Depth dependant element analysis of PbMg$_{1/3}$Nb$_{2/3}$O$_{3}$ using muonic X-rays

TL;DR

This study uses muonic X-ray analysis to investigate how element concentrations in PbMg$_{1/3}$Nb$_{2/3}$O$_{3}$ vary with depth, revealing surface-related compositional changes affecting its properties.

Contribution

It provides the first depth-dependent elemental analysis of PMN using muonic X-rays, clarifying the origin of surface and bulk phase differences.

Findings

Pb content is uniform across depths.

Mg increases by 25% near surface.

Nb decreases by 5% near surface.

Abstract

The relaxor PbMg$_{1/3}$Nb$_{2/3}$O$_{3}$ (PMN) has received attention due to its potential applications as a piezoelectric when doped with PbTiO$_{3}$ (PT). Previous results have found that there are two phases existing in the system, one linked to the near-surface regions of the sample, the other in the bulk. However, the exact origin of these two phases is unclear. In this paper, depth dependant analysis results from negative muon implantation experiments are presented. It is shown that the Pb content is constant throughout all depths probed in the sample, but the Mg and Nb content changes in the near-surface region below 100$\mu$m. At a implantation depth of 60$\mu$m, it is found that there is a 25% increase in Mg content, with a simultaneous 5% decrease in Nb content in order to maintain charge neutrality. These results show that the previously observed skin effects in PMN are due to a change in concentration and unit cell.