiO3 affects charged domain wall structure and conductivity, revealing fragmentation and loss of conductivity below 5°C.

Contribution

It provides in-situ optical microscopy evidence of domain wall fragmentation and conductivity loss during the phase transition in BaTiO3.

Findings

Charged domain walls become twinned and fragmented below the phase transition.

Conductivity of charged domain walls decreases by several orders of magnitude below 5°C.

Fragmentation of superdomain walls disrupts macroscopic conductivity.

Abstract

Ferroelectric charged domain walls are known for their high electrical conductivity, making them promising candidates for applications in modern electronics. A remarkably high conductivity and nominal charge density has been found in the head-to-head ferroelastic domain wall of tetragonal barium titanate. Interestingly, the conductivity of this domain wall decreases by several orders of magnitude when the temperature drops down below about 5 degrees Celsius when the tetragonal phase transforms to the orthorhombic one. We thus explored the evolution of the ferroelectric charged domain walls in BaTiO3 crystals while they undergo this phase transition by in-situ optical microscopy. Our results reveal that, below the phase transition, the domains adjacent to charge domain walls become twinned and the head-to-head charged domain wall transforms into a superdomain wall, which is broken into alternating micron-scale segments with and without the excess bound charge. These observations naturally explains the observed loss of the domain wall conductivity below the phase transition because the macroscopic conductive channel along such fragmented superdomain wall is disrupted.