Atomic-level structural correlations across the morphotropic phase boundary of a ferroelectric solid solution: xBiMg1/2Ti1/2O3-(1\u2009\u2212\u2009x)PbTiO3

Kaustuv Datta,Boriana Mihailova,Joerg C Neuefeind,Reinhard B Neder,Jun Chen

doi:10.1038/s41598-017-00530-z

Abstract

Revelation of unequivocal structural information at the atomic level for complex systems is uniquely important for deeper and generic understanding of the structure property connections and a key challenge in materials science. Here we report an experimental study of the local structure by applying total elastic scattering and Raman scattering analyses to an important non-relaxor ferroelectric solid solution exhibiting the so-called composition-induced morphotropic phase boundary (MPB), where concomitant enhancement of physical properties have been detected. The powerful combination of static and dynamic structural probes enabled us to derive direct correspondence between the atomic-level structural correlations and reported properties. The atomic pair distribution functions obtained from the neutron total scattering experiments were analysed through big-box atom-modelling implementing reverse Monte Carlo method, from which distributions of magnitudes and directions of off-centred cationic displacements were extracted. We found that an enhanced randomness of the displacement-directions for all ferroelectrically active cations combined with a strong dynamical coupling between the A- and B-site cations of the perovskite structure, can explain the abrupt amplification of piezoelectric response of the system near MPB. Altogether this provides a more fundamental basis in inferring structure-property connections in similar systems including important implications in designing novel and bespoke materials.

Highlights

Room-temperature neutron total scattering data were collected at the Nanoscale Ordered Materials Diffractometer (NOMAD) at the Spallation Neutron Source of Oak Ridge National Laboratory
The starting models for different compositions were built using the structural parameters determined from prior Rietveld refinements of the neutron powder diffraction pattern
Raman spectra were collected with a Horiba T64000 triple-grating spectrometer equipped with an Olympus B41 confocal microscope (50x objective), and a Symphony liquid-N2-cooled CCD detector

Summary

Introduction

The proposed model featuring distinct static and dynamic characteristics might be applicable for a broad range of perovskite-based ferroelectric solid solutions especially with Pb and Bi where similar behaviour of the average structure have already been reported. It entreats on a number of colligated issues, such as the distinction of the composition-driven phase boundaries from the temperature or pressure-induced phase boundaries, nature of the B-site chemical disorder (here Mg acts as a modifier of the coupling processes between the ferroelectrically active elements), combination of ferroelectric-antiferroelectric order (as in PZT), and especially the MPBs of Pb-free systems in order to develop efficient design rules. Roomtemperature powder x-ray diffraction data (Stoe Stadi-MP powder X-ray diffractometer) were collected to verify the formation of a single perovskite phase.

Results

Conclusion