Structure and dielectric response in the high $T_c$ ferroelectric Bi(Zn,Ti)O$_3$-PbTiO$_3$ solid solutions

TL;DR

This study combines theoretical and experimental approaches to analyze the structure and dielectric behavior of high-temperature ferroelectric Bi(Zn,Ti)O$_3$-PbTiO$_3$ solid solutions, revealing covalent bonding effects and phase transition characteristics.

Contribution

It provides new insights into the atomic bonding and phase transition mechanisms in BZT-PT solid solutions through combined ab initio and experimental analysis.

Findings

Covalent Zn-O bonds facilitate strong polarization.

High tetragonality and transition temperature observed.

Diffuse phase transition due to local structural heterogeneities.

Abstract

Theoretical {\em ab initio} and experimental methods were used to investigate the $x$Bi(Zn,Ti)O$_3$-(1-$x$)PbTiO$_3$ (BZT-PT) solid solution. We find that hybridization between Zn 4$p$ and O 2$p$ orbitals allows the formation of short, covalent Zn-O bonds, enabling favorable coupling between A-site and B-site displacements. This leads to large polarization, strong tetragonality and an elevated ferroelectric to paraelectric phase transition temperature. nhomogeneities in local structure near the 90$^\circ$ domain boundaries can be deduced from the asymetric peak broadening in the neutron and x-ray diffraction spectra. These extrinsic effects make the ferroelectric to paraelectric phase transition diffuse in BZT-PT solid solutions.