A Universal Phase Diagram for PMN-xPT and PZN-xPT

TL;DR

This paper presents a comprehensive phase diagram for PMN-xPT and PZN-xPT, revealing structural differences between surface and bulk regions and challenging previous assumptions about their ground states.

Contribution

It introduces a unified phase diagram for PMN-xPT and PZN-xPT, highlighting discrepancies between surface and bulk structures and providing new insights into their phase behavior.

Findings

Bulk of PMN-xPT is nearly cubic at low temperatures.

Surface layers show rhombohedral distortion, unlike the bulk.

Neutron data reveal a single (111) peak indicating no rhombohedral distortion in the bulk.

Abstract

The phase diagram of the Pb(Mg1/3Nb2/3)O3 and PbTiO3 solid solution (PMN-xPT) indicates a rhombohedral ground state for x < 0.32. X-ray powder measurements by Dkhil et al. show a rhombohedrally split (222) Bragg peak for PMN-10%PT at 80 K. Remarkably, neutron data taken on a single crystal of the same compound with comparable q-resolution reveal a single resolution-limited (111) peak down to 50 K, and thus no rhombohedral distortion. Our results suggest that the structure of the outer layer of these relaxors differs from that of the bulk, which is nearly cubic, as observed in PZN by Xu et al.