Direct observation of the near-surface layer in Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_{3}$ using neutron diffraction

TL;DR

This study uses neutron diffraction to reveal a distinct near-surface layer in Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_{3}$, showing significant changes in lattice parameters and Bragg peak intensity within approximately 100 micrometers of the surface.

Contribution

It provides direct neutron diffraction evidence of a near-surface region in relaxor ferroelectric Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_{3}$, confirming previous x-ray based assertions.

Findings

Presence of a near-surface region with different lattice parameters

Significant change in Bragg peak intensity near the surface

Surface effects impact diffraction measurements

Abstract

Spatially resolved neutron diffraction as a function of crystal depth in Pb(Mg$_{1/3}$Nb$_{2/3}$)O$_{3}$ reveals the presence of a distinct near-surface region. A dramatic change in both the lattice constant and the Bragg peak intensity as a function of crystal depth is observed to occur in this region over a length scale $\sim$ 100 $\mu$m. This confirms a previous assertion, based on a comparison between high-energy x-rays and neutrons, that such a near surface region exists in the relaxors. Consequences to both single crystal and powder diffraction measurements and previous bulk neutron diffraction measurements on large single crystals are discussed.