Time-of-flight neutron total scattering with applied electric fields: Ex situ and in situ studies of ferroelectric materials

Tedi-Marie Usher; Jennifer S Forrester; Marshall McDonnell; Joerg Neuefeind; Katharine Page; Peter F Peterson; Igor Levin; Jacob L Jones

doi:10.1063/1.5037609

Time-of-flight neutron total scattering with applied electric fields: Ex situ and in situ studies of ferroelectric materials

Rev Sci Instrum. 2018 Sep;89(9):092905. doi: 10.1063/1.5037609.

Authors

Tedi-Marie Usher¹, Jennifer S Forrester², Marshall McDonnell¹, Joerg Neuefeind¹, Katharine Page¹, Peter F Peterson¹, Igor Levin³, Jacob L Jones⁴

Affiliations

¹ Neutron Scattering Division, Oak Ridge National Laboratory, Oak Ridge, Tennessee 37831, USA.
² School of Chemical and Process Engineering, University of Leeds, Leeds LS2 9JT, United Kingdom.
³ Materials Measurement Science Division, National Institute of Standards and Technology, Gaithersburg, Maryland 20899, USA.
⁴ Department of Materials Science and Engineering, North Carolina State University, Raleigh, North Carolina 27695, USA.

PMID: 30278694
DOI: 10.1063/1.5037609

Abstract

Characterizing the structural response of functional materials (e.g., piezoelectrics and ferroelectrics) to electric fields is key for the creation of structure-property relationships. Here, we present a new sample environment and data reduction routines which allow the measurement of time-of-flight neutron total scattering during the in situ or ex situ application of high voltage (<10 kV) to a sample. Instead of utilizing the entire detector space of the diffractometer, only selected regions of detector pixels with scattering at the desired angle to the sample electric field are interrogated, which allows the generation of orientation-dependent reciprocal space patterns and real-space pair distribution functions (PDFs). We demonstrate the method using the relaxor ferroelectric Na_1/2Bi_1/2TiO₃ and observe lattice expansion parallel and contraction perpendicular to the electric field for both in situ and ex situ experiments, revealing the irreversible nature of the local scale structural changes to this composition. Additionally, changes in the distributions of nearest neighbor metal-oxygen bond lengths are observed, which have been difficult to observe in previously measured analogous orientation-dependent X-ray PDFs. Considerations related to sample positioning and background subtraction are discussed, and future research directions are suggested.