Tuning Relaxor-Antiferroelectric Order in (1 - <i>x</i>)PbMg_1/3Nb_2/3O₃-(<i>x</i>)PbZrO₃ Thin Films.

Abstract

Relaxor antiferroelectrics offer potential advantages such as enhanced energy-storage capacity and improved electromechanical properties over antiferroelectrics or relaxors alone. The fundamental nature of and mechanisms leading to these enhanced properties, however, are understudied. Here, epitaxial thin films of the relaxor-antiferroelectric (1 - <i>x</i>)PbMg_1/3Nb_2/3O₃-(<i>x</i>)PbZrO₃ (1 ≥ <i>x</i> ≥ 0.86) are studied to understand the evolution of the crystal and domain structure and dielectric and polarization properties. X-ray diffraction and scanning transmission electron microscopy studies show a structural transition with increasing PbMg_1/3Nb_2/3O₃ content, from an orthorhombic (<i>Pbam</i>) antiferroelectric phase (<i>x</i> = 1) to an intermediate state of coexisting phases (<i>x</i> = 0.96-0.92) characterized by relaxor-like regions in the antipolar ground state that grows into a rhombohedral (<i>R</i>3<i>m</i>) relaxor phase (<i>x</i> = 0.86, with more randomly arranged dipoles). This transition corresponds to increasing dielectric response and reducing polarization-electric field hysteresis. These relaxor-antiferroelectric films also have 1.5-1.8-times larger electrical breakdown fields than PbZrO₃, resulting in enhanced maximum electromechanical strains (as large as 1.6% and ∼60% larger) and energy-storage density (∼86% larger) and efficiency (∼33% larger) as compared to PbZrO₃. Overall, this study elucidates the fundamental nature of thin-film relaxor antiferroelectrics in terms of their macro- and nanostructures, and corresponding evolution of electrical, electromechanical, and other properties.