Role of dislocation climb on twin boundary and antiphase boundary formations in inverse-spinel MnAl2O4

Abstract

The defects, e.g., stacking faults (SFs), antiphase boundaries (APBs), and twin, have been considered the critical components commonly introduced during the synthesis process of spinel oxides. In this study, employing advanced transmission electron microscopy, the formation mechanisms of twin and APBs in MnAl2O4 spinel oxide were clarified. Atomic resolution scanning transmission electron microscopy image and image simulation clarify that MnAl2O4 holds the inverse-spinel-typed structure. Detailed analysis of the twin structure reveals that the asymmetric twin structure in MnAl2O4 forms through an (Mn, Al)-containing plane missing by dislocation climb-up and then continuous shearing on {111} plane. APB forms by dislocation climb-down on an (Mn, Al)-containing {111} plane. The detailed lattice distortion induced by dislocation climb-down was analyzed by geometric phase analysis. The burgers vector for APB formation is identified as a/61̅1̅1+a/411̅0. Frank dislocation of a/61̅1̅1 climb-down and the lattice strain from introducing the extra plane brings a displacement of a/411̅0, which results in terrace-ledge-like morphology of APBs. This study provides a detailed understanding of twin and APB formation mechanisms in inverse-spinel-typed MnAl2O4.