The defect structure of LaCoO_3 based ferroic perovskites has been studied by TEM. The dynamics of the temperature-induced ferroelastic to paraelastic phase transition was directly monitored by in-situ TEM during thermal cycles from room temperature to 700 deg C. Different types of structural features of LaCoO_3 based perovskites have been observed, such as twins, antiphase domains, stacking faults, and dislocations. Domain motion and de-twinning during heating, and the reappearance of twins during cooling have been demonstrated. This is important for the understanding of ferroelastic hysteretic behavior of LaCoO_3 based perovskite ceramics.
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