Determination of the ordered structures of Pb(Mg1/3Nb2/3)O3 and Ba(Mg1/3Nb2/3)O3 by atomic-resolution Z-contrast imaging

Abstract

The atomic structure of ordered domains in ${\mathrm{Ba(Mg}}_{\text{1/3}}{\mathrm{Nb}}_{\text{2/3}}){\mathrm{O}}_3$ and La-doped and undoped ${\mathrm{Pb(Mg}}_{\text{1/3}}{\mathrm{Nb}}_{\text{2/3}}){\mathrm{O}}_3$ is studied by high-resolution Z-contrast imaging. The ordered domain structure in both doped and undoped ${\mathrm{Pb(Mg}}_{\text{1/3}}{\mathrm{Nb}}_{\text{2/3}}){\mathrm{O}}_{\mathrm{3}}$ is determined to be in agreement with the charge balanced random-layer model and inconsistent with the space-charge model. It is shown that La doping in ${\mathrm{Pb(Mg}}_{\text{1/3}}{\mathrm{Nb}}_{\text{2/3}}){\mathrm{O}}_3$ enhances not only the domain size but also the degree of ordering.